Study: Cannabis smoke exposes body to less toxic chemicals than tobacco

A recent study reports that cannabis smoke raises levels of potentially harmful chemicals in the body, but confirms that the plant is less harmful than tobacco smoke.  

Researchers at the Dana Farber Cancer Institute and the Centres for Disease Control and Prevention found that people who smoked only cannabis had several smoke-related toxic chemicals in their blood and urine, but at lower levels than those who smoked both tobacco and cannabis or tobacco only.

The institute, which is an affiliate of Harvard Medical School, says the study uncovers new evidence of the potential health risks of chemicals in both tobacco and cannabis smoke.

The researchers collected data from participants’ medical records and analysed their blood and urine samples for substances produced by the breakdown of nicotine or the combustion of tobacco or cannabis.

Two of the chemicals identified in participants, acrylonitrile and acrylamide, are known to be toxic at high levels. The investigators also found that exposure to acrolein, a chemical produced by the combustion of a variety of materials and a contributor to cardiovascular disease, increases with tobacco smoking but not cannabis smoking.

“Marijuana use is on the rise in the United States with a growing number of states legalising it for medical and non-medical purposes – including five additional states in the 2020 election,” said the senior author of the study, Dana Gabuzda, of Dana-Farber.

“The increase has renewed concerns about the potential health effects of marijuana smoke, which is known to contain some of the same toxic combustion products found in tobacco smoke.

“This is the first study to compare exposure to acrolein and other harmful smoke-related chemicals over time in exclusive marijuana smokers and tobacco smokers, and to see if those exposures are related to cardiovascular disease.”

Looking at the study from a medical standpoint, Professor Mike Barnes, chair of The Medical Cannabis Clinicians Society, believes the results should not be used as an argument against the use of medicinal cannabis.

“First, smoking is not recommended in any case and not legal in the UK even as medicine,” Barnes told Cannabis Health.

“Second, the evidence for any carcinogenic effects of cannabis smoke is very thin and certainly not proven.

“There is also no real substantial evidence that cannabis smoking causes cancer.”

The paper, published in EClinicalMedicine earlier this week, was based on data collected from 245 HIV-positive and HIV-negative participants from three studies of HIV infection in the US.

The scientists behind the study say they used studies on HIV as a basis for the research because smoking amongst individuals with the condition is proportionally higher than average.

The results of the study suggest that high acrolein levels may be a sign of increased risk of cardiovascular disease and that reducing exposure to the chemical may lower that risk. Dana-Farber says this is particularly important for people infected with HIV, the virus that causes AIDS, given high rates of tobacco smoking and the increased risk of heart disease in this group.

Gabuzda added: “Our findings suggest that high acrolein levels may be used to identify patients with increased cardiovascular risk and that reducing acrolein exposure from tobacco smoking and other sources could be a strategy for reducing risk.”