Exploratory sampling of asbestos in residences near Thetford Mines: the public health threat in Quebec

Our plain-English summary of Exploratory sampling of asbestos in residences near Thetford Mines: the public health threat in Quebec, by M. Marier, W. Charney, R. Rousseau, et al (International Journal of Occupational and Environmental Health, 2007).

The study

• Authors: M. Marier, W. Charney, R. Rousseau, R. Lanthier, J. van Raalte
• Journal: International Journal of Occupational and Environmental Health
• Published: 2007;13(4):386-97
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In 2003-2004, the Asbestos Victims Association of Quebec undertook an exploratory sampling of the air and soil in the residential community of asbestos mining towns. In the 26 houses in the Thetford Mines area, 28 air samples were collected; one outdoor air sample was collected; 14 soil samples were taken; one dust sample was taken from a windowsill. The AHERA criterion was exceeded in 15 of the 28 air samples collected and the World Trade Center criterion was exceeded in five of 26 cases. The risk of developing asbestos-related cancer following such in-home exposures over 30 years is estimated at 1 in 10,000. Soil from the driveways or backyards of nine homes was covered with residue from a tailing pile. Of 14 samples, seven had chrysotile content in excess of 10%; in three, content exceeded 60%, and one reached 100%. Dust from the windowsill had a chrysotile content of 1.2 million structures of all lengths/sq cm. These results suggest a real public health threat in the Quebec mining areas.

In plain English

In 2003-2004 the Asbestos Victims Association of Quebec sampled 26 houses in the Thetford Mines area, chosen mainly by location relative to mines and tailing piles. A hygienist collected 28 indoor air samples, one outdoor air sample, 14 soil samples from nine yards, and one windowsill dust sample. Fifteen of the 28 indoor air samples exceeded the AHERA criterion used for US schools. The outdoor yard sample showed no asbestos fibers. At a 95% confidence level, at least five of 26 recounted samples exceeded a World Trade Center residential benchmark. That benchmark was set at a level estimated to add a cancer risk of 1 in 10,000 over 30 years. Nearly all fibers were chrysotile. Seven of 14 soil samples contained more than 10% asbestos, and one reached 100%. The windowsill dust held 1.2 million chrysotile structures per square centimetre. The authors concluded that the residential environment near Thetford Mines was severely contaminated. They judged that tailing piles, yard and alley tailings, and dust from tailings trucks seemed the main sources in the homes visited. Limited resources restricted the number of houses sampled.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Exploratory environmental sampling survey of indoor air, outdoor air, soil and windowsill dust, carried out by the Asbestos Victims Association of Quebec (AVAQ)
• Who was studied: 26 houses in the Thetford Mines area of southeast Quebec, Canada, sampled in August 2003, November 2003 and July-August 2004. Houses were selected mainly by location relative to tailing piles. 28 indoor air samples were taken in the 26 houses, plus one outdoor air sample, 14 soil samples from the yards of nine houses, and one windowsill dust sample.
• Exposure: Asbestos in residential air, soil and dust near chrysotile mines and tailing piles, including mine waste used in earthwork and dust from trucks carrying tailings. Fibers counted were chrysotile, except in four air samples where one tremolite or actinolite fiber was found.
• Main results:
  • 15 of the 28 indoor air samples exceeded the AHERA criterion. This criterion is used in US schools after asbestos corrective work and is set at 70 structures per square millimetre of filter.
  • The one outdoor air sample, taken in the yard of the first house, showed no asbestos fibers.
  • Using 95% confidence intervals, at least 5 of the 26 indoor air samples recounted under the NIOSH 7402 protocol exceeded the World Trade Center (WTC) residential benchmark.
  • By the laboratory's raw count, 13 of these 26 samples exceeded the WTC criterion. The authors based their reported figure on the 95% confidence level instead, because the air volume sampled was below the NIOSH 7402 optimum.
  • Comparison standard, not a finding of this study: a US EPA-led working group set the WTC benchmark at 0.0009 f/mL for all forms of asbestos. The group estimated that residential exposure at that level over 30 years would add a cancer risk of 1 in 10,000.
  • All houses that exceeded the WTC criterion at the 95% confidence level were downwind from a tailing pile and less than 1 km from it.
  • Of 14 soil samples from around nine houses, 7 contained more than 10% asbestos and 3 exceeded 60%.
  • One soil sample, from mud on the surface of an alleyway, reached 100% asbestos.
  • Dust from an exterior windowsill facing a road used by tailings trucks contained 1.2 million chrysotile structures of all lengths per square centimetre, and 110,000 per square centimetre counting only fibers longer than 5 micrometres.
  • The authors judged that tailing piles, tailings used in yards or alleys, and dust from trucks carrying tailings seemed to be the main sources of contamination in the homes visited.
  • One house more than 5 km upwind of tailing piles exceeded the AHERA criterion. The authors could not explain this result.
• The authors' conclusion: The authors concluded that the residential environment in areas near Thetford Mines is severely contaminated by asbestos.
• Limitations the authors state:
  • The authors would have liked to take more samples and repeat them. Some residents withdrew permission, and limited funds reduced the number of houses included.
  • The air volume sampled under the AHERA protocol was less than NIOSH 7402 stipulates for an optimum count. The authors could not determine with statistical certainty whether the results reflect reality.
  • Soil results were not correlated with indoor air results from the same property.
  • The soil analysis method could not detect or quantify asbestos below 1%.

Topics

Medical terms in this study, explained in our Lexicon: Thetford Mines, AHERA, Chrysotile.

Related studies

• Long-term mortality experience of chrysotile miners and millers in Thetford Mines, Quebec — W.J. Nicholson, I.J. Selikoff, et al. (1979)
• Lung mineral fibers of former miners and millers from Thetford-Mines and asbestos regions: a comparative study of fiber concentration and dimension — A. Nayebzadeh, A. Dufresne, et al. (2001)
• Increased risk of lung cancer mortality among residents near an asbestos product manufacturing plant — S. Kumagai, N. Kurumatani, et al. (2010)
• The health of chrysotile asbestos mine and mill workers of Quebec — J.C. McDonald, M.R. Becklake, et al. (1974)
• Mortality in the chrysotile asbestos mines and mills of Quebec — J.C. McDonald, A.D. McDonald, et al. (1971)
• The search for asbestos within the Peter Mitchell Taconite iron ore mine, near Babbitt, Minnesota — M. Ross, R.P. Nolan, et al. (2008)

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