Study links childhood toxin exposure, poverty to lower IQs
Source: Amanda Peterka, E&E reporter • Posted: Tuesday, May 5, 2015
Columbia University researchers found that children from low-income households who are exposed to airborne chemicals before birth demonstrated lower IQs than children from more economically secure households who were exposed to less pollution.
The study is significant, researchers said, because it adds to growing evidence that poverty increases the negative health effects of toxic substances.
It also shows that the developing fetus is particularly susceptible to negative impacts from pollution, they said. Previously, the research team linked prenatal exposure to polycyclic aromatic hydrocarbons (PAHs) with increased risk of attention deficit hyperactivity disorder (ADHD) (E&ENews PM, Nov. 5, 2014).
“The findings support policy interventions to reduce air pollution exposure in urban areas as well as programs to screen women early in pregnancy to identify those in need of psychological or material support,” said Frederica Perera, lead author of the study and director of the Columbia Center for Children’s Environmental Health, in a statement last week.
The study was first published online April 23 in the journal Neurotoxicology and Teratology. It was funded by the National Institute for Environmental Health Sciences and U.S. EPA.
The Columbia team followed 276 children from gestation through age 7 whose mothers lived in New York City. They obtained information about socioeconomic status from the mothers through interviews.
The researchers used biomarkers to assess a child’s exposure at birth to PAHs, which are released through the incomplete combustion of fossil fuels. At age 7, trained research workers administered an IQ test.
The relationship between PAH exposure and lower IQs was statistically significant for children whose mothers reported high hardships — defined as the lack of food, clothing or housing — during gestation and after birth.
Among the group of children with high levels of hardship, children scored between 5 and 7 points lower on tests measuring overall IQ, perceptual reasoning and working memory.
“The findings are of concern because, as has been shown with lead, even a modest decrease in IQ can impact lifetime earnings,” the researchers wrote. “They are also consistent with studies showing modification of the neurotoxic effect of lead by social class.”
There was no significant relationship between PAHs and IQ levels in children whose mothers reported economic security.
The authors said mechanisms that accounted for the greater effects on children from low-income households were not well understood. They suggested that chronic psychosocial stress brought about by economic hardship could interfere with the normal functioning of the body.
Another possibility is that PAHs are equally toxic regardless of economic status, but that families with fewer economic hardships have access to resources that lead to the development of healthier children and buffer the impacts of PAH exposure.
“The present results suggest the need for a multifaceted approach to reduce PAH exposure and alleviate material hardship in