An analysis of occupational blood lead trends in Manitoba, 1979 through 1987

Background: While regulations for workplace lead exposure become more strict, their effectiveness in decreasing blood lead concentrations and the method by which this is attained have not been evaluated. Methods: An analysis was conducted of 10,190 blood lead samples from employees of 10 high-risk workplaces collected in Manitoba, 1979-87, as part of regulated occupational surveillance. Results: A significant decrease in blood lead concentrations was observed overall as well as for each individual company. A 1979 government regulation to reduce blood lead to below 3.38 μmol/L (70 μg/dl) was followed by a drop in blood lead concentrations; a 1983 order to reduce blood leads to below 2.90 μmol/L (60 μg/dl) was not followed by such a drop. Longitudinal analysis by individual workers suggested that companies were complying by use of administrative control, i.e., removing workers to lower lead areas until blood lead levels had fallen, then returning them to high lead areas. Conclusion: Focusing upon blood lead as the sole criterion for compliance is not effective; regulations must specifically require environmental monitoring and controls. Biological surveillance serves as ''back-up'' to environmental surveillance and this database illustrates the usefulness of a comprehensive centralized surveillance system.