MONTREAL -- Exposure to some chemicals during pregnancy seems to have negative effects on the fertility of mother's sons 20 years later, according to a new study.

The problem lies with endocrine-disrupting chemicals (EDCs), which mess with the body’s hormones. They’re found in household products, like lead paint, cosmetics, lotions, fragrance products, pesticides, and anti-bacterial soaps.

Some processed foods can also contain EDCs, which can leach out of food containers or be introduced during manufacturing.

The study, published in the medical journal Human Reproduction, is reportedly the most comprehensive look at the subject ever.

"This is a high-quality study with reliable results," said Maryse Bouchard, a professor at the School of Public Health at the Universite de Montreal.

Researchers at the National Institute of Health and Medical Research in France studied 1,045 Swiss Army recruits.

They found that those young men, who were between 18 and 22 years old, were twice as likely to have reduced fertility (in terms of the quantity and quality of their sperm) if their mother, during her pregnancy, had been exposed to at least four EDCs.

The fact that the study took place in Switzerland, a developed western country with strict standards, and that the subjects were young men who should normally be at their peak of fertility, is worrying, Bouchard said.

"We know that fertility can decline with age, but here they should be at the peak of their fertility," she said.

"The exposure levels [in Switzerland] were certainly exposure levels that would be deemed safe."

Researchers have been concerned for decades about this decline in male fertility, and it has long been suspected that environmental contaminants may have something to do with it.

"It is a study that raises important questions," Bouchard said.

The study showed that the perinatal period, both before and after pregnancy, is a "critical" phase in which to be "very careful," she said.


It is essentially impossible to escape exposure to EDCs, which are pervasive in the products we use on a daily basis, according to Bouchard.

"It's very difficult to reduce our exposure," she said. "There are certain choices we can make. But some of these products are all over the place, in all kinds of everyday products that we don't suspect."

"The truth is, we don't really know the level of risk."

Bisphenol A (BPA) is an EDC, and was once a common additive to plastic products, but it has fallen out of use, with "BPA free" labels now on water bottles and other plastic containers.

It’s mostly been replaced with "Bisphenol S" (BPS), which may be as harmful, according to some reports.

Traces of BPS have been found in the majority of tested people, according to Bouchard.

The same goes for pesticides, which can also contain EDCs. There is strong evidence that there are pesticide residues on many foods, and "almost everyone has detectable pesticide residues," Bouchard said.

What may be the biggest obstacle in limiting our EDC intake is that many companies are not required to label their products as containing the harmful chemicals, with the exception of food or certain personal products.

"We cannot always know what is in the products we are using," Bouchard said. "It can even be in our furniture or our electronic devices, which release chemicals."

"These are products that are everywhere."

The solution, she believes, would be to put in place collective measures that would protect the entire population, since you cannot isolate pregnant women or ask them to behave in a completely different way from others.

"It would be unreasonable to put this responsibility on the backs of women," she said.

-- This report by The Canadian Press was first published on April 27, 2021.