The applicability of the flow cytometric sperm chromatin structure assay in epidemiological studies. Asclepios

The impact of demographic, lifestyle, and seminal factors on the sperm chromatin structure assay (SCSA) parameters was evaluated in a population of 277 healthy Danish men. This cohort was established within the framework of a European Concerted Action on occupational hazards to male reproductive capability in order to examine the possible reproductive effects of exposure to styrene or pesticides. The SCSA measures the susceptibility of sperm DNA to in-situ acid-induced denaturation, by multiparameter flow cytometric analysis after staining with the DNA-specific fluorescent dye acridine orange. The green versus red bivariate cytogram patterns were quite variable among donors, showing a wide heterogeneity of sperm DNA denaturability. Nevertheless, in those cases where we had the possibility to measure two semen samples from the same donor, the cytogram pattern remained stable over time (0.64 < r < 0.78). Analysis of variance demonstrated that the SCSA results can be influenced by the age of the donor (P < 0.0001), smoking habits (P < 0.05), the presence of leukocytes and immature germ forms in the ejaculate (P < 0.0001), and the duration of sexual abstinence (P < 0.0001). Furthermore, the relationship between the SCSA data and sperm concentration, morphology, and vitality was weak (-0.22 < r < -0.46). Therefore, the SCSA provides independent and complementary measurements of semen quality and is thus a useful tool for epidemiological studies, but the effects of some confounders should be accounted for in the survey design and analysis.     

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. III. Guidelines for field studies of male reproductive disorders

Exposures to environmental toxicants can have detrimental effects on several aspects of human male reproduction: fertility, sexual function, hormone status, and pregnancy/birth outcomes. However, no simple prescreening methods are available for reliably identifying potential hazards; questionnaires alone are relatively imprecise and inefficient in the absence of field data. Multidisciplinary field studies are required that include detailed exposure information, health and reproductive histories, physical examinations, semen analyses, and possibly, hormone analyses. Semen analysis is a critical component of field studies for evaluating two aspects of male reproduction: 1) changes in sperm or seminal content, which may be indicative of adverse effects on the male reproductive system with possible implications for fertility potential; and 2) defects in sperm DNA or chromosomes, which may be associated with subsequent changes in viability during embryonic development and health risks to the offspring. Semen analyses may be tiered: 1) initially, each semen study may include conventional semen assays (concentration, motility, and morphology) as well as specific biomarkers indicated by the health effect of concern in the study cohort: and 2) archived samples (i.e., frozen, videotaped, or smeared) may be utilized in later second-tier analyses to further characterize specific findings. Before initiating any field study, it is cost effective to critically evaluate the suitability of the cohort by confirming exposure and determining that there are adequate numbers of male participants in each exposure category. Such evaluations must be based on the statistical sensitivities of the specific tissue biomarkers and health endpoints for detecting changes. This article summarizes the components of the ideal field study and identifies research needs for improving field studies of male effects and for understanding the mechanisms of male reproductive toxicity. Several promising semen methods currently under development are also discussed.     

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

OBJECTIVE: To determine whether there has been a decline in semen quality in a group of healthy men during the past 21 years. DESIGN: Retrospective analysis of the relationship between time and changes in semen parameters over 21 years using regression analysis. SETTING: A tertiary university center. PATIENTS: Five hundred ten healthy, normal men who donated multiple semen samples as participants in clinical studies between 1972 and 1993. MAIN OUTCOME MEASURES: Sperm concentration, semen volume, total numbers of sperm per ejaculate, and percent spermatozoa with normal morphology. RESULTS: There was no decrease in sperm concentration, semen volume, total number of sperm per ejaculate, and percent normal sperm morphology in 510 healthy men studied between 1972 and 1993. CONCLUSION: We conclude that in this population of healthy young men there has not been any decline in semen quality in the past 21 years.     

