Analysis of the Ontario Ministry of Labour’s MESU exposure database


The goal of this project was to identify priority workplace carcinogens and analyze exposure to these substances in Ontario, based on the Ministry of Labour’s MESU dataset.

In collaboration with CAREX Canada, the data was also used to create exposure matrices for use in cancer surveillance and future research.

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The Ontario Ministry of Labour collected exposure measurements in Ontario workplaces to determine compliance with occupational exposure limits between 1981 and 1996. These data were preserved in the MESU database. There are approximately 300,000 measurements in the MESU database, many of which are for known or suspected carcinogens.


The MESU database includes exposure measurements taken between 1981 and 1996 in a wide variety of Ontario workplaces. Data for priority carcinogens were extracted from the database, and statistical analyses were performed to determine the levels of exposure, and the occupations and industries most affected by the substances.


Analyzing past exposure data can give us important information on which occupations and industries were overexposed in the past and may continue to be overexposed in the future, where there are gaps in our knowledge, and where intervention efforts should be targeted. Moreover, exposures that occurred 15 to 40 years ago are highly relevant in terms of current cancer risks.


This study is complete. These data have contributed to CAREX Canada’s national carcinogen surveillance project; the Canadian Workplace Exposure Database; and research studies including the Burden of Occupational Cancer in Canada.

Scientific Articles
  • Historical occupational isocyanate exposure levels in two Canadian provinces

Research Team
Paul Demers (PI)
Victoria Arrandale
Cheryl Peters
CAREX Canada
Chun-Yip Hon
Ryerson University
Kate Jardine
Garthika Navaranjan
University of Toronto
Joanne Kim
McGill University