London – Second-hand marijuana smoke is more than three times as damaging as exhaled tobacco fumes over the course of a minute, research shows.
Scientists believe cannabis smoke may cause the arteries to harden, increasing the risks of heart attacks and strokes.
They say the findings will further dispel the widespread belief that smoking called marijuana, is harmless.
Many academics and medical professionals say that Governments should legalise it, claiming it has numerous health benefits, such as alleviating pain.
University of California researchers found rats’ arteries were impaired for an average of 90 minutes after smoking cannabis, while for tobacco the effect lasted for 25 minutes.
Dr Matthew Springer, lead author, said the plant materials from cannabis were more harmful to blood vessels than nicotine and tobacco from cigarettes. He said that because rats’ blood cells are very similar to humans’, long-term exposure to second-hand cannabis smoke could harden and block our arteries.
He called for the public health community to make similar statement about the dangers of cannabis smoke to the ones it has issued about tobacco.
He added: ‘The public’s perception of risk from marijuana second-hand smoke has been limited to a few publicised studies.
‘Increasing legalisation of marijuana makes it more important than ever to understand the consequences of exposure to second-hand marijuana smoke.’
Canada will legalise cannabis from next year. Italy could soon follow suit.
Campaigners claim legalisation would cut crime because sales could be regulated and some doctors say the drug has numerous health benefits.
However, a 20-year study into its effects published in 2014 concluded it was highly addictive, caused mental health problems, and leads users to other drugs.