DAVIS (CBS13) — A new warning from researchers at the University of California, Davis to people using marijuana as medicine. A recent study found people with weakened immune systems are at a greater risk of infection from bacteria and fungi found on medical marijuana samples.

Dr. George Thompson with UC Davis specializes in patients with fungal infections. He noticed a strange trend in patients with depleted immune systems.

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STUDY: Medical Marijuana Mold Study

“Pneumonia basically; they cough, they can have nose bleeds from sinus infections,” said Thompson.

The common thread? The patients were all taking medical marijuana for pain relief.

“This is a material that’s in nature, it’s full of bacteria and fungi it would make since that that could be a point source that the patients were getting their infection,” explained Thompson.

He and Dr. Joseph Tuscano used an off-campus lab to test 20 samples of marijuana from 20 different dispensaries.

“All of them had bacteria and fungal organisms present,” said Thompson.

The contaminants are nearly harmless to people with a strong immune system, but to people receiving chemotherapy for leukemia, lymphoma or other disorders like organ transplants or aids, the bacteria can be devastating.

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“We’re really trying to caution those patients,” said Thompson, “you may have unknowingly used a product that could be lethal.”

“People have an expectation that the stuff that the get a dispensary is going to be safe and clean and well tested, but the fact is, this is an unregulated environment up till now,” said Tony Daniel with Steep Hill Labs.

There are no state warnings or regulations for people using marijuana as medicine.

But they’re coming by Jan. 1 of next year.

“We’re responsible for the state licensing and enforcement structure for medical cannabis,” explained Lori Ajax with the Bureau of Medical Cannabis Regulation.

Ajax is heading up the agency piecing together the rules.

“Making sure we’re protecting the patient, the public, the environment,” said Ajax.

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For now, dispensaries and cultivators follow their own best practices, which may differ from business to business.