). However, the case-only approach provides important advantages over traditional analyses, including reduction of potential confounding by variables typically associated with mortality, simplification of modeling, and reduction of results sensitivity to model misspecification bias of particular interest, the long term trend and periodicity in mortality whose modeling is quite complex, drops out in case-only approach. It was encouraging that in this study, seasonal pattern and temperature levels did not appear to confound the interaction of interested modifiers and pollution.Additionally control for the interactions with season (a sine and cosine term with 365.24-day period) and temperature levels did not change the results and show the modification of individual characteristics on pollution effects were stable.