The healthy men study: design and recruitment considerations for environmental epidemiologic studies in male reproductive health

Association Between Male Use of Pain Medication and Fecundability

Administration of pain relievers has been associated with both lower and higher risks of adverse reproductive outcomes in animals. In the sole investigation of male pain-reliever use and human fertility carried out to date, Smarr et al. (Hum Reprod. 2016;31(9):2119-2127) found a 35% reduction in fecundability among males with urinary acetaminophen concentrations in the highest quartile (>73.5 ng/mL) versus the lowest (<5.4 ng/mL). We analyzed data from 1,956 males participating in Pregnancy Study Online, a preconception cohort study of North American couples enrolled between 2013 and 2019. Males and females completed baseline questionnaires on sociodemographic characteristics, lifestyle, medication use, and medical history; females completed bimonthly follow-up questionnaires for up to 12 months. We categorized pain medications by active ingredient (ibuprofen, acetaminophen, naproxen, aspirin) and cumulative monthly dose. We used proportional probabilities models to calculate fecundability ratios and 95% confidence intervals, adjusting for potential confounders. In the 4 weeks before baseline, 51.7% of males used pain medications. Adjusted fecundability ratios were 1.02 for ibuprofen (95% confidence interval (CI): 0.91, 1.13), 0.89 for acetaminophen (95% CI: 0.77, 1.03), 1.07 for naproxen (95% CI: 0.85, 1.35), and 1.05 for aspirin (95% CI: 0.81, 1.35), as compared with nonuse of each medication. In this study, male use of pain medications at low doses was not notably associated with fecundability.

Associations of blood trihalomethanes with semen quality among 1199 healthy Chinese men screened as potential sperm donors

BACKGROUND

Trihalomethanes (THMs) have demonstrated adverse effects on male reproductive systems in experimental animals, but human evidence has been inconsistent. Prior researches have been limited by small sample sizes and inadequate exposure assessment.

OBJECTIVES

To investigate the association between blood THMs and repeated measurements of semen quality parameters among 1199 healthy men screened as potential sperm donors.

METHODS

We recruited healthy men presenting to the Hubei Province Human Sperm Bank from April to December 2017. At study entry, each participant provided a spot blood sample which was used to quantify blood concentrations of four THMs: chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (TBM). The summary measures of exposure for brominated THMs (Br-THMs; molar sum of BDCM, DBCM and TBM) and total THMs (TTHMs; molar sum of TCM and Br-THMs) were also calculated. We used multivariable linear regression models to estimate the cross-sectional associations of tertiles of blood THM concentrations with semen quality parameters measured at study entry, and mixed-effect models to estimate the longitudinal associations accounting for repeated measures of semen quality, adjusting for relevant confounding factors.

RESULTS

In the cross-sectional analysis, several inverse dose-response relationships were observed across tertiles of blood TCM concentrations and sperm count, total motility and progressive motility, and between blood DBCM, and Br-THMs, and TTHMs and sperm count and concentration. The inverse associations of blood TCM, DBCM, Br-THMs and TTHMs with sperm count were confirmed in the longitudinal, repeated measure analysis.

CONCLUSION

Our results suggest that exposure to THMs from drinking water may be related to decreased semen quality in young healthy men.

Male urinary biomarkers of antimicrobial exposure and bi-directional associations with semen quality parameters

Antimicrobials including parabens, triclosan, and triclocarban have endocrine disrupting properties. Among 501 male partners of couples planning to become pregnant, preconception urinary biomarkers of parabens, triclosan and triclocarban exposure were quantified in spot urine samples. Men also provided two fresh semen samples collected approximately one month to undergo 24-h semen quality analysis. Linear mixed-effects models, adjusted for creatinine, race, age and body mass index, were utilized to assess the relationship between log transformed chemical concentrations rescaled by their standard deviations and semen parameters. Methyl, ethyl and butyl parabens, were associated with diminished sperm count and several sperm motility parameters. Hydroxylated paraben metabolites and triclosan were significantly positively associated with select semen quality parameters. Overall, our findings suggest that specific urinary parabens found in consumer goods (methyl, ethyl and butyl parabens) may adversely impact sperm quality parameters among reproductive-age male partners of couples trying for pregnancy.