Reproductive hormone profile among pesticide factory workers

Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels, as well as urinary levels of FSH, LH, and E1C, a metabolite of testosterone, were measured to investigate the adverse reproductive effects of organophosphate pesticides among Chinese factory workers who were occupationally exposed to ethylparathion and methamidophos. Thirty-four exposed workers were randomly chosen and recruited from a large pesticide factory, and 44 unexposed workers were selected from a nearby textile factory. A quantitative pesticide exposure assessment was performed among a subset of the exposed and unexposed workers. Information on potential confounders was collected in an interview. A single blood sample was collected at the end of a work shift, when each subject also donated a semen sample. Three first-voided urine samples were collected from each worker on 3 consecutive days. Urinary p-nitrophenol level at 1 hour after the work shift correlated with serum (r = 0.71, P < 0.01) and urinary (r = 0.51, P = 0.04) FSH levels. Stratifying by the subjects' exposure status, we found a significant negative correlation among the exposed group between urinary FSH level and sperm count (r = -0.61, P < 0.01) and between urinary FSH level and sperm concentration (r = -0.53, P = 0.03). Pesticide exposure alone was significantly associated with serum LH level (beta [coefficient of exposure effect] = 0.79; 95% confidence interval [CI] = 0.42, 1.16) but not with serum FSH or testosterone or with any urinary hormone levels. With adjustment for age, rotating shift work, current cigarette smoking, and current alcohol consumption, exposure significantly increased the serum LH level by 1.1 mIU/mL (95% CI = 0.34, 1.82). Meanwhile, the serum FSH level was slightly elevated (beta [coefficient of exposure effect] = 1.38; 95% CI = -0.09, 2.85) and the serum testosterone level was decreased (beta = -55.13; 95% CI = -147.24, 37) with increased pesticide exposure. Age and rotating shift work appeared to act as confounders. We conclude that organophosphate pesticides have a small effect on male reproductive hormones, suggestive of a secondary hormonal disturbance after testicular damage.     

Relation between semen quality and fertility: a population-based study of 430 first-pregnancy planners

BACKGROUND: Semen analysis is part of the routine assessment of infertile couples. WHO defines a sperm concentration above 20x10(6) per mL seminal fluid as normal. We studied the association between semen quality and the probability of conception in a single menstrual cycle in Danish couples with no previous reproductive experience. METHODS: In 1992-94, we invited 52,255 trades-union members aged 20-35 years, who lived with a partner and had no children to take part in the study; 430 couples agreed. The couples discontinued use of contraception, and were followed up for six menstrual cycles or until a pregnancy was verified within this period. Each man was asked to provide a semen sample at enrolment (which was analysed without freezing). Women kept a daily record of vaginal bleeding and sexual activity. The association between semen quality and likelihood of pregnancy was assessed by logistic regression, adjusted for sexual activity and female factors associated with low fertility. RESULTS: There were 256 (59.5%) pregnancies among the 430 couples: 165 (65.0%) among those with a sperm concentration of 40x10(6)/mL or more and 84 (51.2%) among those with lower sperm concentrations. The probability of conception increased with increasing sperm concentration up to 40x10(6)/mL, but any higher sperm density was not associated with additional likelihood of pregnancy. The proportion of sperm with normal morphology was strongly related to likelihood of pregnancy independently of sperm concentration. Semen volume and motility were of limited value in pregnancy prediction. INTERPRETATION: Our study suggests that the current WHO guidelines for normal semen quality should be used with caution. Some men with sperm counts above the lower limit of the normal range defined by WHO may in fact be subfertile.     

Declining male fertility and environmental factors

Male reproductive function has recently attracted increasing attention due to reports on time-related decline in semen quality. Analysis of retrospective data indicates that sperm counts may have declined in some parts of the world, but there seem to be regional differences both in the quality of semen and regarding the secular trend. Whereas data on sperm counts may be somewhat difficult to interpret, there is no doubt that incidence of testicular cancer has increased worldwide. In occupational studies, only a few types of exposures were shown to have an impact on male reproductive function; lifestyle and general environmental factors may play a more important role. Prospective studies on secular and geographic trends in male reproductive function are warranted.     

Is today's man really less fertile?

In 1992, a statistical analysis of data from 61 studies of semen quality among normal men led to the conclusion that human sperm count fell of 40% from 1940 to 1990. This meta-analysis has since been invalidated for methodological reasons as well as for statistical reasons, but it caused enormous concern to both the scientific community and to the international media. A decline of human fertility was speculated. To date, the most popular hypothesis offered to explain this alleged decline has been increasing exposure to environmental estrogen mimicking chemicals. However, there is no evidence that male or mammal fertility is declining. Moreover, the sperm count of breeding mammals did not declined in the meanwhile. Since 1992, numerous papers reported on men investigated during the last 20 years have shown conflicting results, from sperm count improvement to sperm count decline. However, several publications included methodological and analytical biases. In fact, the techniques used for semen analysis have to be questioned. It is a subjective exam, lacking laboratory standards and quality control procedures. This induces very important variations between laboratories and between biologists. For the sperm count itself, numerous errors can occur, provoked by the technique, the equipment and the reader: for the same sperm, the coefficient of variation can exceed 40% between two technicians. Therefore, the current techniques of semen analysis cannot warrant epidemiological studies. It is indispensable to admit the limits of the semen analysis in order to improve as much as possible its quality and its reliability.     

