In the lab, Springer puts a cigarette or a joint in a plexiglass box, lights it and lets the chamber fill with smoke. Then he vents out most of the smoke to the point that it is hardly visible, to simulate being around a smoker. Then an anesthetized rat is exposed to the smoke for one minute. ... just this one minute of exposure to secondhand smoke makes it harder for the rats’ arteries to expand and allow a healthy flow of blood.
With tobacco products, this effect lasts about 30 minutes, and then the arteries recover their normal function. But if it happens over and over, the arterial walls can become permanently damaged, and that damage can cause blood clots, heart attack or stroke.
Springer demonstrated that, at least in rats, the same physiological effect occurs after inhaling secondhand smoke from marijuana. And, the arteries take 90 minutes to recover compared with the 30 minutes with cigarette smoke.
Springer’s discovery about the effect on blood vessels describes just one harmful impact for nonsmokers who are exposed to marijuana. Statewide sampling surveys of cannabis products sold in marijuana dispensaries have shown that the items may contain dangerous bacteria or mold, or residue from pesticides and solvents.
Upshot: It is wrong to smoke either tobacco or marijuana as innocent people can be harmed or even killed by exposure to second-had smoke.