This paper was written in June 2000 to satisfy the written requirement for a BS in Chemistry at the University of Pittsburgh.
The fact that synthetic chemicals can mimic naturally occurring estrogens has been known since the 1930s (Jordan et al. 97). In recent years, however, there has been a large increase in the discussion of environmental estrogens (also known as hormonally active agents, xenoestrogens, and endocrine disruptors) in the scientific literature as well as in the popular press. The hypothesis is that exogenous estrogen-mimicking chemicals can interfere with key stages of development and contribute to hormonally related diseases in human and non-human animals. These xenoestrogens are compounds like phytoestrogens, synthetic estrogens, dietary estrogens from meat and dairy products, and a host of chemicals used for other purposes that happen to have estrogenic properties (e.g., pesticides, alklyphenol esters, and plastics). While many things are known for sure, important pieces of evidence are weak or missing. Few, however, will deny the basic facts.
Many chemicals are capable of binding to estrogen receptors and eliciting a response. Under specific conditions where wildlife has been exposed to large amounts of xenoestrogens, endocrine disruption has occurred. This is most notable when feminization of males occurs, as in the case of male fish who produced yolk proteins that are normally produced only by females (Folmar et al. 1096). Experiments show that exposure to xenoestrogens at critical stages of development can permanently alter an animal, e.g., reversing the sex of a reptile (Guillette et al. "Organization" 157).
People are exposed to xenoestrogens through a multitude of pathways. Bisphenol-A is used in composite tooth fillings; it also leaches from the lining of canned goods and from plastic food containers when heated. Dairy products are often obtained from pregnant cows and contain high levels of estrogen (Sharpe and Skakkebæk 1393). Polychlorinated biphenyls (PCBs), DDT and other pesticides bioaccumulate and are found in fish and other meats. Water contains pesticide runoff from agriculture, and fruits and vegetables contain pesticide residues. Alkylphenol ethoxylates (APEs) are used as detergents, emulsifiers, wetting agents, and dispersing agents. Humans can be exposed to APEs through the water supply, sewage sludge used for fertilizer, seafood, food packaging, and spermicides (Nimrod and Benson 338).
Evidence of endocrine disruption in humans comes almost exclusively from evidence about children whose mothers, during pregnancy, were given diethylstilbestrol (DES), a powerful synthetic estrogen. Daughters who were exposed have higher rates of reproductive tract deformities, infertility, and a rare form of vaginal cancer, among other things (Colborn, vom Saal and Soto 379). Less research has been done on sons, but they may have higher rates of abnormal sperm, immune system problems like arthritis, undescended testicles, epididymal cysts and possibly testicular cancer (Colborn, Dumanoski and Myers 59). Even with a potent estrogen deliberately administered to pregnant women, only high doses led to effects. According to toxicologist Robert Golden, "for some reason the lowest doses were prescribed at the Mayo Clinic (in Rochester, New York [sic]) and the highest at the University of Chicago. When you look at Mayo (results), there's nothing coming out of there. Yet out of the University of Chicago, there are all sorts of reproductive problems such as small penises, decreased sperm, abnormal sperm" (qtd. in Fumento).
Despite all of the above, there is no causal evidence that widespread endocrine disruption is occurring in humans. Increases in breast cancer, testicular cancer, male genital deformities and a drop in sperm count are the most commonly cited indicators of endocrine disruption in humans. But all of the evidence is strictly correlative, sometimes wildly so when endocrine disruptors are blamed for things like a drop in SAT scores (Colborn, Dumanoski and Myers 235) and the breakdown of the traditional family (Colborn, Dumanoski and Myers 237). Not only does the lack of compelling evidence cast doubt on the belief that endocrine disruption is occurring in humans, but it also strengthens the belief that disruption is not occurring at all. If such hormone sensitive systems have not been clearly affected following the post-World War II barrage of endocrine disrupting chemicals, then it is unlikely that low doses of these chemicals are harming human health—the heart of the endocrine disruption theory. Although any hormone in the body could be subject to disruption, only estrogen mimics will be discussed here as they have by far received the most attention from both scientists and the public.
A Century of Change
The key date for the beginning of endocrine disruption is the end of WWII. This was when large quantities of known and suspected endocrine disruptors came into widespread use (Colborn, vom Saal, and Soto 378). However, there were other important changes over the past century—most notably in diet. In the US, daily carbohydrate consumption is down from 497 g in 1904 to 388 g in 1974. At the same time, total protein intake remained constant at around 100 g, but it went from being 50% animal and 50% vegetable to 70% animal and 30% vegetable (Gortner 3248). Total fat increased from 127 g to 158 g. Since 1940, pork and milk consumption dropped significantly while margarine, oil, and beef consumption increased markedly (Gortner 3251). Poultry consumption saw a "dramatic" increase with new techniques used to breed chickens on a mass scale (Gortner 3249). USDA figures also show that daily caloric intake has increased by 800 calories since the 1950s (Hunter, "America’s" 12). People are eating out more now (34% vs. 19% in the 1970s) and portions are increasing—for example, a fast food hamburger used to contain 1 oz of cooked meat in the 50s whereas today it is 6 oz (Hunter, "America’s" 12).
Another unprecedented change this century is the trend toward delayed childbirth. "For the first time in recorded history, the number of births for every thousand British women in their early 30s has recently exceeded that in women in their early 20s. The rate in older women is climbing too" (Gosden and Rutherford 1585). This paper will show that these and other lifestyle changes frequently offer a simpler and more compelling explanation for many problems that some would like to attribute to endocrine disruption.
Numerous ideas exist about how xenoestrogens may cause breast cancer. They may simply increase a woman’s overall estrogen exposure, they may act to increase the potency of endogenous estrogens, or prenatal exposure may cause permanent susceptibility (Colborn, Dumanoski and Myers 183). In the US, a 1% per year rise in breast cancer incidence has been documented since the 1940s (Feuer and Wun 1424). This is taken as evidence of endocrine disruption since women have been exposed to increasing amounts of hormonally active compounds since World War II.
However, the trend toward increasing breast cancer began well before WWII. Breast cancer incidence increased has from 1935 (with no prior data available) (Sullivan 1067). Despite this, mortality has been constant since the mid-1940s (Sullivan 1067-8). In Norway, the incidence trend has been increasing nearly steadily since 1916 (Tretli and Gaard 510). That the trend began well before the widespread use of suspect chemical indicates that other factors caused the trend initially and probably still account for the increase. Recent increases above the 1% trend can be attributed to better detection. In women over 40, rates have increased since 1982, but this is attributable to increased use of mammography (Feuer and Wun 1434; Wun, Feuer and Miller 142). In women aged 40-59, mammography may account for more than the reported rate increase; that is, there could even be a decrease in actual rates of incidence (Wun, Feuer and Miller 1433).
The idea that breast cancer can be caused by exposure to the strongly estrogenic DDT and PCBs has been disproven. Past correlations have been minimal (not even statistically significant) and based on six comparatively small epidemiological studies (Key and Reeves 1520). A much larger study (having as many women with breast cancer as all of the previous studies combined) showed no correlation between serum levels of DDE (a metabolite of DDT) or PCBs and breast cancer (Krieger et al. 589-90). Additionally, these samples were collected an average of 14 years prior to diagnosis (the time period from 1964-1971—a peak in exposure), which could better account for causality than the previous studies that collected samples at the time of diagnosis. The largest study to date, using blood samples taken from 1974 and 1989, showed no increase in risk corresponding with higher levels of DDE (Helzlsouer et al. 529). Blood samples taken from 1989-1990 also reveal that there is no correlation (Hunter, "Plasma" 1256). Recent studies of breast adipose tissue found no difference in the concentration of DDT and its metabolites in women with breast cancer and in women without breast cancer (Bagga et al. 751; Zheng et al. 455). This is particularly significant because even if studies using plasma or gluteal adipose tissue are discounted, it appears that even measuring the organochlorine concentration directly in the breast still fails to produce a correlation.
Additionally, because DDT is still used in other countries, one would expect skyrocketing rates of hormonally dependent cancers in developing nations. This is not the case. Furthermore, in a relatively small study of northern Vietnamese women, whose DDE levels are on average more than double that of US women, no correlation between DDE and breast cancer was found (Schecter et al. 454). DDT is also still in use in Mexico. A study there found no correlation between the concentration of DDE and breast cancer incidence, although DDE levels were similar to US women (López-Carrillo et al. 3730).
Another troubling point for endocrine disruption theory is that African American women have adipose DDE levels that are on average 74% higher than white Americans (Cocco et al. 3), yet rates of breast cancer are higher in whites (Zheng et al. 457).
In a large accidental exposure of humans (976 males and 1062 females) to PCBs, no increase was reported in the incidence of breast cancer, and there was actually a decrease in overall cancer mortality except perhaps for liver cancer (Hsieh et al. 417). Similarly, the results of a study on a population exposed to 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) as a result of an accident 15 years ago in Sevoso, Italy, show a decrease in breast, uterine and ovarian cancer (Bertazzi et al. 649). The weight of evidence concludes that increased exposure to DDT and PCBs does not increase breast cancer risk (Helzlsouer et al. 529).
In fact, women with the highest levels of DDE and PCBs consistently have the lowest risk of breast cancer (Cocco et al. 3, Dorgan et al. 7, Helzlsouer et al. 529, López-Carrillo et al. 3730, van’t Veer et al. 85). These decreases in breast cancer and the inverse association with DDE levels could ironically be explained in terms of endocrine disruption. Instead of increasing overall estrogen exposure, the less potent xenoestrogens bind to estrogen receptors without triggering transcription, thus decreasing the effect of endogenous estrogen exposure. Yet no one on either side of the question has seized upon these results as evidence of endocrine disruption. In Our Stolen Future, the authors initially point out that while DDT mimics estrogen, DDE depletes hormones in the body, including estrogen susceptibility (Colborn, Dumanoski and Myers 85), but later cited the studies available at that time that indicated increased DDE levels were associated with increased risk of breast cancer, especially in women with estrogen-responsive tumors (Colborn, Dumanoski and Myers 184). This highlights the ease with which endocrine disruption claims can be "proven" if the desired result is not found—the chemical must simply act in the opposite manner.
Proponents of endocrine disruption theory claim that even if DDE or some PCBs do not cause breast cancer, there are a myriad of other estrogen mimics that could cause breast cancer (Colborn, Dumanoski and Myers 184). But this type of dismissal belies the strength of their initial claim—that the estrogenicity of these compounds is to blame. DDE is a potent estrogen and if it does not cause breast cancer, this casts serious doubt on the idea that chemicals are dangerous simply because of their estrogenicity.
There is a simpler explanation for the long-term increase in breast cancer. An established risk factor for breast cancer is a diet high in fat, calories and protein and low in complex carbohydrates and fiber (Adlercreutz, "Diet" 281; Stephens 756). Additionally, "certainly the incidence is lower in women who adhere to a strict vegetarian diet" (Stephens 756). Clearly, the standard American diet increases women’s risk for breast cancer.