Engaging African Americans in Research: The Recruiter's Perspective

Purpose

To examine barriers recruiters encounter when enrolling African American study participants, identify motivating factors to increase research participation, and provide recommendations to facilitate successful minority recruitment.

Background

Recruiters are often the first point of contact between the research study and potential African American participants. While challenges in enrolling African Americans into clinical and epidemiologic research has been reported in numerous studies the non-physician recruiter's role as a determinant of overall participation rates has received minimal attention.

Methods

We conducted four 90-minute teleconference focus groups with 18 recruiters experienced in enrolling African Americans for clinical and epidemiologic studies at five academic/medical institutions. Participants represented diverse racial and ethnic backgrounds and were asked to reflect on barriers preventing African Americans from participating in research studies, factors that motivated participation, and recommendations to increase participation of African Americans in research. Multi-coder and thematic data analysis was implemented using the Braun and Clarke method.

Results

Prominent concerns in recruitment of African Americans in research include fear and mistrust and inflexible research protocols. The participants suggest that improved recruitment could be achieved through cross-cultural and skillset building training opportunities for recruiters, greater community engagement among researchers, and better engagement with clinic staff and research teams.

Male urinary paracetamol and semen quality

The endocrine-disrupting properties of paracetamol have been previously demonstrated in rodent studies of abnormal sperm morphology and diminished testosterone production, in addition to epidemiologic studies of diminished couple fecundity. In this study, we examined the relationship between paracetamol and its metabolite p-aminophenol quantified in a single spot urine and semen quality among 501 male partners of couples planning for pregnancy. Men provided a urine specimen and two fresh semen samples collected approximately one month apart and underwent 24-h analysis for 35 semen quality parameters. Paracetamol and p-aminophenol were quantified in urine by ultra-high-performance liquid chromatography coupled with an electrospray triple quadrupole mass spectrometry. The relationship between natural-log-transformed urinary paracetamol and p-aminophenol rescaled by their standard deviation and 21 Box-Cox-transformed, 14 non-transformed semen parameters was assessed using linear mixed-effects models. The median concentrations (IQR) of urinary paracetamol and p-aminophenol were 15.5 ng/mL (5.44, 73.5) and 978 ng/mL (500, 1596), respectively. Following adjustment for creatinine and age, a 1-standard deviation increase in log-transformed urinary paracetamol was associated with a reduction in beat cross-frequency and an increase in DNA fragmentation [β (95% CI): -0.59 Hz (-1.16, -0.03) and 0.05% (0.01, 0.09), respectively]. These findings were corroborated in models of categorical chemical concentrations; higher concentrations of paracetamol remained associated with reduced beat cross-frequency and increased DNA fragmentation. A 1-standard deviation increase in log-transformed urinary p-aminophenol was associated with a reduction in sperm head area [β (95% CI): -0.1 μm2 (-0.18, -0.02) and width -0.02 μm (-0.04, -0.01)]. However, only the association with sperm head area remained statistically significant in models of p-aminophenol quartiles. Our findings suggest that adult male urinary paracetamol is associated with sperm motility and DNA fragmentation, while the metabolite, p-aminophenol, is predominantly associated with sperm head morphometry.

Semen quality and pregnancy loss in a contemporary cohort of couples recruited before conception: data from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study

OBJECTIVE

To study the relationship between semen quality and pregnancy loss in a cohort of couples attempting to conceive.

DESIGN

Observational prospective cohort.

SETTING

Not applicable.

PATIENT(S)

Three hundred and forty-four couples with a singleton pregnancy observed daily through 7 postconception weeks of gestation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Association between semen quality and pregnancy loss.

