Study: Chemical exposure and pollutants may impact ability to conceive

Researchers at the National Institutes of Health are reporting that couples with high levels of PCBs and similar environmental pollutants take longer to conceive a child.

PCBs (polychlorinated biphenyls) are chemicals that have been used as coolants and lubricants in electrical equipment. They are part of a category of chemicals known as persistent organochlorine pollutants and include industrial chemicals and chemical byproducts as well as pesticides.

The compounds are also resistant to decay, and may persist in the environment for decades. Some, known as persistent lipophilic organochlorine pollutants, accumulate in fatty tissues. Another type, called perfluorochemicals, are used in clothing, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces, and the insulation of electrical wire.

Exposure to these chemical pollutants is known to have a number of effects on human health, but their effects on human fertility-- and the likelihood of couples achieving pregnancy-- have not been extensively studied.

To conduct the study, the researchers enrolled 501 couples from four counties in Michigan, and 12 counties in Texas, from 2005 to 2009. Couples provided blood samples for the analysis of organochlorines (PCBs) and perfluorochemicals (PFCs). Women kept journals to record their monthly menstrual cycles and the results of home pregnancy tests. The couples were followed until pregnancy or for up to one year of trying.

For each standardized increase in chemical concentration the researchers measured, the odds of pregnancy declined by 18 to 21 percent for females exposed to PCB congeners 118, 167, 209, and the perfluorchemical, perfluorooctane sulfonamide. Perfluorooctane sulfonamide is one of a broad class of compounds known as perfluoroalkyls, which have been used in fire fighting foams.

With increasing exposure, the odds for pregnancy declined by 17 to 29 percent for couples in which males were exposed to PCB congeners 138, 156, 157, 167, 170, 172, and 209 and to DDE, produced when the pesticide DDT degrades in the environment. DDT is banned for use in the United States, but is still used in some countries.

The investigators noted that they cannot rule out that some of the delays they observed may have been due to exposure to multiple chemicals. They added that these associations would need to be confirmed by other researchers.

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