Impact of black carbon exposure on length of hospital stay in asthma patients: a retrospective cohort study in yulin, China

Short-term BC exposure was significantly associated with extend asthma hospitalization duration, with critical exposure windows at lag9 and pronounced vulnerability in children and middle-aged adults during non-pollen seasons. These findings provide quantitative evidence supporting BC-specific emission controls in air quality policies and highlight the need for targeted protection of vulnerable populations, particularly in high-population regions.