Occupational Asthma Fatality in Cannabis Industry: A Comprehensive Public Health Investigation


The cannabis cultivation and production industry has witnessed a surge in popularity, but with growth comes the need for increased awareness and management of occupational health and safety risks. Recent studies have shed light on various respiratory hazards faced by employees in this industry, including exposure to microbial and plant allergens, irritants, as well as chemicals like pesticides.

This article delves into a tragic case involving a 27-year-old woman employed in a Massachusetts indoor cannabis cultivation and processing facility, whose work-related respiratory symptoms ultimately led to a fatal occupational asthma attack. The subsequent public health investigation aimed to determine the cause of this fatality and identify preventive measures for the industry.

TABLE 1 – Occupational Hazards in Cannabis Production: A Comprehensive Analysis of NIOSH HHE Program Findings

The National Institute for Occupational Safety and Health (NIOSH) Hazardous Health Evaluation (HHE) program plays a crucial role in investigating and addressing workplace exposures, evaluating health concerns, and recommending measures to mitigate hazards. Over the years, the program has received an increasing number of requests related to the cannabis industry, reflecting the growing significance of occupational safety and health in this emerging sector.


Since 2004, the NIOSH HHE program has responded to 10 cannabis-related requests, originating from diverse sources such as law enforcement agencies, state-approved cannabis grow operations, and a coroner’s office. While initial requests focused on law enforcement activities and crime scene investigations involving potential illicit drug exposures, recent trends indicate a shift towards occupational exposures during cannabis harvesting, cultivation, processing, and packaging.

Context of Cannabis Legalization:

The dichotomy between federal and state regulations regarding cannabis is crucial to understanding the complexities of occupational safety in this industry. Despite the federal classification of cannabis as a Schedule I substance by the United States Drug Enforcement Administration, many states have legalized its use for medicinal and recreational purposes. This incongruity necessitates a closer examination of occupational safety and health information in the cannabis industry.

Limited Pre-existing Research:

Before the recent surge in cannabis-related HHEs, occupational safety and health research on cannabis exposure were severely limited. Earlier studies primarily focused on microbiological hazards associated with European industrial hemp fiber facilities, revealing potential risks to workers. These studies laid the foundation for understanding the challenges posed by cannabis production, particularly in the realms of harvesting, cultivation, processing, and manufacturing.

Occupational Exposure and Health Effects:

Workers involved in cannabis-related activities face potential exposure to delta-9-tetrahydrocannabinol (Δ9-THC) and proteins derived from various parts of the Cannabis sativa plant. Previous studies have highlighted a spectrum of health effects, ranging from pruritus and urticaria to respiratory symptoms such as asthma and dyspnea. Notably, law enforcement officers routinely handling cannabis plants have demonstrated an increased risk of developing allergic rhinitis and work-related contact urticaria.

Microbiological Hazards:

Research has shown that workers handling cannabis products can be exposed to elevated levels of microorganisms, including bacteria and fungi. Hemp production workers, especially those involved in tasks that disturb dust, have faced endotoxin exposures exceeding recommended levels. The inhalable levels of bacteria and fungi reported in factory floor samples further underscore the potential respiratory health impact on workers in cannabis production settings.

Cannabis Sensitization and Allergies:

Although cannabis allergy was reported as early as 1971, limited studies on cannabis sensitization prevailed due to the lack of commercial extracts and legal constraints. Recent European studies have identified and characterized Cannabis sativa immunoglobulin E (IgE) binding allergens, with the 9-kDa non-specific lipid transfer protein (nsLTP) emerging as a significant allergen named ‘Can s 3.’ This allergen has broad cross-reactivity with fruits, vegetables, and tobacco, emphasizing the need for heightened awareness of potential allergic reactions in workers.

