(Beyond Pesticides, April 9, 2012) A new study finds that exposure of pregnant women to organophosphate (OP) pesticides —a widely used class of pesticides in North American agriculture— may affect both length of pregnancy and birth weight. Environmental Health Perspectives published the paper, “Associations of Prenatal Exposure to Organophosphate Pesticide Metabolites,” last Thursday, April 5, 2012. The study, by a Simon Fraser University researcher, finds that the population of 306 women in Cincinnati, Ohio, is representative of the type of exposures most North American women and their children experience. Although the use of OPs in Canada and the U.S. has declined in recent years, exposures remain widespread, and these findings add to growing evidence about the harmful effects of low-level exposures to environmental toxicants.
The researchers collected urine from each of the women in Cincinnati twice during their pregnancies for organophosphate metabolites as well as other factors that could influence the fetus’ health, including exposure to second hand smoke, race, and poverty. Women with higher levels of organophosphates were found to have pregnancies that were three to four days shorter and babies that were about â…“ pound lighter on average than women with lower levels of pesticides.
“For an individual child, a decrement of 150-gram reduction in birth weight is of little consequence, but this is just one of many risk factors that a pregnant woman might encounter. If a woman has four or five risk factors, the impact can be substantial,” explains the study’s senior author, SFU health sciences professor Bruce Lanphear, M.D. “The decrement in birth weight that we found for OP pesticide exposure was comparable with the decrement seen for women who smoke cigarettes.”
Organophosphates are a common class of chemicals used in pesticides and are considered to be among the most likely pesticides to cause an acute poisoning. Many are already banned in several European countries. Organophosphate pesticides are extremely toxic to the nervous system, as they are cholinesterase inhibitors and bind irreversibly to the active site of an enzyme essential for normal nerve impulse transmission.
Despite numerous organophosphate poisonings of farmworkers, homeowners, and children, the U.S. Environmental Protection Agency (EPA) has allowed the continued registration of these products. In some cases, such as those of chlorpyrifos and diazinon, household uses of the products have been cancelled because of the extreme health risks to children, but agricultural, golf course, and “public health” (mosquito control) uses remain on the market. Furthermore, the cancellation of household uses does not restrict, the use of remaining stocks, meaning homeowners who purchased diazinon, for example, before the 2004 phase-out, may still use this product. Malathion, another common organophosphate, is still permitted for residential use as an insecticide and nematicide, even though all organophosphates have the same mode of action in damaging the nervous system. According to EPA, approximately one million pounds of malathion are applied annually for residential uses.
In order to reduce exposure to these chemicals, Dr. Lanphear recommends that expectant mothers choose organic foods. He also recommends that families stop using pesticides in and around the home and to advocate banning cosmetic pesticides in their communities. For more information on what you can do, see our materials for new parents with tips on food choices and safer pest management, specifically designed for new moms and dads.
To see more scientific research on the effects of pesticides on human health, including birth defects, see our Pesticide-Induced Diseases Database.