May 19, 2021

More information about how air pollution harms reproduction

We have begun the work of producing three educational videos on how air pollution harms reproduction. It is an effort that involves many scientists with an interest in this field and the Campion Fund is extremely gratified for their efforts with a special shout out to Nabu Creative Studios. We anticipate that we will have the videos finalized and posted in the spring of 2022. In the course of writing dialog, I have come across a published systematic review written by scientists in Toulouse, France that I urge you to read for an understanding of the issues on air pollution and its effects on reproduction: Carré J, Gatimel N,  Moreau J, Parinaud J, Léandri R. Does air pollution play a role in infertility?: a systematic review. Environmental Health  2017, 16:82 DOI 10.1186/s12940-017-0291-8

Their conclusion is “both animal and human epidemiological studies support the idea that air pollutants cause defects during gametogenesis lead to a drop in reproductive capacities in exposed populations. Air quality has an impact on overall health as well as on the reproductive function, so increased awareness of environmental protection issues is needed among the general population and authorities”.

The authors screened 425 articles in April 2016 using the PubMed database. After excluding papers that did not focus on fertility, studies of animals that were not mammals and studies from in vitro culture they systematically analyzed their findings with appropriate methodologies. They did however look at non-mammal and in vitro studies for the purpose of understanding the mechanisms of how pollution causes harm to fertility. Sixty-one articles were included in the analysis.

Of interest are their descriptive list of the four mechanisms that are possible causes of the action of air pollution on fertility.  These are: 1. Change in hormones due to endocrine disruptors (compounds in polluted air that exhibit estrogenic, or anti-estrogenic or anti-androgenic activity). One example is the action of compounds found in diesel exhaust. 2. Induction of reactive oxygen species (ROS). These are compounds such as ozone (O3), heavy metals, or polycarbonates (found in plastics) which produce oxidized proteins in the body that harm normal biochemical pathways. For instance, a reaction called peroxidation of sperm DNA can lead to breakage of the DNA strands and can cause genetic mutations. These events can lead to a decrease of the sperm’s ability to fertilize the egg (oocyte). ROS (reactive oxygen species) can also lead to a type of cell death called apoptosis. 3. Another mechanism of action of air pollution is the induction of alterations in cell DNA. As an example, decreased telomere lengths can occur on exposure to air pollution due to this mechanism. Telomeres are sections of DNA found at the end of each chromosome. As individuals age and each cell divides the telomeres get shorter and shorter. Exposure to air pollution will also cause telomere lengths to shorten. 4. Epigenetic modifications occur.  Epigenetic changes cause modifications in gene expression but do not involve alterations in the DNA sequence itself.  These changes can be due to hypo- or hyper methylation or alterations in microRNAs (small non-coding RNAs that function in RNA silencing and post-transcriptional regulation of gene expression. In a study of placentas microRNAs, (MiR-21, MiR-146a, MiR-222) were harmed by exposure to PM 2.5 air pollution in the second trimester of pregnancy.

Good reproductive health is vital to all humans.  Our very survival depends on healthy reproduction. It is very important therefore that the general public and scientists alike increase awareness of how air pollution harms reproduction.

Phyllis C. Leppert, MD, PhD