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October 16, 2003


Uncovering high lead levels in St. John’s soil

By Deborah Inkpen
An interim report on a study conducted during the summer of 2003 to investigate the levels and sources of lead and other metals in St. John’s urban environment was released by researchers in Memorial’s Department of Geography last week.

Dr. Trevor Bell, project leader, said the research project was conceived after reading the results of an earlier study on lake sediment chemistry in St. John’s. The earlier study suggested that with 100 years of coal combustion and 40 years of leaded gasoline use, the city’s soils may have become a large reservoir of potentially toxic metals. The research speculated that, “This reservoir and the availability of the metals may also play an important part in the general uptake in the population through the ingestion of soil and dust. Further work is needed to establish the conditions of these soils.

“The lake sediment study prompted us to test whether soils in St. John’s contained high metal values and whether sources and pathways of metals in soils could be revealed through a targeted sampling program,” said Dr. Bell.

“Since the preliminary findings indicate that a number of our samples exceed the Canadian Council of Ministers of the Environment (CCME) Canadian Environmental Quality guidelines for soils, we decided to report our initial results at this early stage of the project.”

With owners’ permission, soil samples were taken at a number of locations in St. John’s. Homeowners in the city, the City of St. John’s, and the Avalon East School District (school grounds were sampled) were informed of the results pertaining to their properties. The provincial Department of Environment, and Health and Community Services St. John’s Region were also informed of the findings.

Soil-lead values in St. John’s range from 17 to 7048 parts per million, with a median value of 203. The CCME guideline, as adopted by the provincial Department of the Environment for soil-lead, is 140. A total of 140 samples or 60 per cent exceeded this guideline. Dr. Bell noted that, “These preliminary findings are based on a small, targeted sampling program that is insufficient for a rigorous statistical analysis.”

Lead is a metallic element that occurs naturally in all soils and waters. Past human activities have resulted in a legacy of lead concentrations exceeding the naturally occurring, “background” level for local soils. Lead does not biodegrade and is not rapidly absorbed by plants, so it remains in the soil at elevated levels or is removed to local drainage systems through soil disturbance and erosion. Elevated lead levels in urban soil come from a combination of different sources, including the natural bedrock that forms the soil, lead-based exterior paint, automobile tailpipe emissions from vehicles burning leaded gasoline, and coal combustion.

Dr. Bell said that common high lead levels in soils in St. John's suggests that in addition to airborne transport of lead from coal burning and leaded gasoline prior to the 1980s, lead-based paint and coal ash may have been important sources of lead in the soils of St. John's. He said many sites, particularly in the downtown district, may have been influenced by a mixture of sources and as a result show higher soil-lead levels and that these results suggest that a more comprehensive and statistically reliable survey is warranted.

David Allison, the chief medical officer for health and community services in St. John's, said he did not find the results of the pilot study alarming. But he said parents should take some precautions to ensure their children wash their hands often, and do not play in contaminated soil.

Memorial and the Department of Environment are providing soil sampling analysis at no cost to property owners in St. John’s who are concerned about the lead levels in their soil. The samples will be analyzed and the results will be provided to the owners and used confidentially in an expanded study. Test kits can be picked up at Memorial’s Science Building, Room SN-1016 on Mondays and Wednesdays between 5-7 p.m. The program ends Dec. 1.



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Next issue: October 30, 2003

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