Hypersensitivity Reactions to Cannabis

Hypersensitivity reactions to cannabis have become a subject of growing concern, prompting research initiatives by the National Institute for Occupational Safety and Health (NIOSH). Beyond Health Hazard Evaluation (HHE) requests, the NIOSH has explored cases of hypersensitivity reported not only in workers but also in individuals handling or consuming cannabis for medical or recreational purposes. This chapter delves into the observations, prevalence, and characteristics of hypersensitivity reactions associated with cannabis exposure, drawing on both North American and European studies.

Regional Variances in Hypersensitivity

In regions where cannabis use is legalized, such as Colorado, clinicians have reported an uptick in patients exhibiting hypersensitivity to cannabis. Notably, the profile of Immunoglobulin E (IgE) reactivity in North American populations appears to differ from that observed in European study populations. Collaborative research between NIOSH and the University of Toronto has uncovered high molecular weight allergens from various Cannabis sativa sources, including roots, leaves, buds, and flowers. This section explores the identified allergens and their implications for understanding regional variations in hypersensitivity reactions.

Allergen Characterization

The research conducted by NIOSH investigators revealed intriguing insights into the allergens responsible for sensitizing individuals to cannabis. Among the identified allergens were a 23-kDa oxygen-evolving enhancer protein 2 and a 50-kDa protein recognized as the photosynthetic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase. Notably, sensitization to Can s 3, a significant allergen in European studies, was absent in the North American analysis. This section provides a detailed exploration of the allergen characterization, emphasizing the implications for understanding the diverse nature of cannabis hypersensitivity.

Occupational Sensitization in the US Cannabis Workforce

Despite the surge in cannabis cultivation and processing in the United States, the prevalence of occupational sensitization to Cannabis sativa remains largely unknown. This section discusses the potential implications of the expanding workforce in the emerging cannabis industry and the likelihood of increased hypersensitivity reactions among industrial cultivation workers. The need for ongoing research and surveillance to monitor and mitigate occupational sensitization is emphasized.

Lessons Learned

Δ9-THC and Δ9-THCA: Differentiating Occupational Exposures

The psychoactive properties of Δ9-tetrahydrocannabinol (Δ9-THC) have made it a focal point of concern in the cannabis industry. This chapter explores the distinctions between Δ9-THC and its precursor, Δ9-tetrahydrocannabinolic acid (Δ9-THCA), highlighting the importance of differentiating between the two in epidemiological studies. The potential health effects of these cannabinoids, including the lesser-studied cannabidiol (CBD), are considered in the context of occupational exposures.

Exposure Assessment: Surface Sampling and Analytical Methods

The intricacies of exposure assessment in the cannabis industry are examined, particularly in distinguishing between Δ9-THC and Δ9-THCA. The chapter discusses the challenges associated with surface wipe samples, utilizing different analytical methods, and the decision-making process for exposure assessors. The trade-offs between methods with varying limits of detection (LOD) are explored, emphasizing the need for purpose-driven sampling to identify workplace contamination or differentiate between potential cannabinoid exposures.

Airborne Exposure: A Comprehensive Approach

In addition to surface and dermal sampling, this section advocates for a comprehensive assessment of airborne Δ9-THCA and Δ9-THC levels. The importance of considering airborne exposures is highlighted, especially in commercialized grow operations with workplace policies prohibiting cannabis use. The chapter calls for future research to develop and validate multiple phytocannabinoid LC–MS–MS methods, providing LOD values for all measured cannabinoids to enhance the accuracy of exposure assessments in the cannabis industry.

Understanding Distinct Exposures: Occupational vs. Personal

Exposure to cannabis varies significantly between occupational settings and personal usage scenarios. Employees working in cannabis cultivation and processing facilities face inhalation and dermal exposures, inhaling plant materials and having direct or indirect skin contact with cannabinoids. The potential for dermal absorption of cannabinoids and ingestion through hand-to-mouth activities further complicates the exposure pathways in occupational settings. In contrast, individuals using cannabis for medicinal or non-medical (recreational) purposes predominantly ingest Δ9-THC-containing materials or inhale cannabis smoke through combustion. This chapter delves into the nuanced differences in exposure routes and their implications for health.

