EXPERT REACTION: Air pollution may affect female fertility

This is further proof environmental toxins have adverse effects on human health and reproduction.

So-called hormone disruptors are chemicals which, when present in certain concentrations, can interfere with the normal functioning of human hormonal systems. These chemicals have been associated with learning disabilities and brain development problems in children exposed to them during embryonic development as well as a number of cancers affecting both men and women.

A new European study has been released, looking specifically at nitrogen dioxide and particulate matter (levels in the atmosphere and their effects on women of childbearing age. The measured levels of these pollutants were well below the limits recommended by local authorities, but importantly, still had deleterious effects on the study population.

More than 1,300 Italian women in the Modena area had AMH (anti-Mullerian hormone) levels measured between 2007 and 2017. The study concluded that exposure to specific environmental pollutants (nitrogen dioxide, PM10 and PM2.5) was associated with a proportional decrease in AMH which is a marker of ovarian reserve and resultant female fertility.

Although the most common reason for falling AMH levels remains increasing age, the authors have concluded that air pollution may also be a significant factor and that “living in an area associated with high levels of air pollutants in our study increase the risk of severely reduced ovarian reserve by a factor of two or three.

Unfortunately, age and air pollution are factors that women can do little about.

Eating a diet rich in antioxidants, from a variety of brightly coloured fruit and vegetables, may be a positive strategy that women can undertake to prevent the damage caused by air pollution.

Early research studies also suggest that an adequate vitamin D intake and a healthy weight may also be beneficial for ovarian reserve.

It is an interesting finding but this epidemiological is relatively small and the conclusions must be interpreted with caution.

There is no evidence that air pollution is the cause. It may be that people living in more polluted areas have other unhealthy habits that may not have been taken into account in the study.

Smoking is recognised by the authors as an important confounder but the press release remains silent on whether they corrected for smoking status. Even if they did, the fact that certain people live in more polluted areas may be associated with other lifestyle factors associated with lower socioeconomic status.

It’s very hard to say whether they are on to something without seeing the detailed analysis.

This is an interesting study showing that air pollution can interfere with the finely tuned reproductive system and lower the production of Anti-Mullerian Hormone (AMH) in women.

While AMH levels are not a reliable measure of a woman’s fertility potential, the findings point to the possibility that reproductive function can be affected by environmental factors.

This fits with evidence from animal and human studies that some man-made chemicals can alter reproductive function in women and men. These chemicals are called endocrine disrupting chemicals (EDCs) and are found in every-day products such as pesticides, metals, additives or contaminants in food, and in personal care products.

However, it is important to remember that, in the case of AMH, the most important determinant of decreasing levels is the women’s age. Also, since smoking and obesity are more common in socioeconomically disadvantaged groups, it is unclear if the lower levels of AMH found in this study were linked to pollution or living in a poorer area where more people smoke and are obese.

These are very interesting findings and raise the possibility, for the first time, that changes in environmental air pollution could have serious deleterious effects on the fertility of a female population. However, it’s important to be aware that there are many interacting factors that affect long term fertility and this is, therefore, a relatively small study for such a complex area. As a result, the implications for any individual woman and her fertility remain unclear.

Ovarian reserve is an important surrogate of female fertility which declines with age and closely related to women’s various reproductive hormones. Decreased ovarian reserve is increasingly acknowledged as a significant infertility factor. Hence assessment of it has become an extremely important part of female reproductive disorder management. Anti-Mullerian hormone (AMH) produced by follicles is considered to be an effective and sensitive indicator for ovarian reserve evaluation.
 
Air pollution has adverse effects on overall health including on fertility. However, through which mechanisms air pollution impairs fertility has remained unclear until this presented big-data trial to evaluate the influence of air pollution on AMH, which revealed that exposure to increased air pollution leads to age-independent declined AMH (and thus reduces ovarian reserve) during adulthood. Women, especially in urban areas, could experience fertility issues from inhaling high concentrations of air pollution, so enhanced awareness of environmental protection (air pollution reduction) is needed among general public and authorities.
 
In Australia, infertility affects about one in six couples of reproductive age. Although by world standards Australia enjoys ‘clean’ air, our air is still polluted on a daily basis sometimes. In many Australian communities, air quality levels frequently exceed current national standards, while in other communities, inadequate monitoring means we couldn’t know enough about the levels of dirty air. Furthermore, harmful health effects occur even below levels set by air quality standard previously considered to be safe − some pollutant such as PM2.5 has been regarded with no safe level. Therefore, we still need to limit air pollution as much as possible and better pollution monitoring.