On Sept. 28, 2021, Quest Diagnostics reported that one in two (50.5%) American children under six years of age tested have detectable levels of lead, a toxic metal, in their blood, according to a new Health Trendsﾮ study published in JAMA Pediatrics. Young children living in areas with the highest percentages of pre-1950s housing and low incomes were most at risk.

The study by investigators from Quest Diagnostics and Boston Children’s Hospital is based on analysis of de-identified laboratory tests performed by Quest on 1,141,441 children under 6 years of age living in 50 states and the District of Columbia who had lead blood testing during the study period, October 2018 to February 2020. Most (71%) of the children were between the ages of 0 and 2.9 years.

With this study, Quest Diagnostics seeks to bolster incomplete national data on childhood lead exposure and investigate the individual- and community-level factors associated with blood lead levels (BLLs) in children. It is the first study of its size and scale to examine BLLs as low as 1.0 µg/dL, which the researchers deemed “detectable” BLL. In the United States, an “elevated” BLL is typically identified as ≥5.0 µg/dL, although there is no known threshold for lead-based health effects.ⁱ

While the researchers found that a little more than half of the children tested (50.5%) had a BLL of ≥1.0 µg/dL (detectable BLL), 1.9% had elevated BLL of ≥5.0 ug/dL, a more than 36% decline from the 3% identified with BLL at this level in a Quest study published previously in the Journal of Pediatrics based on data from 2009-2015. 

Still, the new Quest analysis reveals that the majority of American children have been exposed to lead, despite decades of public policies to reduce lead poisoning. A neurotoxin that causes irreversible health effects, including lower IQ, lead is found in many settings, including older homes, water pipes, and areas with heavy industry, as well as some consumer products. “No safe level of lead exposure in children has been identified,” according to the Centers for Disease Control and Prevention.