46 Environmental Geoscience/Hydrogeology

Tuesday, 24 March 2009
8:00 AM - 10:00 AM

ENVIRONMENTAL LEAD EXPOSURE IN ST. JOHN'S, NEWFOUNDLAND, CANADA: A CASE EXAMPLE OF NON-INDUSTRIALIZED CONTAMINATION IN AN URBAN SETTING

Program: Technical Sessions
Time: 8:00 AM – 8:20 AM

Authors

Abstract

Residential soil and house dust were collected in St. John's, Newfoundland, Canada, to assess the levels of lead exposure and potential human health risk. Although St. John's does not have an identified major point-source for lead nor is it a heavily industrialized or populated city, it does have a long history of domestic coal burning, vehicular traffic, and painted clapboard houses. The legacy of these activities appears to be levels of lead (and other metals) in urban soils that exceed national soil guidelines. For example, 51% of all soil samples (n=1231) exceeded the Canadian Council of Ministers of the Environment (CCME) residential soil lead guideline of 140 ppm, 26% exceeded the 400 ppm United States Environmental Protection Agency (US EPA) guideline for soil in children's play areas, and 9% exceeded the 1200 ppm US EPA guideline for soil outside play areas. Lead also naturally occurs in the rocks and soils of the St. John's area, albeit at much lower levels.

High soil lead concentrations, particularly those above 1200 ppm, are clustered in the older downtown core. Samples located along exterior house walls (dripline) have the highest mean soil lead concentrations, followed by open spaces in yards and roadside sites. Lead in dripline soil samples from older housing stock is sourced to paint using lead isotopes (low 206,Pb/207Pb (~1.12-1.13) and high 208Pb/206Pb (~2.13-2.14) ratios). Lead from both dripline and ambient samples on properties developed between the 1940s and 1980s have a mixture of sources including coal ash, paint and leaded gasoline. Approximately 12% of house dust samples (n=96) exceeded the US EPA guidelines for lead in indoor dust, all from pre-1950s housing and all associated with dripline soil lead concentrations greater than 900 ppm. Human health risk predictions suggest that while the wider St. John's community may not be at risk of adverse health effects, there may be an increased risk for children living in pre-1970s housing.