While average blood lead levels in the U.S. have declined, millions of children and adults are still exposed to various sources of lead. (1?3) Although there are known sources of lead exposure (e.g., paint in older homes, drinking water from lead pipes, soil, and consumer products), (4) it is difficult to identify communities that may have disproportionate exposures because of limitations in children’s blood lead surveillance data and gaps in environmental and other exposure data. (5) There is no known level of lead exposure to be without risk, (6?8) and many communities are disproportionately impacted. (9,10)

Identifying and addressing remaining lead exposure risk hotspots are priorities in the United States. The Federal Lead Action Plan (10) and the U.S. Environmental Protection Agency (EPA) Lead Strategy (e.g., Goal 2, “Identify Communities with High Lead Exposures and Improve Their Health Outcomes”) (9) highlight the need for lead mapping as part of whole-of-government efforts to address high exposure risk locations and disparities. Data mapping can inform screening and prioritization efforts to guide interventions and “deeper dive” analyses (such as enhancing children’s blood lead level (BLL) surveillance data analyses and lead source apportionment analyses). These analyses can assist in efforts around primary prevention; lead-based paint mitigation; lead remediation, enforcement, education, and outreach. (11) Federal agencies are collaborating to identify geographic locations and populations at risk for lead exposure so that they can be addressed proactively. Examples include targeting HUD remediation grants, EPA environmental cleanup actions, and CDC primary prevention and enhanced blood lead testing programs for children. (5)

The general approach taken for this analysis consists of the following four steps:
1. Statistically evaluated hotspots identified with lead indices against children’s BLL surveillance data:
(a) from Michigan (MI) and Ohio (OH), using the BLL data and statistical methods described in Xue et al. (12) and Stanek et al., (13) respectively, and an expanded set of national lead indices;
(b) from matching hotspots identified using lead indices with community hotspots identified in 9 state health department public reports (listed in Zartarian et al. (5)) and quantifying the percent; a match is defined here as a community with at least one census tract identified by the lead indices in our analyses;
2. Compared existing national indices against each other and against available BLL surveillance data using sensitivity, specificity, and Cohen’s kappa score to determine which indices are the statistically strongest predictors of hotspots for the national-scale analysis;
3. Produced census tract-level maps for the United States that visualize the intersection and collective combination of hotspots based on the two methods discussed in Xue et al., (12) top 20 (i.e., 80th–100th) percentiles and Getis-Ord Gi* (14) geospatial cluster hotspots analysis methods;
4. Conducted national-scale analyses to identify states and counties with the highest potential lead exposure risk, based on the considered indices and the number of children younger than six years old in the identified 2010 census tracts (n = 73,086 census tracts containing at least one child less than 6 years old in the 50 states)...