Research Links Mixture of Old and Current Pesticides in the Environment to Developmental Effects


(Beyond Pesticides, July 11, 2011)

The findings of a research team suggest that the concentrations of the banned but still persistent insecticide chlordane and the widely used insecticide permethrin in cord blood may be associated with inflammatory cytokines (signaling molecules of the nervous and immune system important to intercellular communication) in the fetus. The results from the research team were significant because few studies on the developmental effects of chlordane and permethrin in humans have been performed, and they were the first to demonstrate an association between in utero exposures with changes in the immune systems of newborns. The data and findings are found in this month’s Research Brief by the National Institute of Environmental Health Sciences (NIEHS) Superfund Research Program, which highlights the widespread aggregate pesticide exposure that individuals in the U.S. experience, focusing on a recent study on the developmental effects of chlordane and permethrin mixtures. The study looks at the relationship between cord serum concentrations of chlordane and permethrin pesticides, gestational age, size at birth and the presence of inflammatory cytokines, which are endogenous proteins secreted as signaling compounds to coordinate immune system functions. The study, entitled “Fetal Exposure to Chlordane and Permethrin Mixtures in Relation to Inflammatory Cytokines and Birth Outcomes” was published in Environmental Science and Technology journal in January.

The research team, a collaboration between Johns Hopkins University, Centers for Disease Control and Prevention (CDC) ad Arizona State University, set out to determine whether in utero exposure to chlordane or permethrin is associated with changes in levels of cytokines at birth. A previous study by the team showed that exposure to these two pesticide compounds was ubiquitous among newborns. In the current study, researchers measured serum levels of nine cytokines and recorded birth weight, length, head circumference, and gestational age. They then collected umbilical cord serum from 300 newborns at the Johns Hopkins Hospital, and measured concentrations of cis- and trans-permethrin, oxychlordane, trans-nonachlor, and piperonyl butoxide (PBO) at the CDC.

Permethrin, belongs to the chemical class of synthetic pyrethroid pesticides which are chemically formulated versions of the natural-based pesticide pyrethrum, made from extracts from plants in the chrysanthemum family. Due in part to the prevalent myth that it is “natural,” synthetic pyrethroids are a widely used class of insecticides. Unfortunately, they have not been widely evaluated for developmental toxicity, despite the fact that they are designed to be more toxic and longer lasting than pyrethrum, and therefore more potent to insects and pose elevated risks to humans. Permethrin is a potential neurodevelopmental toxicant, a possible human carcinogen and endocrine disruptor, and exposure can cause immunotoxicity, and reproductive effects.

Furthermore, permethrin is often combined with piperonyl butoxide (PBO), also known as a synergist, to increase its toxicity. PBO is a highly toxic substance that causes a range of short- and long-term effects, including cancer and adverse impacts on liver function and the nervous system. A study published earlier this year found that children with high exposure to pyrethroid insecticides and PBO have an increased chance of learning problems.

Chlordane, the other pesticide implicated in this body of research, is an organochlorine chemical  classified by the EPA as a probable human carcinogen and is also associated with adverse neurological and gastrointestinal effects. Studies also report an association between chlordane exposure and non-Hodgkins’s lymphoma. Chlordane was registered in the U.S. in 1948 and was used as a pesticide on agricultural crops and gardens until 1978 when its registered uses on food crops and other above ground uses were cancelled. In 1988, chlordane’s termicide use and all other uses were cancelled.

Though chlordane has been cancelled for a while, this bioaccumulative chemical still persists in the environment. Current research measuring pesticide residues in the home found high levels for chlordane and permethrin, suggesting that these compounds are essentially “ubiquitous in our living areas and that popular use, both past and present, has a major influence on their occurrence in homes.” Last year, researchers found detectable levels of common, nonpersistant pesticides in umbilical cord blood. These persistent residues continue to expose people, especially vulnerable children, to the health risks associated with these chemicals.