 Exposure-response relationships for a given risk factor are commonly obtained from epidemiological studies.For example, the disease burden of outdoor air pollution for Santiago, Chile, was calculated by measuring the concentration of atmospheric particulate matter (PM10), estimating the susceptible population, and combining these data with relevant dose-response relationships.A reduction of particulate matter levels in the air to recommended standards would cause a reduction of about 5,200 deaths, 4,700 respiratory hospital admissions, and 13,500,000 days of restricted activity per year, for a total population of 4.7 million.