Asbestos
Environmental Estimate
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
Potential lifetime excess cancer risk is an indicator of Canadians’ exposure to known or suspected carcinogens in the environment. If measured levels of asbestos in relevant exposure pathways (outdoor air and indoor air) decrease, the risk will also decrease.
Watch a video about the chart below. (with French subtitles)
More than one unit risk factor may be available, because agencies interpret the underlying health studies differently, or use a more precautionary approach. Results using unit risk factors the California Office of Environmental Health Hazard Assessment (OEHHA), and the US Environmental Protection Agency (US EPA) are presented here.
Potential lifetime excess cancer risk assumes exposure occurs at the same level, 24 hours per day, for 70 years. This is rarely true for any single individual, but using a standard set of assumptions allows us to provide a relative ranking for known and suspected carcinogens across different exposure routes.
Provincial Tables & Maps
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
Exposure may have occurred historically in communities close to asbestos mines, and may still be occurring when waste piles containing asbestos are present1, 2, 3. In the past, people who lived near manufacturing facilities producing insulation with asbestos-contaminated vermiculite from Libby, Montana may have been exposed4, 5, 6; and recent studies also suggest that exposure might occur when naturally occurring asbestos deposits are disturbed .7 Vermiculite produced by the Libby Mine in Montana from the 1920s-1990 and sold as Zonolite® Attic Insulation may contain amphibole asbestos8, and potential exposures may occur in homes where Zonolite® insulation is disturbed.
| Asbestos Production | Vermiculite Processing | Home Insulation | Maps |
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Asbestos Production
1. Bourgault MH, Belleville D. 2011. Presence of asbestos fibres in indoor and outdoor air in the city of Thetford Mines: Estimation of lung cancer and mesothelioma risks. Institut National de Sante Publique du Quebec. ISBN 978-2-550-60762 (English) or 978-2-550-55640-4 (French).
2. Lajoie P, Dion C, Droui L et al. 2003. Asbestos Fibres in Indoor and Outdoor Air: The Situation in Quebec. Institut National de Sante Publique du Quebec. ISBN 2-550-43778-0.
3. Marier M, Charney W, Rosseau R et al. 2007. Exploratory Sampling of Asbestos in Residences Near Thetford Mines: The Public Health Threat in Quebec. International Journal of Occupational and Environmental Health. Vol 13: pp 386-397.
4. Alexander BH, Raleigh KK, Johnson J et al. 2012. Radiographic Evidence of Nonoccupational Asbestos Exposure from Processing Libby Vermiculite in Minneapolis, Minnesota. Environmental Health Perspectives. Vol 120 (1): pp 44-49.
5. Elashheb MI, Spear TM, Hart JF et al. 2011. Libby Amphibole Contamination in Tree Bark Surrounding Historical Vermiculite Processing Facilities. Journal of Environmental Protection. Vol 2: pp 1062-1068.
6. Kelly J, Pratt GC, JohnsonJ and Messing RB. 2006. Community Exposure to Asbestos from a Vermiculite Exfoliation Plant in NE Minneapolis. Inhalation Toxicology. Vol 18: pp941-947.
7. Naturally Occurring Asbestos: Clear Creek Management Area. Unites States Environmental Protection Agency Region 9 website: http://www.epa.gov/region09/toxic/noa/clearcreek/index.html
8. Health Canada. 2009. Vermiculite Insulation Containing Amphibole Asbestos – It’s Your Health. http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/prod/insulation-isolant-eng.php
