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The Canadian Council of Occupational Hygiene (CCOH/CCHT) is a not-for profit organization that has been established with the goal of Improving Workplace Health through education, awareness and advocacy.

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Occupational Exposure to Chemical and Physical Contaminants: Sex-Differentiated Analysis

The IRSST just published a research report on occupational exposure to chemical and physical contaminants. The occurrence of occupational injuries differs by sex. One of the main explanations put forward is the existence of clear differences in exposure in the workplace, stemming in particular from differences in the jobs held by men and women and the nature of the tasks involved. However, there is a lack of solid data to support this claim, and most traditional workplace analyses have been limited to reporting risks based on sex, but without identifying the reasons that might explain the observed risk differences.

The researchers explore the existence of differences in occupational exposure between men and women using current epidemiological databases.

Two epidemiological studies done in Montreal in the late 1990s provided the exposure data; they investigated the relationship between environmental risk factors (including occupational environment) and cancer (lung cancer and breast cancer). Based on subjects’ work history, experts assigned one or more exposures, from a list of 243 possible substances, to each job occupied by 1,657 men and 2,073 women. In our study, the occupational exposure associated with jobs held by men was compared with that of jobs held by women (all occupations and industries combined) to reveal any exposure differences. Exposures were subsequently compared between the jobs held by both sexes within the same occupational groups, then the same occupations and finally the same “occupational group/industry group” pairs. For the purpose of the comparisons, the agreement between the exposure of men’s jobs and that of women’s jobs was calculated using intraclass correlation coefficients. Then, “notable difference” proportions were calculated from the modelling of the male/female exposure differences by applying hierarchical Bayesian models.

As anticipated, given men’s and women’s different employment profiles, the analysis of all occupations and all economic sectors revealed differences in occupational exposure between the jobs held by men and those held by women for a large number of chemicals and some physical agents. Generally speaking, the jobs held by men were found to have higher exposure proportions, especially to motor vehicle exhaust, petroleum fractions, polycyclic aromatic hydrocarbons, building material dust and abrasive dust. In contrast, jobs held by women were found to have greater exposure to fabric and textile fibre dust and to aliphatic aldehydes.

Most of these differences in exposure proportions disappeared when the analysis was restricted to a male-female comparison within the same occupational group: out of 4,269 points of comparison for which more than 5% of jobs held by men or women were found to be exposed, only 326 (7.6%) of the points showed notable differences. However, where men’s jobs and women’s jobs involved exposure to a given substance, the time-weighted intensity of exposure was similar. Of the 326 notable differences in exposure proportions between men and women, 187 (57.4%) were due to a lack of precision in the occupational code, 78 (23.9%) to differences in the tasks reported by the subjects and 51 (15.6%) to differences related to the industry in which the work was done. Finally, once occupation and industry were taken into account, only 3.1% of the differences in occupational exposure proportions were left with no obvious explanation.

To conclude, sex-differentiated analyses are needed to highlight differences in occupational exposure and injuries, as conducting analyses based on occupation and economic sector alone is not sufficient to reveal the subtle differences in job-associated tasks that are also gender related.

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Thermal Stress and Chemicals - Knowledge Review and the Highest Risk Occupations

The IRSST just published a report entitled Thermal Stress and Chemicals - Knowledge Review and the Highest Risk Occupations in Québec. Exposure to cold or heat triggers a series of compensatory physiological responses enabling the human body to maintain its internal temperature despite thermal stress. These thermoregulation mechanisms are well documented and the resulting physiological changes can modify organ functions related to the absorption and metabolism of chemical substances.

Pharmacological and epidemiological studies report an increase in the absorption and effects of certain drugs, and higher human mortality associated with air pollution, on simultaneous exposure to heat and xenobiotics. Extrapolation of these data to occupational health suggests that concurrent exposure to thermal stress and chemical substances is likely to increase the absorption and effects of some xenobiotics.

The primary objective of this research was to survey all data published in recent scientific literature. The second objective was to identify Quebec workers exposed to chemical substances who might be the most affected by thermal stress. Careful attention was given to the presence of chemical substances likely to affect thermoregulation mechanisms.

By identifying higher-risk occupations, this report will help guide occupational health professionals in assessing risk in cases of simultaneous exposure to thermal stress and chemical substances.


Carcinogenic Substances - Exposure Profile of Quebec Workers

The IRSST just published the first report that estimates Quebec workers’ exposure to carcinogens. This document is a significant contribution to knowledge in this area, and the findings should be of use to anyone interested in this problem.

Exposure estimates were compiled for 38 carcinogenic substances listed in Schedule I of the Regulation respecting occupational health and safety (designation C1, C2 or C3) and in the known or probable carcinogens list published by the International Agency for Research on Cancer (groups 1 and 2A). The number of workers potentially exposed to each carcinogen was obtained by applying the percentages of exposed workers in a given industry, calculated from various data sources, to the number of people working in that industry in Québec according to the 2006 census data. The information on exposure was based on laboratory tests performed by the IRSST for the Réseau public de la santé au travail, the results from a number of special projects carried out by the IRSST, data from Santé-Québec's survey on health and wellbeing (Enquête sociale et de santé 1998), Health Canada data on occupational radiation exposure, and exposure data compiled as part of the CAREX Canada project conducted by the University of British Columbia. For some carcinogens, the exposure data came from two French sources: the SUMER survey of occupational physicians by France's Ministère du travail, and the MATGÉNÉ job exposure matrices developed by the Institut de veille sanitaire.

According to these calculations, the ten substances or conditions to which the greatest number of Québec workers are exposed are as follows: solar radiation (6.6%), night work or rotating shifts including night work (6.0%), diesel exhaust (4.4%), wood dust (2.9%), polycyclic aromatic hydrocarbons (excluding diesel exhaust) (2.0%), benzene (1.7%), silica (1.5%), lead (1.3%), artificial ultraviolet rays (1.1%) and mineral oils (1.0%).

In several industries, over 20 different carcinogens are present; these industries include manufacturing, construction, other services except public administration, utilities, professional, scientific and technical services, and administrative, support, waste management and remediation services. Among the manufacturing industries with exposure to multiple carcinogens are non-metallic mineral products, transportation equipment, primary metals, chemicals and paper.

Based on these percentages, it is estimated that at least 230,300 Quebecers are exposed to solar radiation and more than 150,000 to diesel exhaust in their jobs. Over 50,000 are exposed to carcinogens in manufacturing, transportation and warehousing, agriculture, forestry, hunting and fishing, and health care and social assistance.

Exposure to polycyclic aromatic hydrocarbons (PAHs), diesel exhaust, benzene and solar radiation affects most of the industries with a young labour force, including retailing, arts, entertainment and recreation, and accommodation and food services.

A breakdown of the data according to sex shows that more women are exposed to carcinogens in health care and social assistance (ionizing radiation, night work, artificial UV rays and solar radiation). Men are present in greater proportions in agriculture, forestry, hunting and fishing, mineral extraction, oil and gas, construction, utilities, manufacturing and transportation and warehousing; these industries are characterized by exposure to solar radiation, wood dust, night work, silica, diesel exhaust, mineral oils and lead.

Despite their limitations, the estimates are useful indicators of the extent of Québec workers' potential exposure to carcinogenic substances, mainly because this is the first portrait of its type based on data aggregated from various sources.

Because cancers take several years to develop and it can be difficult to establish a link between a cancer and a given occupational exposure, the best strategy is prevention. The preventive approach for exposure to carcinogens is the same as for any occupational hazard: anticipation, identification, assessment and control (through elimination at source, substitution and reduction of exposure), as well as informing and educating employers and workers about carcinogenic substances.

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