(Beyond Pesticides, October 20, 2008) Organophosphate (OP) pesticides are among a toxic soup of hazardous chemicals found in the bodies of pregnant women, according to an National Institutes of Environmental Health Sciences (NIEHS) led study doi:10.1016/j.envres.2008.07.014 published in the October issue of the journal Environmental Research. The population-based birth cohort study analyzed urine specimens of one hundred pregnant women. The study builds on the existing body of evidence that shows that low-level exposure to chemicals impact human health, especially pregnant women and their children.
The research is part of the Generation R Study, which includes 9778 participants in the Netherlands and focuses on growth and physical development, behavioral and cognitive development, childhood diseases and health, and health care for pregnant women and children. The Generation R Study allows the researchers to follow-up with the study participants and “provides an opportunity to efficiently address questions regarding the reproductive and development effects of prenatal exposures.”
Besides finding high levels of OP pesticides, the researchers find some suspected endocrine disrupting compounds including bisphenol A (BPA) and phthalates. Animal studies show that these chemicals can affect brain and reproductive development. According to the researchers, exposure to OP pesticides and some phthalates were significantly higher for the subjects from the Generation R study when compared to similar populations in other studies. The scientists agree that it may be necessary to obtain and analyze data throughout the entire pregnancy in order to identify critical time periods of exposure.
The study’s lead author, Xibiao Ye, Ph.D., is a member of the NIEHS Biomarker-based Epidemiology Group, which is headed by co-author and Principal Investigator Matthew Longnecker, M.D., Sc.D. The Biomarker-based Epidemiology Group focuses on health effects of early exposure to background levels of environmental contaminants. This study is the first report of biological monitoring of these specific pollutants in a general population in the Netherlands.
Levels of 6 dialkyl phosphate (DAP) metabolites of OP pesticides, a specific metabolite of the widely used pesticide chloropyrifos, TCPy, BPA and fourteen phthalate metabolites were analyzed by the research team. BPA is used in the manufacturing of plastics and epoxy resins. Phthalates are commonly included in cosmetics and polyvinyl chloride plastics.
Organophosphates, derived from World War II nerve agents, are a common class of chemicals used in pesticides and are considered to be the most likely pesticides to cause an acute poisoning. Many are already banned in England, Sweden and Denmark. Organophosphate pesticides are extremely toxic to the nervous system. They are cholinesterase inhibitors and bind irreversibly to the active site of an enzyme essential for normal nerve impulse transmission- acetylcholine esterase (AchE), inactivating the enzyme. Researchers show that animal studies and residual effects in humans following acute intoxication suggest that organophosphates can be toxic to the developing brain at exposure levels below those inducing overt signs.
Earlier this year, a team of University of Michigan scientists discovered that interactions between genes and organophosphate exposure can cause some forms of motor neuron disease (MND). The scientists also find the mutations caused changes in a protein already known to be involved when people develop neurologic disorders as a result of exposure to toxic organophosphate chemicals.
Many U.S. residents carry toxic pesticides in their bodies above government assessed “acceptable” levels, the highest being children and women, according to several biomonitoring studies and reports published over the several years. A study published in February 2008 finds that children who eat a conventional diet of food produced with chemical-intensive practices carry residues of organophosate pesticides that are reduced or eliminated when they switch to an organic diet. In 1997 a study conducted in a Central Valley farming community in California found that residents have significant levels of the organophosphate chlorpyrifos in their bodies during the spraying season. The levels topped what the U.S. Environmental Protection Agency (EPA) considers acceptable for pregnant and nursing women.
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. The cancellation of household uses does not restrict, however, the use of remaining stocks. That is to say, 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 the EPA, approximately one million pounds of malathion are applied annually for residential uses.