9. Statistics Canada Report P82-105. Canadian production of principal non-metallic minerals, 1998 to 1975.
10. Natural Resources Canada. Minerals Year Book for each year 1975 to 2010 inclusive.
11. Natural Resources Canada. Minerals Year Book for each year 1943 to 2006 inclusive.
Vermiculite Processing
In 1916, the world's largest deposit of vermiculite was discovered near Libby, Montana. The vermiculite was mined primarily for use as an insulating material. Crude (or raw) vermiculite was shipped from the mine to processing plants across the US and in Canada, where it was exfoliated using high temperatures causing it to expand significantly. In 1935, a report from the US Bureau of Mines noted the presence of a series of amphibole asbestos dikes, up to 10 feet thick intersecting the vermiculite deposit. Over the entire operating life of the Libby mine (1921 to 1992), the vermiculite extracted and shipped for processing was contaminated with this particularly carcinogenic form of asbestos.9, 10
Vermiculite was mined and processed commercially in Canada only for a very short time (1956, 1957, and 1966) and in very small quantities at a location near Stanleyville, Ontario. All other vermiculite processed in Canada was imported from the United States, predominantly from Libby mine, or from South Africa (presumed to be uncontaminated).
Available data sources regarding Canadian imports of vermiculite include: 1) general information on all imports to Canada from South Africa or the United States reported in mineral yearbooks from the United States Geological Survey and Natural Resources Canada, and (2) invoices of vermiculite shipments from the Libby Montana Mine to companies in Canada from the United States Environmental Protection Agency. See more information about each data source below.
Canadian Imports Reported in Mineral Yearbooks (CAN & US)
The graph below shows tonnes of crude vermiculite imported from the US and South Africa for years with available data. USGS Bureau of Mines reports note that vermiculite from the Libby mine was being exported to Canada for processing as early as 1935 (Winnipeg, MB and Paris, ON).9 See the map for more information on processing sites in Canada.
Libby Mine Invoices
The United States Environmental Protection Agency (EPA) has compiled a database documenting W.R. Grace invoices for shipments from the Libby Mine from 1964 to 199011. The database includes company name, shipping destination, and total tonnage shipped. The EPA database may not include every shipment made during this time.
Although the number of sites and amount of ore received may be understated by invoices in the database, the EPA has investigated sites in the United States thought to have received ore to determine if remediation activities are necessary. Investigations have not been carried out for Canadian shipment locations.
The following table reports W.R. Grace invoices for shipments of vermiculite from Libby Mine to Canadian locations from the EPA database. No information is available on the end uses of vermiculite shipped to reported Canadian locations; some may have been shipped directly to facilities engaged in vermiculite processing, while others may have been subsequently transported to other locations for other intended purposes.
At least 8,252 shipments of vermiculite were made from Libby, MT to locations in Canada; the majority of shipments and total tons to Ontario, Quebec, and Alberta. See the table below and map for more information on shipment locations in Canada.
1. Bourgault MH, Belleville D. 2011. Presence of asbestos fibres in indoor and outdoor air in the city of Thetford Mines: Estimation of lung cancer and mesothelioma risks. Institut National de Sante Publique du Quebec. ISBN 978-2-550-60762 (English) or 978-2-550-55640-4 (French).
2. Lajoie P, Dion C, Droui L et al. 2003. Asbestos Fibres in Indoor and Outdoor Air: The Situation in Quebec. Institut National de Sante Publique du Quebec. ISBN 2-550-43778-0.
3. Marier M, Charney W, Rosseau R et al. 2007. Exploratory Sampling of Asbestos in Residences Near Thetford Mines: The Public Health Threat in Quebec. International Journal of Occupational and Environmental Health. Vol 13: pp 386-397.
4. Alexander BH, Raleigh KK, Johnson J et al. 2012. Radiographic Evidence of Nonoccupational Asbestos Exposure from Processing Libby Vermiculite in Minneapolis, Minnesota. Environmental Health Perspectives. Vol 120 (1): pp 44-49.
5. Elashheb MI, Spear TM, Hart JF et al. 2011. Libby Amphibole Contamination in Tree Bark Surrounding Historical Vermiculite Processing Facilities. Journal of Environmental Protection. Vol 2: pp 1062-1068.
6. Kelly J, Pratt GC, JohnsonJ and Messing RB. 2006. Community Exposure to Asbestos from a Vermiculite Exfoliation Plant in NE Minneapolis. Inhalation Toxicology. Vol 18: pp941-947.
