Subject: Marijuana Safer than Tobacco - Medical Post, Sept./94
From: Christopher Clay <[email-masked]>
Date: Sun, 25 Jun 1995 17:15:10 GMT
Newsgroups: alt.hemp

Marijuana Less Harmful to Lungs
than Cigarettes
     by Louise Gagnon
Medical Post, Sept. 6 1994

L'ESTEREL, Quebec -- Heavy marijuana smokers show less evidence
of lung injury than heavy tobacco smokers, and it may be
cannabinoids that are protecting them from developing a condition
like emphysema.

That's according to the principal investigator of a study done at
the University of California at Los Angeles (UCLA).

Speaking at the third annual meeting of the International
Cannabis Research Society here, Dr. Donald Tashkin, a
pulmonologist and UCLA professor of medicine, concluded heavy
marijuana use did not cause the same degree of lung injury as
tobacco smoke.  

"My own feeling is that marijuana smokers probably will not
develop emphysema as a consequence of smoking marijuana," he
said, but cautioned that does not rule out the development of
other conditions like respiratory carcinoma.

"It may be that the THC (delta-9-tetrahydrocannabinol) in
marijuana could have different effects on inflammatory cells,
which may mediate injury in the lung."

His study, which aimed to measure the pulmonary effects of
habitual marijuana use, followed nine tobacco smokers, 10
marijuana smokers, 10 nonsmokers and four smokers of both
marijuana and tobacco.  He gave both quantitative and qualitative
explanations for his finding.

Marijuana users in the study smoked three or four joints daily
for 15 years on average, while tobacco smokers in the study
smoked 25 cigarettes daily over a period of 20 years, indicating
a marked difference in exposure to smoke.

"There is a seven-fold difference in the amount of smoke to which
marijuana and tobacco smokers are exposed," he said.

"It's the quantitative difference in smoke exposure that might
explain the difference in the degree of lung injury as assessed
by these physiologic indices."

Moreover, the phagocytes gathered from the lungs of marijuana
smokers do not have the same properties as those gathered from
the lungs of tobacco smokers.

"We have previously shown that the macrophages that are harvested
from the rinse-out of the lungs of marijuana smokers seem not to
be activated," he said.  "They do not release toxic oxygen
species, either under basal conditions or under stimulated
conditions nearly to the extent that tobacco macrophages do.  If
anything, basal secretion of superoxide seems to be reduced in
the marijuana smokers."

Dr. Tashkin measured the clearance of the molecule diethylene
triamine penta-acetate (DTPA) from the lung, believed to be a
more sensitive indicator of lung injury than measuring the lung's
diffusing capacity.

If DTPA clearance is accelerated, then it implies an increase in
the leakiness of the alveolar epithelial membrane, which implies
injury to the membrane, he said.

Dr. Tashkin noted DTPA clearance is accelerated in tobacco smoke-
related lung injury.

Initially, the chronic effects of marijuana smoke were measured
in comparison to those of tobacco smoke: DTPA clearance was
measured at about 12 hours after the last marijuana or tobacco
cigarette smoked.

To determine the acute effects of marijuana and tobacco smoking,
Dr. Tashkin restudied these smokers a week or two later, giving
them a single joint of marijuana or a single tobacco cigarette or
both, and then measuring DTPA clearance 15 minutes subsequently. 

"What we found was the clearance of DTPA was abnormally rapid
from the lung in the tobacco smokers," he said.  "It was about
twice the rate of non-smokers.  In the marijuana smokers, there
was a tendency toward a much less rapid rate of clearance.  There
was no acute effect in either tobacco or marijuana, and there was
no added effect of marijuana or tobacco."

As with the lungs to tobacco smokers, when the lungs of marijuana
smokers are "washed out", a marked increase in the number of
alveolar macrophages is witnessed.

But whereas tobacco smoke has a concomitant effect of activating
the macrophages, leading to the subsequent release of certain
toxic substances, marijuana smoke fails to activate the
macrophages, Dr. Tashkin said.  He noted this difference could be
attributed to differential regulation of cytokins.

"It may be that the macrophages from marijuana smokers release
certain suppressive cytokins, like transforming growth factor-
beta, which is known to suppress the inflammatory activity of
nearly all of the site populations," he said.  "That's our
hypothesis, which we are currently exploring."