196

It's mostly about the dose of carcinogens. THC is far less addictive than nicotine, so on average people who exclusively use cannabis inhale less smoke than people who smoke tobacco. A pack a day of cigarettes is a very common amount for people who smoke tobacco. That's 20 cigarettes, or 14-16 grams of tobacco a day. Few people who exclusively use cannabis are smoking 14grams/half oz a day.

There are two other major factors limiting our knowledge of the health impacts of cannabis smoking: 1) it remains federally illegal and therefore hard to get research funding. 2) a large proportion of the studies over the past several decades with people who smoked cannabis were confounded by many of the participants also smoking tobacco

TLDR: it's not great to inhale smoke of any kind, as it does contain an abundance of carcinogens.