Environmental lead exposure and socio-behavioural adjustment in the early teens: the birth to twenty cohort.

Lead exposure remains high in South Africa. Environmental lead exposure has been associated with behaviour problems in childhood and adolescence. The objective of this study was to determine the relationship between blood lead levels and socio-behavioural problems among young adolescents in the Birth to Twenty cohort (Bt20). The uniquely South African Bt20 cohort started in 1989 and is a long-term prospective follow-up study of the health and well-being of children born in the Greater Johannesburg area. The total analytical sample size consisted of 1041 adolescents (487 males and 554 females). Blood lead levels were obtained from whole venous blood that was collected. Thirty two items representing Rule-breaking and Aggressive behavioural characteristics from the Youth Self Report (YSR) were assessed. Bivariate and multiple regression analyses were conducted to assess for associations between blood lead levels and socio-behavioural problems at 13 years of age. The geometric mean blood lead level was significantly (P value < 0.001) higher in boys (6.0 μg/dl) compared to girls (4.5 μg/dl). In the total analytical sample four behavioural items were significantly associated with the geometric mean blood lead levels. When stratifying the sample by sex, the bivariate analyses showed that boys' blood lead levels were significantly associated with four types of aggressive behaviour. There were no significant associations found in girls. The multivariate analysis was conducted in the boys sample and after adjusting for socio-economic factors "Attacking People" remained significantly associated with blood lead levels. High blood lead levels are associated with anti-social and destructive behaviour amongst boys in their early teens. However, the relationships are complex and confounded by other aspects of adversity.