Is semen quality related to the year of birth among Danish infertility clients?

BACKGROUND: There is circumstantial evidence that human sperm count may have declined during past decades. The purpose of this study was to identify the association between semen quality and year of birth. METHODS: The study comprised 8608 men consulting four Danish medical centres from 1968 to 1992 because of infertility. Data on semen quality and urogenital disorders were obtained from medical records while lifestyle data were collected from a subset of the population by a postal questionnaire (response 80%). Semen characteristics were analysed as a linear function of year of birth, centre, season and calendar year at time of semen examination, sexual abstinence and lifestyle factors. Effects of age were accounted for by restriction and stratified analysis. RESULTS: The sperm count declined with increasing year of birth at two of the four centres, but this association disappeared when confounders were adjusted for. Within the subset of men born 1950-1970 we revealed a decrease in the average sperm count by 1.9 mill/ml (95% confidence interval [CI]: 1.45, 2.27) per one advancing year of birth. This finding was consistent across centres even after adjustment for effects of covariates. The proportion of morphologically normal sperm cells changed in parallel with the sperm count, while semen volume did not decline in any time periods. CONCLUSIONS: We found a birth cohort effect on sperm count and morphology among Danish infertile men born after 1950 but not in men born in the first part of the century. The findings are compatible with an environmental impact during prenatal life but the evidence is far from unequivocal.     

Comparison of sperm separation methods: effect on recovery, motility, motion parameters, and hyperactivation

OBJECTIVE: To compare the Enhance (Percoll; Conception Technologies, San Diego, CA) and PureSperm (Gen X International, Madison, CT) sperm preparation methods with respect to recovery (percentage of motile sperm), motility (%), path and progressive velocities (microm/s), and hyperactivation (%). DESIGN: Comparison of sperm processing methods. SETTING: University medical center-based clinical andrology laboratory and infertility program. PATIENT(S): Twenty-five men who presented for semen analysis. INTERVENTION(S): Each of 25 semen specimens were divided and each aliquot was prepared using two different density gradient centrifugation methods. MAIN OUTCOME MEASURE(S): The motile sperm recovery, percent motility, motion parameters, and percent hyperactivation were measured for each semen specimen (n=25) before and after separation with the use of the two methods. RESULT(S): There was no difference in the percent motility and motile count between specimens prepared with Enhance (Percoll) and PureSperm and fresh specimens. Statistically significant differences were found (fresh versus test) in the velocities and in hyperactivation (PureSperm only), and no differences were found between the processing methods. CONCLUSION(S): PureSperm appears to be as effective as Percoll (Enhance) for the recovery of good, progressively motile sperm for use in IUI or other assisted reproductive techniques.     

Expression of purine metabolism-related enzymes by microglial cells in the developing rat brain

The effects of elevated blood lead on semen quality were evaluated in the rabbit model and compared to published effects in humans. Mature, male rabbits were given lead acetate by subcutaneous injection in the dose range of 0 to 3.85 mg/kg on a Monday-Wednesday-Friday basis. In each of eight treatment groups, a dosing regimen was developed to produce blood lead levels of 0, 20, 40, 50, 70, 80, 90, and 110 microg/dL. A 5-week pre-exposure period was followed by a 15-week exposure testing period allowing for response through six cycles of the seminiferous epithelium. Semen analyses revealed that increased blood lead levels were associated with adverse changes in the sperm count, ejaculate volume, percent motile sperm, swimming velocities, and morphology. Hormonal responses were minimal. Testicular pathology revealed a dose-dependent inhibition of spermiation. For six measures of semen quality, threshold estimates ranged from 16 to 24 microg/dL. Using the species extrapolation factor derived in this study, a rabbit dose would have to be divided by 1.56 to obtain the equivalent human dose for an equal percentage decrease in sperm concentration; however, rabbits are 3.75 more sensitive in terms of absolute decrease in sperm count for a given blood lead level.     

