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Cancer and Occupational Exposure to Pentachlorophenol and Tetrachlorophenol
RS2001/02-020
Final Report Date: August 2005
| Principal Investigator: | Paul Demers (University of British Columbia) |
| Co-investigators: | Kay Teschke (University of British Columbia), Clyde Hertzman (University of British Columbia) |
For more information about this study, please contact Dr. Paul Demers.
Issue
Pentachlorophenol (PCP) and tetrachlorophenol (TCP) are two fungicides that were broadly used in BC’s lumber industry between 1950 and 1990. Both substances are chlorophenols – a group of chemicals classified as potential carcinogens by the International Agency for Research on Cancer (IARC).
This project examined the risk of seven types of cancer for sawmill workers who were exposed to PCP and TCP. The research used data on over 27,000 men from the BC Sawmill Cohort, linked with cancer registry data and other administrative data sources. It is one of the largest studies ever conducted on the risk of cancer for workers exposed to chlorophenols and phenoxy herbicides. It is also the first cohort study of workers exposed to this family of chemicals to focus on dermal exposure.
Key findings
- Associations between the risks of non-Hodgkin’s lymphoma, multiple myeloma, and kidney cancer and dermal exposure to chlorophenol fungicides in sawmills were observed. This relationship was strongest for all three cancers when exposure was restricted to pentachlorophenol.
- While the relative risks among the most highly exposed were only slightly or moderately elevated compared to the general population, strong dose-response relationships were observed compared to the least exposed workers.
- The study did not find any evidence of an increased risk of other cancers examined, including soft tissue sarcoma or connective tissue cancers alone as well as lung, sinonasal, or nasopharyngeal cancer.
Objectives
- To examine the effects of occupational exposure to PCP and TCP using data from the BC sawmill workers cohort study, with the extended follow-up data.
Method
The BC sawmill cohort consists of men employed for one year or more at one of 14 BC sawmills between 1950 and 1995. The cohort worker records were linked with national cancer registry data to determine the incidence of and fatalities from cancer.
The proportion of dermal exposure to chlorophenols for each job was estimated by senior workers and managers in each mill. Mill records and interviews were used to identify specific fungicide formulations used during different time periods, and to differentiate between exposure to pentachlorophenol and tetrachlorophenol.
Statistical analyses were conducted to compare rates of cancer for exposed workers with rates for the general BC population and to assess dose-response relationships. The analyses focused on cancer sites observed to be in excess (i.e., non-Hodgkin’s lymphoma, soft tissue sarcoma, multiple myeloma, lung, kidney, sinonasal, and nasopharangeal) in earlier studies of workers exposed to chlorophenols or related phenoxy herbicides.
Results
The updated cohort consisted of 27,464 men. Overall there were 5,850 (21% of all cohort members) deaths and 977 (4%) people were lost to follow-up and had their person-years truncated at date of last employment. For the cancer incidence analyses, cohort members who died or were lost to follow-up prior to 1969 (the first year of cancer registration in BC and most other provinces) were excluded leaving 25,685 men.
Overall there were 2,571 cancers diagnosed, excluding non-melanoma skin cancers, which are poorly identified. Overall cancer incidence and mortality were similar to that of the general population and there were no striking overall excesses of any of the specific cancers.
Associations between the risks of non-Hodgkin’s lymphoma, multiple myeloma, and kidney cancer and dermal exposure to chlorophenol fungicides in sawmills were observed. This relationship was strongest for all three cancers when exposure was restricted to pentachlorophenol. While the relative risks among the most highly exposed were only slightly or moderately elevated compared to the general population, strong dose-response relationships were observed compared to the least exposed workers.
This study did not find any evidence of an increased risk of other cancers of a priori interest, including soft tissue sarcoma or connective tissue cancers alone as well as lung, sinonasal, or nasopharyngeal cancer.
Conclusions
Compared with previous studies that used BC Sawmill Cohort data, this study found much stronger associations between the risks of non-Hodgkin’s lymphoma, multiple myeloma, and kidney cancer and level of dermal exposure to chlorophenol fungicides in sawmills, particularly with PCP. However, this study did not find evidence of an association between chlorophenol exposure and other cancers that were of interest based on earlier, inconclusive evidence, including soft tissue sarcoma, lung cancer, sinonasal, or nasopharyngeal cancers.
Publications
Demers PA, Friesen MC, Davies HW, Hertzman C, Marion S, Ostry A, Teschke K. Cancer and Occupational Exposure to Pentachlorophenol and Tetrachlorophenol. Cancer Causes Controls 2006;17(6):749-758
Additional information
Information on the UBC sawmill study is available on the website of the UBC Centre for Health and Environment Research (CHER) at http://www.cher.ubc.ca/UBCsawmillstudy/