Occupational health: A modified approach to mitigating the burden of work-related asthma

Tags: ,

By: Simeon Gotzev
Supervisor: Dr. Susan Tarlo

Work-related asthma (WRA) is a serious and burdensome occupational health problem. It is the most common chronic occupational lung disease in industrialized countries, with 10-15% of all new asthma cases in adults triggered by workplace exposures.1 From 2001 to 2005 the Workplace Safety and Insurance Board (WSIB) accepted 182 claims of WRA from the health care sector, paying $525 169 in compensation.2 This represents 17.5% of the total cases (n = 1043) accepted by the WSIB for that time period. Data made available from the WSIB reveals 54% of total claims submitted were accepted for the same time period, a rate much lower than was in the past, with accepted claims making up 90% of total accepted claims for the same time interval a decade earlier. Moreover, these figures do not account for persons diagnosed with WRA who did not submit a claim. Based off data from our lab’s clinical population under study, 34% of patients diagnosed with WRA chose not to submit a WSIB claim. In addition, many cases of WRA are left undiagnosed by physicians (due to lack of education of occupational medicine covered in medical school curricula and residency training programs).3 The overall impact of WRA on patients’ health and society necessitates an increase in awareness to medical professionals and the general public. In an effort to improve diagnosis and awareness of WRA in the clinical and research setting, we conducted a retrospective analysis of a WRA clinical population from the Asthma & Airways Centre at the Toronto Western Hospital.

Understanding the predominant occupations and related exposures inducing WRA in the modern work environment are necessary in deciding where future preventative efforts and research should be focused. Historically, the manufacturing industry has been identified as one of the main contributing work environments inducing WRA, varying in degree based on the demographic and socioeconomic nature of the clinic population under study.4,5 While it remains the most common occupational setting responsible for WRA in our clinic, its prevalence has dropped by 30%. Interestingly, this subsiding trend is mirrored by a decline in isocyanate related cases–which are recognized as the major WRA-inducing agents in the manufacturing industry. Since the early 1980s, the Ontario Ministry of Labour has implemented preventative efforts.6,7 The observed declining trend in our clinic reflects an effective preventative program and suggests an explanation for the parallel fall in manufacturing related cases. The prevalence of manufacturing cases remains very high, comprising 40% of total cases in 2008 to 2015. However, the rate of isocyanate exposures has been minimal in recent years. In the future, further preventative programs should be targeted at other agents common in the manufacturing industry, namely: flour and other baking products (n=10), welding fumes (n=7), cleaning products (n=7), oil and coolant mists (n=6), paint fumes (n=5), and epoxy resins (n=5).

While some efforts are in place to reduce the WRA burden of the manufacturing industry, a growing and unrecognized problem is being observed in the health care and education industries. From 2000 to 2007 and 2008 to 2015, cases from health care industries increased from 3% to 10% of total cases. Even more dramatically, the education industry increased from 1% to 10% of total cases. Collectively, they account for over one fifth of WRA cases observed in our clinic in the more recent cohort, a five-fold increase from the earlier cohort. Data collected from Statistics Canada shows a similar gross employment trend in Ontario. The health care industry has increased from 5% in 2003 of the total workforce to 11% in 2013. The Education industry has increased from 2% in 2003 to 11% in 2013. It is likely that the patterns of employment in Ontario have influenced the increase in prevalence of these industries in our clinic.

The most common occupation noted amongst the health care and education industries were cleaners. Correspondingly, cleaning agent exposures have considerably increased in prevalence, from 5% from 2000 to 2007 to 17% from 2008 to 2015 in our clinic, overtaking isocyanates as the most prevalent exposure. Common cleaning products observed in our clinic consistent with the study include: quaternary ammonium compounds used as disinfectants for surface cleaning, and products containing bleach, ammonia and hydrochloric acid. Exposures to these asthma triggers identified by workers may be reduced or eliminated from health care and education industries by replacement with safer substitutes. Further research into cleaning agents and asthma should be encouraged, as it remains a relatively understudied, yet prominent occupational group.


1. Gautrin D, Newman-Taylor A, Nordman H, et al. Controversies in epidemiology of occupational asthma. European Respiratory Journal. 2003;22(3):551-559.

2. Liss G. Work related asthma. Occupational and Environmental Medicine. 2002;59(8):503-504.

3. “Portrait of Canada’s Labour Force.” Portrait of Canada’s Labour Force. N.p., n.d. Web. 10 Aug. 2015.

4. Pechter E, Davis L, Tumpowsky C, et al. Work related asthma among health care workers: Surveillance data from California, Massachusetts, Michigan, and New Jersey, 1993-1997. Am J Ind Med. 2005;47(3):265-275.

5. Rosenman K, Reilly M, Kalinowski D. A State-Based Surveillance System For Work Related Asthma. Journal of Occupational & Environmental Medicine. 1997;39(5):415-425.

6. Tarlo S, Banks D, Liss G, et al. Outcome determinants for isocyanate induced occupational asthma among compensation claimants. Occupational and Environmental Medicine. 1997;54(10):756-76.

7. Tarlo S, Liss G, Dias C, et al. Assessment of the relationship between isocyanate exposure levels and occupational asthma. Am J Ind Med. 1997;32(5):517-52.