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The legal cannabis industry has a big environmental footprint using lots of water and energy. But researchers have another concern. Could the plant itself be contributing to air pollution? Colorado Public Radio's Michael Elizabeth Sakas has this story.
MICHAEL ELIZABETH SAKAS, BYLINE: In Garden City right outside of Greeley, there are three cannabis grow houses within a square mile. One is Smokey's. Scott Brady, operations manager, says they try to be environmentally friendly.
SCOTT BRADY: We have an obligation to make sure that we are an addition to our communities and not a drag on our communities.
SAKAS: Brady says that's why Smokey's volunteered to be part of a state study that's trying to figure out if cannabis contributes to air pollution. No, this isn't about the pot smoke. This is about terpenes, the organic compounds that make the cannabis plant smell, well, like pot. Brady opens up a big bag of bud.
BRADY: You can have the fruity smells and the earthy smells and the very spicy smells.
SAKAS: Those strong-smelling terpenes are classified as volatile organic compounds, or VOCs. Lots of consumer products release VOCs, like acetone in nail polish remover. And many different plants produce terpenes, not just cannabis. Think lavender. VOCs from cannabis are harmless until they combine with other gases to create ozone.
KAITLIN URSO: Here in Colorado, as far as air quality concerns go, ozone is our largest pollutant of concern. We are not meeting the national ambient air quality standards for ozone.
SAKAS: That's Kaitlin Urso with the Colorado Department of Public Health and Environment. She says they're trying to figure out how cannabis might be contributing to ozone because the equation for the harmful gas is VOCs plus sunlight plus combustion emissions like cars. And unlike other VOC-emitting plants, cannabis is often grown in greenhouses in cities where there are lots of cars.
URSO: We kind of need to step in and do a study and quantify how many pounds of VOCs are emitted into our atmosphere per pound of marijuana grown?
SAKAS: Some research is already finding this to be an issue, but it turns out to be a tricky thing to study. The Environmental Protection Agency can't research it since marijuana is still federally illegal. So states and academics are stepping in, like William Vizuete, an associate professor at North Carolina Chapel Hill. He came to Colorado to team up with the National Center for Atmospheric Research in Boulder. He thought in a legal state his work would be in the clear. But he found out he wasn't allowed to grow pot in the federally supported research labs. He had to improvise.
WILLIAM VIZUETE: We grew them in a garage. We set up some grow lights and, you know, we had friends help out and water and take care of the plants.
SAKAS: He tested air samples collected from different strains of marijuana.
VIZUETE: The types of gases that the plant was emitting really varied by the strain and the lifecycle of the plant itself. As it grew older and matured, the types of gases that it was releasing also changed.
SAKAS: With more than 600 strains of cannabis in Colorado, Vizuete says there could be a wide range of how much terpene gas is emitted by these plants. So he's working with Kaitlin Urso in the state study for a more precise look at marijuana's emissions. But he says what's really needed is federal support to help decide if this is a public health issue.
VIZUETE: And so now it's on to the states, with limited budgets, now have to fill the role of what the federal government would do in determining the basic science and developing the tools that are needed to make decisions.
SAKAS: To get more funding, Vizuete might work with Canada, who's expressed interest in his research now that the country has legalized marijuana.
For NPR News, I'm Michael Elizabeth Sakas in Denver.
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