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Cannabis Smoke Raises Blood Toxin Levels, But Not as Much as Tobacco Smoke, Study Finds

By Alexander Beadle

Published: Jan 14, 2021   
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Cannabis smoking raises the levels of toxic chemicals in the blood, but not to the same extremes seen in tobacco smokers, say scientists.

In a new study, published in the journal EClinicalMedicine, researchers from the Dana-Farber Cancer Institute and the Centers for Disease Control and Prevention also found that tobacco smokers and those who smoke a mixture of cannabis and tobacco had elevated blood and urine levels of an additional chemical, acrolein, which was not seen in exclusive cannabis smokers.

Upon further analysis, having high levels of acrolein metabolites in the body also appeared to correlate with an increased risk of developing heart disease.

Cannabis smokers exposed to fewer toxins than tobacco smokers

Cannabis smoke is known to contain many of the same chemicals present in tobacco smoke, and yet far fewer studies to date have examined the presence of smoke-related biomarkers in the bodies of cannabis smokers versus tobacco smokers, and those who use both substances.

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

“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,” she explained

This newly published work is the first longitudinal study to make comparisons between all three groups of smokers in terms of smoke-related biomarker levels, and the first to look at the potential effects on cardiovascular disease risk as a result of these biomarkers.

The study looked at data from 245 HIV-positive and HIV-negative participants in three studies of HIV infection in the United States, which provided a useful dataset given the high prevalence of cannabis and tobacco smoking within this demographic.

The researchers found exclusive cannabis smokers to have elevated levels of several smoke-related chemicals present in the blood and urine samples provided by these participants, including two compounds that are known to be toxic at high concentrations, acrylonitrile and acrylamide.

However, the levels of these compounds in the exclusive cannabis smokers’ bodies were lower than those found in the samples belonging to tobacco smokers, and in those who smoke both tobacco and cannabis.

Both groups that used tobacco also appeared to have been exposed to the chemical acrolein, as a metabolite of this compound were found in the blood plasma and urine samples provided. No unusual amounts of the acrolein metabolite, 3HPMA, were seen in the samples provided by those who only used cannabis.

Cardiovascular disease risk

The researchers also looked at the medical records and health survey results of participants. By combining these data sets with the chemical biomarker information gathered during the blood plasma and urine analysis, the researchers were able to trace links between elevated levels of certain compounds and the development of any adverse health problems.

They found that high 3HPMA – the acrolein compound found in the bodies of tobacco and dual cannabis and tobacco smokers – was associated with an increased risk of developing cardiovascular disease, independent of HIV status and other risk factors, such as high blood pressure or diabetes.

“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,” Gabuzda said.

“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.”

While exclusive cannabis users did not have elevated levels of this chemical, the results of this study may have particular relevance to many cannabis users in Europe – where it is relatively common practice to mix tobacco and cannabis into a single cigarette.

And while this study did not explicitly link cannabis use to cardiovascular disease risk, the current position of the American Heart Association (AHA) is that cannabis presents “substantial risks, no benefits” to heart health.

In a recent scientific statement published in the AHA’s flagship journal, Circulation, researchers concluded that cannabis has no well-documented benefits for cardiovascular conditions and that cannabis use may in fact be linked to an increased risk of heart attacks, atrial fibrillation, and heart failure.

“We do acknowledge the limited scope of evidence defining the cardiovascular safety of marijuana at present,” Muthiah Vaduganathan, a co-author of one of the studies reviewed and a cardiologist at Brigham and Women's Hospital, Boston, told Analytical Cannabis following his study’s publication. “However, based on what we know, we believe there is sufficient evidence to give us pause.”


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