Background: Little is documented for UV exposure to ‘grow’ lights used by indoor farms as well as the cannabis industry. The purpose of this study was to characterize UV light exposure in nursery and grow rooms in two medical cannabis production facilities using area and personal sampling.
Methods: Three different light spectrums were assessed: UV-Broadband (180 to 400 nm), UVA (315 to 400 nm) and blue light (305 to 700 nm). The radiometer hub supported one spectral sensor at a time, therefore the spectrums were assessed consecutively rather than simultaneously. Area surveys were accomplished by consecutively mounting the spectral sensors on a tripod at a fixed height of 1.6 meters for several minutes per sample. In grow rooms, the tripod was systematically moved to 32 to 37 locations; in nurseries samples were taken from 4 to 6 locations. Personal sampling utilized sensors consecutively mounted on a helmet worn by the worker. In each facility, one worker wore each sensor for 20 minute periods in the grow room.
Results: In both area and personal sampling, the ACGIH TLV (American Conference of Governmental Industrial Hygienists, Threshold Limit Value) for UV Broadband exposure was exceeded. For area sampling in grow rooms, 8 of 69 (12%) samples exceeded the UV Broadband TLV of 0.003 J/m 2 in under 8 hours, and all (n=10) area nursery room samples exceeded this TLV. In area grow room and nursery samples, the average number of exposure-minutes resulting in a TLV exceedance was 318 and 61 minutes, respectively. Personal grow room sampling in the UV Broadband spectrum resulted in a mean (SD) effective irradiance of 0.0001 (3.807e-5) Eff mW /cm 2 over a 20 minute interval. At this mean exposure level, the worker did not exceed the UV Broadband TLV during the 20 minute sample but would be projected to exceed the TLV in 446 minutes (less than 8 hours). No sample from any facility or room type exceeded the ACGIH TLVs for UVA or blue light.
Conclusion: While data is limited for the three light spectrums surveyed, the UV Broadband spectrum did have samples that exceeded the ACGIH TLV. Nurseries had more UV Broadband exposure than grow rooms. Additional assessment, particularly personal sampling, is needed to more fully characterize cannabis workers’ exposure to UV light. Further research is needed to establish validated UV light sampling methods, to examine the effectiveness of protective equipment, and to establish employer best practices.