Dorian Kenleigh

Project title: Cannabis Allergy in Occupationally Exposed Cannabis Workers, Recreational Users and Non-Users

Degree: MPH | Program: Occupational and Environmental Medicine (OEM) | Project type: Thesis/Dissertation
Completed in: 2022 | Faculty advisor: Coralynn Sack


Introduction: The expansion of the U.S. cannabis industry has created thousands of new jobs in cultivation, processing and distribution. While little is known about occupational hazards in the Cannabis industry, pilot studies suggest an increased risk of respiratory exposures and associated adverse health outcomes, including immunologic sensitization to Cannabis. These prior studies are confounded by a high rate of personal cannabis use among employees. Our current study addresses this limitation by characterizing the prevalence of work-related allergic and irritant respiratory symptoms in cannabis employees compared to recreation cannabis users and non-cannabis users without workplace exposure.

Methods: A cross-sectional study of cannabis workers, recreational users (defined as cannabis use ≥ 3 days/ week) and non-users was conducted. Cannabis workers (n=42) were recruited from two indoor cannabis grow facilities in Seattle, Washington. A demographically similar group of recreational cannabis users (n=20) and non-users (n=20) without history of occupational or personal cannabis cultivation were recruited from the surrounding community. A questionnaire was used to gather information on respiratory, ocular, nasal and dermal health symptoms as well as health history, cannabis use history, smoking status, and occupational exposure to dusts, gases and other respiratory hazards from all participants. A subset of consenting employees with work-related symptoms (n = 21) and the non-occupationally exposed participants underwent measurement of spirometry, fractional exhaled nitrogen oxide (FeNO) and skin prick testing (SPT) for sensitization to cannabis / hemp and other common allergens. Independent sample t-tests with unequal variances or linear ANOVA were used to compare spirometry and FeNO results between 1) occupationally exposed vs non-occupationally exposed participants and 2) recreational-cannabis users and non-cannabis users. A chi-quared test was used to compare skin prick test results. Adjusted odds ratios were determined using multivariate logistic regression to characterize the association between atopic symptoms and cannabis exposure in occupationally exposed and non-occupationally exposed participants.

Results: Ninety-seven percent (97%) of the employees surveyed were recreational cannabis users, with 81% (n = 25) smoking cannabis multiple times per day. Per study inclusion criteria, all of the recreational-cannabis users reported cannabis use at least three times per week and the non-users denied recent cannabis exposure. While the average age of participants across exposure categories were similar, the cannabis employees were more likely to be male and non-Hispanic white than the non-occupationally exposed participants (55% vs 33% and 81% vs 65% respectively). Cannabis employees had an average 9.2 ppb (95% confidence interval 0.17 to 18.6, p-value 0.05) higher FeNO in comparison to the non-occupationally exposed participants. While there was a trend towards decreased spirometry in the cannabis employees vs non-occupationally exposed participants (mean FVC% predicted: 96.4% vs 101.7% and mean FEV1% predicted: 91.0% vs 96.8% respectively), these differences did not reach statistical significance. There were no significant differences in FeNO or spirometry between recreational users and non-users. The odds of having a positive skin prick test to cannabis was 2.97 (95% CI 1.11- 7.11, p-value 0.008) in the occupational vs non-occupational exposed group. Multivariate analysis demonstrated that occupational exposure to cannabis was associated with a 56% increase in FeNO among cannabis workers (95% CI 3% - 125%). Adjusting for medical history, tobacco use and demographics, the odds ratio of atopic or irritant symptoms among cannabis workers compared to non-users of cannabis without occupational exposure 30.06 (95% CI 5.77, 231.38; p<0.001).

Conclusions: Cannabis employees exhibited a higher FeNO, a trend towards decreased spirometry and increased odds of cannabis sensitization on SPT in comparison to recreational-cannabis users and non-users. More robust observation of these workers, the work environment and their occupational exposures should be undertaken to develop appropriate preventive strategies and to develop respiratory protection standards for workers in this adolescent industry.