Currently, the National Toxicology Program (NTP) in the US produces the Report on Carcinogens (RoC) every two years, and the year 2012 features the latest edition. The report lists about 300 studied carcinogens out of the many thousands of chemicals that humans have so far produced. The whole idea behind listing and examining toxic carcinogens is to err on the safe side and thus prevent needless suffering.
I find it strange that wood smoke is not listed yet, since smokeless tobacco is to tobacco smoke just like wood dust is to wood smoke. Smokeless tobacco, tobacco and wood dust are all listed and described as carcinogens, but wood smoke is not listed. The Environmental Protection Agency (EPA) estimates the cancer risk from wood smoke to be about one magnitude (10 times) greater than an equal amount of tobacco smoke.
Why is wood smoke not listed in the RoC? Wood smoke is one of the oldest human produced toxic chemicals. Maybe wood smoke is considered natural because of forest fires. Maybe wood smoke is too widespread and entrenched in history. Maybe there are still too many wood burners on the NTP committees. Wood smoke is not harmless and its effect depends on location and dose in crowded areas.
Many wood burners insist that the wood smoke issue was resolved in their favour long ago. In my opinion, this issue will not be decently resolved until politicians either enforce bylaws better or totally ban wood smoke in city limits. Banning wood smoke will be a hard sell for those who insist on dying with a wood poker in hand. Maybe the next generation will have the sense to leave the cavemen days behind and embrace best modern heating practices.