Pubdate: Wed, 04 Feb 2015
Source: Alaska Dispatch News (AK)
Copyright: 2015 Alaska Dispatch Publishing
Contact:  http://www.adn.com/
Details: http://www.mapinc.org/media/18
Note: Anchorage Daily News until July '14
Author: Scott Woodham

HOW MUCH SHOULD I WORRY ABOUT SECONDHAND CANNABIS SMOKE?

For the inaugural installment of Highly Informed, our new regular 
feature that seeks to answer your questions about legal cannabis in 
Alaska, Melanie asks a few related questions about second-hand smoke.

Readers should keep in mind an important context right up front. 
There are many ways to consume marijuana, and burning it is just one 
of them. The answers below pertain to smoking, not vaporizing (which 
involves no combustion) or eating an infused product.

What happens if I walk down the street and walk through someone's 
smoke, and then I have a reaction and heaven forbid hurt someone? Who 
is responsible?

Walking through a cloud of marijuana smoke outside is extremely 
unlikely to cause "a reaction" in terms of getting you high. Science 
has found that a cannabis smoker's lungs absorb essentially all of 
the psychoactive compounds present at inhalation, so there's 
basically none being exhaled into the atmosphere.

Since you won't be in danger of catching an unwanted buzz, you'd be 
responsible for any harm you do to another person. If by "reaction" 
you mean something more like road-rage than intoxication, then it's 
also still your responsibility.

Can I fail a drug test from walking through someone's second-hand smoke?

That is very unlikely. The threshold for a positive drug test is 
customarily set high enough, and the THC content of an outdoor cloud 
is low enough and dispersed enough, that you're in very little danger 
of failing a drug test that way. Studies have shown that non-smokers 
do show detectable levels of marijuana in their bloodstream and urine 
after second-hand exposure, but most studies have focused on enclosed 
areas. According to most, however, resulting levels in non-smoking 
test subjects were not large enough to trigger a positive drug test 
after a day, and in many cases mere hours. In 2010, researchers 
concluded that passively inhaling second-hand smoke in a real-life 
scenario was unlikely to trigger a positive drug test in someone who 
didn't directly smoke any herb. A more recent study published in the 
Journal of Analytical Toxicology last October found similar results.

However, it's worth noting that no one should take any chances. 
Sitting a few hours in a smoke-filled room or car on the way to the 
testing facility is a bad idea. But just walking down the street? No worries.

Second-hand smoke from cigarettes is bad. How bad is second hand 
smoke from marijuana?

The short answer is the jury's still out on that, and depends on how 
we define "bad." Any amount of smoke could pose a danger to people 
with certain health problems. It's also worth noting that research on 
second-hand marijuana smoke nearly always involves rolling marijuana 
into cigarette papers, which is only one of the ways marijuana is 
smoked in real life. Pipes and bongs don't usually involve burning 
paper, and usually do not give off continuous smoke the way a lit 
cigarette does.

Both tobacco and marijuana smoke contain chemicals that are known to 
cause a variety of health problems in humans. A study in 2008 that 
used machines to "smoke" cannabis cigarettes found that marijuana 
"mainstream" smoke (the kind coming out of the business end of a 
joint) showed a lower concentration of some toxic chemicals than in 
tobacco smoke, but more in the "sidestream" smoke (the smoke coming 
from the burning tip). Although both contain substances known to be 
harmful, science is still working to learn more about the long-term 
effects of exposure to second-hand cannabis smoke.

A recent study involving THC-free smoke and mice has indicated 
second-hand cannabis smoke constricts blood vessels in a similar way 
to second-hand tobacco smoke, but it has not been done on humans, and 
is considered a starting point for further research.

Matthew Springer, Ph.D., the senior author of the study, summed up 
his early conclusions: "If you're hanging out in a room where people 
are smoking a lot of marijuana, you may be harming your blood 
vessels. There's no reason to think marijuana smoke is better than 
tobacco smoke. Avoid them both."
- ---
MAP posted-by: Jay Bergstrom