Preschool blood lead levels, language competency, and substance use in adolescence.

BACKGROUND

Elevated lead levels in children are a persistent public health problem, particularly in urban areas in the United States, yet few prospective studies have examined the association of childhood lead levels with substance use in adolescence.

OBJECTIVES

To determine the association of early lead levels with adolescent substance use and whether childhood IQ, language skills, and externalizing (aggressive and disruptive) behavior mediate the association, controlling for confounding biological and environmental factors.

METHODS

The participants (N = 265) were a subsample of a prospective birth cohort study on the developmental effects of prenatal cocaine exposure in the Midwest United States. Blood lead levels (BLL) were assessed at age 4, IQ at age 11, language skills and externalizing behavior at age 12, and substance (alcohol, tobacco, marijuana) use and substance use-related problems at age 15. Biologic assays (hair, urine, bloodspots), along with self-report, were utilized to determine adolescent substance use. Path analyses were conducted to examine the direct and indirect associations of BLL with adolescent substance use.

RESULTS

The children's mean BLL at 4 years of age was 7.07 (SD = 4.12) μg/dL. Approximately 31% of adolescents used tobacco or marijuana, 40% used alcohol, and 23% reported experiencing substance use-related problems at age 15.7 (SD = 0.28). Elevated BLL was related to a higher likelihood of substance use. Childhood language skills fully mediated the relationship of BLL with substance use-related problems. IQ was related to neither substance use nor substance use-related problems.

DISCUSSION: Elevated BLL in preschool years is a risk factor for adolescent substance use and related problems. Early screening and intervention for language impairment may reduce substance use-related problems.