Lead accumulation leads to lead poisoning, which can include symptoms like abdominal pain, headache, anemia, kidney dysfunction, and memory problems in adults. But, unfortunately, as Gibson saw a century ago, the highest risk of lead poisoning falls on children. Children’s growing bodies absorb more lead and, due to their exploratory nature, they tend to come into contact more with their surroundings, which potentially exposes them more.

Lead poisoning in children sets off a cascade of negative behavioral outcomes, including learning problems, hearing loss, and intellectual impairment, all linked to impaired brain development. Adults who were exposed to lead during their childhood have decreased brain volume, specifically in areas that are in charge of executive functions and decision-making such as the prefrontal cortex.

However, other factors also affect brain development, among them socioeconomic status. For example, socioeconomic status plays an important role in determining cognitive performance in children.

The study, led by Elizabeth Sowell, Professor of Pediatrics at the University of Southern California, used data from the Adolescent Brain Cognitive Development (ABCD) Study, one of the largest studies of childhood brain development. From this data, they obtained demographic, cognitive testing, and brain imaging data from 9,712 children nine to 10 years of age across 21 different sites in the United States.

The study replicated previous findings that show that children from the low-income group have lower cognitive test scores than children from middle or high-income families. The authors also examined brain imaging data, looking at the thickness, surface area, and volume of the cortex, the outer layer of the brain responsible for many higher-order functions. They found that children from low-income families had decreased cortical area and volume.

However, what was most interesting about this study was that they found a negative association between lead risk and cognitive test scores and brain morphology — but only in the low-income group. With increasing risk of lead exposure, cognitive test scores and brain volume decreased. The analysis revealed that there was an interaction between lead exposure and family income that determined worse outcomes of cognitive testing and brain structure in children.

Children from low-income families living in high-risk areas had lower cognitive test scores and smaller cortical volume than children from high-income families living in the same areas. Although these differences between low and high-income children were also present in areas that had a low risk of lead exposure, they were not as dramatic, meaning that poverty worsens the effects of lead exposure on the brains and behavior of children.

This suggests that children from low-income families may be more susceptible to toxic environmental hazards such as lead exposure and that children from higher-income families may be protected.

Recently, health and environmental agencies have attempted to significantly curtail exposure to lead by setting important limits. For example, the Center for Disease Control (CDC) set the baseline of “elevated” blood lead levels for children to 5 micrograms of lead per deciliter of blood (μg/dL), decreasing from the previous value of blood lead level of “concern” of 10 μg/dL.

In spite of more regulations, poor governmental decisions continue to plague low-income communities. One important case of lead exposure is the Flint water crisis. In 2014, the city of Flint, Michigan, changed its water source and began to obtain its water from the Flint River in a move meant to save money. With this change, came undrinkable, foul-smelling water and disease. Flint residents complained about water quality, but their objections fell on deaf ears.

Only after Virginia Tech researchers started testing the water and proving that lead levels were much higher than normal, did government officials take action. But it may have been too late. Elevated blood lead levels were found in 4.9% of children in comparison to 2.4% prior to the water source change. Children from disadvantaged neighborhoods had the greatest blood lead level increases.

This new study is important to cities like Flint, where approximately 40% of residents live in poverty. As of now, we do not know how lead exposure will affect Flint’s children, particularly those in low-income communities. Seeing as there exist socioeconomic disparities in toxic exposure to lead and other environmental pollutants in the United States, more studies need to be done to assess how these factors interact to affect brain and behavior in children in response to toxic insults. Further, using these results, it is imperative to address lead poisoning by implementing policies that have these vulnerable communities at the center.