Unfortunately, this western diet is spreading worldwide, particularly to cities in developing countries where the traditional diet was low-fat vegetarian or semi-vegetarian. It is not surprising that western diseases like breast cancer would follow. Breast cancer rates in Japan increased following the introduction of a diet rich in meat, eggs and animal fat (Rose et al. 2367; Hirayama 179). A study from 1950-1975 revealed that increased breast cancer rates in Japan corresponded strongly with increases in non-fish animal fat (particularly strong with pork) (Kagawa 211; Hirayama 179).
In the past, breast cancer rates declined for Japanese women, while in the US that risk has always increased. The trend in Japan is now toward increased risk for postmenopausal women, but no data from either country indicates a change in the rates of younger women, which would suggest xenoestrogen involvement (Kodama, Murakami and Kodama 795). Regarding research back to 1970 as well as a plot of breast cancer incidence rates in Japan from 1959-1987, Kodama et al. conclude "There is no explanation feasible other than the Westernization effect" (Kodama, Murakami and Kodama 795). Data from England from the 1960s to mid-1980s reveals the same phenomenon—some increase in cancer incidence in postmenopausal women, but no change in the risk for young women (Kodama, Murakami and Kodama 795). These facts are inconsistent with a xenoestrogen explanation, but are consistent with the Westernization effect.
Numerous studies over the past 20 years have documented the phenomenon that migrants to the United States from areas of low breast cancer incidence tend to adopt the cancer rates of the new country (Dunn 3240; Stanford et al. 182; Hirayama 194). Immigrants from China and Japan, for example have breast cancer rates that are 50% lower than white American women, but only 25% lower for first generation US born Asian-Americans (Stanford et al. 182). After successive generations, the disparity between immigrant families and natives decreases even further (Stanford et al. 182), which corresponds to increasing Westernization of diet. An explanation based on chemical contaminates could certainly be devised, but their major weakness is in explaining why the rate of breast cancer continues to grow in successive generations. If the xenoestrogens are ubiquitous, the first American generation ought to be affected just as much as anyone else born here is.
Not only does the Westernization effect explain increases in breast cancer in other countries, but it also explains the steady increase in Western countries where the diet has been changing for the worse in terms of breast cancer risk factors. The marked halt in the trend of increasing breast cancer for women who experienced adolescence during WWII provides evidence for the diet-breast cancer relationship (Tretli and Gaard 511). During WWII in Norway energy intake decreased by 22%, especially with a drop in fat consumption. While the consumption of meat had increased up until the war, it "dropped substantially" during the war along with milk intake. There was increased intake of vegetables and fish as well as increased physical activity (Tretli and Gaard 511). Breast cancer is also correlated with height; the height of adolescent girls in Oslo steadily increased from 1920-1975, except for a decline during WWII (Tretli and Gaard 510). Interestingly, US breast cancer mortality declined from 1940-1946 (Sullivan et al. 1068).
Several mechanisms can explain why diet affects breast cancer. First, a high protein/carbohydrate ratio decreases the level of sex hormone binding globulin (SHBG) in the blood and enhances 2-hydroxylation of estradiol, resulting in higher estrogen concentrations than with lower protein/carbohydrate ratios (Adlercreutz, "Western" 6). The lowest protein/carbohydrate ratios are found in vegetarians and the highest in breast cancer patients (Adlercreutz, Western 6). Second, high fiber diets increase fecal weight and thus the amount of estrogens excreted while a diet higher in fat decreases the amount of estrogen found in feces. Additionally, a high fiber diet decreases the intestinal reabsorption of estrogen, and some fibers even bind directly to sex hormones (Adlercreutz, "Western" 5). Overall, a low fat-to-fiber ratio reduces the amount of biologically available estrogen, thus theoretically decreasing the risk of cancer (Adlercreutz, "Western" 6).
Finally, a separate lifestyle factor that could explain at least some of the rise in breast cancer is the trend toward delayed childbirth. The risk of breast cancer increases with age at first birth (Tretli and Haldorsen 215). Fifteen percent of Norway’s increase in breast cancer can be attributed to delayed childbirth (Tretli and Haldorsen 218).
Xenoestrogens have been cited as the cause of the falling age of menarche, the age at first menstruation (Birnbaum 676). A potential mechanism is simply that high levels of estrogen trigger menarche in young women whose natural estrogen levels otherwise would not.
First, there is no longer even a trend toward earlier menarche; in Europe the trend has largely stopped (Tanner 160). In Denmark, for example, between 1966 and 1983, the trend toward lower ages stopped (Helm and Grolund 198). In Belgium, the average age was 13 in both 1965 and 1981 (Helm and Grolund 198). In America, the age of menarche in white girls has been stable at 12.9 since at least 1948, although there may have been a slight decline in the age for black girls (Herman-Giddens et al. 505).
Second, the claim that the trend post-WWII is due to increased exposure to xenoestrogens is refuted by the fact that the trend began by at least 1835—over 100 years before the widespread use of suspected endocrine disruptors. In Denmark from around 1835 to 1945, the age went from 17 to 14 in a linear decline. Then from 1950 to 1966 it went from 13.8 to 13.4 (Helm and Grolund 199)—the trend slowed when, according to the endocrine disruption hypothesis, it should have increased.
Finally, the trend toward earlier menarche can be best explained by rising standards of living—particularly in food quality. Prior to WWII, but less so after WWII, there was a sharp increase in height and weight of children in places like Europe, the US, Canada, and Australia (Tanner 157). Increased size alone can explain the drop in the age of menarche, given that it seems to be linked to attaining a critical weight or percent body fat. Higher levels of the hormone leptin, which increases with the amount of body fat, result in lower ages of menarche (Matkovic et al. 3243). Eating more protein and fat lowers the age, while a diet consisting mainly of plants and carbohydrates raises the age (Sanchez et al. 1341); vegetarian girls have a later menarche than their peers (Sanchez et al. 1342). In Japan, the age of menarche dropped from 15.2 in 1950 to 12.2 in 1974 (Kagawa 211). This corresponds to a time when some Westernization occurred to the Japanese diet: milk, meat, and fat intake increased respectively to 15, 7.5 and 6 times their previous levels (Kagawa 206). Adolescent girls went from being 133 cm tall and weighing 30 kg in 1900 to 148.5 cm and 41 kg in 1974, increasing slowly at first then rapidly after 1950 (Kagawa 210). Thus, it is clear that worldwide changes in diet have brought about changes in age at menarche before the introduction of xenoestrogens.
Endometriosis is a disease characterized by lesions in other parts of the female body caused by cells that normally line the uterus; a major symptom is extreme pain. Estrogen is known to aid the spread and growth of endometrial cells. Factors such as smoking and exercise are associated with lowered risk of endometriosis, presumably because of the decreased estrogen levels caused by these activities (Eskenazi and Warner 253).
The supposed increasing incidence of endometriosis has been cited as an indication of endocrine disruption (Birnbaum 676, National Research Council 135). Some even went so far as to declare, "Prior to 1921, there were only twenty reports of the disease in the worldwide medical literature," absurdly implying that the disease did not even exist prior to the industrial era (Colborn, Dumanoski and Myers 181). This is false, however, as remarkably accurate and detailed reports of the symptoms and manifestations of the disease have existed throughout history, dating back to at least 1690, when even then, it was regarded as a relatively common disorder (Knapp 11).
In fact, the frequency of severe endometriosis has probably not changed since at least the 1940s (Vercellini and Crosignani 111), which, again, is particularly problematic since the vast majority of suspected xenoestrogens were not released until after 1940. The increase in mild cases of endometriosis is probably due solely to the use of naval laparoscopy, which can detect cases that would have otherwise gone undiagnosed (Vercellini and Crosignani 111).
If environmental estrogens do affect humans, one would expect to see an increase in severe endometriosis because endometrial cells require estrogen for proliferation and long-term survival (Bergqvist 33). These cells that once lined the uterus continue to react to changes in estrogen levels even once they are outside the uterus; the activation of these cells during menstruation is what causes the severe pain associated with endometriosis. Since "no association between endometriosis and prenatal DES exposure has been established" (Haney 3), there is probably no critical time during pregnancy where a dose of excess estrogens later causes endometriosis. Because lifetime estrogen (or xenoestrogen) exposure would be the cause of excess cases of endometriosis, there has been more than adequate time for a trend to emerge. Furthermore, case control studies reveal no association between incidence of endometriosis and plasma levels of 14 PCB congeners, 11 organochlorine pesticides, or dioxin (Lebel et al. 222, 225).
One explanation for any apparent or future increase in endometriosis could simply be that awareness about endometriosis on the part of both women and doctors has increased. Consequently, women are actually diagnosed with the disease instead of being dismissed as mental cases. Seventy percent of women who are ultimately diagnosed with endometriosis were told at some point that it was only psychological (Ballweg 444). Of 850 women who were referred as mental cases to a doctor who happened to be both a psychiatrist and a gynecologist, he discovered that 92% of the women actually had endometriosis (Ballweg 453).
Perhaps the most important piece of evidence cited by endocrine disruption proponents is that of falling sperm counts (Sharpe and Skakkebæk 1392). Numerous mechanisms exist based on exposure to xenoestrogens in utero and up until puberty (Sharpe and Skakkebæk 1394-5). Falling sperm counts have been referred to as "the most dramatic and troubling sign that hormone disruptors may already have taken a major toll" (Colborn, Dumanoski and Myers 172). The dramatic nature of the claim has made it a key factor in influencing public opinion and public policy; Greenpeace’s slogan, "You are half the man your grandfather was," made it into Congressional debates. Because of its central role in the endocrine disruption controversy, the issue of sperm counts will be discussed in detail.
The idea that sperm counts are decreasing at all has been widely criticized. The only evidence of a global decline is a meta-analysis by Carlsen et al., which analyzed 61 studies that took place over 50 years from 1938-1990. They found a stunning decline in sperm counts—nearly 50% (Carlsen et al. 610). However, this study is fraught with uncertainty.
Many methodological problems have been noted such as publication selection bias, patient selection bias, method of sperm collection, small sample size of many studies, length between data collection and publication, use of an arithmetic mean, and use of a simple regression line (Farrow 1; Paulsen, Berman and Wang 1019; Olsen et al. 890). These variables are significant—take method of sperm collection for example. Some samples are collected at home, while others at a clinic. Stress is known to decrease sperm counts, so clearly, where the sample is collected could have a direct impact on sperm count. It is reasonable to assume that over time, as sperm banks became more popular, more of the later samples were collected in clinics. Additionally, sperm was counted using many different protocols and counting chambers (Fisch et al. 1012). Furthermore, "The men in these studies ranged in age from 17 to 64 years, the duration of abstinence was for the most part neither controlled nor recorded, and the mean sperm concentration varied threefold" (Sherins 327). Finally, sperm counts vary over course of the year, with high levels in February and March and low levels in September (Tjoa 454; Gyllenborg et al. 31). This is yet another variable that was not taken into account by the Carlsen study.
