Are Blood Lead Levels in the United States Still Declining? The US National Health Nutrition and Examination Survey (NHANES) 1999-2016

Abstract

Background: Lead is toxic without a safe limit. The current upper reference blood lead level (BLL), 5 μg/dL, came from the 97.5th percentile in children aged 1-5 years in NHANES 2007-2010.Objectives: We studied the latest trend in BLL in US NHANES and estimated the proportion of children with BLL ≥5 μg/dL, which would inform the setting of an upper reference level.Methods: We analyzed 68877 participants (aged 1 to 85 years) with BLL measurements in NHANES 1999-2016 using SPSS complex sample module v25.0.Results: In NHANES 2011-2012, 2013-2014, and 2015-2016, the mean and 95% confidence intervals (CIs) of BLLs (μg/dL) were 0.97 (0.96, 0.99), 0.86 (0.85, 0.87), and 0.82 (0.81, 0.83), respectively (P <0.0001). The estimated proportion (95% CI) of children aged 1-5 years with elevated BLL (EBLL) in 2011-2012, 2013-2014, and 2015-2016 were 2.0% (1.3, 3.0), 0.5% (0.4, 0.7), and 1.3% (0.8, 2.3), respectively (P=0.267). In 2015-2016, the proportion of children with EBLL was similar in high- and low-income groups (P = 0.9979). The estimated 97.5th percentile of BLL in children was 3.71 μg/dL in NHANES 2015-2016.Conclusions: BLL continued to decline in the overall US population. The disparity in BLL in children from higher and lower income families has decreased. Our findings support a reduction in the reference BLL, continual monitoring of population BLL and continual efforts to reduce environmental exposure to lead.