7. Naturally Occurring Asbestos: Clear Creek Management Area. Unites States Environmental Protection Agency Region 9 website: http://www.epa.gov/region09/toxic/noa/clearcreek/index.html
8. Health Canada. 2009. Vermiculite Insulation Containing Amphibole Asbestos – It’s Your Health. http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/prod/insulation-isolant-eng.php
9. United States Geological Survey: Bureau of Mines Minerals Yearbooks. 1932 to 1992. http://minerals.usgs.gov/minerals/pubs/myb.html
10. Natural Resources Canada: Canadian Minerals Yearbooks. 1941 to 1992. http://www.nrcan.gc.ca/minerals-metals/business-market/canadian-minerals-yearbook/4070.
11. Unpublished data from an EPA database of W.R. Grace invoices for shipments of vermiculite from the Libby mine from 1964 through 1990.
Home Insulation
The number of homes in Canada insulated using Zonolite® is unknown; however, it is estimated to be present in 3% of low-rise houses across Canada, or 242,000 homes in residential neighbourhoods, including First Nation Housing, and on Canadian military bases9.
From 1977-1986 the Canadian Home Insulation Program (CHIP) provided grants to homeowners for improving the energy efficiency of their homes. During this time 2,592,392 grants were issued for approximately 150 different types and brands of insulation products, including Zonolite® vermiculite insulation10. The actual number of homes which insulated using Zonolite® under the program is unknown, as CHIP was instituted prior to digital record-keeping. Existing paper records may contain information on a residence-by-residence basis on the products purchased under the grant to upgrade home insulation. These paper records may indicate potential exposure in homes that were insulated with Zonolite®, but would not reflect those that have since been remediated.
Indian and Northern Affairs Canada (INAC) has reviewed their records to attempt to identify where vermiculite insulation containing asbestos may have been used in the construction of houses on reserves11. Of houses built between 1960-1990, INAC found 597 references to houses that may have been built using Zonolite® Loose-Fill Vermiculite Insulation in the provinces of Saskatchewan (276), Manitoba (234), British Columbia (28), Quebec (28), and Alberta (5). An additional 6 references in the Yukon identified the use of vermiculite in general, but not specifically the Zonolite® brand. No records were available for the Northwest Territories of Nunavut, as housing is under the jurisdiction of Territorial Governments.
The Department of National Defence has assessed their complete housing portfolio9.
Health Canada has posted extensive information about vermiculite insulation that may contain asbestos on their website8.
1. Bourgault MH, Belleville D. 2011. Presence of asbestos fibres in indoor and outdoor air in the city of Thetford Mines: Estimation of lung cancer and mesothelioma risks. Institut National de Sante Publique du Quebec. ISBN 978-2-550-60762 (English) or 978-2-550-55640-4 (French).
2. Lajoie P, Dion C, Droui L et al. 2003. Asbestos Fibres in Indoor and Outdoor Air: The Situation in Quebec. Institut National de Sante Publique du Quebec. ISBN 2-550-43778-0.
3. Marier M, Charney W, Rosseau R et al. 2007. Exploratory Sampling of Asbestos in Residences Near Thetford Mines: The Public Health Threat in Quebec. International Journal of Occupational and Environmental Health. Vol 13: pp 386-397.
4. Alexander BH, Raleigh KK, Johnson J et al. 2012. Radiographic Evidence of Nonoccupational Asbestos Exposure from Processing Libby Vermiculite in Minneapolis, Minnesota. Environmental Health Perspectives. Vol 120 (1): pp 44-49.
5. Elashheb MI, Spear TM, Hart JF et al. 2011. Libby Amphibole Contamination in Tree Bark Surrounding Historical Vermiculite Processing Facilities. Journal of Environmental Protection. Vol 2: pp 1062-1068.
6. Kelly J, Pratt GC, JohnsonJ and Messing RB. 2006. Community Exposure to Asbestos from a Vermiculite Exfoliation Plant in NE Minneapolis. Inhalation Toxicology. Vol 18: pp941-947.
