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Tainted marijuana’s possible health effects include allergic reactions, experts say

Smoking moldy weed usually won’t cause serious health problems for most people. Though reports are rare, one type of mold has caused hospitalizations and deaths.

Dr. Enid Neptune, former co-chair of the American Thoracic Society Tobacco Action Committee and an associate professor of medicine at the Johns Hopkins University School of Medicine.
Dr. Enid Neptune, former co-chair of the American Thoracic Society Tobacco Action Committee and an associate professor of medicine at the Johns Hopkins University School of Medicine, says a big problem in assessing health risks from marijuana is a lack of rigorous research.
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While cannabis has been embraced for health uses for conditions ranging from Parkinson’s disease to post-traumatic stress disorder, experts say the effects of inhaling contaminants in weed aren’t fully understood.

What is known is that smoking moldy weed can cause allergic reactions in some people. Those sensitive to a common mold called Botrytis cinerea, which causes “gray mold” or “bud rot” on marijuana plants, can experience inflammation of the lungs. The illness is known as “winemaker’s lung” because the mold’s often found on grapes.

Smoking weed contaminated with one particular type of mold, Aspergillus, can be dangerous. Though rare, there are documented cases of hospitalizations and deaths in cannabis users consuming weed for medical reasons who got lung infections from Aspergillus.

Dr. Jordan Tishler, president of the Association of Cannabinoid Specialists and an instructor at Harvard Medical School, says ingesting cannabis contaminated with pesticides and heavy metals can pose serious health risks. He says there’s far less evidence that mold and coliforms are as problematic, though Aspergillus can be especially dangerous for people with weakened immune systems.

Dr. Jordan Tishler, president of the Association of Cannabis Specialists and a Harvard Medical School instructor.
Dr. Jordan Tishler, president of the Association of Cannabis Specialists and a Harvard Medical School instructor.
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For people with normal immune systems, Tishler says the risks from mold “are pretty low. We’ve got millions of Americans who have been smoking marijuana, even untested marijuana, for decades upon decades, and we don’t see former potheads developing Aspergillus lung infections in their old age.”

The dangers of heavy metals to the human body are well-known, and cannabis plants are particularly good at absorbing these metals if exposed to them through soil or water.

Rosalie Pacula, a University of Southern California economist who studies cannabis regulation, says the lack of federal legalization creates obstacles to safety. With the current patchwork system, weed products sold in one state might not be required to be as contaminant-free as in other states.

And unlike what’s required with pharmaceutical products, cannabis producers in most states don’t have to report adverse events. For medical marijuana users, that presents a potentially serious safety gap, Pacula says.

A big problem in assessing health risks from marijuana is a lack of rigorous research, mostly because it’s still illegal at the federal level, lumped in with hard drugs like heroin and cocaine, says Dr. Enid Neptune, a Johns Hopkins University Medical School professor and former co-chair of the American Thoracic Society’s Tobacco Action Committee.

With limits on contaminants differing from state to state, “It’s a hugely problematic area,” Neptune says, that “doesn’t really protect the users of cannabis.”