Non-persistent Pesticides Found in U.S. Mothers' Breast Milk

UC Berkeley scientists published the first pilot study of a U.S. population that found newborns and young children may be exposed to non-persistent pesticides through breast milk. Persistent pesticides and polychlorinated biphenyls, or PCBs, were also detected. Some of these non-persistent pesticides are emerging chemicals of concern because they have been associated with neurodevelopmental effects in children.

The study examined women’s breast milk samples from the urban Bay Area and rural Salinas Valley in California. All of the samples revealed measurable pesticide concentrations. For 13 of the 24 chemicals tested, including the non-persistent insecticides chlorpyrifos and cis- and trans-permethrin, the frequency of detection exceeded 90%. For most chemicals, the detection limit averaged 0.02 to 5 ng g-1 (parts per billion).1

“Non-persistent pesticides break down quickly in the environment. Since they are rapidly metabolized and excreted in the body, it was thought previously that they wouldn’t be found in breast milk,” explains lead author Rosana Hernandez Weldon, a post-doctoral fellow at UC Berkeley’s Center for Environmental Research and Children’s Health.

Non-persistent pesticides were widely adopted after persistent organochlorine pesticides were banned from manufacture and use in the United States in the 1970s, but how exposure to non-persistent pesticides affects most people is still largely unknown, according to the Centers for Disease Control and Prevention (pdf).

“One of the motivations for conducting this investigation was to understand the exposures of neonates so that we could develop better informed epidemiological studies of the health effects,” says Weldon. Recently, her co-authors from the CHAMACOS study have found associations between organophosphate pesticides and neurodevelopment.2 Others have shown that persistent pesticides and PCBs are potential endocrine disruptors.

The authors do not speculate on the source of exposure for non-persistent pesticides, but Weldon believes the findings point to nutrition. “It was interesting that the median concentrations of non-persistent pesticides were similar for urban and rural populations,” says Weldon. “The urban population doesn’t have any direct exposure from their environment for the most part, so we suspected it was diet. Persistent pesticides also tend to accumulate higher in the food chain, such as fatty foods.”

Recognizing that many people cannot afford organic produce, Weldon recommends washing fruits and vegetables to remove any excess pesticide residue. Study authors also stress that breast feeding remains the optimal source of nutrition for infants.3 ”The benefits of breast feeding outweigh the risks of pesticide exposure, such as mother child bonding and the health benefits to the mother and child postpartum,” says Weldon.

The pilot, funded through a fellowship from the Environmental Protection Agency (EPA), was designed to inform an in depth study of pesticide exposure and lactation. Currently, researchers are measuring non-persistent and persistent pesticides in subset of approximately sixty mothers from the CHAMACOS study. Participants provided milk samples near the time of birth and again six months postpartum. Weldon notes, “Ultimately, we would like to see our research determine sources of exposure so effective policies can be developed to protect mothers of childbearing age and their breast feeding infants.”

The EPA has shown interest in the multiresidue laboratory method developed to measure non-persistent pesticides, according to Weldon. She suggests the findings on non-persistent pesticides, such as chlorpyrifos, will likely be considered in the current (EPA) review.

UC Berkeley co-authors of the paper, published in the Journal of Environmental Monitoring, include CERCH investigators Celina Trujillo, Asa Bradman, Nina Holland, and Brenda Eskenazi.

1,3 Weldon RH, Barr DB, Trujillo C, Bradman A, Holland N, Eskenazi B. A Pilot Study of Pesticides and PCBs in the Breast Milk of Women Residing in Urban and Agricultural Communities of California. J Environ Monit. 2011 Nov;13(11):3136-44

Eskenazi B, Huen K, Marks A, Harley KG, Bradman A, Barr DB, Holland N. PON1 and neurodevelopment in children from the CHAMACOS study exposed to organophosphate pesticides in utero.Environ Health Perspect. 2010 Dec;118(12):1775-81.

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