RESULT(S)

Ninety-eight (28%) of the couples experienced a pregnancy loss after singleton pregnancy. No differences were observed in semen volume, sperm concentration, total sperm count, sperm viability, or sperm morphology (World Health Organization [WHO] and strict criteria) by couple's pregnancy loss status irrespective of whether they were analyzed continuously or as dichotomous variables per the WHO 5th edition semen criteria. A dichotomous DNA fragmentation measure of ≥30% was statistically significantly associated with pregnancy loss. No association was identified with other sperm morphometric or movement measures. Of the 70 couples who re-enrolled after a pregnancy loss, 14 experienced a second loss. Similar findings were identified when examining semen quality from couples with recurrent pregnancy loss.

CONCLUSION(S)

Although a few trends were identified (e.g., DNA fragmentation), general semen parameters seemed to have little relation with risk of pregnancy loss or recurrent pregnancy loss at the population level. However, given that 30% of pregnancies end in miscarriage and half the fetal genome is paternal in origin, the findings await corroboration.

Fathers Matter: Why It's Time to Consider the Impact of Paternal Environmental Exposures on Children's Health

PURPOSE

Despite accumulating evidence from experimental animal studies showing that paternal environmental exposures induce genetic and epigenetic alterations in sperm which in turn increase the risk of adverse health outcomes in offspring, there is limited epidemiological data on the effects of human paternal preconception exposures on children's health. We summarize animal and human studies showing that paternal preconception environmental exposures influence offspring health. We discuss specific approaches and designs for human studies to investigate the health effects of paternal preconception exposures, the specific challenges these studies may face, and how we might address them.

RECENT FINDINGS

In animal studies, paternal preconception diet, stress, and chemical exposures have been associated with offspring health and these effects are mediated by epigenetic modifications transmitted through sperm DNA, histones, and RNA. Most epidemiological studies have examined paternal preconception occupational exposures and their effect on the risk of birth defects and childhood cancer; few have examined the effects of low-level general population exposure to environmental toxicants. While the design and execution of epidemiological studies of paternal preconception exposures face challenges, particularly with regard to selection bias and recruitment, we believe these are tractable and that preconception studies are feasible.

SUMMARY

New or augmented prospective cohort studies would be the optimal method to address the critical knowledge gaps on the effect of paternal preconception exposures on prevalent childhood health outcomes. Determining if this period of life represents a window of heightened vulnerability would improve our understanding of modifiable risk factors for children's health and wellbeing.

Urinary Phytoestrogens Are Associated with Subtle Indicators of Semen Quality among Male Partners of Couples Desiring Pregnancy

BACKGROUND

Phytoestrogens have been associated with subtle hormonal changes, although effects on male fecundity are largely unknown.

OBJECTIVE

We evaluated associations between male urinary phytoestrogen (isoflavone and lignan) concentrations and semen quality.

METHODS

This study was a prospective cohort study of 501 male partners of couples desiring pregnancy and discontinuing contraception. Each participant provided up to 2 semen samples that were analyzed for 35 semen quality endpoints the following day. Linear mixed-effects models were used to estimate associations between baseline urinary phytoestrogen concentrations and semen quality parameters, adjusted for age, body mass index (BMI), research site, and serum lipid and cotinine concentrations.

RESULTS

Most associations between urinary phytoestrogens and semen quality parameters were null. However, select individual phytoestrogens were associated with semen quality parameters, with associations dependent on the class of phytoestrogens and modified by BMI. Specifically, genistein and daidzein were associated with a lower percentage of normal sperm and increased abnormalities in semen morphology, with reduced associations observed as BMI increased (P < 0.05) [percentages (95% CIs) of normal morphology by WHO traditional criteria: genistein, main effect: -5.61% (-9.42%, -1.79%); interaction: 0.19% (0.06%, 0.31%) per log unit increase; daidzein, main effect: -5.35% (-9.36%, -1.34%); interaction: 0.18% (0.05%, 0.32%) per log unit increase]. Enterolactone was associated with fewer abnormalities in semen morphometry and morphology and decreased DNA fragmentation, with reduced associations observed as BMI increased (P < 0.05) [percentages (95% CIs) of abnormalities in the neck and midpiece: enterolactone, main effect: -3.35% (-6.51%, -0.19%); interaction: 0.11% (0.01%, 0.21%) per log unit increase].

