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Exposure to ambient particulate matter and cigarette smoke linked with increased mortality risk
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Low levels of fine particulate matter from either cigarette smoke or other air pollution may be associated with an increased risk for mortality from CVD.
The researchers examined an analytic cohort of approximately 1 million participants from the American Cancer Society Cancer Prevention Study II (217,000 were current smokers at the time of enrollment). Using a Cox proportional hazard regressions model, they adjusted for education, body mass, increments of cigarette smoking, occupational exposure to particulate matter and other variables. The researchers then integrated the data with data from other studies of secondhand smoke and air pollution and plotted the adjusted relative mortality risk against the estimated daily average dose of fine particulate matter from cigarette smoke and other air pollution.
According to the study results, there was an increased risk for CV mortality at even low levels of active cigarette smoking that were greater than the risk from low levels of exposure to air pollution and secondhand cigarette smoke. Risk for CV mortality increased at low levels of exposure to ambient particulate matter and secondhand smoke but not to the extent observed with active cigarette smoking. The exposure–response relationship leveled off as exposure to active cigarette smoke increased but remained elevated for all exposure levels. The RRs of cigarette smoking were also greater for younger and middle-aged participants compared with older individuals.
“The empirical findings of this analysis have important public health implications,” the researchers concluded. “Our analysis contributes much-needed empirical evidence on the shape of the exposure–response relationship of the health impacts of fine particulate matter exposure from cigarette smoke and combustion-related ambient air pollution.”
In an accompanying editorial, Annette Peters, PhD, head of research at Helmholtz Zentrum München–German Research Center for Environmental Health, praised the researchers for their findings and noted that efforts to reduce ambient particulate matter have already been linked with improved life expectancy and other outcomes in Europe.
“Pope and colleagues need to be highly complimented for this daring endeavor to find a scale on which these different estimates of particulate matter exposure can be integrated,” Peters wrote. “Recent abatement of smoking in public places in Europe has had significant effects on hospital admissions for CVD and in particular for CAD. When this recent evidence is considered, it calls for sustained efforts to reduce the exposure to particulate matter indoors and outdoors.” – by Eric Raible
Pope CA. Circulation. 2009;doi:10.1161/CIRCULATIONAHA.109.857888.