December 19, 2019

William Vizuete

Dr. William Vizuete

The emissions from cannabis cultivation factories (CCFs) for recreational and medicinal use could strongly impact the regional air quality in Denver, Colorado, according to research from William Vizuete, PhD, associate professor of environmental sciences and engineering at the UNC Gillings School of Global Public Health.

As more and more bills are passed in the United States to legalize recreational cannabis, the industry boom has become one of the largest in the country. Cultivation, sale and consumption of cannabis in the state of Colorado totaled $1.5 billion in 2017 – higher than the revenue for its grain farming industry. But despite its climbing revenues, the cannabis industry is not subject to the same environmental impact monitoring as the industries it rivals. Previous legal restrictions have limited the scope of this research, and prior studies pertain only to the impact of outdoor cultivation on ecosystems and watersheds, as well as to the energy consumption of indoor cultivation and its impact on greenhouse gas emissions (such as carbon dioxide).

Vizuete’s research, published by Atmospheric Chemistry and Physics in November, examined the impact on air quality in Colorado from biogenic volatile organic compounds (BVOCs) emitted by CCFs. BVOCs are chemicals produced naturally by plants, but their high volatility can have significant ramifications on air quality if emission rates increase. The BVOCs produced in cannabis cultivation, like monoterpenes and sesquiterpenes, can lead to the formation of excess aerosols and ozone – both of which have climate-relevant implications and can contribute to air pollution that is harmful to health, according to the U.S. Environmental Protection Agency (EPA).

The Denver region, in particular, has been classified by the EPA as an ozone nonattainment area, meaning it does not meet federal standards for ozone emissions. At the time of this study, it was classified as “moderate,” but the EPA has recently reclassified it as “serious.” Ozone concentrations in the Denver area are sensitive to volatile organic compounds (VOCs), and an increase in their emissions, such as the ones produced by the cannabis industry, will also increase ozone production.

Using Colorado’s data on recreational and medical CCFs within the state and the limited data available to estimate emission rates, Vizuete and his team took an emission inventory of VOCs and BVOCs from CCFs by creating seven possible scenarios that accounted for variances in emission rate data. These scenarios estimated rates in Colorado as a whole, as well as in Denver County, Colorado Springs, Pueblo and Boulder.

Denver County, which houses 41% of all CCFs in Colorado, produced the highest results. The concentrated presence of CCFs in the area produced BVOCs at rates that were high enough to affect the local atmospheric chemistry and air quality, especially at night.

These results, while uncertain, highlight the need for further and more detailed analysis of how the cannabis industry could affect regional air quality in Denver. The models show that ozone levels are responsive to emissions from CCFs. However, emissions are too uncertain to fully understand the significance of the impact on ozone and the implications on the state’s strategy to address Denver’s ozone nonattainment status and health outcomes in the area.

“Denver’s change in status puts more scrutiny on all emission sources that could contribute to ozone in the region,” Vizuete said. “I hope this study highlights the places where more study is needed so we can understand the significance of this new industry.”

Vizuete has been collaborating with the Colorado Department of Public Health and Energy (CDPHE) to design a field study that will measure inside CCFs to further understand their emissions. This field study was recently completed, and the team is beginning to analyze the data for future use.

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