CONCLUSIONS

These results suggest that male urinary phytoestrogen concentrations characteristic of the US population may be associated with subtle indicators of male fecundity and semen quality but were not associated with couple fecundity.

Persistent organic pollutants and semen quality: The LIFE Study

Growing evidence suggests that persistent environmental chemicals such as polychlorinated biphenyls may adversely affect human fecundity. The purpose of this study was to evaluate associations between persistent environmental chemicals and semen quality among 501 male partners of couples discontinuing contraception for purposes of becoming pregnant. Men provided a blood specimen and two fresh semen samples collected approximately a month apart that underwent next day analysis for 35 semen quality endpoints. Serum samples were analyzed for 36 polychlorinated biphenyls (congeners #18, 28, 44, 49, 52, 66, 74, 87, 99, 101, 114, 118, 128, 138, 146, 149, 151, 153, 156, 157, 167, 170, 172, 177, 178, 180, 183, 187, 189, 194, 195, 196, 201, 206, 209); 1 polybrominated biphenyl (#153); 9 organochlorine pesticides; and 10 polybrominated diphenyl ethers (congeners #17, 28, 47, 66, 85, 99, 100, 153, 154183) using high resolution mass spectrometry. To estimate the effect of chemicals on semen quality, we regressed each semen marker on each chemical while adjusting for research site, age, body mass index, serum lipids, and cotinine levels. Males with chemical concentrations in the fourth quartile, as compared to the first quartile, showed significant associations for several individual chemicals in each chemical class and type of semen quality parameter indicating negative and positive associations with semen quality. Polybrominated diphenyl ethers in particular were associated with several measures of increased abnormal morphology. These exploratory results highlight the role of environmental influences on male fecundity, and are of particular interest given the ubiquitous exposures to these compounds.

Design and Conduct of an Internet-Based Preconception Cohort Study in North America: Pregnancy Study Online

BACKGROUND

We launched the Boston University Pregnancy Study Online (PRESTO) to assess the feasibility of carrying out an Internet-based preconception cohort study in the US and Canada.

METHODS

We recruited female participants age 21-45 and their male partners through Internet advertisements, word of mouth, and flyers. Female participants were randomised with 50% probability to receive a subscription to FertilityFriend.com (FF), a web-based programme that collects real-time data on menstrual characteristics. We compared recruitment methods within PRESTO, assessed the cost-efficiency of PRESTO relative to its Danish counterpart (Snart-Gravid), and validated retrospectively reported date of last menstrual period (LMP) against the FF data.

RESULTS

After 99 weeks of recruitment (2013-15), 2421 women enrolled; 1384 (57%) invited their male partners to participate, of whom 693 (50%) enrolled. Baseline characteristics were balanced across randomisation groups. Cohort retention was similar among those randomised vs. not randomised to FF (84% vs. 81%). At study enrollment, 56%, 22%, and 22% couples had been trying to conceive for < 3, 3-5, and ≥ 6 months, respectively. The cost per subject enrolled was $146 (2013 US$), which was similar to our companion Danish study and half that of a traditional cohort study. Among FF users who conceived, > 97% reported their LMP on the PRESTO questionnaire within 1 day of the LMP recorded via FF.

CONCLUSIONS

Use of the Internet as a method of recruitment and follow-up in a North American preconception cohort study was feasible and cost-effective.

Perfluorochemicals and human semen quality: the LIFE study

BACKGROUND

The relation between persistent environmental chemicals and semen quality is evolving, although limited data exist for men recruited from general populations.

