MARIJUANA SPECIAL REPORT: CLAIM THREE:

"Smoking marijuana can lead to abnormal functioning of lung tissue . . ."

Smoking a couple of joints is as bad for your lungs as consuming a whole
packet of cigarettes, say the anti-dope brigade. Their opponents say
smoking marijuana has never caused anyone to die from lung cancer. So, is
marijuana smoke more -- or less -- dangerous than tobacco smoke?

The person to ask is Donald Tashkin, a lung expert at the University of
California at Los Angeles. For the past 15 years, Tashkin's team has been
keeping a close eye on the respiratory systems of more than 130 regular
marijuana smokers, comparing them with groups of people who smoke either
just tobacco, tobacco and marijuana, or nothing at all. It's the biggest
study of its kind in the world. And the results so far suggest that in some
respects, yes, marijuana is more dangerous than cigarettes. But in one
important respect, joints may actually be better for you -- especially if
you're an athlete.

First, the bad news. While the cigarette smokers in the study were
ploughing through 20 or more a day, the marijuana smokers seldom consumed
more than three or four joints. Despite this, the marijuana smokers coughed
and wheezed as much as the cigarette smokers. In both groups, about one in
five people complained of coughing up phlegm and suffering bouts of
bronchitis.

And when it came to cellular damage to the lungs, there was also little to
choose between them. Both groups had too many mucus-secreting cells lining
their airways and too few hair cells, and both groups showed evidence of
abnormalities in cell nuclei and changes in genes known to have an early
role in the development of cancers.

The similarity may seem puzzling given that the marijuana smokers were
consuming so much less plant material. But there are good reasons for it,
says Tashkin. The first is that joints yield up to three times the tar of
cigarettes because they are more loosely packed and don't have filters. The
second reason is that marijuana smokers inhale more deeply and hold their
breath longer.

"We actually quantified this and found that the breath-holding time was
increased about fourfold," says Tashkin. "That resulted in about a 40 per
cent greater deposition of tar." Tashkin's final factor -- contested by
some researchers -- is that marijuana smoke is richer in benzopyrene and
other polycyclic aromatics known to trigger cancerous changes in cells.

So smoking marijuana can cause lung cancer, after all? Well, maybe. Despite
the gloomy cell biology, epidemiologists have so far failed to find a link
between marijuana and serious lung diseases. That might be because there
isn't one. Or it might be because "the marijuana epidemic" (as Tashkin
calls it) is still young and the people who started smoking in the 1960s
haven't reached an age when cancers become common.

Meanwhile, some researchers are worried about another aspect of marijuana
smoke -- its ability to interfere with immune cells that help to fight off
lung infections. Tashkin's team has just discovered that immune cells
isolated from the lungs of marijuana users are unusually bad at killing
bacteria, 35 per cent worse, in fact, than similar cells taken from
cigarette smokers. The marijuana-exposed cells were also below par at
producing molecules needed to mount inflammatory responses. In normal
marijuana smokers, the effects may be too slight to make much difference.
Tashkin fears, however, that the same might not be true in people with
AIDS, many of whom use cannabis to stimulate their appetites.

Footballer's fancy

There's some good news, though, for dope-smoking cricketers and
footballers: marijuana smoke won't lead to blocked airways or emphysema.
Despite all the cellular changes noted by Tashkin's team, the researchers
found that even heavy smoking of marijuana had no impact on any physical
measure of lung function. In fact, among their subjects, smoking three
joints per day caused no greater rate of decline in lung capacity and the
ability to breathe than smoking no marijuana per day.

And the reason for this silver lining? It could well be back to those
sluggish immune cells, speculates Tashkin: "If cannabis impairs the ability
of immune cells to produce inflammatory cytokines, you might be spared
mucosal damage in peripheral airways."