Vapors from butane hash oil - a marijuana extract commonly heated, vaporized and inhaled- could produce significant amounts of carcinogens when heated to high temperatures, according to a Portland State University study published Monday.

The study, led by PSU chemistry professor Robert Strongin, showed that oils present in the extract release potentially cancer-causing chemicals when heated to temperatures above 750 degrees. When heated above 932 degrees, the oils released benzene, a known carcinogen.

"The higher temperatures go, the more risk that (users) will be inhaling things that could be harmful," Strongin said.

Butane hash oil can be dangerous to manufacture. Three people in Oregon died from injuries related to butane hash oil production this year. Two men died in Portland after an illegal butane hash oil lab caused an explosion in July.

Hash oil is commonly consumed by dabbing, when a small amount of oil is placed on a heated metal or glass compartment known as a nail, turning the oil into vapors that the consumer inhales. It can also be used in vape pens or electronic cigarettes.

The study simulated dabbing by vaporizing terpenes, naturally occurring oils in marijuana that are present in hash oil.

Strongin and his team found that the terpenes did not release high levels of dangerous chemicals at low temperatures. But when they were heated above about 750 degrees, they released methacrolein, a chemical similar to the carcinogen acrolein.

At about 932 degrees, the terpenes began to release significant levels of benzene, Strongin said. Though the levels were not as high as those found in cigarettes, they were far greater than levels found in the air, Strongin said.

"It's not a huge amount of benzene, but any benzene ingestion is concerning," he said.

This could expose hash oil users to risk if they are not carefully regulating the temperature of the dab rig's nail, Strongin said. Typically, users posting online report heating the nail to about 700 degrees, though some prefer to keep temperatures lower to preserve the oil's flavor, according to the study.

But it's common for people to use a creme brulee torch, Strongin said, which has no temperature control and can make the nail much hotter.

That's where the concern is, Strongin said.

"At the upper range of what people are doing, you'll start to see benzene," he said.

Previous studies have shown terpenes in electronic cigarettes can also release toxic chemicals when used at high temperatures. But Strongin said it's less likely that electronic cigarette and vape pens users will be exposed to carcinogens because the devices don't get as hot.

Patricia Rodriguez, who works at the medical marijuana dispensary CannaSource and has used hash oil since 2011, isn't concerned about the results of the study, she said Monday.

Rodriguez uses hash oil to treat chronic pain from multiple surgeries. She typically dabs using an electronically-controlled nail or "e-nail," which keeps the temperature low and controlled. Most people she knows don't typically heat hash oil using temperatures above 700 degrees, she said.

It's good for people to be aware of the risks that come with using high temperatures to dab, she said. But, she said, she hopes the study doesn't add to stigma around hash oil.

"As long as they use carefully, like anything else, there shouldn't be an issue," she said.

Strongin echoed that sentiment. The takeaway from his study, he said, should be that users can minimize risk if they keep temperatures low. As long as users are careful to regulate temperatures when dabbing, they should not be in danger of exposure to carcinogens, he said.

"We don't want to say things like this are just bad," he said. "It really depends on the user."

-- Samantha Matsumoto