OBJECTIVES

We examined the relation between perfluorinated chemicals (PFCs) and semen quality among 501 male partners of couples planning pregnancy.

METHODS

Using population-based sampling strategies, we recruited 501 couples discontinuing contraception from two U.S. geographic regions from 2005 through 2009. Baseline interviews and anthropometric assessments were conducted, followed by blood collection for the quantification of seven serum PFCs (perfluorosulfonates, perfluorocarboxylates, and perfluorosulfonamides) using tandem mass spectrometry. Men collected a baseline semen sample and another approximately 1 month later. Semen samples were shipped with freezer packs, and analyses were performed on the day after collection. We used linear regression to estimate the difference in each semen parameter associated with a one unit increase in the natural log-transformed PFC concentration after adjusting for confounders and modeling repeated semen samples. Sensitivity analyses included optimal Box-Cox transformation of semen quality end points.

RESULTS

Six PFCs [2-(N-methyl-perfluorooctane sulfonamido) acetate (Me-PFOSA-AcOH), perfluorodecanoate (PFDeA), perfluorononanoate (PFNA), perfluorooctane sulfonamide (PFOSA), perfluorooctane sulfonate (PFOS), and perfluorooctanoic acid (PFOA)] were associated with 17 semen quality end points before Box-Cox transformation. PFOSA was associated with smaller sperm head area and perimeter, a lower percentage of DNA stainability, and a higher percentage of bicephalic and immature sperm. PFDeA, PFNA, PFOA, and PFOS were associated with a lower percentage of sperm with coiled tails.

CONCLUSIONS

Select PFCs were associated with certain semen end points, with the most significant associations observed for PFOSA but with results in varying directions.

Lipid concentrations and semen quality: the LIFE study

The decline in sperm count rates over the last 50 years appears to parallel the rising prevalence of obesity. As lipid levels are strongly associated with obesity, high lipids levels or hyperlipidaemia may thus play an important role in the decline in fertility in addition to other environmental or lifestyle factors. The objective of this population based cohort study was to evaluate the association between men's serum lipid concentrations and semen quality parameters among 501 male partners of couples desiring pregnancy and discontinuing contraception. Each participant provided prospectively up to two semen samples (94% of men provided one or more semen samples, and 77% of men provided a second sample approximately 1 month later). Linear mixed effects models were used to estimate the associations between baseline lipid concentrations and semen quality parameters, adjusted for age, body mass index and race. We found that higher levels of serum total cholesterol, free cholesterol and phospholipids were associated with a significantly lower percentage of spermatozoa with intact acrosome and smaller sperm head area and perimeter. Our results suggest that lipid concentrations may affect semen parameters, specifically sperm head morphology, highlighting the importance of cholesterol and lipid homeostasis for male fecundity.

Limited representation of drinking-water contaminants in pregnancy-birth cohorts

Water contamination and noise have been consistently the least assessed environmental/lifestyle exposures in pregnancy-birth cohorts (PBC). Water quality surveillance data collected during the past decade within urban drinking-water distribution systems call for re-evaluation of water and health issues in the developed world. The objectives of this scientific commentary were to (i) highlight the extent of appraisal of water contamination in exposure assessment studies of PBC, worldwide, and (ii) propose recommendations to increase awareness of emerging water-related risks through their improved representation into PBC study designs in urban centers. Three scientific literature databases (Scopus, PubMed, and Web of Science) were used for a systematic search on worldwide PBC and their publications that considered water contamination and health outcomes. Publicly-available e-databases (ENRIECO, BIRTHCOHORTS, and CHICOS) were also employed for detailed exploration of existing European Union (EU)-based PBC. Out of the 76 PBC identified in the EU territory, only 12 of them incorporated water contamination into their study designs. Among which only 6 PBC published scientific articles that either included data on water contamination and/or water intake estimates. Trihalomethanes but not other disinfection by-products were mostly studied in the PBC around the globe, while fluoride, atrazine, perfluorinated compounds, tetrachloroethylene, and lead were studied to a lesser extent as water contaminants. It appears that chemical-based water contamination and corresponding human exposures represent a largely underappreciated niche of exposure science pertaining to pregnant mother and children's health in PBC. Future PBC studies should grasp this opportunity to substantially reform elements of water contamination in their exposure assessment protocols and effectively combine them with their epidemiological study designs.

