Fertility rates have been decreasing around the world since the 1960s by about 1 percent each year, according to WorldBank. The reasons are multifactorial and include both environmental and lifestyle factors, such as putting off childbirth until later years. Still, one factor that cannot be ignored is the role of environmental exposure and pollution. Chemicals, air pollution and climate change affect miscarriage rates, ovarian aging, sperm quality, stillbirth rates and hormone regulation.
Environmental effects on fertility can be difficult to measure and track, but many studies have linked environment to issues with sperm, oocytes and the ability to carry a pregnancy to term. Sharing this information with patients can be challenging. Many of them have little to no control over their level of exposure in the past and may struggle with how to address their exposure before and during pregnancy. Here is what fertility experts and OB/GYNs need to know about three key areas of environmental exposure and their effects on fertility.
Endocrine-Disrupting Chemicals
Endocrine-disrupting chemicals (EDCs) are substances that interfere with the endocrine system, thereby upsetting the body's hormonal balance. These chemicals are found in many products intended for daily use and have been linked to impaired fertility or worse pregnancy outcomes in a large body of literature over the past few decades.
EDCs include pesticides, heavy metals, parabens and other chemicals found in household cleaners and cosmetic products. Research published in Human Reproduction Update found that prolonged exposure to EDCs correlates with almost all reproductive disorders. The most evidence is found for lower fertility and lower birth weight. The researchers suggest that EDCs harm fertility by disrupting the body's hormone regulation and affect pregnancy by interfering with placental function.
Further research published in the Journal of Endocrinology analyzed multiple studies to summarize the effects of EDCs on various aspects of female reproduction in humans and animals. Pesticide exposure appears to affect ovarian and uterine tissue and function and correlates with reduced fertility. Limited studies have evaluated exposure to heavy metals — found in cigarettes, alcohol, dietary supplements, air and water — but some epidemiological studies have correlated exposure with worse pregnancy outcomes and a negative effect on in vitro fertilization (IVF) and resultant pregnancies, including fewer mature oocytes, low birth weight and preeclampsia.
Overall, studies have shown negative effects on fertility based on exposure in adulthood. Wide variability in included studies and the combination of human and animal studies makes it difficult to make any conclusions about a specific level of exposure that causes harm.
EDCs may also affect male fertility as well, but the evidence is still based on a mix of animal and human studies, making definitive conclusions difficult. Some research from Global Reproductive Health suggests that EDC exposure during gestation and before puberty could decrease sperm quality and cause testicular dysgenesis syndrome.
Your patients cannot go back in time, but they can exert some control over the chemicals they are exposed to now. If they are concerned about their exposure levels, encourage patients to eat organic produce (or, if cost is an issue, at least avoid the "dirty dozen" fruits and vegetables that the Environmental Working Group identified to be highest in trace pesticides); use natural home cleaning products, detergents and soap; and look for cosmetics without EDCs.
Air Pollution
Contaminants in the air represent a highly studied area in both humans and animals, with substantial findings of impaired fertility in men and women who live in places with high levels of air pollution. Common air pollutants include EDCs, ground-level ozone, particulate matter, benzo(a)pyrene and nitrogen dioxide. The levels of these chemicals vary widely around the world.
A study in Reproductive Biology and Endocrinology found that nitrogen dioxide, ozone and particulate matter at a level of 10 inverse megameters (mm) negatively affected IVF outcomes. Exposure to particulate matter between 2.5 mm and 10 mm was associated with reduced fertility.
Similarly, another study published in Epidemiology found that increased exposure to particulate matter may accelerate ovarian aging. China, where air pollution levels are high in many regions, has been the site of landmark research in this area. An extensive study of more than 10,000 Chinese couples who had the potential to become pregnant, published in Environment International, found that women who live in areas with high levels of particulate matter in the air had a 20 percent greater risk of infertility.
Men also experience the effects of air pollution. Many countries have observed a decline in sperm quality in the past few decades, according to a paper from Environment Health. Air pollution and other environmental exposures constitute one possible cause. Numerous studies have found a decrease in sperm quality after exposure to air pollution, including reduced sperm mobility, altered sperm morphology and reduced sperm concentration in semen.
Overall, exposure to poor air quality seems to affect fertility, with an increase in miscarriage, faster ovarian aging and reduced sperm quality. The exact exposure limits and the role of specific pollutants are difficult to pin down in studies.
Although patients may not be able to change where they live or work, they can take some steps at critical times to reduce their exposure to air pollution. Keep car windows up when driving on the highway, use an air purifier at home and, if work allows, consider staying home on days of low air quality. These additional steps may be most important when trying to get pregnant — especially when undergoing IVF — and during pregnancy.
Climate Change
Emerging research is looking for direct correlations between fertility and climate change. One area that appears impactful is human behavior. Recent research from Environmental Research Letters has suggested that the effects of climate change may encourage people in lower-income equatorial countries to have more children and prioritize work, while families in richer nations have fewer children and prioritize education. Research in the U.S. also found fewer births after extreme heat and a general move to avoid reproducing to help reduce global warming and prevent the next generation from suffering the effects.
Studies in animal species are finding that rising temperatures may affect fertility, particularly male fertility. This research finds that fertility can be impaired at temperatures below the critical thermal limit, or the maximum temperature at which a species can live. Species with external testicles require a specific temperature range; getting above that range can cause sterility. Future research is still needed to understand the effects of extreme heat on human fertility.
When it comes to climate change, little is within your patients' control, and you may even have patients with anxiety related to climate change. Talk to them about their desires for a family and listen to specific concerns. If their anxiety is more severe, you may want to refer the patient to a counselor.
Discussing Environmental Effects on Fertility With Patients
Overall, a wealth of research has shown that environmental toxins, chemicals in daily life and even climate change all play a role in male and female fertility. It can be stressful for your patients to think about these effects, especially when they have little control over some of them.
Focus on the areas your patients can control, such as choosing different cleaning products at home, and encourage individuals or couples to focus on their goals. It may help to have more specific guidance for patients to avoid air pollution, pesticides and other harmful contaminants during fertility treatment. With compassion and empathy, you can help your patients navigate these challenging issues.