Subsequent reevaluation of Carlsen’s data by other researchers indicates that "nearly all of the observed decline in mean sperm count may be a consequence of the reduction of the lower reference value" (Bromwich et al. 21). That is, the minimum sperm count considered "normal" was lowered over the years. Earlier studies may have excluded "low" counts that were included in later studies.
Differences in recruitment of donors can also explain a decline in sperm count. As the number of prospective donors increases, as it has over the past 50 years, the sperm banks can be more selective (Fisch et al. 1012). Donor recruitment bias is significant. Over a 15-year period at the same facility, five studies requiring sperm samples were conducted. Comparisons between the mean sperm count in each study revealed statistically significant differences between the studies (although there was no overall downward trend for the time period) (Handelsman 2703). This highlights the bias of self-selected donors, rather than a true random sample of the population (which for the most part has been lacking in sperm count studies). Handelsman also stated, "It is notable that this large bias effect size within a single centre is comparable with the magnitude of the alleged effect size for decrease in sperm concentration over six decades, according to the Carlsen meta-analysis" (2703).
Adjustment for age and duration of abstinence (which were not controlled for in Carlsen’s analysis) shows no decline (Fisch et al. 1013). Abstinence is a very important variable, yet only 53% of the Carlsen studies provided data on the recommended length of abstinence (let alone the actual length of abstinence) (Olsen et al. 891). Furthermore, a large study comprising 1/3 of all the post-1971 data was conducted using men who were undergoing a vasectomy (Tjoa et al. 454). The men in this study were far less likely to comply with abstinence guidelines, since they had no interest in what their sperm count was (Olsen et al. 891). Abstinence periods could explain the decline in the 1960s. Birth control may have led to shorter abstinence periods, which is in accord with the decline in semen volume noted by Carlsen (Suominen and Vierula 1579). At least one study from 1955 noted a significantly longer abstinence period than is standard in present studies (Suominen and Vierula 1579).
If the statistical model of continuous linear decline in sperm count proposed by Carlsen is accepted, it would also indicate that sperm counts have been declining before 1940 and thus the phenomenon must be attributable to something other than or in addition to endocrine disruptors (Olsen et al. 887-93). There is also a "need for caution in using regression models to determine the statistical significance of the results, because the correlation coefficients were very small, indicating that variables other than the sperm concentration contributed to the determination of statistical significance" (Sherins 327). A stair-step model more accurately fits the data. This model indicates a rapid decline in sperm count in the mid-1960s (such as one due to shorter abstinence periods caused by the birth control pill) but no further declines (Olsen et al. 891). This leaves open the question as to what the trend looked like before 1940. Perhaps there was a spike in sperm counts due to WWII caused by any number of factors, such as longer periods of abstinence.
The Carlsen study and any attempt to analyze sperm levels suffer from the fact that there is very little data prior to 1970. Analysis of post-1970 data indicates no decline or a slight increase (Olsen et al. 891). This is very different from the linear decline that endocrine disruptor proponents promote to the public.
Geographical differences can also explain the apparent decline or at the very least, raise serious concerns about the effects of sample selection bias. New Yorkers have consistently had higher than average sperm counts (Fisch et al. 1013). In the data before 1970, 94% of the men were from the US and 87% of those from New York City. After 1970, 50% of the men were from the US and only 25% from New York City (Fisch et al. 1013). If the Carlsen data is analyzed without the large studies from New York, then there is no decline in sperm count (Lipshultz 910). An analysis of only the US data from the Carlsen data plus later US studies indicates no decline from 1938-1996 when New York and non-New York data are analyzed separately (Saidi et al. 460). If the distinction is ignored, however, a decline can be shown (Saidi et al. 460).
When well-controlled studies from one geographical location are studied, there is typically no trend toward lower counts. The downward trend seems only to emerge when a huge number of variables are introduced from many cross-geographical studies. A series of studies performed at a Los Angeles fertility clinic have revealed no differences in sperm count from samples taken in 1951, 1979, and 1994-97 (Acacio et al. 596). Similarly, a study of 20,411 infertile men from 1960 to 1996 in Northeast Spain revealed no decline in sperm count (Andolz, Bielsa, and Vila 734). A meta-analysis of six Finish studies from 1958 to 1992 revealed no decline (Suominen and Vierula 1579). Studies using sperm collected from the 1970s to the 1990s have noted an increase in four US locations and in Denmark (Paulsen, Berman and Wang 1019; Fisch et al. 1012; Gyllenborg et al. 30). A more recent Korean study revealed no decline from 1989 to 1998 (Seo et al. 194). A unique Danish study used men who were married to infertile women seeking in vitro fertilization to achieve a random sample of the general male population. The samples were collected from 1990-1996 and no associations were noted between year of birth and sperm concentration (Rasmussen 1060). For example, there was no difference in counts from men born before 1955 and those born after 1964 (Rasmussen 1060).
There are exceptions—some studies from one geographical location do reveal a decline. A study of Scottish men showed a decline in sperm count associated with year of birth (Irvine et al. 467). However, this study suffers from the fact that the older group contained men of proven fertility (they had fathered children) and the younger men contained men of unconfirmed fertility. In fact, 81% of those born before 1960 had proven fertility compared to only 5% of those born from 1970-74 (Irvine et al. 469). The younger men were more likely to contain some infertile men, which would drive down the mean sperm count for the younger men (Farrow 1). Furthermore, the results obtained were consistent with either an increase in sperm count with age or a decline in count associated with year of birth. The authors discounted the former, despite the obvious fact that older men probably have longer periods of abstinence, and thus higher sperm counts. Another study indicated that older men did have higher sperm counts (Raab 44; Joffe 44). Also, the younger group being undergraduates, were perhaps more likely to have lower sperm count due to alcohol and smoking (Eccersley 43).
A study of Parisian men reported a decline in sperm concentration from 1973 to 1992 (Auger et al. 281). Only fertile, accepted sperm donors were included, which excluded all fertile men who were rejected as sperm donors. However, the selection criteria or any changes in it over time were not noted (Lipshultz 910). "In addition, differences in age, abstinence before semen analysis, ejaculatory frequency, and the number of samples analyzed per person were not controlled for" (Sherins 327). This study too could suffer from the fact that older men in general have higher sperm concentration than younger men (Joffe 44). Rasmussen et al. note the importance of variation over even a short time period: "In our study, the average sperm concentration varies by >30% from year to year. The variation persists even after correction is made for differences in the age and number of patients, and the variation from one half-year period to another is greater than the entire difference for the period 1973-1992 in the study by Auger et al." (1062).
In case sperm counts really have fallen (or, at the very least, to add another variable that sperm researchers must control for) those who manufacture suspected endocrine disruptors have proposed their own creative explanation. Dow Chemical Company’s Health and Environmental Research Laboratory recently published a study proposing that the introduction of iodized salt is responsible for the drop in sperm count (Crissman 400). This would mean that sperm counts really have not fallen so much as returned to normal levels from abnormally high levels caused by iodine deficiency. Animal studies suggest that individuals who experienced iodine deficiency in the womb have higher sperm counts. The iodine deficiency leads to hypothyroidism, which causes a longer period of growth for sperm-producing Seritoli cells, so that ultimately those individuals possess a larger number of them. The elimination of iodine deficiency would mean that men do not develop additional Seritoli cells and therefore their sperm counts would fall. This hypothesis even explains the decline in the Parisian men because iodized salt was not introduced in France until 1952, in the middle of the years in which the men studied were born (Crissman 408). But it is also worth noting that "in 1923 William J. Hale, a chemist at the Dow Chemical Company in Midland, Michigan, made the first iodized salt in America" (Crissman 408).
Ultimately, there are an incredible number of variables associated with measuring sperm count. Even individual men experience a wide range of "normal" values. Terrifying claims of a universal, global 50% decline in semen quality are made to get people’s attention. And that is precisely what happened. Yet such claims are easily refuted. Those with an interest in preserving the status quo can use the evidence to dismiss the whole theory. Rather than making broad doomsday predictions, those who fear endocrine disruption ought to make highly conservative claims that cannot be refuted. They should want to make highly specific claims so than a very strong correlative link can be made. For example, one study of sperm counts in London noted a decline in sperm counts from 1978 to 1989. But upon closer examination, the decline was observed only among men who lived in a particular water district (Ginsburg et al. 230). Further research could lead to the identification of the responsible compound(s), which will certainly not turn out to be iodized salt.
The increasing rate of testicular cancer is widely cited as evidence of endocrine disruption (Sharpe and Skakkebæk 1392; National Research Council 168). The mechanism is not clear, but is probably the result of exposure in the womb (Sharpe and Skakkebæk 1394). Both high and low levels of estrogen during pregnancy pose an increased risk of testicular cancer. High levels of estrogen (found in older women, women with a large placenta, and women of low parity) are associated with the seminoma variety of testicular cancer. Low levels of estrogen (young women, low birth weight) are associated with non-seminoma (Ekbom and Akre 227).
One problem with claiming that the increasing rate of testicular cancer is caused by endocrine disruption is the paucity of data before WWII. In Australia for example, there is no reliable incidence data prior to 1950 (Stone et al. 211). Given that cancer rates could have very well been increasing prior to 1950 (just like menarche ages were decreasing prior to 1950), any claims based on rates of testicular cancer are inherently on questionable ground.
When there is data, it shows that the trend existed before the widespread use of the suspect chemicals. In Australia, mortality rates from testicular cancer increased from 1910 to 1969 and fell afterward (Stone et al. 211). (It is acceptable to use mortality rates for older data; it is only in the past 3 decades that improvements in treatment have allowed declines in mortality that do not correspond to declines in incidence) (Davies 930; Stone et al. 211). A study in England and Wales showed that testicular cancer mortality rates have been increasing since the beginning of the 20th century, with men born as early as 1881 being affected (Davies 930). Furthermore, it is not that there is no trend in the 19th century—there is simply a lack of data for that time period. A study of the US indicated that testicular cancer incidence has been increasing since 1935 among men aged 15-44, with no data prior to that time (Brown et al. 166). Brown actually noticed two trends, from 1935-50 there was an increase in seminoma, while in the 1970’s there was an increase in nonseminoma (169; Stone et al. 217). There were either two separate factors for the increases, or one factor has a different on men depending on when they are exposed. Thus, while testicular cancer rates are perhaps increasing due to xenoestrogens, there is definitely another factor that explains the earlier increase, and perhaps explains the present continuation of that trend as well.
In the US from 1973-1984 there was a 33% increase in testicular cancer among whites, but no increase among blacks (Van Den Eeden and Weiss 1553). This is particularly difficult to explain since blacks have higher concentrations of suspected endocrine disruptors in their bodies.
