November 13, 2018

Researchers at the UNC Gillings School of Global Public Health are designing an air quality model that could predict how the commercial cultivation of cannabis affects the atmosphere. The first of its kind, the study lays the groundwork for further research on the environmental impact of legal cannabis production.

Dr. William Vizuete prepares to take air samples in Boulder, Colo.

Dr. William Vizuete prepares to take air samples in Boulder, Colo.

William Vizuete, PhD, associate professor of environmental sciences and engineering at the Gillings School, is lead author on the paper, “Leaf enclosure measurements for determining volatile organic compound emission capacity from Cannabis species,” published online Oct. 30 in the journal Atmospheric Environment.

Chi-Tsan Wang, doctoral student in environmental sciences and engineering at the Gillings School, is first author of the article.

As of 2018, 10 states and Washington, D.C., have legalized marijuana for recreational and medical use for adults over the age of 21, and 33 states have legalized medical marijuana. Vizuete’s team traveled to Colorado, where cannabis is legal, to collect data on the emissions of cannabis plants as they grow.

The researchers set out to identify the types of volatile organic compounds (VOCs) that were emitted by each plant. VOCs are gases released by all living things which, when reacting with the air, can produce harmful pollutants. To produce and collect data, team members enclosed four different live, commercially available strains of cannabis – Critical Mass, Lemon 25 Wheel, Elephant Purple and Rockstar Kush – in a chamber during a 90-day growing period. They estimated the emission capacity range and the kind of terpenes, a type of VOC, which were emitted at each stage of growth.

Vizuete said researchers have studied how water and energy are used to support the cannabis industry, but much less is known about what happens to air quality as a result of production. As the industry grows, such pollution could be harmful to public health, given there are no standards to follow.

“We don’t have the tools we need to study this, and we are lacking robust measurement standards,” Vizuete said. “I wanted to produce an air quality model that can help people decide whether they’re building these facilities in the right places, and if they are causing potential harm to others with the emissions from cannabis growth. We need to identify the chemicals emitted into the air from the different strains so we can predict and reduce their impact on air quality.”

Vizuete said the current study paves the way for necessary emissions inventories that will enable the industry to determine an impact on regional air quality.

“Ultimately our goal is improving public health by improving air quality, both indoor and outdoor,” Vizuete said. “We need basic information to do that, so this study provides the first step toward determining how much of a public health issue cannabis production is. A big impact of the study is proving that we do need to spend more time and effort understanding the effects of the cannabis industry on indoor and outdoor air quality.”

Vizuete’s collaborators on the study are Christine Wiedinmyer, PhD, associate director for science at the University of Boulder (Colorado) Cooperative Institute for Research in Environmental Sciences; Dr. Kirsti Ashworth, Royal Society Dorothy Hodgkin Research Fellow at Lancaster University’s Lancaster Environment Center, in the U.K.; and Peter Harley and John Ortega, of Denver, Colo.


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