Comparing Nature of Exposures: Occupational vs. Personal Use

The nature of exposures in occupational and personal contexts is distinct. Employees in cultivation and processing are primarily exposed to raw cannabis and its organic material, with heat applied only during the final processing stages. Conversely, non-medical and medicinal users combust raw cannabis, activating Δ9-THC and inhaling it deeply. This section explores the health effects directly related to the inhalation of smoke and psychoactive effects of Δ9-THC in personal use. Occupational exposures may result in lower-level inhalation hazards and more frequent skin contact with cannabinoids and plant proteins, depending on workplace policies.

Ventilation Challenges in Occupational Settings

While ventilation was not a primary focus in completed Hazardous Health Evaluations (HHEs), it poses a critical challenge in indoor cannabis grow facilities. The absence of specific guidance from ASHRAE for such facilities compounds the complexity. This section details the intricate balance required for optimal growth conditions while ensuring safe working environments. Factors like CO2 enrichment, ozone generation, high-intensity grow lights, odors, and microbial contamination prevention contribute to the need for sophisticated ventilation systems. The potential hazards associated with CO2 concentrations during enrichment and fumigation are highlighted, emphasizing the importance of effective workplace entry restriction programs.

Medicinal/Non-Medical Cannabis and Industrial Hemp

This section provides an overview of the classifications of cannabis plants—medicinal, non-medical, and industrial hemp—derived from various species such as C. sativa, Cannabis indica, and Cannabis ruderalis. The most crucial distinctions lie in Δ9-THC and cannabinoid concentrations. The 2018 U.S. Farm Bill’s impact on the legal status of industrial hemp, no longer considered a controlled substance, is discussed. The chapter explores the potential crosswalk of exposure characterization information between the hemp industry and medicinal/non-medical cannabis sectors, emphasizing the need for specific exposure studies tailored to industrial hemp.

REFERENCE LINK: https://academic.oup.com/annweh/article/64/7/693/5735589

Case Report

The employee, hired in May 2021, initially worked as a cycle counter throughout the facility, including areas where cannabis was ground. In late July, she began experiencing symptoms such as nausea, loss of taste and smell, earache, and cough. Despite two negative SARS-CoV-2 tests, bilateral wheezing was noted during a physical examination. The employee’s mother reported the development of work-related respiratory symptoms after a few months of employment.

On October 1, the employee transitioned to flower production, involving grinding cannabis flowers for approximately 15 minutes, three times a day, leading to increased dust exposure. Despite efforts to minimize exposure, including the use of a non-HEPA filtered vacuum, visible dust escape occurred during grinding and other product handling processes. Colleagues noted an escalation in her cough, especially when the grinder was operational. The employee utilized her own N95 respirator and followed company-mandated protective measures.

A critical incident occurred on November 9 when the employee experienced acute dyspnea at work, necessitating emergency medical services. Enroute to the hospital, she received albuterol nebulization, and her symptoms temporarily resolved. However, she reported work-related respiratory issues, and her prescribed inhaler was nearly empty. Subsequent worsening symptoms on January 4, 2022, led to another EMS call. Despite resuscitation efforts, she suffered a cardiopulmonary arrest and was diagnosed with anoxic brain death, ultimately succumbing to the condition.

Public Health Investigation

A comprehensive investigation by the Massachusetts Department of Public Health revealed that the employee had undergone a pulmonary evaluation in 2016 for chronic cough, which was attributed to cigarette and marijuana smoking, gastroesophageal reflux disease, and rhinitis. The pulmonologist ruled out asthma at that time. The employee’s primary care physician had not seen her since 2015 and had not prescribed any allergy or asthma medication subsequently.

