Medical Research: Impacts of childhood lead-exposure risk and family income on brain development

Cognitive and brain development impairment associated with lead exposure in childhood could be exacerbated by poverty, according to a study published in Nature Medicine.

Lead exposure in childhood, even in small concentrations, is known to negatively affect cognitive and behavioural development and has also been associated with lower socioeconomic status in later life. However, the relationship of socioeconomic status in childhood and exposure to lead, and effects on brain development is not well understood.

Elizabeth Sowell, Andrew Marshall and colleagues assessed brain structure and cognitive test scores of 9,712 children 9 to 10 years of age across the United States. The authors then estimated lead exposure using lead-risk scores from the Washington State Department of Health based on each child’s residential census tract. They found that mean cognitive test scores in children from low-income families were 9% lower than those in children from high-income families. They also show that that children from low-income families living in areas with highest risk of lead exposure had an additional 3.1% reduction in cognitive testing performance compared with children from higher-income families living in the same areas. Children from lower-income families with high risk of lead exposure were also found to have increased impairment in brain structure development compared with children of similar socioeconomic status living in areas with a lower risk of lead exposure.

The authors note that they have yet to directly measure levels of lead in the children’s blood and acknowledge that the risk of exposure is a proxy measure. They conclude that small reductions in lead exposure might provide greater benefit to children experiencing more environmental adversity.