The relationship between male BMI and waist circumference on semen quality: data from the LIFE study

STUDY QUESTION

What is the relationship between body size, physical activity and semen parameters among male partners of couples attempting to become pregnant?

SUMMARY ANSWER

Overweight and obesity are associated with a higher prevalence of low ejaculate volume, sperm concentration and total sperm count.

WHAT IS KNOWN ALREADY

Higher BMI is associated with impaired semen parameters, while increasing waist circumference (WC) is also associated with impaired semen parameters in infertile men.

STUDY DESIGN, SIZE, DURATION

Data from the Longitudinal Investigation of Fertility and the Environment (LIFE) Study were utilized. The LIFE study is a population-based prospective cohort of 501 couples attempting to conceive in two geographic areas (Texas and Michigan, USA) recruited in 2005-2009. Couples were recruited from four counties in Michigan and 12 counties in Texas to ensure a range of environmental exposures and lifestyle characteristics. In person interviews were conducted to ascertain demographic, health and reproductive histories followed by anthropometric assessment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We categorized BMI (kg/m(2)) as <25.0 (underweight and normal), 25.0-29.9 (overweight) 30.0-34.9 (obese, class I) and ≥35 (obese, class II) for analysis. Data were available for analysis in 468 men (93% participation), with a mean ± SD age of 31.8 ± 4.8 years, BMI of 29.8 ± 5.6 kg/m(2) and WC of 100.8 ± 14.2 cm. The majority of the cohort (82%) was overweight or obese with 58% reporting physical activity <1 time/week. The median sperm concentration for the men in the cohort was 60.2 M/ml with 8.6% having oligospermia (<15 M/ml).

MAIN RESULTS AND THE ROLE OF CHANCE

When examining semen parameters, ejaculate volume showed a linear decline with increasing BMI and WC (P < 0.01). Similarly, the total sperm count showed a negative linear association with WC (P < 0.01). No significant relationship was seen between body size (i.e. BMI or WC) and semen concentration, motility, vitality, morphology or DNA fragmentation index. The percentage of men with abnormal volume, concentration and total sperm increased with increasing body size (P < 0.05). No relationship between physical activity and semen parameters was identified.

LIMITATIONS, REASONS FOR CAUTION

Our cohort was largely overweight and sedentary, which may result in limited external validity, i.e. generalizability. The lack of physical activity did preclude examination of exercise more frequently than once per week, thus our ability to examine more active individuals is limited.

WIDER IMPLICATIONS OF THE FINDINGS

Body size (as measured by BMI or WC) is negatively associated with semen parameters with little influence of physical activity. Our findings are the first showing a relationship between WC and semen parameters in a sample of men without known infertility. Given the worldwide obesity epidemic, further study of the role of weight loss to improve semen parameters is warranted.

STUDY FUNDING/COMPETING INTEREST(S)

Supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (Contracts #N01-HD-3-3355, N01-HD-3-3356 and N01-HD-3-3358). There are no competing interests.

Semen quality and time to pregnancy: the Longitudinal Investigation of Fertility and the Environment Study

OBJECTIVE

To assess semen parameters and couple fecundity as measured by time to pregnancy (TTP).

DESIGN

Observational prospective cohort with longitudinal measurement of TTP.

SETTING

Sixteen Michigan/Texas counties.

PATIENT(S)

A total of 501 couples discontinuing contraception were followed for 1 year while trying to conceive; 473 men (94%) provided one semen sample, and 80% provided two samples.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Using prospectively measured TTP, fecundability odds ratios (FORs) and 95% confidence intervals (CIs) were estimated for 36 individual semen quality parameters accounting for repeated semen samples, time off contraception, abstinence, enrollment site, and couples' ages, body mass indices, and serum cotinine concentrations.

