Researchers from the Columbia Center for Children's Environmental Health at the Mailman School of Public Health report evidence of a link between prenatal exposure to the insecticide chlorpyrifos and deficits in IQ and working memory at age seven. This is the first study to evaluate the neurotoxicity of prenatal chlorpyrifos exposure on cognitive development at the time of school entry. Findings are online in Environmental Health Perspectives.
Until banned for indoor residential use by the U.S. Environmental Protection Agency in 2001, chlorpyrifos, an organophosphate pesticide, was one of the most widely used insecticides for residential pest control. In a sample of 265 New York City minority children, born prior to the ban, the researchers found evidence that increases in the amount of chlorpyrifos in the babies' umbilical cord blood were associated with decreases in performance on a measure of cognitive functioning at age 7. Specifically, higher prenatal exposure was associated with lower scores on two different scales of the Wechsler Intelligence Scales for Children (WISC-IV). On average, for each standard deviation increase in chlorpyrifos exposure, the full-Scale IQ was reduced by 1.4% (0.94 to 1.8 points) and Working Memory was reduced by 2.8% (1.6 to 3.7 points). This means that those children who have exposures in the upper 25% of the exposure distribution will score, on average, 5.5% (or 5.3 points) lower on the test of Working memory, and 2.7% (or 2.7) points lower on Full-scale IQ, as compared to those children in the lowest quartile. Furthermore, the decline in test scores begins at the lowest exposures and continues downward with increasing exposure levels. This suggests no evidence of a threshold, below which exposures are completely safe.
The Columbia researchers had previously reported that, prior to the ban, chlorpyrifos was detected in 100% of personal and indoor air samples, and 70% of umbilical cord blood collected from babies. They also reported that the amount of chlorpyrifos in babies' blood was associated with neurodevelopmental problems at age three. The new findings suggest that the relationship between prenatal chlorpyrifos exposure and neurodevelopmental deficits among cohort children persists through age seven, with possible longer-term educational implications.
"These observed deficits in cognitive functioning at 7 years of age could have implications for school performance," noted Virginia Rauh, ScD, deputy director of the Columbia Center for Children's Environmental Health (CCCEH), and lead author of the study. "Working memory problems may interfere with reading comprehension, learning and academic achievement, even if general intelligence remains in the normal range."
The good news, reports Robin Whyatt, DrPH, senior author on the paper, is that since the EPA ban took effect, exposure to the organophosphate has measurably declined. CCCEH scientists have found a 3-fold decrease in chlorpyrifos levels in personal and indoor air samples in the cohort and a more than 5-fold decrease in blood levels.
"However, agricultural use of chlorpyrifos is still permitted in the U.S.," says Dr. Whyatt, professor of Clinical Environmental Health Sciences and deputy director of CCCEH. "It is vitally important that we continue to monitor the levels of exposure in potentially vulnerable populations, especially in pregnant women in agricultural communities, as their infants may continue to be at risk."
Also published in Environmental Health Perspectives today, two other NIEHS/EPA funded Children's Environmental Health Centers present independent investigations of organophosphate pesticides and neurodevelopment. Although findings cannot be directly compared, these studies also found early cognitive and behavioral effects associated with prenatal organophosphate exposure.
The study at the Columbia Center for Children's Environmental Health was supported by the National Institute of Environmental Health Sciences, EPA, and several private foundations.
About the Mailman School of Public Health
Founded in 1922 as one of the first three public health academies in the nation, Columbia University's Mailman School of Public Health pursues an agenda of research, education, and service to address the critical and complex public health issues affecting New Yorkers, the nation and the world. The Mailman School is the third largest recipient of NIH grants among schools of public health. Its 300 multi-disciplinary faculty members work in more than 100 countries around the world, addressing such issues as infectious and chronic diseases, environmental health, maternal and child health, health policy, climate change & health, and public health preparedness. It is a leader in public health education with over 1,000 graduate students from more than 40 nations pursuing a variety of master's and doctoral degree programs. The Mailman School is also home to numerous world-renowned research centers including the International Center for AIDS Care and Treatment Programs (ICAP), the National Center for Disaster Preparedness and the Center for Infection and Immunity. For more information, please visit www.mailman.columbia.edu
About the Columbia Center for Children's Environmental Health
The Columbia Center for Children's Environmental Health (CCCEH) carries out community-based research in northern Manhattan and the South Bronx to examine the health effects of prenatal and early postnatal exposures to common urban air pollutants, with the aim of preventing environmentally related disease in children. The Center is unique in the field of scientific research because it applies the results of its research to interventions that reduce toxic pesticide use; conducts a community education campaign to increase environmental health awareness among local residents, parents, health professionals and educators; and informs public interest groups, elected officials, and other policymakers who can shape policies to improve the environmental health status of underserved neighborhoods. The Center's overall mission is to improve prevention and clinical treatment, and work with community-based organizations to improve their neighborhood's environmental health. Our lead community partner is WE ACT for Environmental Justice. For more information, please visit www.ccceh.org