Time Required for Blood Lead Levels to Decline in Nonchelated Children

Abstract

Objective: To determine the time for a decline in blood lead to less than 10 μg/ dL in nonchelated children who are enrolled in case management. Study Design: Retrospective analysis of venous blood lead data of lead-poisoned children followed in a case management program designed to decrease lead exposure. Children were excluded if their blood lead had not yet declined to less than 10 μg/dL, if they received chelation therapy, or if they had not received follow-up for more than 15 months. We calculated the time between peak elevation of lead and decline to less than 10 μg/dL. Data were categorized based on the child's peak blood lead and season in which their peak blood lead occurred. Data were analyzed using ANOVA and linear regression. Kaplan-Meier survival analysis was used to describe data in population form. Results: 579 patients were included in the analysis. Blood leads of 25–29, 20–24, 15–19, and 10–14 μg/dL required 24.0, 20.9, 14.3, and 9.2 months, respectively, to decline to less than 10 μg/dL. For continuous data, a linear relationship was described by the following equation: Time (# of months required to achieve a blood lead less than 10 μg/dL) = 0.845 × peak lead; p < 0.0001. Kaplan-Meier curves complement the findings in a population-based fashion. Conclusions: The mean time for blood lead to decline was linearly related to the peak in blood lead. The time for 50% of the blood lead to decline to less than 10 μg/dL was not linear and varied with peak lead.