DENVER — Cancer-care expert Dr. Diana Martins-Welch finds herself in an unusual position: Last week she started telling her medical marijuana patients to quit vaping cannabis and pick up a joint instead.

“I would never have thought I’d be in a position to tell someone to smoke marijuana. But if the choice is between smoking and vaping, smoke marijuana.”

Martins-Welch specializes in caring for patients with cancer and chronic pain, and she's certified more than 700 of them to use marijuana under New York's tightly controlled cannabis program, which permits vape extracts with THC, the component of marijuana that produces a high, but bans joints.

However, Martins-Welch is now worried more about whether any kind of vape products are safe to use, given the national outbreak of severe respiratory illnesses linked to vaping nicotine and marijuana. The Centers for Disease Control said Thursday there are 380 confirmed and probable cases and six people have died. No single substance or product has been pinpointed, but the leading suspected cause is chemical exposure.

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“I tell them vape at your own risk, because we just can’t trust this mechanism," said Martins-Welch, an attending physician in palliative medicine at Northwell Health in New Hyde Park, New York. The risk is so great, she said, she's even telling Stage 4 cancer patients — people who may only have a few months to live — to steer clear of vaping and find another way to consume marijuana. “All of this is buyer beware because it doesn’t have FDA approval.”

The outbreak has highlighted a growing concern nationwide: There's no federal regulation of marijuana products because the federal government bans its sale, use and possession, and considers it a substance on par with heroin and LSD.

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Each of the 11 states where it is legal for recreational use by adults created a completely different system, meaning that Alaska's rules are different from Nevada's, which are different again than those in Colorado or California, or those still being developed in Illinois. And the 33 states that permit medical marijuana use have all adopted different rules.

Colorado for instance, on Sunday will start requiring testing for potentially harmful mycotoxins produced by fungal infections on plants, more than four years after voters approved legal pot there. But California has required the same testing — conducted differently — since the end of 2018.

And since legal marijuana products cannot be sold across state lines, even products sold under the same branding are manufactured to meet different standards depending on the state. In other words, because the FDA doesn’t regulate cannabis products, THC cartridges used in vaping get less federal scrutiny than Advil or the coloring in cosmetics.

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In an interview with CNBC, former FDA head Dr. Scott Gottlieb said he believes federal intervention is necessary.

"People who are vaping nicotine and having these reactions probably are vaping illegal products that are counterfeit,” Gottlieb said in a “Squawk Box” interview. “We have to have a federal reckoning here.”

Chemicals in vaping products

In a statement, the FDA said it was examining whether vitamin E acetate, a vape-juice thickener, may have played a role in the respiratory illnesses and deaths. "Because consumers cannot be sure whether any THC vaping products may contain vitamin E acetate, consumers are urged to avoid buying vaping products on the street, and to refrain from using THC oil or modifying/adding any substances to products purchased in stores," the agency said in a Sept. 6 statement.

The Centers for Disease Control and Prevention called for a more broad halt to all e-cigarette use, both nicotine and THC.

Marijuana vaping company owners say they're being unfairly maligned by government regulators and an alarmist media that fail to distinguish between state-licensed legal and black-market products, which are completely unregulated.

"We're throwing vaping in general under the bus here. We need to distinguish between nicotine and cannabis and black market," said Arnaud Dumas de Rauly, CEO of vape manufacturer The Blinc Group. "It's funny how all of the anti-vaping crowd has jumped on this. When you look at the data, it is clearly black market illegal products."

Nicotine vape "juice" is easy to make because anyone can buy bulk nicotine extract online, mix it with flavors or additives and thickeners and then retail it to customers either online or in stores.

For cannabis vape juice, manufacturers must extract THC from marijuana, sometimes using liquid butane or carbon dioxide, then dissolve it into a liquid with additives like vitamin E acetate or propylene glycol, a substance also used as aircraft de-icer or in eye drops.