Once again, lifestyle factors could easily explain the rise in testicular cancer. It has been known for over 20 years that fat and meat intake corresponds to testicular cancer rates (Armstrong and Doll 627; Paulozzi, "Effects" 527; Sigurdson et al. 22). Similar to the breast cancer trend, there was a drop in testicular cancer in Denmark for men born during World War II (Møller, "Decreased" 1669). This is in accord with Paulozzi, who found a slightly higher correlation with fat consumption at age of birth, rather than at time of diagnosis ("Effects" 527). Ekbom and Arke point out that New Zealand, Switzerland and Denmark have the highest incidences of testicular cancer (226). New Zealand and Denmark have among the highest per capita meat and fat consumption rates (data on Switzerland was not provided) (Armstrong and Doll 625). Additionally, any study of testicular cancer confirms that rates increase with affluence (Stone et al. Trebling 218; Davies 931), which may or may not be related to fat consumption.
Another clear risk factor for testicular cancer is a sedentary lifestyle. Exercise decreases risk while sitting around increases the risk (Gallagher et al. 401; "Aetiology" 1397). The use of computers, televisions, and video games are all novel sedentary activities that appeared post-WWII. Physical activity has declined since 1950 (Hunter, "America’s" 13).
Perhaps most intriguing is that the risk of testicular cancer declines as the age of puberty rises (Gallagher et al. 404; "Aetiology" 1396). Also, not surprisingly, the age of puberty in places like Canada, the US, and Europe has decreased (Gallagher et al. 404), perhaps due to a similar mechanism as the decline in age of menarche, namely that higher standards of living bring about faster maturity. The lower age of puberty alone could explain the increase in testicular cancer rates ("Aetiology" 1397; Weir, Kreiger, and Marrett 257).
Male Genital Defects
Increases in hypospadias, a urethral opening on the underside of the penis, and cryptorchidism, undescended testes, are cited as evidence of endocrine disruption (Kelce and Wilson 202; Sharpe and Skakkebæk 1392). This idea is based on animal studies and a supposed increase in these disorders among sons who were exposed in utero to high levels of the synthetic estrogen DES.
There is uncertainty as to whether or not the rates of these problems in the general population are even increasing. A study that examined the rates based on groupings of countries according to gross domestic product (GDP) showed no increase anywhere in cryptorchidism since 1910 and a decrease in most countries since 1985 (Paulozzi, "International" 299-300). In the least affluent areas (China, Czech Republic, Hungary, Mexico, and South America) the rates of hypospadias have been stable since around 1974 (Paulozzi, "International" 300). In countries with the second lowest GDPs (Mediterranean nations and Ireland) there were no true increases, only an artifactual increase in Italy due to the initiation of a hypospadias study, and perhaps in Israel where the rate fluctuated wildly due to unknown reasons (Paulozzi, "International" 299). There were no increases anywhere following 1985 (Paulozzi, "International" 299). There have been increases in Scandinavia, Japan and two studies in the US, all of which are in the highest GDP grouping (Paulozzi, "International" 298, 299). However, there are no linear increases. The trend fluctuates up and down with a slight net increase. One of the US studies was stable from 1968 to 1982, there was an increase until 1985, and then it was stable again (Paulozzi, "International" 298). It seems apparent that these defects are affected by affluence, perhaps dietary as in the case of testicular cancer.
Any trend toward increasing hypospadias could be explained by a change in the definition to include more mild forms. If only severe forms, of which the definition has not changed, are examined, there is either no change or a decrease (Paulozzi, "International" 300). Also, improved documentation by physicians can account for increases in both hypospadias and cryptorchidism, especially given the emergence of the knowledge that undescended testes are more likely to become cancerous and are therefore given more attention (Paulozzi, "International" 301).
Cryptorchidism is associated with low birth weight and high maternal age (Møller and Skakkebæk 909). Thus the increasing age at which women give birth could lead to an increase in cryptorchidism. Paternal age may also be associated with increased risk but no studies have included information on paternal age.
Because both human exposure to xenoestrogens and rates of prostate disease have increased, endocrine disruptor theorists believe there could be a causal relationship (Colborn, Dumanoski, Myers 180). In mice and rats at least, increased estrogen levels are associated with enlarged prostate glands and long-term exposure to estrogen is associated with prostate cancer (Colborn, Dumanoski, Myers 179). Furthermore, prostate cancer is a hormonally influenced cancer—endogenous hormones affect it and hormone therapy is used in treatment—therefore, it ought to be affected by exogenous estrogens.
Prostate cancer incidence rates suffer from the common problem of a lack of earlier data. There appears to be a long-term slow rise in incidence since 1935 (Sullivan et al. 1069). Mortality, however, has been constant or in slight decline since 1935 in whites, but there has been an increase for nonwhites (Hsing and Devesa 527; Sullivan et al. 1069). Better detection may have allowed more tumors to have been detected, but the lack of a corresponding increase in mortality could perhaps indicate that true incidence has remained the same. The sudden introduction of chemicals should have caused a birth year cohort effect, but there is none (Hsing and Devesa 527). Finally, the rapid increase in incidence in the early 1990s was a result of new screening programs that used prostate specific antigen (Dennis and Resnik 257).
Diet plays a role in causing prostate disease and could explain the increase in incidence. Global food consumption patterns and cancer incidence rates indicate that prostate cancer correlates also highly with total fat consumption (Armstrong and Doll 626). Following the introduction of a western diet in Puerto Rico and Japan, both countries experienced increased rates of prostate cancer (Rose et al. 2367). Cross-country comparisons show that increasing animal fat intake increases the risk of prostate cancer (Rose et al. 2366; Boyle and Zaridze 1057). Much like breast cancer rates, migrants quickly achieve the rates of the new country, whether those rates are higher or lower (Boyle and Zaridze 1048; Dunn 3244). Japanese men have the same amount of small and latent prostate tumors as men in the US, but US men have a much greater mortality from prostate cancer because the tumors grow instead of remaining dormant (Moyad 98; Armstrong and Doll 626). Even latent tumors are more proliferative in Japanese men living in Hawaii than those living in Japan are (Dunn 3242). Exposure to xenoestrogens should be comparable in Japan and America since they are both industrialized nations. The major difference between Japan and the US is that Japan still has a diet lower animal products than the US—although this is rapidly changing. Despite dramatic increases in animal product consumption beginning in the late 1940s, compared to the US in 1975, Japan’s consumption was "negligible"—1/6 the amount of meat, 1/5 the milk, and 1/2 the fat (Kagawa 206). It was studies at that time that initially revealed the differences in incidence of Western cancers.
Case-control studies, in which a group of men with prostate cancer is matched with a control group who does not, highlight any factors the groups do not have in common. Consistent with the geographical information, studies show that vegetable consumption lowers the risk of prostate cancer (Cohen, Kristal, and Stanford 63) while animal fat increases risk (Rose 2366). Furthermore, foods high in phytoestrogens are also associated with a decreased risk of prostate cancer (Strom et al. 22).
The Framingham study of 2,164 men revealed an additional factor that could contribute to the rise in incidence of prostate cancer—advanced paternal age at birth increases the risk for prostate cancer (Zhang et al. 1211). A potential explanation is that "continuous male germ cell division may increase the rate of mutation due to replication error" (Zhang et al. 1211). The trend toward later childbirth would inherently bring about an increase in prostate cancer.
Another factor cited as an example of endocrine disruption is the decline since 1950 in the sex ratio, which is the proportion of live newborn boys to girls (Møller, Trends 232; National Research Council 135). Often expressed as a percentage, the typical rate is 51% male. An increasing percentage of female infants could hypothetically be the result of higher estrogen levels. The major reason for this theory is that following the accidental exposure to high levels of dioxin in Sevoso, an unexpectedly high number of babies born were female (48 out of 74, or 35% male) (National Research Council 135). Although dioxin is not a xenoestrogen, it may interfere indirectly with the endocrine system.
A number of studies have indicated that sex ratios are falling. Data from the Netherlands from 1950-1995 shows a decline, although the author noted that values from 1950-54 were somewhat higher than the rest of the data (van der Pal-de Bruin et al. 62). Post-1950 data for England and Wales also shows a decline (Dickinson and Parker 227), as does US data from 1970-1990 (Allan et al. 40). Unfortunately, these studies, again, do not look back far enough and ignore significant historical events.
Data from Germany and the Netherlands from 1871 to 1995 revealed spikes in sex ratio immediately following the World Wars; similar patterns occurred in other combatant nations, while neutral nations experienced much smaller rises (van den Broek 805). Additional German data also revealed peaks at 1920 and 1945 with the level after 1945 slightly higher than the period from 1870-1914 (Bromen and Jöckel 804). That is, even if levels are falling today, they still have not fallen below what was the norm before 1920. Allan et al. plotted Canadian sex ratios from 1930-1990 and plotted a smoothed curve through the data. Unfortunately, the curve obscured the tremendous spike that occurred post-WWII. Additionally, by not knowing what the trend was prior to 1930, it is impossible to make judgements about the current downward trend. Canada was a major player in WWI, and undoubtedly experienced an earlier spike in sex ratios as European nations did. Plots from Denmark, Sweden, Norway and Finland from 1850 to 1996 reveal peaks at WWI and WWII (Møller, "Change" 232). The appropriate question is clearly not why is the sex ratio declining—it is why were there peaks following the World Wars from which we are seeing a return to normal levels. Claiming that the decline represents a problem is like worrying about a warming trend following an ice age—it would be a problem if the trend did not exist.
One possible explanation for the large increase in male birth following WWII is the baby boom. It has been shown that conception early in the menstrual cycle is likely to produce a boy, while fertilization at ovulation is likely to produce a girl. While individual couples cannot use this slight difference to control the sex of their child, the effect can be seen statistically in large groups (Møller, "Trends" 238). If we can assume that the baby boom was accompanied by an increase in the frequency of intercourse, then an increase in sex ratio would be the expected—and observed—result (van den Broek 805).
This same idea can be applied in reverse to the Sevoso incident. Following a major disaster, intercourse rates probably dropped dramatically, which could account for at least a portion of the high frequency of females who were born. For example, following the earthquake in Kobe, Japan, the sex ratio declined significantly 9 months later and there was a 6% decline in fertility as well (Fukuda et al. 2321). Low sex ratios have also followed floods, severe air pollution and other highly stressful events (Møller, "Trends" 235).
There is still an on-going slow decline in sex ratio that perhaps cannot be explained by the baby boom alone (although the sex ratio has not fallen below pre-WWI levels). Additional social changes may play a role in the continued stabilization/decline of the sex ratio. The use of fertility drugs that induce ovulation is known to produce a high proportion of girls (Allan et al. 40; Møller, Change 829). Additionally, women over 35 are less likely to have boys, so delaying childbirth would have the result of lowering the sex ratio (Dickinson and Parker 228).