Effect of restricted daylength during the growing period on semen quality and fertility of turkey toms

Two trials were conducted in which three daylength and light intensity treatments were applied to 144 growing turkey toms from 8 to 28 weeks of age. Treatments were (1) six hours of artificial light, (2) natural light and daylength, and (3) simulated natural daylength. At 28 weeks of age all toms were placed on 14 hours of daily light. Individual tom semen quality was evaluated every two weeks for six months, and on alternate weeks, eight hens were inseminated with semen pooled by treatment replicate to obtain fertility (May to December). Seasonal decline in semen production, sperm concentration, semen volume, and fertility was observed for toms on natural daylength after three months of production. Toms on six hours of light and those on simulated natural light maintained high levels of production and quality for the entire six month period. Semen production expressed as the average number of toms producing semen, sperm concentration, and fertily were significantly lower (P less than .01), and semen volume was significantly lower (P less than .05) for toms on natural light after six months. It was concluded that natural light was less desirable than controlled light for "off season" growing of toms.     

Effects of p,p'-DDE on male reproductive organs in peripubertal Wistar rats following a single intraperitoneal injection

The effects of p,p'-DDE on male reproductive organs were investigated in detail in peripubertal Wistar rats following a single intraperitoneal injection. 220 mg/kg of p,p'-DDE (1/4 of LD50) were injected once into prepubertal and postpubertal Wistar rats and its effects were observed until 20 weeks of age. Weights of the body and reproductive organs in p,p'-DDE-injected rats were similar to those in control rats, who were injected with corn oil only. Sperm profile parameters such as spermatid number within the testis, sperm number within the epididymis, sperm motility and its morphology were not different between the prepubertal or postpubertal p,p'-DDE-exposed group and the control group. Like-wise, the histopathological examination at stage VII of the seminiferous epithelium cycle, when the germ cells are sensitive to testosterone, was similar in all three groups during the observation period. Serum levels of testosterone also showed no significant changes by exposure to p,p'-DDE under the conditions of this study. From these results, the antiandrogenic or estrogenic activity attributed to p,p'-DDE was not confirmed in male reproductive organs and no impairment of sperm profile was observed. This study confirmed that the reproductive functions of matured animals are scarcely affected by p,p'-DDE exposure during the peripubertal period and revealed that they might be relatively resistant to exogenous endocrine-disrupting chemicals. p,p'-DDE may threaten the hormonal equilibrium required for normal gonadal development during the organogenesis period, at an earlier stage of life. Further studies are necessary to fully reveal all the effects of p,p'-DDE on male reproductive organs and sperm profile.     

No evidence of deteriorating semen quality among men in infertile relationships during the last decade: a study of males from Southern Sweden

The aim of this study was to investigate whether the quality of semen has deteriorated during the last decade. Laboratory records containing semen analysis results were reviewed. The records, arranged according to date of birth, are kept in shelves. Every fifth record for analyses performed between 1985 and 1995, and only those of men in infertile relationships, were included. The data were abstracted in a data base, and time-related changes in semen characteristics were studied using linear regression analyses. During the study period, there was a slight, but significant increase in sperm concentration, percentage of motile spermatozoa, percentage of spermatozoa with normal morphology, and the base-value of the penetration test. The seminal volumes decreased slightly, but significantly. Sperm characteristics were not associated with age or date of birth of the men. In conclusion, these data show no evidence of deterioration in sperm quality during the last decade among men in infertile relationships.     

Improvement in semen quality associated with decreasing occupational lead exposure

BACKGROUND: Cross-sectional studies have suggested that occupational lead exposure may adversely affect sperm quality. METHODS: Sperm quality changes were prospectively assessed in 19 men employed at a car battery plant where efforts were made to decrease the exposure level. The participants delivered monthly samples of semen and venous blood during their employment at the factory. The factory then closed, and additional samples were obtained from 16 of the men. RESULTS: Average blood-lead concentrations decreased from 2.03 mumol/l to 0.96 mumol/l during the observation period. Concomitantly, significant improvements were seen in the proportion of motile cells both at sample delivery and after 24 hr, and in penetration. However, the sperm cell concentration and the proportion of morphological abnormalities did not change. CONCLUSIONS: These results support the notion that occupational lead exposure at currently acceptable levels has a small adverse effect on sperm quality, especially sperm motility, and that this effect is at least partially reversible.     

