Effect of radon exposure on asthma morbidity in the School Inner-City Asthma study

Radon may have a role in obstructive lung disease outside its known carcinogenicity. Little is known about radon's effects on asthma morbidity.

To determine the effect of radon on fractional exhaled nitric oxide (F_E NO), asthma symptom-days, and lung function in inner-city asthmatic school children.

Two hundred ninety-nine school-aged asthmatic children enrolled in the School Inner-City Asthma Study (SICAS-1) were followed. One and two-month averaged radon was assessed using a spatiotemporal model predicting zip code-specific monthly exposures. F_E NO and spirometry were measured twice during the academic year. Asthma symptoms were assessed four times during the academic year. The interaction between indoor radon exposure (Bq/m³ ) and seasonality predicting log-transformed F_E NO, forced expiratory volume in 1 s (FEV₁ ) % predicted, forced vital capacity (FVC) % predicted, FEV₁ /FVC, and asthma symptom-days was evaluated.

Participants with high radon exposure had greater change in F_E NO from warm to cold periods compared to low radon exposure (interaction p = 0.0013). Participants with >50th percentile radon exposure experience significant F_E NO increase from warm to cold weather ( $\beta$  = 0.29 [95% confidence interval [CI]: 0.04-0.54], p = 0.0240). We report a positive association between radon 1-month moving average (incidence rate ratio [IRR] = 1.01, p = 0.0273) and 2-month moving average (IRR = 1.01, p = 0.0286) with maximum asthma symptom-days (n = 299, obs = 1167).

In asthmatic children, radon may be associated with increased asthma morbidity, suggesting radon may be a modifiable environmental risk factor for airway inflammation.