Academic journal article Environmental Health Perspectives

Lung Cancer and Cardiovascular Disease Mortality Associated with Ambient Air Pollution and Cigarette Smoke: Shape of the Exposure-Response Relationships

Academic journal article Environmental Health Perspectives

Lung Cancer and Cardiovascular Disease Mortality Associated with Ambient Air Pollution and Cigarette Smoke: Shape of the Exposure-Response Relationships

Article excerpt

BACKGROUND: Lung cancer and cardiovascular disease (CVD) mortality risks increase with smoking, secondhand smoke (SHS), and exposure to fine particulate matter <2.5 urn in diameter [PM.sub.2.5] from ambient air pollution. Recent research indicates that the exposure-response relationship for CVD is nonlinear, with a steep increase in risk at low exposures and flattening out at higher exposures. Comparable estimates of the exposure-response relationship for lung cancer are required for disease burden estimates and related public health policy assessments.

OBJECTIVES: We compared exposure-response relationships of [PM.sub.2.5] with lung cancer and cardiovascular mortality and considered the implications of the observed differences for efforts to estimate the disease burden of [PM.sub.2.5]

METHODS: Prospective cohort data for 1.2 million adults were collected by the American Cancer Society as part of the Cancer Prevention Study II. We estimated relative risks (RRs) for increments of cigarette smoking, adjusting for various individual risk factors. RRs were plotted against estimated daily dose of [PM.sub.2.5] from smoking along with comparison estimates for ambient air pollution and SHS.

RESULTS: For lung cancer mortality, excess risk rose nearly linearly, reaching maximum RRs>40 among long-term heavy smokers. Excess risks for CVD mortality increased steeply at low exposure levels and leveled off at higher exposures, reaching RRs of approximately 2-3 for cigarette smoking.

CONCLUSIONS: The exposure-response relationship associated with [PM.sub.2.5] is qualitatively different for lung cancer versus cardiovascular mortality. At low exposure levels, cardiovascular deaths are projected to account for most of the burden of disease, whereas at high levels of [PM.sub.2.5] lung cancer becomes proportionately more important.

Key WORDS: air pollution, cardiovascular disease, lung cancer, mortality, particulate matter, smoking. Environ Health Perspect 119:1616-1621 (2011). http://dx.doi.org/10.1289/ehp.1103639 [Online 19 July 2011]

Active cigarette smoking is the major cause of lung cancer and an important established cause of cardiovascular disease (CVD) mortality (U.S. Department of Health and Human Services 2004, 2010). Risks have been shown to increase with even light or intermittent active smoking (Bjartveit and Tverdal 2005; Schane et al. 2010; U.S. Department of Health and Human Services 2010). Secondhand smoke (SHS) is also an established cause of both lung cancer and CVD (U.S. Department of Health and Human Services 2004, 2006, 2010). Since the early 1990s, growing evidence has linked long-term exposure to fine particulate matter (particulate matter with an aerodynamic diameter [less than or equal to]2.5 um; [PM.sub.2.5] air pollution with increases in the risk of cardiovascular mortality (Brook et al. 2010; Dockery et al. 1993; Krewski et al. 2009; Laden et al. 2006; Miller et al. 2007; Pope et al. 1995, 2004; Pope and Dockery 2006) and, to a lesser extent, lung cancer (Chen et al. 2008; Pope et al. 2002).

In a recent analysis, we evaluated the exposure-response relationship for cardiovascular mortality in relation to [PM.sub.2.5] from active cigarette smoking, SHS, and ambient air pollution (Pope et al. 2009). The results suggested a relatively steep exposure-response function at very low levels of exposure and a flattening out of CVD risk at high exposure levels. Previous efforts to estimate the disease burden attributable to [PM.sub.2.5] exposure have assumed that the adverse effects of [PM.sub.2.5] on both cardiovascular and lung cancer mortality flatten out above 50 ug/[m.sup.3] (Cohen et al. 2004). If the lung cancer effects of [PM.sub.2.5], however, do not flatten out at high levels of exposure similar to CVD, the estimates of the lung cancer excess disease burden from air pollution would be substantially underestimated in areas with high levels of [PM. …

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