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How do "skunky" cannabis emissions affect air quality?

A new study from the University of British Columbia is investigating the cause of the “skunky” odor that is emitted by cannabis production facilities. The experts want to understand how cannabis emissions may affect air quality, workers, and the general public.

Davi de Ferreyro Monticelli, a doctoral student in UBC’s Department of Earth, Ocean and Atmospheric Sciences is leading the study. According to Monticelli, knowledge gaps concerning cannabis emissions should be addressed while the industry is still developing.

In a recent interview, Monticelli explained what’s missing in our knowledge about cannabis production emissions, and how their smell compares to other odors.

“One way scientists measure odors is through ‘dynamic olfactometry’ analyses, where people capture a sample of air near a known odorous source and bring it back to the lab so it can be sniffed by trained assessors,” said Monticelli.

“The sample is first diluted with clean air and then concentrated further and further until half of the assessment panel can smell it. When this happens, the level of dilution is converted into an odor concentration. This has been performed for many industries and operations, including cannabis facilities, waste and wastewater treatment, and livestock operations.”

“We found in the literature that a facility that grows about 1,700 cannabis plants can emit the same odor concentration as a livestock operation with about 30 pigs or about 1,600 chickens. So, although their smells are not the same, one cannabis plant might be equivalent to about one chicken with respect to the intensity of the odors it produces.”

Monticelli said that so far, the skunky cannabis smell has been linked to two classes of chemicals that are terpenes and volatile sulphurous compounds, which are volatile organic compounds. “However, we do not really know which type contributes more to the odors, and a better understanding would help the industry and policy makers control odorous emissions more effectively.”

The UBC team conducted a review which identified 16 major gaps that need to be addressed, including the monitoring of air quality in and around cannabis facilities. 

“Most of the chemicals that are emitted react quickly in the atmosphere. Some of these can influence the formation of ultrafine particles and ozone at ground level, which are harmful to people and the environment,” said Monticelli.

“Because of the fast-changing nature of the chemicals released when cannabis is grown, we need to use real-time sampling instruments that can capture changes in the composition of the air within short periods to properly understand the impact of cannabis facilities on overall air quality.”

Monticelli explained that creating and maintaining a database of different cannabis strains and their emissions will improve the accuracy of cannabis cultivation emission inventories over time. “Such inventories provide the basic information needed at the beginning of any air quality assessment.”

“This is a relatively new industry which is growing with the rise in cannabis legalization worldwide. Effective emission control practices and environmental policies are needed before new industrial practices become entrenched, and addressing the gaps identified in our review is a first step.”

The study is published in the journal Environmental Science & Technology.

By Chrissy Sexton, Staff Writer

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