Trends in and risk factors for elevated blood lead concentrations in Broken Hill preschool children in the period 1991 to 1993

Masters Research - Master of Philosophy (MPhil)Background: Elevated blood lead levels (PbB) have been shown to reduce mental function in children. Broken Hill has been an important lead/zinc mining town for more than 100 years. The mine is in the middle of the town, the sire is arid and often with little ground cover. Approximately 400 children are born each year in Broken Hill. Fatal lead poisoning of dogs is common. Aim: To monitor blood lead levels in preschool children and identify risk factors for elevated PbB in the community as part of a program to manage PbB in young children. Methods: The work consists of a cross sectional study of 864 children in 1992, a case control study of 300 children conducted in 1992 and a cross sectional study of 478 children conducted in 1993. The work also uses data from a prevalence study of 899 children conducted in 1991. The children were recruited as volunteers with over 70% of children in the older age groups participating over the study period. Venous blood was collected from the children, soil and other environmental samples taken, and questionnaires completed. Results: The geometric mean PbB was 16.3μg/dl in 1991 but decreased steadily to 12.7μg/dl in 1993. The percentage of children with PbB>25μg/dl decreased from 21.0% to 9.6% and the percentage with PbB>10μg/dl decreased from 84.5% in 1991 to 68.5% in 1993. Risk factors for elevated PbB included soil lead level where the child lived, amount of dirt eaten, frequency of playing in dirt and sandpit, frequency of vacuuming, frequency of changing vacuum filter, hand washing, time spent playing outside, percentage of the yard that was bare dirt and frequency of hand washing. Soil lead levels were elevated but were similar to or lower than those in other mining communities. Unlike other mining sites (PbB is often not elevated), the lead species in Broken Hill are highly bioavailable and the particles are often finely divided. Conclusions: PbB in preschool children was elevated in 1991 and declined significantly over the next two years. The number of children with very high PbB has been halved. The results of the work were used to manage individual cases, produce pamphlets, media releases and a video for Broken Hill parents, influence NSW government, local government and industry practices, and to lobby for funds to continue the management of the situation. The decline in PbB has continued after the completion of this work with the establishment of the Broken Hill Environmental Lead Centre. Awareness of lead and its management in the environment of young children in Broken Hill is now more commonly accepted as standard practice for both parents and also government/industry