People who smoke marijuana could be exposed to toxins found in tobacco, study finds

• A small study found traces of acrylonitrile and acrylamide, chemicals released in cigarette smoke, in the urine and plasma of people smoking marijuana.
• Both chemicals are considered "probable human carcinogens" by the International Agency for Research on Cancer (IARC).
• Researchers say more data is needed, but said people with heart conditions should avoid smoking marijuana with tobacco, and possibly avoid smoking marijuana altogether.

A small new study suggests smoking marijuana may expose users to the same toxins found in tobacco.

The research, published in EClinicalMedicine, looked at 245 people, aged 47 to 59 years old. The sample consisted of 18% marijuana-only smokers, 20% tobacco-only smokers, and 24% marijuana and tobacco smokers, and 38% non-smokers.

The researchers at the Dana Farber Cancer Institute found the same smoking-related toxins typically found in tobacco smokers - like acrylonitrile and acrylamide - in the plasma and urine of marijuana-only smokers.

Those chemicals were found at higher levels in people who only smoked tobacco or smoked tobacco and marijuana together - along with high levels of acrolein, a by-product of smoking tobacco and other natural substances linked to heart problems.

Read More: Drinking one small glass of wine a day is linked to heart problems, study finds

Acrylonitrile and acrylamide are both considered probable human carcinogens

Acrylonitrile is a chemical used to produce processed foods and released when cigarettes are smoked. According to the National Institute of Health's National Cancer Institute, the chemical is reasonably anticipated to be a human carcinogen.

The International Agency for Research on Cancer (IARC) classifies acrylamide, a chemical used to manufacture paper and plastics which is also found in cigarette smoke, as a "probable human carcinogen."

The study had limitations

Because the sample was limited to people over 40 in the US, the results may not be generalizable to a global population.

However, the researchers say those with heart problems should be wary.

As for the risks of smoking marijuana alone, the researchers said more research is needed, but there is previous evidence that suggests smoking cannabis is as risky for people with heart conditions as tobacco.

A priority, they said, is to study the risks associated with smoking marijuana and tobacco.

"These findings identify potentially toxic combustion by-products associated with marijuana and tobacco smoking and suggest the need for further studies on health effects of acrolein and other smoke-related exposures that include participants more representative of the general population," the authors wrote in the study.