How is this even news? I'd think that century-old health data would make it bleedin' obvious that heavy air pollution increases the incidence of lung cancer.
That seems to tell us a lot about the correlation between smoking and lung cancer but I'm not sure how to read from it that there was enough data on non-smokers to talk with certainty about other environmental factors. My understanding is that after the push for women to start smoking around that time it would have been almost impossible to find study subjects who weren't at least exposed to high levels of second hand smoke.