7. Naturally Occurring Asbestos: Clear Creek Management Area. Unites States Environmental Protection Agency Region 9 website: http://www.epa.gov/region09/toxic/noa/clearcreek/index.html
8. Health Canada. 2009. Vermiculite Insulation Containing Amphibole Asbestos – It’s Your Health. http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/prod/insulation-isolant-eng.php
9. The Canadian Real Estate Association. 2007. Vermiculite Insulation and Asbestos. http://www.crea.ca/sites/default/files/Vermiculite.pdf
10. Parliament of Canada. 2012. 41st Parliament, 1st Session. Edited Hansard. Number 136. June 7. Question No. 620 Response by David Anderson.
11. Aboriginal Affairs and Northern Development Canada. 2010. Information on Vermiculite Insulation Containing Asbestos. http://www.aadnc-aandc.gc.ca/eng/1100100016218/1100100016219
Maps
1. Bourgault MH, Belleville D. 2011. Presence of asbestos fibres in indoor and outdoor air in the city of Thetford Mines: Estimation of lung cancer and mesothelioma risks. Institut National de Sante Publique du Quebec. ISBN 978-2-550-60762 (English) or 978-2-550-55640-4 (French).
2. Lajoie P, Dion C, Droui L et al. 2003. Asbestos Fibres in Indoor and Outdoor Air: The Situation in Quebec. Institut National de Sante Publique du Quebec. ISBN 2-550-43778-0.
3. Marier M, Charney W, Rosseau R et al. 2007. Exploratory Sampling of Asbestos in Residences Near Thetford Mines: The Public Health Threat in Quebec. International Journal of Occupational and Environmental Health. Vol 13: pp 386-397.
4. Alexander BH, Raleigh KK, Johnson J et al. 2012. Radiographic Evidence of Nonoccupational Asbestos Exposure from Processing Libby Vermiculite in Minneapolis, Minnesota. Environmental Health Perspectives. Vol 120 (1): pp 44-49.
5. Elashheb MI, Spear TM, Hart JF et al. 2011. Libby Amphibole Contamination in Tree Bark Surrounding Historical Vermiculite Processing Facilities. Journal of Environmental Protection. Vol 2: pp 1062-1068.
6. Kelly J, Pratt GC, JohnsonJ and Messing RB. 2006. Community Exposure to Asbestos from a Vermiculite Exfoliation Plant in NE Minneapolis. Inhalation Toxicology. Vol 18: pp941-947.
7. Naturally Occurring Asbestos: Clear Creek Management Area. Unites States Environmental Protection Agency Region 9 website: http://www.epa.gov/region09/toxic/noa/clearcreek/index.html
8. Health Canada. 2009. Vermiculite Insulation Containing Amphibole Asbestos – It’s Your Health. http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/prod/insulation-isolant-eng.php
9. Unpublished data from an EPA database of W.R. Grace invoices for shipments of vermiculite from the Libby mine from 1964 through 1990.
Compare Substances
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
| Outdoor Air | Indoor Air | Dust | Drinking Water | Food & Beverages |
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Outdoor Air
Indoor Air
Dust
Drinking Water
Food & Beverages
Trends
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
We are planning to update our estimates for 2011 if new data become available. Check here periodically for information on identified trends in measured levels or factors related to exposure.
Methods
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
| Methods Overview | Calculating Lifetime Hourly Concentrations | Standard Assumptions | Unit Risk Factors | Lifetime Excess Cancer Risk |
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Methods Overview
Lifetime excess cancer risk due to exposure to asbestos is calculated by first combining data on measured concentrations in outdoor air and indoor air with standard values for total hours spent outdoors and indoors over 70 years to estimate lifetime hourly concentration. Then, the lifetime hourly concentration is multiplied by a unit risk factor.
Multiplying the lifetime hourly concentration by a unit risk factor produces an estimate of the lifetime excess cancer risk.
