Trends in Blood Lead Levels in the U.S. From 1999 to 2016

Abstract

Introduction: Trends in blood lead levels in the same birth cohort (generation) are necessary to identify the lead load in the population. This analysis uses a nationally representative sample to investigate the trends in blood lead levels from 1999 to 2016 by birth cohort and to revisit the association between blood lead levels and age.

Methods: Data from the 1996 to 2016 National Health and Nutrition Examination Surveys were used to describe the distribution of blood lead levels. Trends in blood lead levels were analyzed using joinpoint regression models. Association of blood lead levels with age was conducted with both cross-sectional and birth cohort analysis. Analyses were conducted in 2020.

Results: In total, 68,877 participants were included (weighted mean age=38.4 years, 50.6% female). From 1999 to 2016, the geometric mean of blood lead levels decreased from 1.68 µg/dL (95% CI=1.63, 1.74) to 0.82 µg/dL (95% CI=0.77, 0.87). The annual percentage change estimated by the joinpoint model was -4.26% (p<0.05). The associations between blood lead levels and age were "U"-shaped by cross-sectional analysis, with higher risks for the lowest and highest ages. However, by birth cohort analysis the blood lead levels declined monotonically with age. The joinpoint analysis indicated the inflection point of age 13-17 years and statistically significant differences in decline slopes before and after this age.

Conclusions: In this nationally representative study of the U.S. population, estimates of blood lead levels showed an overall decrease from 1999 to 2016. Blood lead levels are highest in childhood.