Abstract:Effects of exposures to the PM 2.5 in ambient air have increasingly attracted attention of health communities and government regulatory agencies as it has been implicated with a growing list of adverse health effects, including cardiopulmonary issues, premature death and lung cancer. However, the rates of adverse health effects and long term exposure to PM 2.5 in different populations have not been well quantified due to the lack of data. In this article, 25,427 daily PM 2.5 concentrations collected from the 73 air monitoring stations throughout Taiwan are extrapolated to 290 townships by Kriging method using GIS data. These townships are then stratified into 5 levels (in µg/m 3 ) of PM 2.5 : 20-24, 25-29, 30-34, 35-39, 40 and above. Data on female lung cancer mortality taken from national statistics and the estimated PM 2.5 concentrations, considered as an exposure biomarker are combined to assess the effect of PM 2.5 on lung cancer. The average annual PM 2.5 concentration in Taiwan is 35.6±0.4 µg/m 3 . It is estimated that lung cancer mortality has a mean increase of 16% (6%-25%) for each 10 µg/m 3 increment of PM 2.5 concentration and one out of 9 female lung cancer deaths (11%) in Taiwan is attributed to the PM 2.5 exposures. This assessment is conducted using the commonly accepted principle of making the best use of available data for the stated objective. The limitations of data and the resultant conclusion are carefully articulated and discussed to advance further research.