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Member Research & Reports

Member Research & Reports

UNC Study: Legal Marijuana Sales Creating Escalating Damage to the Environment

Marijuana sales have led to an economic boom in states that fully or partially have relaxed their cannabis laws, but is the increased cultivation and sale of this crop also causing escalating environmental damage and a threat to public health?

[Photo: In an opinion piece in the journal Environmental Science and Technology, Dr. Will Vizuete (left) and a collaborator from the U.K. discussed the environmental impacts of indoor marijuana cultivation. Question marks in the figure indicate that the magnitude of the environmental effect has not been estimated previously. Dr. Vizuete is shown at a site in Colorado, with an outdoor air sampler used to detect emissions from the marijuana plants. Figure credit: Nuno Gomes 2016]

In a recent opinion piece appearing in the journal Environmental Science and Technology, researchers from The University of North Carolina at Chapel Hill and Lancaster University, in the U.K., have called upon U.S. federal agencies to fund studies that will gather essential environmental data from the legal cultivation farms and facilities. These data then can be used to help states minimize any environmental and public health damage caused by this burgeoning industry and aid legal marijuana growers in making their business environmentally sustainable.

State-by-state legalization effectively is creating a new industry in U.S., one that looks set to rival all but the largest of current businesses. In Colorado alone, sales revenues have reached $1 billion, roughly equal to that from grain farming in the state. It is estimated that, by 2020, country-wide legal marijuana sales will generate more annual revenue than the National Football League.

However, the article, “High Time to Assess the Environmental Impacts of Cannabis Cultivation,” co-authored by Dr. William Vizuete, associate professor of environmental sciences and engineering at UNC’s Gillings School of Global Public Health, and Dr. Kirsti Ashworth, research fellow at Lancaster University’s Lancaster Environment Centre, suggests that this expanded cultivation carries with it serious environmental effects.

Their article points out that cannabis is an especially needy crop, requiring high temperatures (25°-30°C for indoor operations), strong light, highly fertile soil and large volumes of water – about twice that of wine grapes. In addition, the authors state that the few available studies of marijuana cultivation have uncovered potentially significant environmental impacts due to excessive water and energy demands and local contamination of water, air and soil.

For example, a study of illegal outdoor growing operations in northern California found that rates of water extraction from streams threatened aquatic ecosystems. High levels of growth nutrients, as well as pesticides, herbicides and fungicides, also found their way back into the local environment, further damaging aquatic wildlife. Moreover, controlling the indoor growing environment requires considerable energy with power requirements estimated to be similar to that of Google’s massive data centers. No significant data have been collected on the air pollution impacts to workers’ health inside these growing facilities or the degradation of outdoor air quality due to emissions produced by the industrial-scale production of marijuana.

The authors emphasize, however, that much of the data on marijuana cultivation to date has come from monitoring illegal cannabis-growing operations.

The illegal status of marijuana has prevented us from understanding the detrimental impacts that this industrial scale operation has on the environment and public health. …This is an industry undergoing an historic transition, presenting an historic opportunity to be identified as a progressive, world-leading example of good practice and environmental stewardship,” they said.

The continued expansion of legalization by the states does offer significant opportunities for the U.S. Department of Agriculture, Environmental Protection Agency, National Institutes of Health, and the Occupational Safety and Health Administration to fund research into legal cannabis cultivation to protect the environment.

Generating accurate data in all the areas we discussed offers significant potential to reduce energy consumption and environmental harm, protect public health and ultimately improve cultivation methods,” Dr. Vizuete said. “There are also significant potential public health issues caused by emissions from the plant itself in addition to those from smoking it. These emissions cause both indoor and outdoor air pollution.”

Dr. Vizuete added that he and his collaborators currently are studying this issue.

The full article can be found here.