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NIOSH Evaluates Hazards during Cannabis Harvesting
In response to a request from the United Food and Commercial Workers International Union, NIOSH staff have evaluated employees’ exposures to ergonomic, chemical, and microbial hazards during cannabis harvesting and processing at an organic farm in Washington State. As described in a report released in April, the evaluation resulted in several recommendations for minimizing ergonomic stressors and potential exposures to delta-9-tetrahydrocannabinol (THC), which is the psychoactive component of cannabis.
When NIOSH staff visited the 5-acre farm in August and October 2015, they observed a 4-person staff performing various tasks related to trimming cannabis plants. The plants stood approximately 8 feet tall and 6 feet wide. One of the tasks required employees to stoop and reach horizontally around screens of green netting to cut stems, adopting postures that put pressure on the lower spine. To remove the plants' flowers, some employees pulled the stems through a hole drilled in the bottom of a tin can, a makeshift tool whose lightweight construction could contribute to hand stress and fatigue.
Employees were asked to simulate the motions involved in trimming and destemming, and NIOSH staff used pinch gauges, digital force gauges, and a virtual-reality electrogoniometer glove to measure the force these tasks exerted. During a 9-minute period of trimming, experienced employees averaged 1.9 repetitive hand motions per second, nearly twice the rate as inexperienced employees. Full-shift breathing zone air samples on all 4 employees established endotoxin concentrations that ranged from 2.8 to 37 endotoxin units per cubic meter (EU/m3), well below the 90 EU/m3 limit recommended by the Dutch Expert Committee on Occupational Safety (DECOS). No occupational exposure limits for endotoxin have been established in the United States. NIOSH conducted wipe sampling for THC and found detectable levels of the chemical on all 27 samples. Because quantification of THC required the laboratory to dilute samples with high THC concentrations, the reported results, which ranged from 0.17 to 210 µg/100cm2, likely underestimate actual concentrations, according to the NIOSH report. Agency staff did not conduct air sampling for THC, citing a previous study of 30 indoor cannabis grow operations, which found that air sampling was unlikely to detect measureable THC concentrations. The health effects of occupational exposure to THC are unknown. Among the agency’s recommendations for minimizing ergonomic stressors during trimming was replacement of the tin can with a tool made from more durable materials to reduce hand fatigue. NIOSH also recommended that the employer remove the green netting so workers could stand closer to the plant while trimming and to develop a job rotation plan that allows employees to alternate tasks that require high hand-and-finger movement with tasks that use different muscle-tendon groups. To control potential exposures to THC, NIOSH suggested that the employer develop a cleaning schedule to remove the chemical from work surfaces and tools, and to train employees on the cleaning, lubrication, sharpening, and maintenance of tools as recommended by the manufacturers. All employees were encouraged to wear non-latex gloves when handling cannabis or equipment that may be contaminated with THC, and to wash with soap and water after removing gloves. The full report is available as a PDF from the website of NIOSH’s Health Hazard Evaluation program.

One of the tasks required employees to stoop and reach horizontally around screens of green netting to cut stems, adopting postures that put pressure on the lower spine.
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