Racially isolated North Carolina neighborhoods are associated with higher blood lead levels in children 

1. Children living in areas of North Carolina composed predominantly of non-Hispanic Black individuals had higher blood lead levels than children living in areas with fewer non-Hispanic Black individuals.

2. This relationship persisted from the early 1990s to 2015, despite the decline of blood lead levels over time in North Carolina.

Evidence Rating Level: 2 (Good)

Study Rundown: Racial residential segregation (RRS) — the geographic separation of racial or ethnic groups — has been linked to worse health outcomes and increased mortality. Given that one’s level of exposure to environmental toxins is affected directly by where one lives, this ecological study sought to determine if living in more racially isolated areas would be associated with increased childhood lead exposure. Even at low levels, lead exposure puts children at risk for learning deficits, decreased intelligence, and lower socioeconomic status in adulthood. The blood lead levels (BLLs) of 320,916 children across North Carolina were analyzed. BLLs obtained during 2 date ranges (from 1992 to 1996, and from 2013 to 2015) were included. The blood lead testing data contained the child’s home address, and the racial isolation (RI) experienced by each neighborhood in the sample was measured by census data. The greater the proportion of non-Hispanic Black (NHB) individuals in a given community, the higher their RI. Regression analysis was applied between BLL and census-tract RI, while controlling for socioeconomic factors. Higher RI was associated with greater BLL in both NHB and non-Hispanic White (NHW) individuals. This relationship persisted from 1992 to 2015, although it diminished over time. This study demonstrates that racial isolation, independent of socioeconomic status, is associated with increased BLLs, and adds to the growing body of evidence suggesting that structural racism may be implicated in health disparities between NHB and NHW Americans. Further investigation into the cause of this relationship and the development of strategies to reduce BLLs is urgently needed.

Click to read the study in Pediatrics

Relevant Reading: Blood lead levels in U.S. children ages 1-11 years 

In-Depth [ecological study]: Blood lead testing data from 320,916 children younger than 7 years of age across all 100 North Carolina counties were obtained from the Childhood Lead Poisoning Prevention Program of the North Carolina Department of Health and Human Services. The sample was restricted to samples collected during 2 date ranges: from 1992 to 1996 (n = 154 366) and from 2013 to 2015 (n = 166 550). Regression analysis was applied between BLL and census-tract RI. The regression models were stratified by race (NHB and NHW) and year (1992-1996 and 2013-2015) and adjusted for the season during which the blood lead test was performed, the census tract-level percentage of the population with at least a college degree, and the census tract-level percentage of the population receiving public assistance. From 1992 to 2015, the distribution of RI across North Carolina remained stable. Between 1992 to 1996 and 2013 to 2015, BLLs declined in both NHB and NHW children across North Carolina, with mean (median) BLLs declining from 6.7 ug/dL (6 ug/dL) to 1.6 ug/dL (1 ug/dL) in NHB children and mean (median) BLLs declining from 4.9 ug/dL (4 ug/dL) to 1.5 ug/dL (1 ug/dL) in NHW children. From 1992 to 1996, a 1-standard-deviation (SD) higher value of RI was associated with a 2.86% [CI 0.96%-4.81%] greater BLL in NHB children and a 2.44% [CI 1.34%-3.56%] greater BLL in NHW children. This relationship persisted but was diminished from 2013 to 2015, with a 1-SD higher value of RI being associated with a 1.59% [CI 0.50%-2.70%] greater BLL in NHB children and a 0.76% [CI 0.08%-1.45%] greater value in NHW children.

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