And the latest news from the lungs seems even worse.

In fact, marijuana seems just as harmful to the lungs as tobacco. And for people who smoke pot and cigarettes, the chances of getting cancer later in life are higher, still.

Why did you think they called it getting high, anyway?

Smoking pure marijuana is at least as harmful to lungs as smoking tobacco, a report from the British Lung Foundation concludes. And in some key ways, it may be more dangerous.

For example, the BLF's review of previous research highlights that just three marijuana joints a day causes the same damage to the lung's airways as 20 cigarettes, mainly because of the way joints are smoked.

Individually, cannabis and tobacco produce the same constituents and quantities of chemicals known to be toxic to respiratory tissue, other than nicotine, the report says. But when cannabis and tobacco are smoked together, the health effects are worse.

"These statistics will come as a surprise to many people, especially those who choose to smoke cannabis rather than tobacco in the belief it is safer for them," says Mark Britton, chairman of the BLF. A UK survey conducted earlier in 2002 found that 79 per cent of children believed cannabis to be 'safe'.