Instrumental variable analysis of 81 million outpatient visits in South Korea established a causal link between air quality index (AQI) and chronic rhinitis consultations, with same-day exposure showing a 7.8% increased risk. The study employed thermal inversion as an instrument to overcome the observational limitations that have plagued previous air pollution research. Adolescents aged 10-19 demonstrated the highest vulnerability, experiencing statistically significant increased risks across all measured time lags from exposure. This represents a methodological breakthrough in environmental health research, as most prior studies could only establish correlation rather than causation between air quality and respiratory conditions. The causal framework addresses confounding variables that typically obscure true relationships in pollution studies. For health-conscious adults, this confirms that air quality directly drives inflammatory responses rather than merely correlating with them. The adolescent vulnerability pattern suggests developmental factors may amplify pollution sensitivity. While the 7.8% effect size appears modest, it translates to substantial population-level healthcare burden given chronic rhinitis affects millions globally. The robust instrumental variable approach provides the strongest evidence to date that air pollution prevention measures would directly reduce respiratory illness, not merely statistical associations.