Summary

It has been recognized that women and men have different occupational profiles which may, therefore, translate into different occupational disease risks. Yet, most of our current understanding of occupational diseases stems from evidence accumulated from studies conducted in men. Meanwhile, women currently represent 48% of the labour force in Québec. Women’s health in the workplace continues to be an under-studied area and we are hindered particularly by the lack of understanding of how gender impacts workplace exposures. There is evidence that task assignments and working conditions may differ even when women and men have the same occupations. These different task assignments may translate into different exposures to toxic chemicals, ergonomic demands, risk of accidents, and psychosocial stressors. Whereas biological differences between women and men may be an underlying causal factor in the etiology of diseases, the consideration of gender differences in exposure assessment remains a challenge in occupational health research given the lack of existing tools that capture gender differences.

In the context of exposures occurring in the past or over a long period of time, expert assessment is superior to self-reported exposures since experts can account for the time period of exposure, local peculiarities of production processes or materials used, as well as particular tasks performed by the subject. Nevertheless, expert assessment remains costly in terms of resource time and thus, several prominent researchers have advocated for the use of job exposure matrices (JEMs). In particular, JEMs built from data derived from expert assessments have been proposed as a cost-efficient alternative to expert assessment. Such a database, known as the Canadian Job Exposure Matrix (CANJEM) was constructed by Drs. Jérôme Lavoué and Jack Siemiatycki from the exposure information obtained within four case-control studies conducted in Montréal between 1979 and 2004, that included over 12,000 subjects (over 30,000 jobs) wherein the majority of study subjects were men.

The improvement of CANJEM estimations of chemical and physical exposures of women in the workplace was one important objective of this project. To this end, expert assessment of the occupational histories of women in the Montréal Breast Cancer Case-Control Study from 2008 to 2011, directed by Mark S. Goldberg and France Labrèche, was employed. A team of trained chemists and industrial hygienists reviewed occupational histories to assign standardized occupation and industry codes, and exposures for each occupation held. Adding this enhanced data to CANJEM, our study aimed to discern whether occupational exposures differ between women and men holding the same jobs. In order to evaluate possible differences in exposure, sex-specific JEMs were developed to compare the frequency of occupations and the prevalence of agents between sexes. Then, the agreement of exposure metrics of the probability, frequency, intensity, and frequency-weighted intensity of exposure between each JEM was calculated. Hierarchical Bayesian models were then created to estimate notable differences between corresponding female- and male-specific JEMs based on the probability of exposure. Lastly, from the enhanced information in CANJEM, we derived estimates of the prevalence of exposure to 258 workplace agents among Montréal women.

Experts conducted assessments of 4,362 job descriptions from lifetime occupational histories provided by women in the Montréal Breast Cancer Case-Control Study. Upon comparison of sex-specific JEMs, the frequency of occupations differed between sexes regardlesss of whether all occupations in each separate JEM or occupations common to both JEMs were examined. Furthermore, the prevalence of agents in each JEM differed, with few overlapping across the most prevalent agents. It was observed that occupations common to both women and men revealed moderate agreement in the probability, frequency, intensity, and frequency-weighted intensity of exposure to CANJEM agents. Occupations held by women were frequently exposed to organic solvents, cleaning agents, and aliphatic aldehydes while occupations held by men were frequently exposed to PAHs (from any source and from petroleum specifically), organic solvents, and carbon monoxide.

From Hierarchical Bayesian analyses, we observed that agent-occupation combinations (using a 5-digit ISCO-68 job code resolution) among men had higher probabilities of exposure to CANJEM agents relative to women in one time period (1933-2011). Among commonly held occupations, different agents in which either women or men had higher probabilities of exposure were observed. Women working in farming had higher probabilities of exposure to a greater number of agents than men. Female Farm Workers (General) had notably higher probabilities of exposure to six agents while male Farm Workers (General) had two agents for which their probabilities of exposure were higher than females. In comparison, men had higher probabilities of exposure to agents in occupations such as labourers and salespersons. Men holding the occupational title of Manager, Retail Trade had significantly higher probabilities of exposure across 16 agents relative to three that were higher in women. In general, notable difference analyses illustrated that women in the workforce had more significantly higher probabilities of exposure to cleaning agents, fabric dust, and ozone while men had more significantly higher probabilities of exposure to PAHs (from any source or from petroleum), carbon monoxide, and lead.

One of the key gaps limiting further understanding of gender differences in occupational exposure is the paucity of reliable information about exposures incurred by women. From the enhancement of CANJEM with the addition of more occupations held by females, occupational titles frequently held by Montréal women and the prevalent exposures incurred in the workplace from 1933 to 2011 were identified. The most frequently held jobs among women tended to be in the textile and production, health care, and service industries. Meanwhile, organic solvents, cleaning agents, and ozone were the most prevalent agents that working women were exposed to. Interestingly, Montréal women were exposed only to 196 CANJEM agents out of 258 and thus, 62 CANJEM agents were not listed in any occupations held by women.

Our findings will assist in the improvement of the ability of CANJEM to evaluate workplace exposures in women. Given the limited data that exists on the relationship between sex and/or gender and exposure, the validity of applying exposure assessment tools developed from information collected from men (or primarily from men) to studies in women is unknown. Our results add to previous findings of industry segregation between women and men in that it is observed that exposure profiles may also differ within the same occupational group due to differences in assigned tasks. Upon observing such exposure differences between women and men across agent-occupation combinations, it is evident that further efforts must be made to incorporate exposure information of female workers into JEMs and that a female JEM may be needed to accurately estimate exposures for certain workplaces. Ultimately, it is clear that we must develop tools whereby we can equitably monitor and inform the safety and health of female workers.