Calculating Lifetime Hourly Concentrations
Lifetime hourly concentrations are calculated for each exposure pathway (outdoor air and indoor air) by multiplying the hourly concentration for every hour spent outdoors or indoors in each lifestage, then dividing by the total hours in a 70 year lifespan. For example:
Standard Assumptions
We assume these characteristics remain constant for each lifestage. This is rarely true for any single individual, but using a standard set of assumptions allows us to provide a relative ranking for known and suspected carcinogens across different exposure routes.
Unit Risk Factors
Lifetime Excess Cancer Risk
The potential lifetime excess cancer risk assumes that pollutant concentrations and intake rate remain the same for an entire lifetime of 70 years. Radon levels may change from place to place due to geological factors and individual building conditions. For any one person, these exposures may change as they move from place to place. Using potential lifetime excess cancer risk allows us to make comparisons between pollutants and exposure routes, but does not allow us to estimate the actual risk for any one individual.
Potential lifetime excess cancer risk indicates how many additional cases of cancer would be expected in a population of 1 million people, given the input pollution concentrations and intake levels.
Data
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
| Overview | Outdoor Air | Indoor Air | Dust | Drinking Water | Food & Beverages |
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Overview
The summary data used to calculate lifetime excess cancer risk and the results for asbestos are provided in the tables below. For more detailed information on supporting data and sources, use the tabs for each exposure pathway.
Environmental Concentrations
Calculated Lifetime Hourly Concentrations
Unit Risk Factors
Sources:
- US EPA:
- United States Environmental Protection Agency Integrated Risk Information System (http://www.epa.gov/IRIS/)
- CA OEHHA:
- California Office of Environmental Health Hazard Assessment, 2009. Air Toxics Hot Spots Risk Assessment Guidelines Part II: Technical Support Document for Cancer Potency Factors, Appendix A. (http://oehha.ca.gov/air/cancer_guide/index.html)
Lifetime Excess Cancer Risk (per million people)
- 1Lifetime excess cancer risk based on average intake x cancer potency factor from each agency
- 2Lifetime excess cancer risk based on maximum intake x highest cancer potency factor
- 3California Office of Environmental Health Hazard Assessment
- 2Lifetime excess cancer risk based on maximum intake x highest cancer potency factor
Outdoor Air
We assume asbestos is present at these levels in all outdoor air, although concentrations may vary from one location to another.
References:
LaJoie P, Dion C, Drouin L, Dufresne A, Levesque B, et al. 2003. Asbestos Fibres in Indoor and Outdoor Air The Situation in Quebec. Sub-Committee on Exposure Measurement. Institut national de sante publique du Quebec.
Lee RJ, Van Orden DR. 2008. Airborne asbestos in buildings. Regulatory Toxicology and Pharmacology 50: 218-225.
Indoor Air
References:
Lee RJ, Van Orden DR. 2008. Airborne asbestos in buildings. Regulatory Toxicology and Pharmacology 50: 218-225.
Marier M, Charney W, Rousseau R, Lanthier R and Van Raalte J. 2007. Exploratory Sampling of Asbestos in Residences Near Thetford Mines. International Journal of Occupational and Environmental Health 13: 386-397.
Dust
Asbestos may be present in dust, but is not expected to be carcinogenic via ingestion.
Drinking Water
Asbestos may be present in drinking water, but is not expected to be carcinogenic via ingestion.
Food & Beverages
Asbestos may be present in food and beverages, but is not expected to be carcinogenic via ingestion.
Data Quality
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
Only publicly available data were used to calculate these indicators. Data that are not publicly available may produce different results.
No systematic method for measuring data quality was possible, so we provide the following assessments of how well the data used may represent the actual Canadian average levels. Quality is rated higher when there are data from a number of Canadian monitors, or from Canadian studies that show results similar to other comparable studies. Quality is rated lower when data from few monitors or studies were available, and lowest when estimates are based on non-Canadian data. Others may rate data quality differently.
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.
Asbestos is a known carcinogen, based on the most recent IARC classification. While ongoing research continually provides new evidence about cancer potency and whether there is a safe threshold of exposure, our approach assumes there are no safe exposure levels.