It appears that people are unaware about the risks of cancer from cannabis use. Cannabis is the most commonly used recreational drug in the UK.

The risks of lung cancer from smoking cannabis, is 20 times more than the risk of the disease from smoking tobacco.
"Young people in particular are smoking cannabis unaware that, for instance, each cannabis cigarette they smoke increases their chances of developing lung cancer by as much as an entire packet of 20 tobacco cigarettes," said Dame Helena Shovelton, chief executive of the British Lung Foundation.
The need of the hour is a public health campaign warning people against cannabis use.
Source-Medindia