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Blood lead declines, leading the CDC to change its reference value

The reference value from the Centers for Disease Control and Prevention for levels of lead in the blood continues to decline, according to a new report in Morbidity and Mortality Weekly. The Blood Lead Reference Value (BLRV) “is not a health-based standard or a toxicity threshold,” the authors note, “but is a value that is or should be used to prioritize mitigation efforts on a population level.”

The BLRV is based on the 97.5th percentile of blood lead levels for children aged 1–5 years in the population as a whole, meaning that 97.5% of children have a value below that level. 

The new reference value is 3.5 micrograms/deciliter of blood, down from the value set in 2012 of 5 μg/dL. The reduction in the BLRV over time is good news, indicating a population-wide reduction of lead in the blood.

The CDC began defining levels of elevated lead in 1970, using 40 μg/dL as indicating “undue or increased lead absorption.” Terminology changed over time, and in 1978, they defined 30 μg/dL as an “elevated blood level.” In 1991, 10 μg/dL was defined as a “level of concern.” They adopted the reference value standard in 2012.

“The geometric mean [blood lead level] in US children aged 1-5 years has declined over time from 15.2 μg/dL in 1976-1980 to 0.83 μg/dL in 2011-2016,” the authors note, but that “certain children remain at substantial risk for exposure to lead and disproportionately experience negative health consequences,” reflecting both persistent unmitigated lead in housing, water supply, and other elements of the environment, and less access to health care. “Thus, lead exposure can be considered both a result and cause of health inequity and environmental injustice.”

Reference

Ruckart PZ, Jones RL, Courtney JG, et al. Update of the Blood Lead Reference Value - United States, 2021. MMWR Morb Mortal Wkly Rep. 2021 Oct 29;70(43):1509-1512.