RESULT(S)

In adjusted models, semen quality parameters were associated with significantly shorter TTP as measured by FORs >1: percent motility, strict and traditional morphology, sperm head width, elongation factor, and acrosome area. Significantly longer TTPs or FORs <1 were observed for morphologic categories amorphous and round sperm heads and neck/midpiece abnormalities. No semen quality parameters achieved significance when simultaneously modeling all other significant semen parameters and covariates, except for percent coiled tail when adjusting for sperm concentration (FOR 0.99; 95% CI 0.99-1.00). Male age was consistently associated with reduced couple fecundity (FOR 0.96; 95% CI 0.93-0.99), reflecting a longer TTP across all combined models. Female but not male body mass index also conferred a longer TTP (FOR 0.98; 95% CI 0.96-0.99).

CONCLUSION(S)

Several semen measures were significantly associated with TTP when modeled individually but not jointly and in the context of relevant couple-based covariates.

What should it take to describe a substance or product as 'sperm-safe'

BACKGROUND

Male reproductive potential continues to be adversely affected by many environmental, industrial and pharmaceutical toxins. Pre-emptive testing for reproductive toxicological (side-)effects remains limited, or even non-existent. Many products that come into direct contact with spermatozoa lack adequate testing for the absence of adverse effects, and numerous products that are intended for exposure to spermatozoa have only a general assumption of safety based on the absence of evidence of actual harm. Such assumptions can have unfortunate adverse impacts on at-risk individuals (e.g. couples who are trying to conceive), illustrating a clear need for appropriate up-front testing to establish actual 'sperm safety'.

METHODS

After compiling a list of general areas within the review's scope, relevant literature and other information was obtained from the authors' personal professional libraries and archives, and supplemented as necessary using PubMed and Google searches. Review by co-authors identified and eliminated errors of omission or bias.

RESULTS

This review provides an overview of the broad range of substances, materials and products that can affect male fertility, especially through sperm fertilizing ability, along with a discussion of practical methods and bioassays for their evaluation. It is concluded that products can only be claimed to be 'sperm-safe' after performing objective, properly designed experimental studies; extrapolation from supposed predicate products or other assumptions cannot be trusted.

CONCLUSIONS

We call for adopting the precautionary principle, especially when exposure to a product might affect not only a couple's fertility potential but also the health of resulting offspring and perhaps future generations.

Preliminary examination of polymorphisms of GSTM1, GSTT1, and GSTZ1 in relation to semen quality

BACKGROUND

Environmental, lifestyle, and occupational exposures on semen quality have been investigated in epidemiological studies with inconsistent results. Genetic factors involved in toxicant activation and detoxification have been examined in relation to the risk of outcomes such as cancer, cardiovascular, and neurologic disorders. However, the effect of common genetic variants in the metabolism of toxicants on semen quality parameters has rarely been evaluated. In this analysis, we evaluated functional SNPs of three genes of the glutathione-S-transferase (GSTM1, GSTT1, GSTZ1) enzyme family.

METHODS

Participants were 228 presumed fertile men recruited as part of a community-based study. Semen outcome data from this study included total sperm count and concentration, sperm morphology, and sperm DNA integrity and chromatin maturity. DNA was obtained from 162 men from a mouth-rinse sample and genotyped for the presence of GSTT1-1 and GSTM1-1 null genotypes and the GSTZ1 SNPs at positions 94 (rs3177427) and 124 (rs3177429). We used multivariable linear regression to assess the relationship between each genotype and sperm outcomes.

RESULTS

Overall, our results did not reveal a consistent pattern between GSTM1 and GSTZ genotypes and increased occurrence of adverse sperm outcomes. However, the GSTT1 non-null genotype yielded the coefficients with the largest magnitude for sperm count and sperm concentration (beta=-0.528, 95% CI -1.238 to 0.199 and beta=-0.353, 95% CI -0.708 to 0.001, respectively), suggesting that it might be adverse.

