This study evaluates age- and disease-specific associations between short-term ambient ozone exposure and morbidity across South Korea. Using a nationwide case-crossover design, the researchers link daily ozone concentrations with hospital admissions for cardiovascular and respiratory illnesses, exploring differences by age group.

• Short-term rises in ozone concentration correlate with increased hospital admissions for respiratory illnesses, especially in older age groups. • The cardiovascular morbidity link is weaker but shows some age vulnerability. • Regional variation suggests urban areas with higher baseline pollution may be more affected.