Couples exposed to common chemicals take longer to conceive

A preliminary study from the National Institutes of Health (NIH), USA, suggests that environmental pollutants including industrial chemicals and pesticides may be impairing human fertility, despite being banned more than thirty years ago.

The researchers identified 501 couples who were trying to conceive within two months and followed them for one year. The results showed that those with high levels of organochlorine compounds, including polychlorinated biphenyls (PCBs), in their bodies took around 20 percent longer to conceive compared to couples with lower exposures. This delay is comparable to that caused by a range of other factors known to significantly reduce fertility, including smoking, obesity and older age.

'Our findings suggest that persistent organochlorine pollutants may play a role in pregnancy delay', said study author Dr Germaine Buck Louis at the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, Maryland.

Although no longer manufactured, PCBs are still found in many old household and building materials, including caulking, oil-based paint, floor varnish and insulation. Part of a group of chemicals called organochlorine compounds, which can cause adverse health effects, PCBs are resistant to decay and easily permeate the environment around them. They are still regularly identified in soil, water and some food products. People can reduce their future exposure to PCBs by limiting their consumption of animal products, especially fatty meat and fish, explained Dr Louis.

The couples in the study were asked to provide regular blood and urine samples before conceiving, as well as daily diaries, interviews and pregnancy tests. They were screened for 63 different environmental chemicals in total.

Virtually everyone had detectable levels of PCBs. They also showed the presence of DDE (1,1-dichloro-2,2-bis(chlorophenyl)-ethylene), a breakdown product of the pesticide DDT (Dichlorodiphenyl-Trichloroacetic Acid), which was removed from use in the UK in 1984. DDT was used as an insecticide during World War II in an attempt to fight malaria and typhus, but was later withdrawn after links were made to miscarriage, low birth weight and an increased risk of developmental problems in children.

Researchers noted that a delay in becoming pregnant could be caused by exposure to a combination of chemicals. They have recommended further studies to examine causation. 'Many factors can affect when or if a pregnancy occurs and, while this study attempted to address some of those outside issues, not all were taken into account', said a spokeswoman for the American Chemistry Council.

'The [study] authors themselves note that the study has significant limitations, including lack of data on specific exposures to some chemicals. Given the large number of statistical analyses involved in this report, it is not surprising that some associations were found', she added.