Changes in plasma LH and testosterone levels and semen quality after a single injection of hCG in two dogs with spermatogenic dysfunction

Plasma LH and testosterone (T) levels and semen quality after a single intramuscular injection of 1,000 IU hCG were investigated in a Beagle dog with azoospermia and a Beagle dog with poor semen quality. The plasma LH levels of both dogs did not change after the treatment. Although the plasma T levels of the dog with azoospermia increased temporarily, no sperm were detected in its semen. In the dog with poor semen quality high levels of plasma T were maintained for 2 weeks after hCG treatment and its semen quality was temporarily improved between 3 and 4 weeks after treatment. These findings indicate that the semen quality of dogs with oligozoospermia can be temporarily improved after a single injection of hCG.     

Preliminary screening for the potential of drinking water disinfection byproducts to alter male reproduction

There is increasing epidemiologic interest in the role drinking water disinfection byproducts (DBPs) may play in adverse reproductive outcomes such as inability to conceive, spontaneous abortion, and low birth weight. Although dozens of DBPs already have been identified, only a few studies have attempted to determine whether DBPs alter male reproductive parameters such as testicular and epididymal histology, testicular and epididymal sperm numbers, and epididymal sperm morphology and motility in laboratory animals. In these studies, alterations in epididymal sperm motility seemed to be predictive of more generalized toxicity of the male reproductive system. Because there is a need to prioritize DBPs for thorough reproductive and developmental toxicity testing, preliminary screening for the potential of DBPs to alter reproductive function seems warranted. Here, we elected to examine only cauda epididymal sperm motion parameters and testicular and epididymal histopathology. The effects of exposure to two commonly occurring DBPs, bromodichloromethane (BDCM) and chloral hydrate (CH), via drinking water were evaluated in F344 rats at an interim (52 week) necropsy during cancer bioassay studies. Exposure to 22 and 39 mg/kg BDCM and 55 and 188 mg/kg CH did not produce any systemic toxicity. Histopathologic evaluation revealed no gross lesions in the reproductive organs, and no tumors were detected in any tissues. In contrast, exposure to 39 mg/kg BDCM significantly decreased the mean straight-line, average path, and curvilinear velocities of sperm recovered from the cauda epididymidis. This BDCM exposure shifted the average path velocity distribution to a lower modal velocity range. Exposure to 188 mg/kg CH significantly decreased both the percentage of motile and progressively motile sperm. This CH exposure shifted the straight-line velocity distribution to a lower modal velocity range. These are the first reproductive toxicity data from exposure to BDCM and CH. The observed effects on sperm motion occurred in the absence of carcinogenesis. Because the effects of BDCM on sperm motility occurred at a lower exposure than that of other DBPs that compromise sperm motility, a thorough reproductive evaluation now is underway.     

Plasma LH progesterone concentrations in the turkey hen during the ovulatory cycle

Progesterone and luteinizing hormone (LH) were measuured in the plasma of Large White turkey hens at frequent intervals during the ovulatory cycle and during the periods when ovulations did not occur. The hormones were quantitated at the beginning and the end of the reproductive season to follow the change in patterns and concentrations of these hormones. Radioimmunoassay procedures were used to assay both hormones. Both progesterone and LH reached a peak amount at about 8 to 2 hours before ovulation. At no time did the progesterone peak precede that of LH. On the other hand, the peak of progesterone was observed to last somewhat longer than the LH peak. Progesterone and LH concentrations demonstrated no peak during the non-ovulatory periods. The patterns of both hormones at the end of the reproductive season was about the same as at the beginning of the season, but with lower concentrations.     

Manual collection and characterization of semen from Asian elephants (Elephas maximus)

The implications of collecting semen from elephants for use in artificial insemination programs are profound in the context of propagating captive elephants. Using a manual manipulation technique, semen was collected and characterized from five adult Asian elephants (Elephas maximus) and ejaculate fluid was obtained from one castrated elephant bull. The penis was stimulated to protrusion and erection by rectal massage of the pelvic portion of the urethra. During an ejaculatory response, massage was also directed onto the area of the ampulla of the ductus deferens. Sperm rich ejaculates were usually collected as a result of each ejaculatory contraction. Ejaculates were evaluated for spermatozoal concentration and pH (when possible) and sperm rich fractions combined for determination of total volume. Mean total volume of each collection was 27.5+/-4.4 ml. Mean concentration of the first and second ejaculatory responses from a collection was 2.05+/-0.17 x 10(9) and 1.34+/-0.19 x 10(9) sperm/ml, respectively. Measurement of seminal pH revealed no significant differences between the fractions. Mean pH of the first and second ejaculatory responses were 7.05+/-0.07 and 7.04+/-0.13. This method of collecting elephant sperm can be utilized for semen evaluation of bulls of unknown reproductive status in conjunction with other evaluation techniques (i.e. ultrasonographic, endocrinologic). It also has the potential for providing valuable genetic material for genome resource banks and for use with assisted reproductive techniques like artificial insemination.     

