The First U.S. Death From Occupational Asthma in Cannabis Production, 2022

Summary

Occupational allergies, including asthma, are an emerging concern in the fast-growing U.S. cannabis industry. In January 2022 a worker at an indoor cannabis cultivation and processing facility in Massachusetts died of an asthma attack — the first U.S. death attributed to occupational asthma in a cannabis production worker.

The case, investigated by the Occupational Safety and Health Administration (OSHA) with the Massachusetts Department of Public Health and reported in CDC's MMWR in 2023, shows missed chances for prevention: controlling exposures at work, medical surveillance, and treatment by current asthma guidelines.

Work-related asthma comes in two forms: occupational asthma (new asthma caused by sensitizers or irritants at work) and work-exacerbated asthma (existing asthma made worse by work). Known hazards in cannabis production include microbial and plant allergens and irritants, pesticides, and allergens from the cannabis plant itself; in some areas workers handle large amounts of ground cannabis.

The case

Timeline of work assignments, symptoms and events, 2021–2022. A cycle counter counts packaged products across the facility, including ground-product areas; a flower technician grinds cannabis flowers and makes prerolls. CDC.

• May 20, 2021. A 27-year-old woman starts as a cycle counter, working throughout the facility, including where cannabis is ground. She has no history of asthma, allergies or skin rash (a 2016 lung evaluation for chronic cough had ruled asthma out).
• After 3–4 months. She develops a work-related runny nose, cough and shortness of breath. In late July she has nausea, lost taste and smell, earache and cough; two COVID-19 tests are negative, and a doctor hears wheezing in both lungs.
• October 1. She moves to flower production: grinding cannabis flowers for about 15 minutes, three times a day, and filling prerolls (cannabis cigarettes). Dust exposure rises. The grinder's shop vacuum has no HEPA filter, and visible dust escapes. Coworkers notice her cough worsens when the grinder runs. The response: covering the vacuum with plastic (which becomes coated with ground cannabis), moving her workstation out of the grinder room, and her own N95 respirator, long sleeves and gloves.
• November 9. She becomes acutely short of breath at work and is taken by ambulance to an emergency department. An albuterol nebulizer relieves her. She says she might be allergic to something at work. She is prescribed 5 days of prednisone, cetirizine and an albuterol inhaler — but no inhaled steroid — and told to follow up with a primary care doctor, who had not seen her since 2015. Her mother later says she was short of breath only at work, and that the inhaler, used mainly at work, was nearly empty: about 200 puffs in about 2 months.
• January 4, 2022. After 2 weeks of worsening breathlessness, she starts sneezing and coughing while filling prerolls. Repeated albuterol does not help. She goes into cardiopulmonary arrest before the ambulance arrives; coworkers resuscitate her, but she never regains consciousness. Anoxic brain death is diagnosed on January 7. There was no autopsy.

The investigation

• Air sampling, done after the grinder got a new HEPA-filtered vacuum: respirable dust at the grinder averaged 0.012 mg/m3 over 8 hours (not detectable for two nearby workers), far below OSHA's limit of 5 mg/m3.
• Endotoxin (an inflammatory contaminant from bacteria growing on organic material such as cannabis flowers): 27 EU/m3 at the grinder and 1.8 and 1.9 for nearby workers, against a Dutch recommended limit of ≤90; 14 EU/m3 in a 15-minute sample during active grinding.
• Low readings do not clear the workplace: dust and endotoxin below limits do not rule out enough cannabis allergen in the air to trigger asthma.
• Coworkers: 4 of 10 with similar duties reported work-related respiratory or skin symptoms. One former worker's symptoms suggested occupational asthma: he had not needed an inhaler since adolescence.

Why this was occupational asthma

No history of asthma and symptoms that tracked her work exposure fit a diagnosis of occupational asthma. Other studies point the same way:

• Washington State surveillance found 7 asthma cases among indoor cannabis workers. One person with occupational asthma had symptoms at two different facilities, with a symptom-free 2-year gap between them while not exposed.
• At one Washington facility, 13 of 31 workers had symptoms suggesting asthma. Of 10 with occupational allergy symptoms, 7 had abnormal lung tests and 5 had skin tests showing cannabis sensitization. Airway inflammation markers rose across the work week.

Risk factors for her death: the emergency visit, a recent course of oral steroids, rising breathlessness and rescue-inhaler use without an inhaled steroid, continued exposure, and no provider with expertise in occupational allergy. Fatal asthma can happen even in disease thought mild, and income, education and access to care all affect the risk.

Timing. Occupational asthma usually takes months to years to appear (a fatal case from powdered shark cartilage came 16 months after exposure began). Her symptoms came quickly after starting the job, but her personal cannabis use meant earlier exposure; cross-sensitivity with other plant allergens may also have played a part.

Limitations: cannabis allergy was not confirmed by skin or IgE tests; airborne cannabis allergen could not be measured; and investigators had to rely on records and interviews rather than the worker herself.

Preventing it

Research gaps: ways to measure and control exposure; how common occupational allergy is in cannabis workers and what raises the risk; and reliable clinical tests for cannabis sensitization.

The bottom line for clinicians: evaluate any worker with new or worsening asthma for a link to work, and recognize cannabis production as a possible cause.

Sources

Based on Virginia M. Weaver et al., "Fatal Occupational Asthma in Cannabis Production — Massachusetts, 2022," Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention (2023), by authors from OSHA, National Jewish Health, the Massachusetts Department of Public Health, the Mayo Clinic and NIOSH; published by CDC.