Exposure to air pollution in utero may affect reproductive health in men

NEW YORK: While pollution has been known to cause infertility among women and even impact the unborn foetus, a new study showed that prenatal exposure to bad air may hurt men’s reproductive health too.

Cross-sectional studies in adult men and women have shown that alterations in anogenital distance -- the length between genitals and the anus -- may be related to hormone levels as well as semen quality, fertility and reproductive disorders.

In animal studies, anogenital distance is used to determine developmental toxicity of pollutants.

One measurable impact is on the reproductive system.

When anogenital distance is reduced in male offspring, it's a sign that a toxic exposure is interfering with foetal testosterone production, said lead author Emily Barrett, Professor in the Department of Biostatistics and Epidemiology at the Rutgers School of Public Health.

In the study, published in the journal Environmental Health Perspectives, researchers speculated that a similar relationship may exist in humans. They used data from an ongoing study involving 700 pregnant women and their children that tracked anogenital distance at birth in children, and at one year for boys.

These data were then compared with levels of nitrogen dioxide and fine particulate matter particle pollution (PM) 2.5 micrometres or smaller released during the burning of gasoline, oil, diesel and wood. By comparing these two measures, the researchers identified a link between exposure to air pollution during key developmental windows and anogenital distance.

For instance, higher PM2.5 exposure during the so-called male programming window at the end of the first trimester, when the male foetus typically receives a surge of hormones, was associated with shorter anogenital length at birth.

The researchers also observed that higher PM2.5 during mini puberty (a period in early infancy when hormone production is high) was associated with shorter anogenital distance in males at age one.

These findings suggest there may be multiple points during early development that the reproductive system may be vulnerable to the impacts of air pollutants.

"PM2.5 is like a trojan horse," said Barrett, adding that particulate matter can carry metals such as cadmium and lead, known endocrine disruptors.

"When these disruptors interfere with the body's hormones, the result could be lifelong impacts on our health, from cancer risks to impaired ability to conceive a child.

"These findings suggest air pollution may interfere with normal hormone activity during critical periods of prenatal and early infant development, and we suspect that disruption may have long-term consequences for reproductive health," Barrett said.