Researchers found that rats' blood vessels took at least three times longer to recover function after only a minute of breathing secondhand marijuana smoke, compared to recovery after a minute of breathing secondhand tobacco smoke.

There is high public awareness that smoking tobacco can impact people standing nearby passive smokers who can also end up suffering from health problems, cardiovascular in particular.

However, most people believe marijuana is less harmful. It is true that few studies have come up so far with evidence that marijuana second-hand smoking can cause acute cardiovascular harm.

But given the chemical and physical similarity between marijuana and tobacco smoke, the scientists believed investigating this further was necessary.

"Arteries of rats and humans are similar in how they respond to secondhand tobacco smoke, so the response of rat arteries to secondhand marijuana smoke is likely to reflect how human arteries might respond," said Springer