Comparison of ambient PM risk with risks estimated from PM components of smoking and occupational exposures

Air pollution studies are based on individual-level health response data an d group-level exposure data. Therefore, exposure misclassification occurs, and the results may be biased to an unknown magnitude and direction. Testin g the validity of such associations requires a study design using individua l-level data for both exposure and response. One can test the plausibility of group-level PM risk estimates by comparing them to individual-level esti mates of risk from constituents of ambient air. The twofold purpose of this review is to consider the internal consistency of risks estimated from the three major PM cohort studies and to determine individual-level mortality risks associated with ambient concentrations of tobacco smoke and occupatio nal exposures and compare them with risks associated with ambient PM. The paper demonstrates the risks are not consistent within and between the PM cohort studies. Higher ambient concentration risks (ACRs) from the ambie nt PM cohort studies are not coherent with ACRs derived from individual-lev el smoking and occupational risks for total, cardiopulmonary, and lung canc er mortality. Individual-level studies suggest increased risk of mortality cannot be measured with reliability at concentrations found in ambient air.