Sociodemographic and behavioural determinants of blood lead concentrations in children aged 11-13 years - The Port Pirie Cohort Study

Objective: To describe the determinants of blood lead concentration in children with long term environmental exposure to lead. Design: Prospective cohort study. Setting: The lead smelting town of Port Pirie, South Australia, and surrounding townships. Participants: 326 children born in and around Port Pirie, 1979-1982, followed up until age 11-13 years in 1993-1994. Main outcome measures: Blood lead concentrations assessed at birth and at multiple ages up to 11-13 years; average lifetime blood lead concentration. Results: Mean blood lead concentration rose sharply over the ages 6 to 15 months, reached a maximum around 2 years of age, and declined steadily as the children grew older. There was no difference in blood lead concentration between boys and girls until they reached the age of 11-13 years, when mean blood lead concentration in boys (8.4 mu g/dL [0.41 mu mol/L]) was slightly higher than in girls (7.5 mu g/dL [0.36 mu mol/L]). Residential area and father's employment site were the two variables most strongly predictive of a child's blood lead concentration at the end of primary school. Poorer-quality home environment was also found to be an independent contributor to blood lead concentrations. Conclusions: Age-related factors, and possibly recent concerted efforts to decrease entry or re-entrainment of lead into the environment at Port Pirie, have resulted in most children in our study having blood lead concentrations below 10 mu g/dL (0.48 mu mol/L) at the end of their primary school years. Lead exposure during a child's early years remains an important contributor to average lifetime exposure.