Exposure to endocrine disruptors in the uterus associated with poorer sperm quality in adulthood
A growing number of studies show that the environmental factors and lifestyle habits of pregnant women play an important role in the health of their child. But what about the semen quality of young men?
Researchers at the University of Geneva (UNIGE) in Switzerland showed two years ago that only 38% of Swiss men had semen parameters that were above the threshold values set by the World Health Organization (WHO) for fertile men. Epidemiologists from the Institute for Research and Environment (IRSET, Rennes, France), in collaboration with the UNIGE team, analyzed the possible effects of endocrine disruptors on the semen quality of men whose mothers worked in the early stages of their pregnancy.
Their results, published in the journal Human Reproduction, show that men who were exposed in the uterus to products known to contain endocrine disruptors were twice as likely to have semen volume and total sperm count per ejaculation below the WHO reference levels.
Endocrine disruptors are chemical substances of natural or synthetic origin that disrupt the endocrine system and, according to the World Health Organization (WHO), can have harmful effects on an organism or its offspring.
Several animal studies have already shown that exposure of pregnancy to certain endocrine disruptors can affect the development of the male reproductive system, as well as sperm production and semen quality in adulthood. Given Serge Nef’s team’s findings on semen quality in young Swiss men, we were interested in investigating the possible effects of exposure to endocrine disruptors during pregnancy as one of many possible reasons for the trends observed. “
Ronan Garlantézec, researcher at IRSET, Rennes University Hospital Center (CHU) and the University of Rennes
Analyzed the semen of more than 1000 conscripts
Serge Nef’s team, a professor in the Department of Genetic Medicine and Development at the UNIGE Faculty of Medicine, assessed the semen quality of around 3,000 conscripts, 1045 of whom had their mothers work during pregnancy. “A semen quality analysis was carried out for each of them in order to determine the semen volume as well as the sperm concentration, motility and morphology,” explains Serge Nef. “Before the semen analysis was carried out, the parents were also sent a detailed questionnaire, which in particular covered the maternal activities carried out during the pregnancy period of the conscripts.”
This made it possible to analyze the semen parameters of men whose mothers were employed during their pregnancy. “The maternal occupations were classified according to the International Occupational Classification (ISCO-88 of the International Labor Office of the WHO),” explains Luc Multigner, Research Director at IRSET. “Exposure to products containing endocrine disruptors during pregnancy was defined using an occupational exposure matrix, which makes it possible to assign a probability value to the exposure of the mother.”
This has enabled epidemiologists to determine probabilities of exposure to one or more categories of products that, depending on the mother’s occupation, may contain endocrine disruptors.
Endocrine disruptors associated with poor sperm quality
The results of this study show that young men exposed to endocrine disruptors in the uterus are twice as likely to have values below the reference values set by the WHO, both in terms of semen volume (threshold value at 2 ml) and the total number of Sperm per ejaculation (40 million). “In our study, pesticides, phthalates and heavy metals were the most common products associated with these anomalies,” notes Ronan Garlantézec.
“These observations do not determine the future fertility of young men, and only a follow-up examination over time will allow the consequences to be assessed. Nevertheless, the results could explain, at least in part, the poor semen quality of some young Swiss men,” continues Serge Nef. An additional study is already planned in the same population to investigate the relationship between occupational exposure of mothers to endocrine disruptors and changes in sex hormones in adulthood.
Preventing exposure to endocrine disruptors
The results of this study suggest a link between occupational exposure of the mother to endocrine disruptors and a decrease in several seminal parameters in her children as adults. “It therefore appears necessary to inform women who are planning to conceive, and in their early stages of pregnancy, about the potential dangers of exposure to these substances, which could affect the fertility of their children,” emphasizes Luc Multigner. “It would also be interesting to do a similar study in women to assess whether the effects of endocrine disruptors on the female reproductive system are the same, although this is much more complex to do,” explains Ronan Garlantézec. After all, the data concern mothers 25 years ago. Since then, the professions performed by women have evolved a lot, as has the presence of endocrine disruptors in the products used. “Hence the crucial preventive role of this study,” concludes Serge Nef.
Istvan, M. et al. (2021) Occupational exposure of the mother to endocrine disrupting chemicals during pregnancy and semen parameters in adulthood: results of a nationwide cross-sectional study among Swiss conscripts. Human reproduction. doi.org/10.1093/humrep/deab034.