Subperiostal hematoma of the orbit and epidural hematoma in patients with skull-brain trauma]

This report describes the types of chromosome damage in peripheral blood found in patients exposed to domestic application of organophosphate pesticides. These changes serve as a biomarker of cumulative toxic exposure. Susceptible individuals show DNA damage as chromosome alterations. The importance of these findings is that the apparent genotoxic changes occurred from domestic application of two of the commonly used organophosphate pesticides in America and adds one more adverse potential effect from these hazardous chemicals. Peripheral blood from eight patients exposed to the domestic spraying of organophosphate pesticides was cultured and the chromosomes photographed. The types of chromosome alterations seen included chromatid and chromosome breaks, single and double minutes, dicentrics, rings, translocations, exchanges (including sister chromatid), and endoreduplications. Our findings support previous findings that organophosphate pesticides have genotoxic effects even at domestically sprayed levels.     

An updated review of environmental estrogen and androgen mimics and antagonists

For the last 40 y, substantial evidence has surfaced on the hormone-like effects of environmental chemicals such as pesticides and industrial chemicals in wildlife and humans. The endocrine and reproductive effects of these chemicals are believed to be due to their ability to: (1) mimic the effect of endogenous hormones, (2) antagonize the effect of endogenous hormones, (3) disrupt the synthesis and metabolism of endogenous hormones, and (4) disrupt the synthesis and metabolism of hormone receptors. The discovery of hormone-like activity of these chemicals occurred long after they were released into the environment. Aviation crop dusters handling DDT were found to have reduced sperm counts, and workers at a plant producing the insecticide kepone were reported to have lost their libido, became impotent and had low sperm counts. Subsequently, experiments conducted in lab animals demonstrated unambiguously the estrogenic activity of these pesticides. Man-made compounds used in the manufacture of plastics were accidentally found to be estrogenic because they fouled experiments conducted in laboratories studying natural estrogens. For example, polystyrene tubes released nonylphenol, and polycarbonate flasks released bisphenol-A. Alkylphenols are used in the synthesis of detergents (alkylphenol polyethoxylates) and as antioxidants. These detergents are not estrogenic; however, upon degradation during sewage treatment they may release estrogenic alkylphenols. The surfactant nonoxynol is used as intravaginal spermicide and condom lubricant. When administered to lab animals it is metabolized to free nonylphenol. Bisphenol-A was found to contaminate the contents of canned foods; these tin cans are lined with lacquers such as polycarbonate. Bisphenol-A is also used in dental sealants and composites. We found that this estrogen leaches from the treated teeth into saliva; up to 950 microg of bisphenol-A were retrieved from saliva collected during the first hour after polymerization. Other xenoestrogens recently identified among chemicals used in large volumes are the plastizicers benzylbutylphthalate, dibutylphthalate, the antioxidant butylhydroxyanisole, the rubber additive p-phenylphenol and the disinfectant o-phenylphenol. These compounds act cumulatively. In fact, feminized male fish were found near sewage outlets in several rivers in the U.K.; a mixture of chemicals including alkyl phenols resulting from degradation of detergents during sewage treatment seemed to be the causal agent. Estrogen mimics are just a class of endocrine disruptors. Recent studies identified antiandrogenic activity in environmental chemicals such as vinclozolin, a fungicide, and DDE, and insecticide. Moreover, a single chemical may produce neurotoxic, estrogenic and antiandrogenic effects. It has been hypothesized that endocrine disruptors may play a role in the decrease in the quantity and quality of human semen during the last 50 y, as well as in the increased incidence of testicular cancer and cryptorchidism in males and breast cancer incidence in both females and males in the industrialized word. To explore this hypothesis it is necessary to identify putative causal agents by the systematic screening of environmental chemicals and chemicals present in human foods to assess their ability to disrupt the endocrine system. In addition, it will be necessary to develop methods to measure cumulative exposure to (a) estrogen mimics, (b) antiandrogens, and (c) other disruptors.