Health Canada recently completed a statistically representative national baseline study for lead concentrations in dust sampled from urban households, entitled the Canadian House Dust Study.
Sampling for the Canadian House Dust Study was conducted between 2007 and 2010 and included vacuum sampling and wipe sampling. The results are published in the Journal of Environmental Science and Technology (PDF Version - 2650 K).
The results provide us with a better understanding of the background levels of lead that Canadians may be exposed to in their homes. Health Canada has not yet set reference levels for lead in house dust, so the measurements are an important starting point for future research and risk management activities related to lead exposure in indoor environments.
Lead exposure in Canada has decreased substantially since the early 1970s, mainly because lead-based paints and leaded gasoline were phased out and the use of lead solder in food cans was almost completely eliminated.
The results of the vacuum method showed that all 1025 homes sampled had measureable concentrations of lead in their house dust, ranging from 8 to 3916 parts per million (ppm). 90% of urban Canadian homes have dust lead levels between 8 and 250 ppm (the "urban background" category). Where elevated levels were found, they predominantly consisted of older homes in central core areas of cities (which is explained largely by the lead content found in older paint).
Of all the homes in the "urban background" category, 33% were built before 1960. These results indicate that many homeowners are effectively renovating older homes to remove lead paint and other sources of exposure. In addition, 10% of homes above 250 ppm were built after 1980, indicating that lead is not only found in older homes.
A large proportion of the wipe sampling measurements in urban Canadian homes did not detect any lead. However, the wipe method provided useful information about differences in lead measurements between rooms in the same home. These differences reflect the different activities conducted in each room.
Most homes showed the highest amounts of lead in the main entryway, which is likely caused by tracking in dirt from outdoor sources. Some homes (less than 5%) had the highest lead wipe measurements in interior rooms, such as bedrooms, indicating that indoor sources also contribute to the level of lead in the home. Only about 1% of homes had wipe samples that exceed the United States Environmental Protection Agency regulation for lead in floor dust (that is, 40 micrograms per square foot or 431 micrograms per square metre).
Detailed results of the Canadian House Dust Study are provided in the following scientific journal articles:
Rasmussen, P.E., Beauchemin, S., ChÚnier, M., Levesque, C., MacLean, L.C.W., Marro, L., Jones-Otazo, H., Petrovic, S., McDonald, L.T., Gardner, H.D. (2011) Canadian House Dust Study: Lead Bioaccessibility and Speciation. Environmental Science and Technology, doi: 10.1021/es104056m.
MacLean, L.C.W, Beauchemin, S., and Rasmussen, P.E. (2011) Lead speciation in house dust from Canadian urban homes using EXAFS, micro-XRF and micro-XRD. Submitted to Environmental Science and Technology, doi: 10.1021/es2001503.
McDonald, L.T., Rasmussen, P.E., ChÚnier, M., Levesque, C. (2010) Wipe Sampling Methodologies To Assess Exposure To Lead And Cadmium In Urban Canadian Homes. In Proceedings of 25th Annual International Conference on Soils, Sediments, Water and Energy, University of Massachusetts, Amherst, USA, October 19-22, 2009, Vol. 15 (Article 6).
McDonald, LT, Rasmussen, PE, Chenier, M., and Levesque, C. (2011). Extending Wipe Sampling Methodologies to Elements Other Than Lead. Journal of Environmental Monitoring, 13, 377-383.
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