A new study published in Environment International assessed the association between air pollutant emissions, ambient concentrations and the effect of implemented emission reduction policies on asthma. In this study, the population of Daejeon in Korea (except Seoul) was used as a reference population to adjust for possible long-term background trend. Trends of air pollutant emissions, ambient concentrations and hospital visit rates in Seoul and Daejeon were evaluated using descriptive statistics. An interrupted time-series analysis was conducted. The findings revealed evidence for the association between emission reductions and reduced ambient concentrations. It was observed that trends in hospital visit rates for asthma, which were previously increasing in Seoul, haddeclined since the implementation of emission reduction policies. Overall, prevented hospital visits cases for asthma in the total population and younger population (0-18 years) were estimated as 500,000 (11.3% of hospital visit cases if there was no intervention) cases and 320,000 (15.5% of hospital visit cases if there was no intervention) cases, respectively in Seoul. Therefore, the results provided evidence for the possible beneficial effect of emission reduction policies on hospital visits for asthma.