Phytoestrogens are compounds produced by plants that mimic herbivores’ endogenous estrogens. Phytoestrogens have a structure highly similar to that of estrogens. Those skeptical of the endocrine disruption hypothesis often point to the large numbers of phytoestrogens consumed in comparison with minute exposures to synthetic xenoestrogens and claim that the effects of the synthetics should be swamped by naturally occurring xenoestrogens.
A common response to the phytoestrogen objection is that phytoestrogens are metabolized and excreted while synthetic hormones accumulate in the body. Colborn, Dumanoski and Myers blithely state "plant estrogens might be eliminated within a day" (82). This ignores the fact that they are eaten everyday, are present in the bloodstream, and perhaps affect hormones more so than synthetic compounds that become sequestered in fat. In addition, phytoestrogens are converted by gut flora to compounds that more strongly estrogenic (Setchell et al., "Nonsteroidal" 573). For example, bacteria in the intestinal tract convert lignans, which are found in grains and other fiber rich foods, to enterolactone and enterodiol (two compounds with estrogenic properties) (Setchell and Adlercreutz 315). Finally, synthetic xenoestrogens have potencies 1e-6 times that of estradiol (E2), whereas phytoestrogens range from 1e-3 to 1e-4 (Safe 349).
Endocrine disruption theorists also respond by stating that somehow we have evolved the ability to deal with phytoestrogens so that they do not cause harm. At first this might seem to be true. Phytoestrogens stimulate the production of sex hormone binding globulin (SHBG) in the liver (Adlercreutz, "Western" 9). These proteins circulate in the blood, bind to testosterone and estrogen, and make them inaccessible to cells. At least some synthetic xenoestrogens also bind to SHBG (Déchaud et al. 332), but there has not been research as to whether or not xenoestrogens stimulate the production of SHBG. The lesser estrogen receptor binding affinity of phytoestrogens allows them to bind to the estrogen receptor and invoke only a minor response compared to E2, while at the same time, prevent the more potent E2 from binding to the receptor. But synthetic xenoestrogens also have lower binding affinities, lower even than phytoestrogens. Their effect should be similar to phytoestrogens, namely, anti-estrogenic when E2 is present. Another potential mechanism by which we have evolved is that in the past, individuals whose fertility was severely impaired by eating phytoestrogens were unable to reproduce and therefore their sensitive genes were removed from the gene pool (Colborn, Dumanoski, and Myers 80). Given that, for example, there has been no decline in male fertility in the past 50 years, the protections that apply to phytoestrogens may well turn out to apply to synthetic xenoestrogens as well.
Regardless of any evolutionary protections that may have developed, phytoestrogens clearly do have physiological effects. In Australia, sheep are known to suffer from Clover Disease, in which sheep become infertile from grazing in areas containing a certain species of clover that is high in isoflavones. Similar effects have been noted in cows, quail, mice, rabbits, et al. (Hughes 173). The pulp mill effluent that causes feminization of male fish has been identified as b -sitosterol, a phytoestrogen (Cooper and Kavlock 160).
Phytoestrogens have real effects in humans as well. Phytoestrogens help alleviate the symptoms associated with menopause and can lengthen the menstrual cycle (Murkies et al. 191; Strauss et al. 351). Phytoestrogens found in the pomegranate, Queen Anne’s Lace, and other plants have been used historically as contraceptives and abortifacients.
Case-control studies show that regular consumption of soy decreases breast cancer risk (Moyad 37). Women with the lowest urinary excretion of lignans and isoflavonoids are consistently at highest risk for breast cancer (Adlercreutz, "Phytoestrogens" 106; Strauss 352). The only study that claims to indicate that soy does not reduce the risk of breast cancer compared soy intake between women with breast cancer and women without breast cancer in two Chinese cities. Unfortunately, both cases and controls consumed the same percentage of soy protein, both in absolute terms and as a percentage of total protein (Yuan et al. 1357). Despite the authors’ claim that this proves that soy offers no protection against breast cancer, this study offers no information on the relationship between soy and breast cancer. For example, if a study tried to determine whether or not smoking causes lung cancer, but both the case and control group smoked the same amount of cigarettes, then clearly one could not comment on the relationship between smoking and cancer. This would indicate that there are factors other than smoking that cause lung cancer, but would not prove smoking is unrelated to lung cancer. In addition, in areas where soy consumption is generally high, the amount of soy eaten is not going to be as an important indicator for breast cancer risk as it is in a society that consumes little soy to begin with. In studies where different amounts of soy are consumed, the groups consuming more soy have lower rates of breast cancer.
For the vast majority of human history and even in most parts of the world today, a plant-based diet is the norm. Extensive replacement of plant foods with animal foods is relatively new. It is conceivable that since humans evolved eating a diet high in phytoestrogens, these compounds became an indispensable factor in hormonal regulation, that is, the human body produces excess hormones to compensate for the sites blocked by the phytoestrogens, or, stated another way, the body is used to overcompensating for the "losses" due to phytoestrogens (Stephens 757). If phytoestrogen consumption were to decrease suddenly in certain populations, those populations would experience hormonally related diseases. This is precisely the result observed with breast cancer and prostate cancer. The problems identified as being the result of endocrine disruption, may in fact be just that, but with quite a different mechanism than is commonly thought.
One area where there seems to be conclusive proof of endocrine disruption is estrogenic responses in wildlife. However, because most examples of endocrine disruption in the wild represent extreme cases of exposure, this does little to further the endocrine disruption theory—the crux of which is that extremely low concentrations (10-15 ppm) of xenoestrogens are causing widespread damage to humans.
Alligators from Florida’s Lake Apopka experienced a population crash in the 1980s perhaps because of reproductive failure due to, among other things, males with allegedly small phalluses. Lake Apopka is not just any lake, however. The alligator populations on most other lakes in Florida are growing. Lake Apopka happens to an EPA Superfund site due to an "extensive spill" in 1980 of pesticides (including up to 15% DDT) and sulfuric acid (Guillette et al., "Developmental" 680). The site also contained elevated concentrations of two pesticides known to cause reproductive problems in humans, though probably not through endocrine disruption (Semenza et al. 1030). These compounds alone could have caused the reproductive problems without looking to the estrogenic effects of DDT. One of the researchers, Timothy Gross, opted not to have his name listed on the final paper. He was concerned that the researchers left out important caveats, like the fact that initially researchers were only grabbing smaller gators for safety reasons. These immature gators may not have had fully developed phalluses. Additionally, because sex can only be confirmed histologically, they may have actually been observing oversized clitorises (Fumento), as was the case for at least two gators later confirmed to be female (Guillette, "Developmental" et al. 683). This is significant because shrinking penises was a major propaganda tool. While alligators actually have phalluses (they are not used for urination), two authors with Ph.D.s in zoology deliberately chose to incorrectly refer to alligator "penises," undoubtedly to increase public attention and alarm (Fumento).
Another often cited example of endocrine disruption is the so-called lesbian gulls in California. The lack of males in the population resulted in female-female pairings to raise the young. This effect was attributed to DDT. However, the area in which the female-female pairing gulls were found was subject to "massive contamination by the discharge of as much as 1.9 million kilograms of commercial DDT from the Los Angeles sewer system" between 1950 and 1970 (Fry and Toone 922). Neighboring gull populations with normal background levels of DDT were not affected; they were even used as controls in laboratory experiments (Fry and Toone 922). "To date, only colonial fish-eating birds breeding in ‘hot spots’ of contamination have been reported with estrogenic developmental defects" (Fry 168).
Endocrine disruption has been observed in male fish that produce vitellogenin (yolk protein), which is normally produced by females only. The effect is most pronounced in fish who live near the effluent of a sewage treatment plants, with a small effect elsewhere (Sumpter and Jobling 175). A separate study found no effect even as close as three miles downstream (Folmar et al. 1099). Other fish experiencing problems live in the effluent of bleached kraft mills, a type of paper mill (Van Der Kraak et al. 224). It is interesting to note that the problematic effluents from paper mills are phytoestrogens from the wood pulp (Davis and Bortone 113). From the sewage treatment plant, birth control pill hormones found in urine are prime suspects because of their known ability to induce vitellogenisis at low concentrations (Folmar 1099). This is an important point. While it is unfortunate that ethynyl estradiol may be causing problems in fish, this "endocrine disruptor" is specifically used in women for that very purpose and does not in any way represent a threat to "our fertility, intelligence, and survival," the claim of those who call attention to potential endocrine disruptors (Colborn, Dumanoski and Myers).
These problems in wildlife do not necessarily merit a ban all of these chemicals. Because these incidents are isolated with clearly identifiable sources, better pollution prevention techniques might be tried first. Even this may not be deemed necessary; for example, "Most pulp mills discharge to larger waterways. This practice dilutes and potentially obscures effects described herin" (Davis and Bortone 123). Furthermore, there is no evidence that the feminization of males negatively affects the species (Davis and Bortone 121-2). Moreover, while the problems experienced by the gulls and the alligators are serious, they are the result of past ignorance/arrogance—not current practices that can be stopped.
Finally, many of the most potent ER binders have already been banned for other reasons (e.g,. DDT, PCBs, chlordane, some APEs in Europe) (Renner 316A). While it is true that these chemicals may still be used in South America, Africa, and Asia, more scientific data showing that these chemicals are harmful is unlikely to sway anybody who would rather live with DDT than malaria.
A Question of Credibility
Our Stolen Future was a 1996 popular book that kicked off the recent interest in endocrine disruptors. Colborn, one of its authors, said in 1997, "There is overwhelming evidence today that every unborn child will be exposed to man-made chemicals that will prevent them from becoming healthy, whole children" (qtd. in Fumento). Such extraordinary statements require extraordinary proof. The authors seemed to have had the above conclusion in mind from the beginning. So rather than pointing to solid examples, the authors made broad claims about what phenomena are caused endocrine disruption—naturally, some or even a good portion of these speculative correlations will eventually be shown not to be causal, or perhaps to not even exist. The credibility of the remaining correlations is then strained. This is significant because much of the evidence for endocrine disruption is, and will need to be, based on epidemiology, an area where there is much room for interpretation. With multiple correlations and shaky causality, the theory that best explains things will be accepted. If the theory of endocrine disruption continually faces major setbacks, it will be difficult to prove even the most well evidenced claims. It would have been better to present the most compelling evidence, reserving everything else for a chapter devoted to other potential areas of research, rather than making countless tenuous claims.
Several major setbacks have already occurred. First, in 1997 Tulane researchers had an article published in Science that detailed the astounding synergistic potency of combinations of estrogenic pesticides (up to 1600 times more potent in combination) (Arnold et al. 1490).
