I'm assuming that my pack a day habit is much more dangerous.
Actually, smoking is protective against variety of toxic exposures, including heavy metals. Some unknown ingredient(s) in tobacco smoke nearly doubles the main internal antioxidants and detox enzymes in human body: glutathione (which, among others, neutralizes and excretes mercury), catalse and SOD.
For example, in a large series of experiments in 1974 (on behalf of National Cancer Institute) on hamsters exposed in groups to variety of industrial pollutants, including toxic metals, which were tested separately on smoking and nonsmoking hamsters, the authors state (see summary of results on page 40 in the pdf file):
With the exception of the two asbestos-exposed groups (Groups 5 and 6), the groups exposed to cigarette smoke lived significantly (p<0.05) longer than their sham-smoke-exposed cohorts. The hamsters exposed to asbestos plus cigarette smoke also outlived their sham-smoke-exposed cohorts; however the difference was not statistically significant. Asbestos decreased the lifespan of the asbestos-exposed groups and thereby masked, to a degree, the difference in the survival between the smoke-exposed animals and their sham-smoke-exposed cohorts which is so readily apparent in other groups (Figure 23).
Here is one of the graphs illustrating the consistent general pattern (upper curve is for survival advantage of smoking vs nonsmoking hamsters exceeding 40%, while the lower curve shows weight difference, with smoking hamsters staying thinner by 12 to 25%):
See also another thread here on FR, where more recent experiments (from 2005; which, as they always do when smoking is put to test, also went the "wrong" way -- smoking mice & rats live longer and stay thinner) were discussed. So, enjoy this ancient miracle medicine and don't listen to antismoking swindlers, since believing them does harm your health (via nocebo or "witch doctor" effect).