Hazards From Harvesting and Processing Cannabis

On March 2, 2018, the CDC published a report that evaluated potential hazards associated with the harvesting and processing of cannabis. Although the possession, use, and sale of all forms of cannabis are illegal under U.S. federal law, since 2012, multiple states have legalized the retail sale of cannabis for medical and recreational use. Previous research studies have indicated that Δ9-tetrahydrocannabinol (Δ9-THC), the principal psychoactive constituent of cannabis, can cause acute and chronic health effects. However, health effects from long-term occupational exposures to cannabis during harvesting and processing are unknown, in part because most studies have focused primarily on nonoccupational settings.


In June 2015, the National Institute for Occupational Safety and Health (NIOSH) received a request for a Health Hazard Evaluation (HHE) from a representative of the United Food and Commercial Workers International Union to evaluate potential health and safety hazards associated with harvesting and processing cannabis. NIOSH’s Health Hazard Evaluation Program helps employees, union officials, and employers learn whether health hazards are present at their workplace and recommends ways to reduce hazards and prevent work-related illness.


In response to the request, NIOSH visited a farm located in Washington in August and October 2015. Washington state legalized cannabis for medicinal use in 1998 and recreational use in 2012. At the time of the HHE, the farm was operated by the owner and three employees. The five-acre farm did not use any pesticides and grew cannabis, vegetables, and fruits. During the visit, the owner and all three employees were interviewed about their work, safety, and health concerns. Work practices were observed, and musculoskeletal risk factors for the hands, wrists, and shoulders during harvesting and processing tasks were evaluated.


The owner and all three employees reported performing several tasks at the farm, including harvesting, bud stripping, and trimming. No one reported hand, wrist, or shoulder symptoms or other musculoskeletal problems. However, employees did express concerns about whether the employees might develop long-term musculoskeletal problems because of manually hand trimming cannabis. Analysis indicated that hand trimming of cannabis involved low hand forces but was highly repetitive work. The findings of this HHE indicated that workers who harvest and process cannabis have exposures to highly repetitive work, most notably during hand trimming activities, which increase workers’ risk for musculoskeletal disorders.


Area and personal air samples were collected to test for gram-negative bacterial lipopolysaccharide (commonly referred to as endotoxin) and to determine bacterial and fungal diversity. Exposure to these biologic hazards can increase the risk for allergic and respiratory symptoms. Personal, full-shift endotoxin air sample concentrations ranged from 2.8 to 37 endotoxin units per cubic meter, which was below the Dutch Expert Committee on Occupational Safety recommended occupational exposure limit of 90 endotoxin units per cubic meter. No U.S. occupational exposure limits for endotoxin are available. Analysis of bacterial diversity revealed outdoor area air samples composed of sequences derived from the phyla Proteobacteria (34 percent) and Actinobacteria (23 percent). However, personal air samples were predominantly composed of sequences derived from the phylum Actinobacteria (47 percent). Analysis of fungal diversity revealed a higher diversity of fungi predominantly from the phylum Basidiomycota in outdoor (91 percent) and drying room samples (70 percent). However, personal air samples had a lower fungal diversity predominantly composed of the Ascomycota fungal species, Botrytis cinerea (59 percent). B. cinerea is a well-characterized aeroallergen and plant pathogen of cannabis. The findings of this HHE indicated that workers who harvest and process cannabis are exposed to aerosolized Actinobacteria and fungi such as B. cinerea from processing and hand trimming activities, which can increase the risk for allergic and respiratory symptoms.


Surface wipe samples were collected and analyzed for Δ9-THC. Δ9-THC was detected in all 27 surface sample wipes collected in cannabis production areas ranging from 0.17 to 210 micrograms per 100 square centimeters. The findings of this HHE indicated that workers who harvest and process cannabis have the potential for dermal and ingestion exposures to Δ9-THC. However, the health implications from long-term occupational exposure to Δ9-THC are unknown.


See the CDC Report


See the Health Hazard Evaluation Report


See also Medical Law Perspectives Report: Complementary and Alternative Medicine: Practitioner Liability