Summary

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 Quebec government, the World Health Organization and the Canadian Institutes of Health Research all recommend conducting sex-specific analyses. Although a few studies have incorporated sex into the analysis of musculoskeletal problems at work, so far only two intermediate-quality studies  have compared male and female exposure to chemicals, taking occupation and economic sector into account. The objective of this study was to explore the existence of differences in occupational exposure between men and women using existing 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 this study, the occupational exposure associated with jobs occupied by men was compared with that of jobs occupied by women (all occupations and industries combined) to reveal any exposure differences. Exposures were then compared between the jobs occupied by both sexes within the same occupational groups, then the same occupations and finally the same “occupational group/industrial group” pairs. For the purpose of the comparisons, the concordance between the exposure of men’s jobs and that of women’s jobs was calculated using intraclass correlation coefficients. Then, “notable difference” rates were calculated from the modelling of the male/female exposure differences by applying hierarchical Bayesian models.

As anticipated, given the different occupational profiles of men and women, 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 a few physical agents. Generally speaking, the jobs held by men were found to have higher exposure rates, especially to motor vehicle exhaust, petroleum fractions, polycyclic aromatic hydrocarbons, construction 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 rates 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 occupied 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 exposure values were similar. Of the 326 notable differences in exposure rates 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 the occupation and the industry were taken into account, only 3.1% of the differences in occupational exposure rates were left with no obvious explanation.

To conclude, sex-specific 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 sex related.