Thursday, July 28, 2011

Comparing the Health Risks of Smoking and Air Pollution

This is an x-ray image of a chest. Both sides ...Image via WikipediaLung Cancer and Cardiovascular Disease Mortality Associated with Ambient Air Pollution and Cigarette Smoke: Shape of the Exposure-Response Relationships (31 page pdf, Pope CA III, Burnett RT, Turner MC, Cohen AJ, Krewski D, Jerrett M, et al, Environ Health Perspect, Jul. 19, 2011)

Today’s review article looks at how the health response of exposure to tobacco smoke and particulate matter compare in terms of the intensity and duration. The main finding is that projections or extrapolations of fatality risk from exposure to low levels can be underestimated while risks from higher levels may be overestimated, thus pointing to the need to monitor and develop public health policies for relatively low levels of ambient air pollution.



Key Quotes:

“Lung cancer and cardiovascular disease mortality risks increase with smoking, second hand smoke (SHS) and exposure to fine particulate matter (PM2.5) from ambient air pollution”

“For cardiovascular disease (and related cause-of-death groupings) the fitted function {RR=1 + 0.2685(dose)0.2730} indicates an exposure-response relationship that is substantially non-linear—that is much steeper at the very low levels of exposure compared with higher levels of exposure"

“For lung cancer mortality, the relative risks steadily increase to nearly 40 at the highest increment of cigarette smoking (>42 cigarettes/day), whereas for cardiovascular disease mortality, the relative risks level off at approximately 2.0-2.5”

“For lung cancer mortality, excess risks rise nearly linearly throughout the full range of exposure from SHS, air pollution, and active smoking, reaching maximum relative risks over 40 for heavy smokers”

“smoking duration appeared to have a much larger impact on lung cancer mortality than cardiovascular disease mortality”

“Carcinogens found in tobacco smoke and in combustion-source air pollution are the likely agents responsible for the excess lung cancer risk. Fine particles transport many of the toxic and carcinogenic substances in smoke, and may contribute to pulmonary and systemic inflammation”

“the steep exposure-response for cardiovascular disease mortality at low levels of exposure and the leveling off at high exposures is a saturation phenomenon whereby relatively low levels of exposure are capable of activating relevant biological pathways”

“For cardiovascular disease, inappropriate extrapolations of linear exposure-response functions may result in substantial over estimates in areas with very high exposures and, in some cases, potential underestimates in areas with relatively low exposures”
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