The Occupational Safety and Health Administration (OSHA) conducted an inspection, including personal air sampling. The grinder operator’s 8-hour time-weighted average respirable dust concentration was 0.012 mg/m3, well below OSHA’s permissible exposure limit of 5 mg/m3. Additional monitoring for endotoxin, a pro-inflammatory contaminant, revealed levels within acceptable limits. However, interviews with coworkers indicated work-related respiratory and skin symptoms, suggesting potential occupational asthma cases.

Discussion : Occupational Asthma in the Cannabis Industry: Unveiling Respiratory Hazards and Preventive Strategies

The burgeoning cannabis industry has not only brought about economic growth but has also raised concerns regarding the occupational health risks faced by employees, particularly those involved in cultivation and production. This discussion explores the respiratory hazards encountered by cannabis industry workers, with a focus on a fatal case of occupational asthma. The nuanced details surrounding allergens, irritants, and risk factors provide valuable insights for both industry stakeholders and occupational health professionals.

Respiratory Hazards in Cannabis Production

Employees in the cannabis industry are frequently exposed to substantial amounts of ground cannabis product, especially in areas involving flower grinding and preroll production. Reports of asthma, allergic rhinitis, and urticaria among cannabis production workers underscore the significance of respiratory health concerns in this occupational setting. Various allergens and irritants have been identified, contributing to the manifestation of respiratory symptoms (1–3).

Work-related asthma is a multifaceted condition encompassing occupational asthma, induced by sensitizers or irritants, and work-exacerbated asthma, which worsens preexisting asthma due to workplace exposures (4). In the case at hand, the absence of a prior asthma history coupled with the temporal relationship between work exposure and the onset of asthma signs and symptoms aligns with a diagnosis of occupational asthma.

Surveillance and Studies: Insights from Washington

Enhanced surveillance in Washington state revealed a notable occurrence of work-related asthma cases among indoor cannabis production facility employees. Seven asthma cases were identified, leading to the discontinuation of cannabis employment for some, while others remained symptomatic across different cannabis facilities. This highlights the persistent nature of occupational asthma, even with changes in work environments.

A study conducted on employees at an indoor cannabis production facility in Washington found that a substantial proportion exhibited symptoms suggestive of asthma. Occupational allergy symptoms were prevalent, with abnormal spirometry and skin prick testing consistent with cannabis sensitization. Additionally, fractional exhaled nitrogen oxide testing revealed increased airway inflammation throughout the work week, emphasizing the dynamic nature of respiratory conditions in this industry.

Fatal Asthma: Risk Factors and Associations

Despite the perception of asthma as a mild condition, fatal outcomes can occur, and various risk factors were identified in the case under consideration. Disparities in income, education, and access to healthcare were associated with a higher risk of death. Work-related asthma was linked to poorer asthma control, highlighting the need for effective preventive measures.

Several risk factors contributed to the fatal outcome, including an emergency department visit, recent use of oral glucocorticoids, increased dyspnea and bronchodilator inhaler use without inhaled glucocorticoids, continued exposure, and the absence of a healthcare provider specializing in occupational allergies.

Occupational Asthma: Latency and Sensitization

Occupational asthma typically exhibits a latency period of months to years between initial exposure and symptom onset. While the reported case demonstrated a shorter latency period from the first occupational cannabis exposure to symptoms, the overall latency was extended due to personal cannabis use. Cross-sensitivity between cannabis and plant allergens may have predisposed the employee to cannabis sensitization, emphasizing the complexity of respiratory health in this context.


The cannabis industry’s rapid growth necessitates a comprehensive understanding of occupational health risks, particularly those related to respiratory hazards. This discussion highlights the intricate interplay of allergens, irritants, and risk factors contributing to occupational asthma in cannabis production. It underscores the urgency of implementing preventive strategies, such as enhanced surveillance, proper respiratory protection measures, and education programs, to safeguard the respiratory well-being of industry employees. By addressing these concerns proactively, the cannabis industry can foster a safer and healthier working environment for its workforce.

reference link : https://www.cdc.gov/mmwr/volumes/72/wr/mm7246a2.htm?s_cid=mm7246a2_w



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