Lead-contaminated soil abatement and urban children's blood lead levels

Abstract

Objective: To test the hypothesis that a reduction of 1000 ppm or more of lead in soil accessible to children would result in a decrease of at least 0.14 mumol/L (3 micrograms/dL) in blood lead levels.

Setting: Urban neighborhoods with a high incidence of childhood lead poisoning and high soil lead levels.

Design: Randomized controlled trial of the effects of lead-contaminated soil abatement on blood lead levels of children followed up for approximately 1 year after the intervention.

Patients: A total of 152 children less than 4 years of age with venous blood lead levels of 0.34 to 1.16 mumol/L (7 to 24 micrograms/dL). Children were largely poor and had a mean age at baseline of 32 months, a mean blood lead level of 0.60 mumol/L (12.5 micrograms/dL), and a median surface soil lead level of 2075 ppm.

Interventions: Children were randomized to one of three groups: the study group, whose homes received soil and interior dust abatement and loose paint removal; comparison group A, whose homes received interior dust abatement and loose paint removal; and comparison group B, whose homes received only interior loose paint removal.

Main outcome measures: Change in children's blood lead levels from preabatement levels to levels approximately 6 and 11 months after abatement.

Results: The mean decline in blood lead level between preabatement and 11 months after abatement was 0.12 mumol/L (2.44 micrograms/dL) in the study group (P = .001), 0.04 mumol/L (0.91 microgram/dL) in group A (P = .04), and 0.02 mumol/L (0.52 microgram/mL) in group B (P = .31). The mean blood lead level of the study group declined 0.07 mumol/L (1.53 micrograms/dL) more than that of group A (95% confidence interval [CI], -0.14 to -0.01 mumol/L [-2.87 to -0.19 micrograms/dL]) and 0.09 mumol/L (1.92 micrograms/dL) more than group B (95% CI, -0.16 to -0.03 mumol/L [-3.28 to -0.56 micrograms/dL]). When adjusted for preabatement lead level, the 11-month mean blood lead level was 0.06 mumol/L (1.28 micrograms/dL) lower in the study group as compared with group A (P = .02) and 0.07 mumol/L (1.49 micrograms/dL) lower than in group B (P = .01). The magnitude of the decline independently associated with soil abatement ranged from 0.04 to 0.08 mumol/L (0.8 to 1.6 micrograms/dL) when the impact of potential confounders, such as water, dust, and paint lead levels, children's mouthing behaviors, and other characteristics, was controlled for.

Conclusions: These results demonstrate that lead-contaminated soil contributes to the lead burden of urban children and that abatement of lead-contaminated soil around homes results in a modest decline in blood lead levels. The magnitude of reduction in blood lead level observed, however, suggests that lead-contaminated soil abatement is not likely to be a useful clinical intervention for the majority of urban children in the United States with low-level lead exposure.