Blood lead screening in Ontario children: blood lead and free erythrocyte protoporphyrin levels.

A blood lead survey was conducted on samples from 2459 children aged 3-6 years to determine the prevalence of lead poisoning in children of this age in the Province of Ontario. Lead poisoning, defined as a blood lead concentration greater than or equal to 1.21 mumol 1-1 (25 micrograms dl-1), was found in 26 subjects (1.1% of the samples). The mean blood lead concentration for children from southern Ontario was 0.50 mumol l-1, and for those from northern Ontario it was 0.37 mumol l-1. Stringent quality controls and independent cross-checks of finger-prick capillary blood sampling were employed in the study. The free erythrocyte protoporphyrin levels were also monitored to detect the presence of iron deficiency in the children.