ST. LOUIS – More than four in five Missouri children under the age of 6 tested have detectable levels of lead in their blood, according to a study appearing in “The Journal of the American Medical Association.”
Researchers from Quest Diagnostics and Boston Children’s Hospital analyzed more than 1.1 million lead blood tests conducted by Quest on children living in all 50 states and the District of Columbia, from Oct. 2018 to Feb. 2020. Approximately 71% of the children tested were less than 3 years old.
This is the first study to examine blood lead levels (BLLs) as low as 1.0 µg/dL, which the researchers called “detectable” BLL. An “elevated” blood lead level is typically is ≥5.0 µg/dL.
Researchers acknowledge there is no known threshold for lead-based health effects, though scientists proved by the mid-20th century that lead poisoning can cause neurological impairments in children, such as brain and nervous system damage, slowed growth and development, learning and behavior problems, and hearing and speech problems.
Any lead found in the human bloodstream is an abnormality and should be considered potentially harmful.
The study shows 50.5% of the children tested had “detectable” blood lead levels and 1.9% had an “elevated” BLL. Quest Diagnostics researchers say this shows the majority of American children have been exposed to lead despite a decades-long campaign to reduce lead poisoning.
The key findings show young children at the greatest risk are those living in homes built before the 1950s and in zip codes with the highest levels of poverty. Children in areas with the highest levels of pre-1950s housing were nearly four times as likely to test for elevated blood lead levels (3.5% to 0.9%).
Twenty-four states had detectable levels of BLL above the 50.5% rate. The five states with the highest rates of detectable BLL are Nebraska (83%), Missouri (82%), Michigan (78%), Iowa (76%), and Utah (73%).
In addition, six states had elevated blood lead levels more than double the national average of 1.9%: Nebraska (6.0%), Ohio (5.2%), Pennsylvania (5.0%), Missouri (4.5%), Michigan (4.5%), and Wisconsin (4.3%).
The study identifies its size and national scope as strengths. The limitations include “reliance on testing orders, rather than population sampling; varying volumes of test results in certain states; and the inability to determine values below the threshold of detection.”