Blood lead and associated risk factors in Ontario children

Abstract

The purpose of this study was to determine blood lead levels in Ontario children and to identify those risk factors associated with higher blood lead levels. A random sample of 1315 children aged 7 and younger from urban, suburban and rural Ontario was selected. Blood lead concentration was determined in finger prick blood samples by graphite furnace atomic absorption spectrophotometry. Measurements of lead in air, tap water, soil, and gasoline were also established. Traffic pattern were determined in each area. A questionnaire was administered to a random sample of 800 families of the children tested to assess the presence of other risk factors. Urban children had higher geometric mean blood lead levels (12.02, S.D. = 4.4 μg/dl than suburban children (9.95, S.D. = 3.5 μg/dl, and they, in turn, had higher blood lead levels than rural children (8.91, S.D. = 3.9 μg/dl. Each of these differences is statistically significant (p < 0.001). Fifty four (4.3%) of all children were at or above the alert level of 20 μg/dl. The proportion above the alert level did not differ significantly between urban, suburban and rural children. Blood lead levels were slightly higher for males than females and for pre-schoolers aged 3 and 4, compared to school age children aged 5 and 6. The blood lead levels of these children were significantly lower than that of children surveyed near a point source of industrial emissions. Multivariate statistical modelling resulted in a set of characteristics which best explained the differences in children's blood lead levels. Five of the seven factors most closely associated with children's blood lead levels are measures of lead in the physical environment. The major contributor to air lead in the areas tested was lead in gasoline.