What I find a bit ironic is that in the face of prop 65, CA doesn't make much of MJ use.
http://www.lung.org/stop-smoking/smoking-facts/marijuana-and...
What? While smoking anything isn't great for your lungs, there's no evidence that marijuana causes lung cancer.
Personally I think the damage done to individual people when aggregated in sum is below the noise when compared with pollution from industrial sources, environmental pollution from consumer products, known-cancerous foods such as bacon, hamburgers, and beer, etc. So it's no reason to outlaw marijuana. But people who partake should not be fooling themselves into thinking it's healthy.
Here's a recent (2016) review: [1] Nature, apparently not paywalled. Lung cancer is the topic in the paragraph immediately before the "Discussion" section.
A recreational pot user may smoke a couple joints a week vs a pack a day of cigarettes.
or see this http://healthland.time.com/2012/01/10/study-smoking-marijuan...
Many people vape, ie extract thc with heat, not fire. I would guess this also reduces carcinogens.
Smoking isn't healthy and no-one should be making such claims. Other respiratory health issues are just as deadly as cancer.
https://www.cancer.gov/about-cancer/treatment/cam/patient/ca...
certainly any kind of inhaled smoke can cause issues for your lungs, but conflating the cancer risk of daily habitual tobacco smoking (very high) with the cancer risk of daily habitual cannabis smoking (probably present, but not yet known how much more risk it causes) is a distortion.