title: Lung cancer and cardiovascular disease mortality associated with ambient air pollution and cigarette smoke: shape of the exposure-response relationships.
abstract: BACKGROUND
  Lung cancer and cardiovascular disease (CVD) mortality risks increase with smoking, secondhand smoke (SHS), and exposure to fine particulate matter < 2.5 μm in diameter (PM₂.₅) 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.
  
  
  OBJECTIVE
  We compared exposure-response relationships of PM₂.₅ with lung cancer and cardiovascular mortality and considered the implications of the observed differences for efforts to estimate the disease burden of PM2.5.
  
  
  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 PM₂.₅ 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 PM₂.₅ 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 PM₂.₅, lung cancer becomes proportionately more important.
authors.affiliation: Economics Department, Brigham Young University, Provo, Utah, USA. cap3@byu.edu
authors.forename: C Arden
authors.initials: CA
authors.lastname: Pope
authors.forename: Richard T
authors.initials: RT
authors.lastname: Burnett
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Turner
authors.forename: Aaron
authors.initials: A
authors.lastname: Cohen
authors.forename: Daniel
authors.initials: D
authors.lastname: Krewski
authors.forename: Michael
authors.initials: M
authors.lastname: Jerrett
authors.forename: Susan M
authors.initials: SM
authors.lastname: Gapstur
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Thun
mesh_terms: D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000633:toxicity*; D002318:Cardiovascular Diseases / Q000139:chemically induced / Q000453:epidemiology / Q000401:mortality*; D015331:Cohort Studies; D004781:Environmental Exposure / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000139:chemically induced / Q000453:epidemiology / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000633:toxicity*; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000401:mortality*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*; D014481:United States / Q000453:epidemiology
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D014028:Tobacco Smoke Pollution