CONCLUSIONS

These results indicate that common polymorphisms in GST genes do not negatively impact sperm parameters in healthy men with good semen quality. Contrary to expectations, the GSTT1 non-null genotype was associated with reduced sperm concentration and count in semen. Further study with a larger study size and inclusion of gene-exposure interactions is warranted.

The effect of ambient air pollution on sperm quality

BACKGROUND

Research has suggested an association with ambient air pollution and sperm quality.

OBJECTIVES

We investigated the effect of exposure to ozone (O3) and particulate matter < 2.5 microm in aerodynamic diameter (PM2.5) on sperm quality.

METHODS

We reexamined a previous cohort study of water disinfection by-products to evaluate sperm quality in 228 presumed fertile men with different air pollution profiles. Outcomes included sperm concentration, total sperm per ejaculate (count), and morphology, as well as DNA integrity and chromatin maturity. Exposures to O3 and PM2.5 were evaluated for the 90-day period before sampling. We used multivariable linear regression, which included different levels of adjustment (i.e., without and with season and temperature) to assess the relationship between exposure to air pollutants during key periods of sperm development and adverse sperm outcomes.

RESULTS

Sperm concentration and count were not associated with exposure to PM2.5, but there was evidence of an association (but not statistically significant) with O3 concentration and decreased sperm concentration and count. Additionally, a significant increase in the percentage of sperm cells with cytoplasmic drop [beta = 2.64; 95% confidence interval (CI), 0.215.06] and abnormal head (beta = 0.47; 95% CI, 0.030.92) was associated with PM2.5 concentration in the base model. However, these associations, along with all other sperm outcomes, were not significantly associated with either pollutant after controlling for season and temperature. Overall, although we found both protective and adverse effects, there was generally no consistent pattern of increased abnormal sperm quality with elevated exposure to O3 or PM2.5.

CONCLUSIONS

Exposures to O3 or PM2.5 at levels below the current National Ambient Air Quality Standards were not associated with statistically significant decrements in sperm outcomes in this cohort of fertile men. However, some results suggested effects on sperm concentration, count, and morphology.

The healthy men study: an evaluation of exposure to disinfection by-products in tap water and sperm quality

BACKGROUND

Chlorination of drinking water generates disinfection by-products (DBPs), which have been shown to disrupt spermatogenesis in rodents at high doses, suggesting that DBPs could pose a reproductive risk to men. In this study we assessed DBP exposure and testicular toxicity, as evidenced by altered semen quality.

METHODS

We conducted a cohort study to evaluate semen quality in men with well-characterized exposures to DBPs. Participants were 228 presumed fertile men with different DBP profiles. They completed a telephone interview about demographics, health history, water consumption, and other exposures and provided a semen sample. Semen outcomes included sperm concentration and morphology, as well as DNA integrity and chromatin maturity. Exposures to DBPs were evaluated by incorporating data on water consumption and bathing and showering with concentrations measured in tap water. We used multivariable linear regression to assess the relationship between exposure to DBPs and adverse sperm outcomes.

RESULTS

The mean (median) sperm concentration and sperm count were 114.2 (90.5) million/mL and 362 (265) million, respectively. The mean (median) of the four trihalomethane species (THM4) exposure was 45.7 (65.3) microg/L, and the mean (median) of the nine haloacetic acid species (HAA9) exposure was 30.7 (44.2) microg/L. These sperm parameters were not associated with exposure to these classes of DBPs. For other sperm outcomes, we found no consistent pattern of increased abnormal semen quality with elevated exposure to trihalomethanes (THMs) or haloacetic acids (HAAs). The use of alternate methods for assessing exposure to DBPs and site-specific analyses did not change these results.

CONCLUSIONS

The results of this study do not support an association between exposure to levels of DBPs near or below regulatory limits and adverse sperm outcomes in humans.