However, when no one (including the original researchers) could duplicate the results, the article was retracted (Ramamoorthy et al. 405; McLachlan 462). A committee that investigated possible scientific misconduct later concluded that Arnold "provided insufficient data to support the major conclusions of the Science paper" (La Rosa 1932). It is interesting to note that the researchers received funding from the W. Alton Jones Foundation, an environmental protection foundation whose director was an author of Our Stolen Future (Arnold 1492; Colborn, Dumanoski, and Myers).
Similarly, when the abundance of deformed frogs (commonly having multiple or missing legs) was noted across the United States, it was hailed as evidence of endocrine disruption (Colborn, Dumanoski and Myers 256). The blame was placed on a pesticide that mimics retanol, which is known to be capable of causing some deformities in frogs (Gardiner and Hoppe 607). Advocates of the endocrine disruption theory used this highly publicized environmental problem to advance their ideas well before the phenomena had been adequately studied. Dr. Gardiner has discussed his theory with numerous reporters. However, new research concludes that the deformities observed in multiple sites across the country were inconsistent with deformities caused by retinoids, but were consistent with deformities that are caused mechanically by trematode cyst infestation, the trematode being a common frog parasite (Sessions, Franssen, and Horner 801). In California, sites with no pesticides, PCBs or heavy metals present still have severely deformed frogs (Johnson et al. 802). Undergraduate research conclusively found those deformities to have been caused by the trematode parasite species Ribeiroia. Not only were deformed frogs found only in ponds that supported the parasite, parasites were found concentrated in the leg area, and laboratory results indicate that deformities were proportional to the amount of exposure to the parasite (Johnson et al. 802). Across the Northwest, in ponds with deformed frogs, 40 out of 42 had the parasite, while ponds with normal frogs "almost never had the parasite" (Kaiser 2434). Parasites cannot explain deformities at every site in the US, and they probably indicate some other environmental change that caused an increase in the trematode population.
The DDT-breast cancer link was highly publicized, but it was based on a few small studies. As discussed earlier, subsequent studies have discredited the idea.
Finally, the National Academy of Sciences’ National Research Council spent four years and $1 million dollars looking at all available evidence on the theory of endocrine disruption. They recommended only further study, but no regulation (National Research Council 1-9). This was despite the fact that the committee included many prominent advocates of the theory.
These examples highlight the cold fusion-like aspect of research on endocrine disruption—results are on the evening news before there is sufficient scientific data to back up the bold claims. What’s worse, perhaps, is that the coverage on how no synergistic effects can be found, or that parasites are causing frog deformities does not receive nearly as much attention. A survey of American women would almost certainly reveal that they believe there is scientific evidence for a link between DDT and breast cancer. The danger here, much along the same lines of the promotion of the "breast cancer gene" (which accounts for about 10% of breast cancer cases), is that the real evidence of how breast cancer can be prevented is lost. Women feel that there is nothing they can do to protect themselves from breast cancer, when in fact studies show repeatedly that changeable lifestyle factors are involved. There is little society can do to clean up persistent organochlorines, but the government, public health organizations, and women’s organizations can promote a plant-based diet. It would literally save lives. Some dismiss dietary changes as "not easily changed by social policy," (Davis et al. 376) which is, of course, absurd. Undoubtedly smoking was once regarded solely as an individual choice that could not be affected through intervention. But just as tobacco is now heavily regulated, the known dangers of the Western diet could, at the very least, be publicized. Whether or not the public would dismiss these "radical changes in diet" (Davis et al. 376) is up to the public, not a patronizing government or scientific community.
Make no mistake, the authors of Our Stolen Future are radical environmentalists dedicated to their cause. To them, "phasing out hormone-disrupting chemicals should be just the first step" (Colborn, Dumanoski, and Myers 247). Ultimately they would not mind a ban on all synthetic chemicals. There is no reason to be ashamed about wanting a ban on synthetic chemicals—they inherently have unintended, unknowable consequences like the hole in the ozone layer or the death of songbirds when spraying DDT to prevent Dutch Elm disease. Nevertheless, the authors do seem ashamed to admit their concern for the environment and this makes their strategy of promoting human health effects vulnerable.
Their focus on specific compounds implies that only those chemicals are harmful. The system and values that create the chemicals receive none of the blame. To be fair, buried in the back of the book they meekly mention that we should get around to making "value judgements" (Colborn, Dumanoski, and Myers 246) and that "The time has come, however, to pause and finally ask the ethical questions that have been overlooked in the headlong rush of the twentieth century. Is it right to change Earth’s atmosphere? Is it right to alter the chemical environment in the womb for every unborn child?" (Colborn, Dumanoski, and Myers 247). Of course the authors have already decided these answers for themselves—no on both counts. But does any of this make it into their media interviews, PBS specials, or to the floor of Congress, which passed four legislative initiatives as a result of their book? No. They are only referred to as environmentalists in the pejorative. Rather than relying on the strength of their ideas, they allow their environmentalism to become a liability.
Trying to beat science and industry at their own game will never work. Modern capitalist society accepts that there will be losses—some wildlife will be harmed through pollution and society accepts an additional 1 in a million cancer risk in order to have the freedom to turn on a light switch. For example, even if APEs do cause a slight increase in breast cancer, industry could rightly point to all of the lives saved by APEs—even through something as simple as spermicide preventing a pregnancy (and its inherent risks) or by something more complex as having abundant, cheap vegetables as a way to prevent breast cancer.
Environmentalists have a totally different worldview: the earth is not here for humanity’s benefit and it must not be exploited. But instead of getting caught up in trying to determine if the effluent from paper mills hurts fish or not, environmentalists should step back and point out that they don’t think it’s OK to cut down old growth trees and grind them up into disposable paper in the first place. That moral question will not be decided in the pages of a scientific journal. Making claims that can, and will, be refuted will only serve to diminish the credibility of the environmental movement. Simply banning bisphenol-A or telling people not to microwave in plastic containers may marginally improve human health, but it does absolutely nothing to further respect for other life on the planet.
The failure of the environmentalists to get their message across is exemplified by a comment from Stephen Safe, a Texas A&M toxicologist whose work is often funded by the Chemical Manufacturers Association. He said, "there's no evidence that any of those compounds, that some groups tout as being horrible endocrine problems for the environment, cause anything in humans" (Fumento). Industry can acknowledge harmful environmental effects, but completely dismiss them as long as humans are not obviously affected. That endocrine disruptors may be harming wildlife on a widespread scale is reason enough to investigate this possibility—out of respect for the earth, not because all other life on the planet is nothing more than a canary in a coal mine. Looking for tenuous effects in humans diverts attention away from and trivializes effects in animals who will likely suffer the greatest effects because of their inability to escape pollution. Ultimately, by relying on the framework built by science and industry, Colborn et al. perpetuate those institutions’ values to the total exclusion and negation of their own.
Acacio, B.D., T. Gottfried, R. Israel, and R.Z. Sokol. "Evaluation of a large cohort of men presenting for a screening semen analysis." Fertility and Sterility 73 (2000): 595-597.
Adlercreutz, H. "Diet, Breast Cancer, and Sex Hormone Metabolism." Annals of the New York Academy of Sciences 595 (1990): 281.
Adlercreutz, H. "Phytoestrogens: epidemiology and a possible role in cancer protection." Environmental Health Perspectives 103 supp. 7 (1995): 103-112.
Adlercreutz, H. "Western diet and Western diseases: some hormonal and biochemical mechanisms and associations." Scandinavian Journal of Clinical Laboratory Investigation 50, supp. 201 (1990): 2-23.
"Aetiology of testicular cancer: association with congenital abnormalities, age at puberty, infertility, and exercise. United Kingdom Testicular Cancer Study Group." British Medical Journal 308 (1994): 1393-9.
Allan, B.B., R. Brant, J.E. Seidel, and J.F. Jarrell. "Declining sex ratios in Canada." Canadian Medical Association Journal 156 (1997): 37-41.
Andolz, P., M.A. Bielsa, and J. Vila. "Evolution of semen quality in North-eastern Spain: a study in 22 759 infertile men over a 36 year period." Human Reproduction 14 (1999): 731-735.
Armstrong, B., and R. Doll. "Environmental factors and cancer incidence and mortality in different countries, with special reference to dietary practices." International Journal of Cancer 15 (1975): 617-31.
Arnold, S.F., D.M. Klotz, B.M. Collins, P.M. Vonier, L.J. Guillette Jr, and J.A. McLachlan. "Synergistic activation of estrogen receptor with combinations of environmental chemicals." Science 272 (1996): 1489-92. Retracted by McLachlan JA. In: Science 277 (1997): 462-3.
Auger, J., J.M. Kuntsmann, F. Czyglik, and P. Jouannet. "Decline in semen quality among fertile men in Paris during the last 20 years." New England Journal of Medicine 332 (1995): 281-5.
Bagga, D., K.H. Anders, H. Wang, E. Roberts, and J.A. Glaspy. "Organochlorine Pesticide Content of Breast Adipose Tissue From Women With Breast Cancer and Control Subjects." Journal of the National Cancer Institute 92 (2000): 750-753.
Ballweg, M.L. "Blaming the victim: the psychologizing of endometriosis." Obstetrics and Gynecology Clinics of North America 24 (1997): 441-453.
Bergqvist, A. "Steroid receptors in endometriosis." Modern Approaches to Endometriosis. Ed. E.J. Thomas and J.A. Rock. Boston: Kluwer Acad., 1991. 33-55.
Bertazzi, P.A., C. Zocchetti, S. Guercilena, D. Consonni, A. Tironi, M.T. Landi, and A.C. Pesatori. "Dioxin Exposure and Cancer Risk: A 15-Year Mortality Study after the ‘Sevoso Accident.’" Epidemiology 8 (1997): 646-652.
Birnbaum, L.S. "Endocrine Effects of Prenatal Exposure to PCBs, Dioxins, and Other Xenobiotics: Implications for Policy and Future Research." Environmental Health Perspectives 102 (1994): 676-69.
Boyle, P., and D.G. Zaridze. "Risk factors for prostate and testicular cancer." European Journal of Cancer 29A (1993): 1048-55.
Bromen, K., and K.H. Jöckel. "Change in male proportion among newborn infants." Lancet 349 (1997): 804-5.
Bromwich, P., J. Cohen, I. Stewart, and A. Walker. "Decline in sperm counts: an artifact of changed reference range of ‘normal’?" British Medical Journal 309 (1994): 19-22.
Brown, L.M., L.M. Pottern, R.N. Hoover, S.S. Devesa, P. Aselton, J.T. Flannery. "Testicular cancer in the United States: trends in incidence and mortality." International Journal of Epidemiology 15 (1986): 164-70.
Carlsen, E., A. Giwercman, N. Keiding, and N.E. Skakkebæk. "Evidence for decreasing quality of semen during past 50 years." British Medical Journal 305 (1992): 609-13.
