Patterns of Children's Blood Lead Screening and Blood Lead Levels in North Carolina, 2011-2018-Who Is Tested, Who Is Missed?

Abstract

Background: No safe level of lead in blood has been identified. Blood lead testing is required for children on Medicaid, but it is at the discretion of providers and parents for others. Elevated blood lead levels (EBLLs) cannot be identified in children who are not tested.

Objectives: The aims of this research were to identify determinants of lead testing and EBLLs among North Carolina children and estimate the number of additional children with EBLLs among those not tested.

Methods: We linked geocoded North Carolina birth certificates from 2011-2016 to 2010 U.S. Census data and North Carolina blood lead test results from 2011-2018. We estimated the probability of being screened for lead and created inverse probability (IP) of testing weights. We evaluated the risk of an EBLL of $\ge 3\mu g/\text{dL}$ at $<30\text{months}$ of age, conditional on characteristics at birth, using generalized linear models and then applied IP weights to account for missing blood lead results among unscreened children. We estimated the number of additional children with EBLLs of all North Carolina children using the IP-weighted population and bootstrapping to produce 95% credible intervals (CrI).

Results: Mothers of the 63.5% of children (402,002 of 633,159) linked to a blood lead test result were disproportionately young, Hispanic, Black, American Indian, or on Medicaid. In full models, maternal age $\le 20y$ [$\text{risk ratio}\left(\text{RR}\right)=1.10$; 95% confidence interval (CI): 1.13, 1.20] or smoking ($\text{RR}=$1.14; 95% CI: 1.12, 1.17); proximity to a major roadway ($\text{RR}=$1.10; 95% CI: 1.05, 1.15); proximity to a lead-releasing Toxics Release Inventory site ($\text{RR}=$1.08; 95% CI: 1.03, 1.14) or a National Emissions Inventory site ($\text{RR}=$1.11; 95% CI: 1.07, 1.14); and living in neighborhoods with more housing built before 1950 ($\text{RR}=$1.10; 95% CI: 1.05, 1.14) or before 1940 ($\text{RR}=$1.18; 95% CI: 1.11, 1.25) or more vacant housing ($\text{RR}=$1.14; 95% CI: 1.11, 1.17) were associated with an increased risk of EBLL, whereas overlap with a public water service system was associated with a decreased risk of EBLL ($\text{RR}=$0.85; 95% CI: 0.83, 0.87). Children of Black mothers were no more likely than children of White mothers to have EBLLs ($\text{RR}=$0.98; 95% CI: 0.96, 1.01). Complete blood lead screening in 2011-2018 may have identified an additional 17,543 (95% CrI: 17,462, 17,650) children with EBLLs $\ge 3\mu g/\text{dL}$.

Discussion: Our results indicate that current North Carolina lead screening strategies fail to identify over 30% (17,543 of 57,398) of children with subclinical lead poisoning and that accounting for characteristics at birth alters the conclusions about racial disparities in children's EBLLs. https://doi.org/10.1289/EHP10335.