Chemicals in Yoga Mats Linked to Infertility in Women

Women with higher urinary concentrations of a common type of flame retardant had reduced likelihood of clinical pregnancy and live birth than those with lower concentrations, according to researchers at Harvard T.H. Chan School of Public Health.

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The study, conducted in the Fertility Clinic at Massachusetts General Hospital, is the first to examine associations between organophosphate flame retardants (PFRs)—which are used in polyurethane foam in many products, including upholstered furniture, baby products, gym mats, and even some phone cases—and reproductive outcomes in women. PFR's can be absorbed by the body through physical contact. These chemicals are not chemically bonded to foam and have been shown to migrate into the air and dust of indoor environments

“These findings suggest that exposure to PFRs may be one of many risk factors for lower reproductive success,” said first author Courtney Carignan. “They also add to the body of evidence indicating a need to reduce the use of these flame retardants and identify safer alternatives.”

Infertility, defined as the inability to get pregnant after 1 y or more of unprotected intercourse, affects one in six couples worldwide. One study found that pregnancy loss (miscarriage) affected approximately 28% of couples planning a pregnancy. Infertility has an associated health-care cost in the billions of dollars per year, not including the physical and psychological burden placed on the couple. Both the high rates of fertility along with the associated high costs should prompt the need to improve our understanding of risk factors that impair the ability to have a child.

One potential risk factor is environmental exposure. Several classes of endocrine-disrupting chemicals (EDCs) with widespread general population exposure, including pesticides and phthalates, have been linked to infertility and adverse pregnancy outcomes. Since EDCs are ubiquitous, only a fraction have been evaluated for effects on infertility and pregnancy. PFRs are a class of EDCs with omnipresent exposure that have been detected in 90–100% of adult urine samples. Over the past decade, PFRs have been used widely in the polyurethane foam of upholstered furniture as replacements for pentabromodiphenyl ether, a flame retardant mixture that was phased out of use in 2005.

Animal studies indicate that exposure to PFRs can disrupt endocrine function through altered thyroid action, steroidogenesis, or estrogen metabolism, and can also impair embryo development. Researchers have observed  increasing PFR exposures were associated with a decrease in sperm motility and increased serum total T3 levels, in a small study of men. 

The aforementioned study explored the association between urinary concentrations of PFRs and pregnancy outcomes among women in a prospective cohort study, the Environment And Reproductive Health (EARTH) study, using assisted reproductive technologies (ART) as a model to study early developmental endpoints and pregnancy outcomes.

In conclusion, using IVF (in vitro fertilization) as a model to investigate human reproduction and pregnancy outcomes, we found that concentrations of some urinary PFR metabolites were inversely associated with proportions of successful fertilization, implantation, clinical pregnancy, and live birth. These results highlight the potential reproductive effects of low-level exposure (i.e., background exposure levels of the general population) to PFRs and adverse IVF outcomes. Future research should focus on potential interactions between PFRs and other chemicals (i.e., mixtures analysis) that adversely affect reproductive health and also explore the potential effect of PFRs on male reproductive health.

The work was supported by grants ES009718, ES022955, ES000002, and T32ES007069 from the National Institute of Environmental Health Sciences (NIEHS).

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References

Carignan, C., Mínguez-Alarcón, L., Butt, C., Williams, P., Meeker, J., Stapleton, H., Toth, T., Ford, J. and Hauser, R. (2017). Urinary Concentrations of Organophosphate Flame Retardant Metabolites and Pregnancy Outcomes among Women Undergoing in Vitro Fertilization. Environmental Health Perspectives, 125(8). http://dx.doi.org/10.1289/EHP1021

Harvard. (2017). Common flame retardant chemicals may reduce likelihood of clinical pregnancy, live birth among women undergoing fertility treatments. [online] Available at: https://www.hsph.harvard.edu/news/press-releases/chemicals-flame-retardants-pregnancy/ [Accessed 31 Aug. 2017].