Cocco, P., N. Kazerouni, and S.H. Zahm. "Cancer mortality and environmental exposure to DDE in the United States." Environmental Health Perspectives 108 (2000): 1-4.
Cohen, J.H., A.R. Kristal, and J.L. Stanford. "Fruit and vegetable intakes and prostate cancer risk." Journal of the National Cancer Institute 92 (2000): 61-8.
Colborn, T., D. Dumanoski, and J.P. Myers. Our Stolen Future. Paperback ed. New York: Plume, 1997.
Colborn, T., F.S. vom Saal, and A.M. Soto. "Developmental Effects of Endocrine-Disrupting Chemicals in Wildlife and Humans." Environmental Health Perspectives. 101 (1993): 378-384.
Cooper, R.L., and R.J. Kavlock. "Endocrine disruptors and reproductive development: a weight-of-evidence overview." Journal of Endocrinology 152 (1997): 159-166.
Crissman, J.W., P.S. Cooke, R.A. Hess, M.S. Marty, and A.B. Liberacki. "Postulated Human Sperm Count Decline May Involve Historic Elimination of Juvenile Iodine Deficiency: A New Hypothesis with Experimental Evidence in the Rat." Toxicological Sciences 53 (2000): 400–410.
Davies, J.M. "Testicular cancer in England and Wales: some epidemiological aspects." Lancet 1 (1981): 928-32.
Davis, D.L., H.L. Bradlow, M. Wolff, T. Woodruff, D.G. Hoel, and H. Anton-Culver. "Medical Hypothesis: Xenoestrogens as Preventable Causes of Breast Cancer." Environmental Health Perspectives 5 (1993): 372-377.
Davis, W.P. and S.A. Bortone. "Sexual Differentiation in Mammals." Chemically-Induced Alterations in Sexual and Functional Development: The Wildlife/Human Connection. Eds. Theo Colborn and Coralie Clement. Princeton: Princeton Scientific, 1992. 113.
Déchaud, H., C. Ravard, F. Claustrat, A.B. de la Perrière, and M. Pugeat. "Xenoestrogen interaction with human sex hormone-binding globulin (hSHBG)." Steroids 64 (1999): 328-34.
Dennis, L.K., and M.I. Resnick. "Analysis of recent trends in prostate cancer incidence and mortality." Prostate 42 (2000): 247-52.
Dickinson, H.O., and L. Parker. "Why is the sex ratio falling in England and Wales?" Journal of Epidemiology and Community Health 50 (1996): 227-8.
Dorgan, J.F., et al. "Serum organochlorine pesticides and PCBs and breast cancer risk: results from a prospective analysis (USA)." Cancer Causes and Control 10 (1999): 1-11.
Dunn J.E. Jr. "Cancer epidemiology in populations of the United States with emphasis on Hawaii and California and Japan." Cancer Research 35 (1975): 3240-3245.
Eccersley, A.P.J. "Declining Sperm Count." British Medical Journal 43 (1996): 43.
Ekbom, A., O. Akre. "Increasing incidence of testicular cancer—birth cohort effects." Acta Pathologica Microbiologica et Immunological Scandinavia 106 (1998): 225-31.
Eskenazi B. and Warner M.L. "Epidemiology of endometriosis." Obstetrics and Gynecology Clinics of North America 24 (1997): 235-58.
Farrow, S. Falling sperm quality: fact or fiction? British Medical Journal 309 (1994): 1.
Feuer E.J., and Wun L. "How much of the recent rise in breast cancer incidence can be explained by increases in mammography utilization?" American Journal of Epidemiology 136 (1992): 1423-36.
Fisch, H., Goluboff E.T., Olson J.H., Feldshuh J., Broder S.J., Barad D.H. "Semen analyses in 1,283 men from the United States over a 25-year period: no decline in quality." Fertility and Sterility 65 (1996): 1009-14.
Folmar L.C., et al. "Vitellogenin induction and reduced serum testosterone concentrations in feral male carp (Cyprinus cario) captured near a major metropolitan sewage treatment plant." Environmental Health Perspectives 104 (1996): 1096-1101.
Fry, D.M. "Reproductive effects in birds exposed to pesticides and industrial chemicals." Environmental Health Perspectives 103 Supp. 7 (1995): 165-171.
Fry, D.M., and C.K. Toone. "DDT-Induced feminization of gull embryos." Science 213 (1981): 922-924.
Fukuda, M., K. Fukuda, T. Shimizu, and H. Moller. "Decline in sex ratio at birth after Kobe earthquake." Human Reproduction 13 (1998): 2321-2.
Fumento, M. "Hormonally Challenged." American Spectator October 1999: 26+. Online. Lexis Academic Universe.
Gallagher, R.P., S. Huchcroft, N. Phillips, G.B. Hill, A.J. Coldman, C. Coppin, and T. Lee. "Physical sctivity, medical history and risk of testicular cancer (Alberta and British Columbia, Canada)." Cancer Causes and Control 6 (1995): 398-406.
Gardiner D.M., and D.M. Hoppe. "Environmentally induced limb malformations in mink frogs (Rana septentrionalis)." Journal of Experimental Zoology 284 (1999): 207-16.
Ginsburg, J., S. Okolo, G Prelevic, and P. Hardiman. "Residence in the London area and sperm density." The Lancet 343 (1994): 230.
Gosden; R., and A. Rutherford. "Delayed childbearing: fertility declines at 30 is almost gone by 40. (Editorial)" British Medical Journal 311 (1995): 1585-6.
Gortner, W.A. "Nurtition in the United States 1900-1974." Cancer Research 35 (1975): 3246-3253.
Guillette, L.J., D.A. Cain, A.A. Rooney, and D.B. Pickford. "Organization versus activation: the role of endocrine-disrupting contaminants (EDCs) during embryonic development in wildlife." Environmental Health Perspectives 101 (1995): 157-164.
Guillette, L.J. et al. "Developmental Abnormalities of the gonad and abnormal sex hormone concentrations in juvenile alligators from contaminated and control lakes in Florida." Environmental Health Perspectives 102 (1994): 680-688.
Gyllenborg J., Skakkebæk N.E., Nielsen N.C., Keiding N., Giwercman A. "Secular and seasonal changes in semen quality among young Danish men: a statistical analysis of semen samples from 1927 donor candidates during 1977-1995." International Journal of Andrology 22 (1999): 28-36.
Handelsman, D.J. "Sperm output of healthy men in Australia: magnitude of bias due to self-selected volunteers." Human Reproduction 12(1997): 2701–2705.
Haney, A.F. "The pathogenisis and aetiology of endometriosis." The Current Status of Endometriosis: Research and Management. Eds. I. Brosens and J. Donnez. New York: Parthenon, 1991. 3-19.
Helm, P., and Grolund L. "A halt in the secular trend towards earlier menarche in Denmark." Acta Obstetricia et Gynecologica Scandinavica 77 (1998): 198-200.
Helzlsouer, K.J., et al. "Serum concentrations of organochlorine compounds and the subsequent development of breast cancer." Cancer Epidemiology, Biomarkers and Prevention 8 (1999): 525-32.
Herman-Giddens, M.E. et al. "Secondary Sexual Characteristics and Menses in Young Girls Seen in Office Practice: A Study from the Pediatric Research in Office Settings Network." Pediatrics 99 (1997): 505-512.
Hirayama, T. "Epidemiology of breast cancer with special reference to the role of diet." Preventative Medicine 7 (1978): 173-95.
Hsieh, S.F., et al. "A Cohort Study on Mortality and Exposure to Polychlorinates Biphenyls." Archives of Environmental Health 51 (1996): 417-24.
Hsing, A.W., and S.S. Devesa. "Prostate cancer mortality in the United States by cohort year of birth, 1865-1940." Cancer Epidemiology, Biomarkers and Prevention 3 (1994): 527-30.
Hughes, C.L. "Phytochemical mimicry of reproductive hormones and modulation of herbivore fertility by phytoestrogens." Environmental Health Perspectives 78 (1988): 171-175.
Hunter, B.T. "America’s Eating Habits." Consumer’s Research 83.2 (2000): 10-15.
Hunter, D.J., et al. "Plasma organochlorine levels and the risk of breast cancer." New England Journal of Medicine 337 (1997): 1253-8.
Irvine, S., E. Cawood, D. Richardson, E. MacDonald, and J. Aitken. "Evidence of deteriorating semen quality in the United Kingdom: birth cohort study in 577 men in Scotland over 11 years." British Medical Journal 312 (1996): 467-71.
Joffe, M. "Declining Sperm Count: Recent decline may be relatively late stage of long-term process." British Medical Journal 313 (1996): 44.
Johnson, P.T., K.B.Lunde, E.G. Ritchie, and A.E. Launer. "The effect of trematode infection on amphibian limb development and survivorship." Science 284 (1999): 802-4.
Jordan ,V.C., S. Mittal, B. Gosden, R. Koch, and M.E. Lieberman. "Structure-activity relationships of estrogens." Environmental Health Perspectives 61 (1985): 97-110.
Kagawa, Y. "Impact of Westernization on the nutrition of Japanese: changes in physique, cancer, longevity and centenarians." Preventative Medicine 7 (1978):205-17.
Kaiser, J. "Deformed frogs. Link to parasites grows stronger." Science 286 (1999): 2434.
Kelce, W., and E. Wilson. "Environmental antiandrogens: developmental effects, molecular mechanisms, and clinical implications." Journal of Molecular Medicine 75 (1997): 198-207.
Key, T., and G. Reeves. "Organochlorines in the environment and breast cancer." British Medical Journal 308 (1994): 1520.
Knapp, V.J. "How old is endometriosis? Late 17th- and 18th-century European descriptions of the disease." Fertility and Sterility 72 (1999): 10-14.
Kodama, M., M. Murakami, and T. Kodama. "Possible implication of environmental hormones in the recent risk increase of cancers of the skin and the liver, but not of the female breast worldwide." Anticancer Research 19 (1999): 789-98.
Krieger N., et al. "Breast cancer and serum organochlorines: a prospective study among white, black and Asian women." Journal of the National Cancer Institute 86 (1994): 589-99.
LaRosa, J.C. "Tulane Investigation Completed." Science 284 (1999): 1932.
Lebel, G., S. Dodin, P. Ayotte, S. Marcoux, L.A. Ferron, and E. Dewailly. "Organochlorine exposure and the risk of endometriosis." Fertility and Sterility 69 (1998): 221-228.
Lipshultz, L.I. "‘The debate continues’—the continuing debate over the possible decline in semen quality." Fertility and Sterility 65 (1996): 909-911.
López-Carrillo, L., et al. "Dichlorophenyltrichloroethane serum levels and breast cancer risk: a case–control study from Mexico." Cancer Research 57 (1997): 3728– 32.
