Public health costs ascribable to air pollution are socialized in our society. To quantify the damage to public health, epidemiologic studies are needed. We present the methods and epidemiologic background data which form the basis for estimating the public health effect ascribable to air pollution. The figures are presented per 1 million "average" Swiss population and per 10 micrograms/m3 increase in long-term annual mean particulate pollution (PM10). Quantification was restricted to the health effects given below (due to lack of complete data for other effects or to avoid duplicating health effects which may be described by overlapping measurements). In parenthesis we present (1) the mean effect estimates (+/-1 SE) (% increase per 10 micrograms/m3 increment in PM10) derived from national and international epidemiologic studies, and (2) the expected absolute additional health effects (+/-1 SE) per 1 million Swiss population and per 10 micrograms/m3 increment in PM10, based on Swiss population statistics: total mortality (long-term estimates from the 2 US cohort studies) (+4.4% [+/-1.1]/349 [+/-91] premature deaths per year); prevalence of chronic bronchitis in adults (+25% [+8.4]/increase in long-term prevalence by 3,513 [+/-1.475]); bronchitis among children (35% [+/-13]/5,180 [+/-2,590] additional children sufferers in a year); repeated cough among children (+54% [+/-8.8]/23,490 [+/-5,873] additional children per year); cough/phlegm in adults (+12.8% [+/-7.8]/1.56 [+/-1.08] million person-days per year); hospital admissions for respiratory diseases (+1.47% [+/-0.5]/71 [+/-24] additional admissions or 1,104 (+/-390) hospital days); admissions for cardiovascular diseases (+0.9% [+/-0.25]/70 [+19] admissions; 970 (+/-270) hospital days); restricted activity days (+10.5% [+/-0.77]/0.42 [+/-0.03] million person-days); days with asthma attacks among the 6.7% asthmatics (Swiss prevalence) (+5.3% [+/-2.1]/ 240,000 [+/-102,000] additional person-days). Conservative assumptions were used throughout the study and thus the true effects are likely to be larger. Estimates of Swiss population exposure distribution would be needed to apply these results to the entire population. This step, and monetary quantification of these total effects, were the second and third elements (not shown in this report) of this Swiss government funded project. Although individual relative risks of air pollution are rather slight, the public health burden of even moderate pollution may be substantial.