According to a preliminary study from researchers at the National Institutes of Health, couples who have high levels of PCBs and other pollutants in their blood may find themselves waiting longer to conceive.
PCBs (polychlorinated biphenyls) were widely used as dielectric and coolant fluids, for example in transformers, capacitors, and electric motors. Due to PCBs’ environmental toxicity and classification as a persistent organic pollutant, PCB production was banned by the United States Congress in 1979 and by the Stockholm Convention on Persistent Organic Pollutants in 2001. Although no longer commercially produced in the United States, PCBs may be present in products and materials produced before the 1979. PCB ban products that may contain PCBs include; oil based paint, plastics and floor finishes. PCBs are part of a category of chemicals known as persistent organochlorine pollutants and include industrial chemicals and chemical byproducts as well as pesticides. In many cases, the compounds are present in soil, water, and in the food chain. The compounds are resistant to decay, and may persist in the environment for decades. PCBs have been demonstrated to cause cancer, as well as a variety of other adverse health effects but their effect on human fertility and the likelihood of couples achieving pregnancy have not been studied extensively until now.
For this study researchers enrolled 501 couples from four counties in Michigan, and 12 counties in Texas, from 2005 to 2009 and were part of the Longitudinal Investigation of Fertility and the Environment (LIFE) study that was formed to investigate the relationship between fertility and exposure to environmental chemicals and lifestyle. An earlier investigation from LIFE had found that high blood levels of lead and cadmium also were linked to pregnancy delay.
The women’s ages in the study ranged from 18 years to 44 years and the men were all over the age of 18. Couples had given blood samples to be analyzed for PCBs and perfluorinated compounds (PFCs) used in manufactured products such as non-stick cookware, waterproof clothing, and fast-food packaging, all women had journals in which to record their monthly menstrual cycles and the results of home pregnancy tests. The couples were followed up to pregnancy or one year after trying to conceive.
By using a statistical measure called the fecundability odds ratio (FOR) in order to calculate the probability the couple would achieve pregnancy for each cycle based on their blood concentrations of the compounds. A ratio less than one suggests a longer time to pregnancy, while a ratio greater than one suggests a shorter time to pregnancy.
The researchers examined PCB congeners, which are single, unique well-defined chemical compounds in the PCB category.
The results revealed the lowest FORs were in couples were the females were exposed to PCB congener 167 and men at 138. Each standardized increase in the chemical concentration the odds of pregnancy declined by 18 to 21 percent for females exposed to PCB congeners 118, 167, 209, and the PFCs.
The odds of pregnancy declined 17 to 29% with increasing exposure in couples were the men’s exposure to PCB congeners 138, 156, 157, 167, 170, 172, and 209 and to DDE, produced when the pesticide DDT degrades in the environment. DDT was banned in the United States in 1972. Today, two dozen countries permit their residents legally to use small amounts for controlling specific insect-borne diseases. Such use releases only tiny amounts of DDT, South Africa is one of the countries
According to researchers some of the delays seen could be due to multiple chemicals and would need to be confirmed by other researchers.
Dr. Germaine Louis, PhD, M.S., Senior Investigator and Director of the Division of Epidemiology, Statistics and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), of the National Institutes of Health, and study’s first author commented in a release “Our findings suggest that persistent organochlorine pollutants may play a role in pregnancy delay.”
The study was published online in Environmental Health Perspectives