Matkovic, V., J.Z. Ilich, M. Skugor, N.E. Badenhop, P. Goel, A. Clairmont, D. Klisovic, R.W. Nahhas, and J.D. Landoll. "Leptin is inversely related to age at menarche in human females." Journal of Clinical Endocrinology and Metabolism 82 (1997): 3239-45.
McLachlan, J.A. "Synergistic effect of environmental estrogens: report withdrawn." Science 277 (1997): 462-3.
Møller, H. "Change in male:female ratio among newborn infants in Denmark." Lancet 348 (1996): 828-9.
Møller, H. "Decreased testicular cancer risk in men born in wartime." Journal of the National Cancer Institute 81 (1989): 1668-9.
Møller, H. "Trends in sex-ratio, testicular cancer and male reproductive hazards: are they connected?" Acta Pathologica Microbiologica et Immunological Scandinavia 106 (1998): 232-9.
Møller H., and N.E. Skakkebæk. "Testicular cancer and cryptorchidism in relation to prenatal factors: case-control studies in Denmark." Cancer Causes and Control 8 (1997): 904-12.
Moyad, M.A. "Soy, disease prevention, and prostate cancer." Seminars In Urologic Oncology 17 (1999): 97-102.
Murkies, A.L., C. Lombard, B.J. Strauss, G. Wilcox, H.G. Burger, and M.S. Morton. "Dietary flour supplementation decreases post-menopausal hot flushes: effect of soy and wheat." Maturitas 21 (1995): 189-95.
National Research Council. Hormonally Active Agents in the Environment. Washington, DC: National Academy Press, 1999.
Nimrod, A.C., and W.H. Benson. "Environmental estrogenic effects of alkylphenol ethoxylates." Critical Reviews in Toxicology 26 (1996): 335-364
Olsen, G.W., K.M. Bodner, J.M. Ramlow, C.E. Ross, and L.I. Lipshultz. "Have sperm counts been reduced 50 percent in 50 years? A statistical model revisited." Fertility and Sterility 63 (1995): 887-93.
Paulsen, C.A., N.G. Berman, and C. Wang. "Data from men in greater Seattle area reveals no downward trend in semen quality: further evidence that deterioration of semen quality is not geographically uniform." Fertility and Sterility 65 (1996): 1015-20.
Paulozzi, L. "Effects of age of diagnosis and latency on the correlation of testicular cancer incidence with fat consumption." International Journal of Cancer 78 (1998): 527-8.
Paulozzi, L. "International trends in rates of hypospadias and cryptorchidism." Environmental Health Perspectives 107 (1999): 297-302.
Paulozzi, L.J., and J.D. Erickson, and R.J. Jackson. "Hypospadias trends in two US surveillance systems." Pediatrics 100 (1997): 831-4.
Raab, G. "Results of Scottish study may be due to confounding with age." British Medical Journal 313 (1996): 44.
Ramamoorthy, K. et al. "Potency of Combined Estrogenic Pesticides" Science 275 (1997): 405-406.
Rasmussen, P.E., K. Erb, L.G. Westergaard, and S.B. Laursen. "No evidence for decreasing semen quality in four birth cohorts of 1,055 Danish men born between 1950 and 1970." Fertility and Sterility 68 (1997): 1059-1064.
Renner, R. "European Bans on Surfactant Trigger Transatlantic Debate." Environmental Science & Technology 31 (1997): 316A.
Rose, D.P, A.P. Boyar, and E.L. Wynder. "International comparisons of mortality rates for cancer of the breast, ovary, prostate, and colon, and per capita food consumption." Cancer 58 (1986): 2363-2371.
Safe, S.H. "Environmental and Dietary Estrogens and Human Health: Is There a Problem?" Environmental Health Perspectives 103 (1995): 346-351.
Saidi, J.A., D.T. Chang, E.T. Goluboff, E. Bagiella, G. Olsen, H. Fisch. "Declining sperm counts in the United States? A critical review." Journal of Urology 161 (1999): 460-2.
Sanchez, A., D.G. Kissinger, and R.I. Phillips. "A hypothesis on the etiological role of diet on age of menarche." Medical Hypotheses 7 (1981): 1339-45.
Schecter, A., P. Toniolo, L.C. Dai, L.T. Thuy, and M.S. Wolff. "Blood levels of DDT and breast cancer risk among women living in the north of Vietnam." Archives of Environmental Contamination and Toxicology 33 (1997): 453-6.
Sherins, R.J. "Are semen quality and male fertility changing?" New England Journal of Medicine 332 (1995): 327-8.
Semenza, J.C. P.E. Tolbert, C.H. Rubin, L.J. Guillette Jr., and R.J. Jackson. "Reproductive toxins and alligator abnormalities at Lake Apopka, Florida." Environmental Health Perspectives 105 (1997): 1030-2.
Seo, J.T., Rha, K.H., Park, Y-S., Lee, M.S. "Semen quality over a 10-year period in 22,249 men in Korea." International Journal of Andrology 23 (2000): 194-198.
Sessions, S.K., R.A. Franssen, and V.L. Horner. "Morphological clues from multilegged frogs: are retinoids to blame?" Science 284 (1999): 800-2.
Setchell K.D.R., and Adlercreutz, H. "Mammalian lignans and phyto-oestrogens recent studies on their formation, metabolism and biological role in health and disease." Role of the Gut Flora in Toxicity and Cancer. Ed. I.R. Rowland. New York: Acad., 1988. 315-45.
Setchell, K.D.R., S.P. Borriello, P. Hulme, D.N. Kirk, and M. Axelson. "Nonsteroidal estrogens of dietary origin: possible roles in hormone-dependent disease." American Journal of Clinical Nutrition 40 (1984): 569-578.
Sharpe R., and N. Skakkebæk. "Are oestrogens involved in falling sperm counts and disorders of the male reproductive tract?" Lancet 341 (1993): 1392-5.
Sigurdson, A.J., S. Chang, J.F. Annegers, C.M. Duphorne, P.C. Pillow, R.J. Amato, L.P Hutchinson, A.M. Sweeney, and S.S. Strom. "A case-control study of diet and testicular carcinoma." Nutrition and Cancer 34 (1999):20-6.
Stanford J.L., L.J. Herrinton, S.M. Schwartz, and N.S. Weiss. "Breast Cancer Incidence in Asian Migrants to the United States and Their Descendants." Epidemiology 6 (1995): 181-183.
Stephens, F.O. "Breast cancer: etiologically factors and associations (a possible protective role of phytoestrogens)." Australian and New Zealand Journal of Surgery 67 (1997): 755-60.
Stone, J.M., D.G. Cruickshank, T.F. Sandeman, and J.P. Matthews. "Trebling of the incidence of testicular cancer in Victoria, Australia" (1950-1985)." Cancer 68 (1991): 211-9.
Strauss, L., R. Santti, N. Saarinen, T. Streng, S. Joshi S, and S. Makela. "Dietary phytoestrogens and their role in hormonally dependent disease." Toxicology Letters 102-103 (1998): 349-54.
Strom, S.S., Y.Yamamura, C.M. Duphorne, M.R. Spitz, R.J. Babaian, P.C. Pillow, and S.D. Hursting. "Phytoestrogen intake and prostate cancer: a case-control study using a new database." Nutrition and Cancer 33 (1999):20-5.
Sullivan, P.D., B. Christine, R. Connelly, and H. Barrett. "Analysis of trends in age-adjusted incidence rates for 10 major sites of cancer." American Journal of Public Health 62 (1972): 1065-71.
Sumpter, J.P. and S. Jobling. "Vitellogenesis as a biomarker for estrogenic contamination of the aquatic environment." Environmental Health Perspectives 103 supp. 7 (1995): 173-178.
Suominen, J., and M. Vierula. "Semen quality of Finnish men." British Medical Journal 306 (1993): 1579.
Tanner, J.M. Foetus into Man: Physical Growth from Conception to Maturity. 2ed. Cambridge: Harvard UP, 1990.
Tretli, S., and T. Haldorsen. "A cohort analysis of breast cancer, uterine corpus cancer, and childbearing pattern in Norwegian women." Journal of Epidemiology and Community Health 44 (1990): 215-9.
Tretli, S., and M. Gaard. "Lifestyle changes during adolescence and risk of breast cancer: an ecologic study of the effect of World War II in Norway." Cancer Causes and Control 7 (1996): 507-12.
Tjoa, W.S., Smolensky M.H., Hsi B.P., Steinberger E., Smith K.D. "Circannual rhythm in human sperm count revealed by serially independent sampling." Fertility and Sterility 38 (1982): 454-9.
van den Broek, J.M. "Change in male proportion among newborn infants." Lancet 349 (1997): 805.
Van Den Eeden, S.K., and N.S. Weiss. "Is testicular cancer incidence in blacks increasing?" American Journal of Public Health 79 (1989): 1553-4.
Van Der Kraak, G.J. et al. "Exposure to bleached kraft pulp mill effluent disrupts the pituitary-gonadal axis of white sucker at multiple sites." Toxicology and Applied Pharmacology 115 (1992): 224-233.
van der Pal-de Bruin, K.M., S.P. Verloove-Vanhorick, and N. Roeleveld. "Change in male:female ratio among newborn babies in Netherlands." Lancet 349 (1997): 62.
van't Veer, P., Lobbezoo I.E., Martin-Moreno J.M., Guallar E., Gomez-Aracena J., Kardinaal A.F., Kohlmeier L., Martin B.C., Strain J.J., Thamm M., van Zoonen P., Baumann B.A., Huttunen J.K., Kok F.J. "DDT (dicophane) and postmenopausal breast cancer in Europe: case-control study." British Medical Journal 315 (1997): 81-5.
Vercellini, P. and Crosignani, P.G. "Episemiology of endometriosis." The Current Status of Endometriosis: Research and Management. Eds. I. Brosens and J Donnez. New York: Parthenon, 1992. 111-130.
Weir, H.K., N. Kreiger, and L.D. Marrett. "Age at puberty and risk of testicular germ cell cancer (Ontario, Canada)." Cancer Causes and Control 9 (1998): 253-8.
Wun, L.M., Feuer E.J., Miller B.A. "Are increases in mammographic screening still a valid explanation for trends in breast cancer incidence in the United States?" Cancer Causes and Control 6 (1995): 135-44.
Yuan, J.M., Q.S. Wang, R.K. Ross, B.E. Henderson, and M.C. Yu. "Diet and breast cancer in Shanghai and Tianjin, China." British Journal of Cancer 71 (1995): 1353-8.
Zhang, Y., et al. "Parental age at child's birth and son's risk of prostate cancer. The Framingham Study." American Journal of Epidemiology 150 (1999): 1208-12.
Zheng T., Holford T.R., Mayne S.T., Ward B., Carter D., Owens P.H., Dubrow R., Zahm S.H., Boyle P., Archibeque S., Tessari J. "DDE and DDT in breast adipose tissue and risk of female breast cancer." American Journal of Epidemiology 150 (1999): 453-8.
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