Methods: Participants were 265 (137 female, 128 male) adolescents, primarily African-American and of low socioeconomic status, prospectively enrolled at birth for a longitudinal neurobehavioral study of prenatal cocaine and ploy drug exposure. Blood lead levels (BLL) were measured at 4 years of age (mean= 7.07 µg/dL (SD = 4.12), range 1.3-23.8). At age 15, substance use (alcohol, tobacco, marijuana) was assessed via self-report and biologic assays (urine, hair, and blood spots). Age at first time of sexual intercourse was assessed via self-report, with early sexual behavior defined as sexual intercourse before 15th birthday. Prenatal drug exposure (cocaine, alcohol, tobacco, marijuana) and maternal psychological distress (α = .95), via the Brief Symptom Inventory, were assessed at birth. Violence exposure (α = .75), parental monitoring (α = .74), and externalizing behavior, using the Youth Self-Report, were assessed at age 12 and used as covariates.
Results: About one-third of the adolescents reported tobacco (31%), alcohol (40%), and marijuana (32%) use; and 36% reported sexual intercourse before 15th birthday. Findings from multiple logistic regression analyses indicated that, after controlling for covariates, higher BLL is related to a greater likelihood of using alcohol (OR = 1.12, 95% CI = 1.04, 1.20, p = .003), tobacco (OR = 1.07, 95% CI = 1.002, 1.15, p = .04), and marijuana (OR = 1.08, 95% CI = 1.001, 1.155, p = .047), and engaging in sexual intercourse before age 15 (OR = 1.12, 95% CI = 1.04, 1.21, p = .004). Child self-reported externalizing behavior was not related to BLL but was related to all adolescent outcomes, except alcohol use.
Conclusions: Elevated BLL in preschool years is a risk factor for adolescent substance use and early sexual behavior, demonstrating the long lasting effects of environmental lead exposure. Given the vulnerability of developing adolescent brain to the effects of drug use, the results of present study raise more attention on the detrimental effects of lead exposure on health. Continued follow-up with this sample into young adulthood will elucidate whether and how elevated BLL in preschool years may affect the chronicity or severity of substance use problems and sexual health over time.