Legal cannabis vape manufacturers are required by their state's regulators to submit either the raw plants or the extract itself for quality and contamination testing, which raises the price. In some cases, black-market cannabis vape juice can cost 5-7 times less than what legal, tested products cost, experts said.

Vaping is popular with consumers because the battery-powered heating devices are more discreet and less smelly than traditional cigarettes or marijuana joints, and are perceive as healthier because they aren't inhaling burning plant matter. The heavy advertising campaign by Juul, pushing its nicotine-based vape pens, has helped raise overall awareness about vaping, experts added.

Vaping marijuana also has grown in popularity because the cartridges are made from what ordinarily would be considered lesser-quality parts of the plant — the leaves to the stems — so are cheaper than high-quality "flower" that people smoke in joints or pipes.

In addition, the vape cartridges generally offer a more consistent and predictable "high," in much the same way that wine is standardized to generally contain about 12% alcohol. But that applies only to legal, state-regulated marijuana products because they must undergo independent testing.

Need for marijuana/vaping regulation

Dumas de Rauly said the situation highlights the need for standardization across the country, noting that testing by different labs has yielded wildly divergent results for identical products made by The Blinc Group. He said few labs even have the "puffer" equipment necessary to test how different chemicals and compounds might affect a user's lungs when they're heated and inhaled.

"That's what standards are for. People tend to forget that. Standards are here to be able to create a common ground on which we can compare things, and then that’s where the regulators come into play," said Dumas de Rauly, who also serves as chairman of the International Organization for Standardization standards committee on vaping products. The Swiss-based ISO is a non-profit group that establishes standards for everything from food safety to shipping containers and the strength of bolts used on railroads.

"Instead of pointing fingers, we need to find a constructive approach: how to stop consumers from turning to the black market for cannabis vaping products. While states can do much more to fight the black market, it will never be fully eliminated until the federal government gets its act together."

Because the federal government still lists marijuana as a Scheduled 1 controlled substance, scientists from the FDA have refused to assist states in developing their piecemeal marijuana-testing requirements.

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Anti-marijuana campaigners have seized upon the illnesses to call for shutting down the vape market, which has become an increasingly important product line for cannabis businesses. Cannabis data company BDS Analytics says vapes represented 14% of sales in Colorado's licensed marijuana stores in 2018, rising to 18% for this year to date.

Industry opponents like Kevin Sabet, the executive director of the anti-cannabis Smart Approaches to Marijuana, have been warning for years that the lack of federal regulation have given pot businesses too much leeway.

“The marijuana vaping crisis is real and poses a significant threat to both physical and mental health. For years, companies like Altria and other major tobacco and e-cigarette brands have demonstrated a willingness to lie to the public about the safety of these products, aggressively marketing these devices as safe, healthy alternatives to traditional smoking,” Kevin Sabet said in a statement. “If this crisis does not convince lawmakers at a state and federal level that today’s high-potency, industrialized marijuana is dangerous, I don’t know what will."

Some marijuana industry leaders say the proper solution is better regulation at the federal level, which could create national quality-control standards and permit their business to expand to new markets. And they note even though the hundreds of cases respiratory illnesses and at least six deaths in recent weeks raise significant alarm, the Trump Administration has taken more action on vaping than it has gun deaths.

"Although investigations and data collection are ongoing, it appears that most, if not all, of the reported cannabis-related cases so far stem from products sourced from the unregulated criminal market," the national Cannabis Trade Federation said in a statement. "Consumers and communities will benefit when all cannabis products are subject to rigorous production, safety, and testing standards at the federal level."

Back in New York, Martins-Welch, the cancer doctor, said she this is precisely situation where the federal government's expertise in regulating health products would be useful. She said permitting more research on cannabis — including vape products — would help doctors like her make better recommendations to their patients and offer more standardized doses.

"A lot of patients who come to me are already at their wit’s end," she said. "They tell me they aren't pill people, they're worried about prescription opioids. They’re so worried about dying of addiction that they’re willing to try anything else.”