Tracing the long-term legacy of childhood lead exposure: a review of three decades of the port Pirie cohort study.

Several prospective cohort studies have demonstrated that childhood lead levels show small but statistically significant adjusted associations with subsequent development in later childhood and adolescence. The Port Pirie Cohort study is one of the few prospective cohort studies to follow participants into adulthood. This paper reviews all childhood and adulthood findings of the Port Pirie Cohort study to date. Cohort members (initially, 723 infants born in/around the lead-smelting town of Port Pirie) showed a wide range of childhood blood lead levels, which peaked around 2 years old (M=21.3µg/dL, SD=1.2). At all childhood assessments, postnatal lead levels - particularly those reflecting cumulative exposure - showed small significant associations with outcomes including cognitive development, IQ, and mental health problems. While associations were substantially attenuated after adjusting for several childhood covariates, many remained statistically significant. Furthermore, average childhood blood lead showed small significant associations with some adult mental health problems for females, including anxiety problems and phobia, though associations only approached significance following covariate adjustment. Overall, there did not appear to be any age of greatest vulnerability or threshold of effect, and at all ages, females appeared more susceptible to lead-associated deficits. Together, these findings suggest that the associations between early childhood lead exposure and subsequent developmental outcomes may persist. However, as the magnitude of these effects was small, they are not discernible at the individual level, posing more of a population health concern. It appears that the combination of multiple early childhood factors best predicts later development. As such, minimising lead exposure in combination with improving other important early childhood factors such as parent-child interactions may be the best way to improve developmental outcomes.

Prospective associations between childhood low-level lead exposure and adult mental health problems: the Port Pirie cohort study.

Low-level environmental lead exposure during childhood is associated with poorer emotional/behavioural functioning in later childhood and adolescence. Scarce research has examined whether these apparent effects persist into adulthood. This study is the first to examine prospective associations between lead exposure across early childhood and several common adult mental health problems. Childhood data (including blood lead concentrations) and adult data (from mental health questionnaires and psychiatric interviews) were available for 210 participants (44% males, mean age=26.3 years) from the Port Pirie cohort study (1979-1982 birth cohort). Participants had a mean childhood (to 7 years) average blood lead concentration of 17.2µg/dL. Among females, childhood blood lead showed small significant positive associations with lifetime diagnoses of drug and alcohol abuse and social phobia, and with anxiety, somatic and antisocial personality problems. For example: for a 10µg/dL blood lead increase, females were 2.84 times (95% CI 1.10, 7.30) more likely to have an alcohol abuse diagnosis. However, adjustment for childhood covariates - particularly stimulation within the home environment - rendered these associations non-significant. No significant or sizeable unadjusted or adjusted associations were seen for males. The associations between early lead exposure and emotional/behavioural functioning in children might persist into adulthood, at least for females. However, it is unclear whether such results arise from residual confounding, or other mechanisms. Interventions that focus on improving the childhood home environment may have a long-term positive impact on adult mental health outcomes. However, more prospective research using large and representative samples is needed to substantiate these results.