Impact of Air Pollutants and Pollen on the Severity of Nonallergic Rhinitis: A Data-Oriented Analysis

Background: Rhino-conjunctivitis symptoms are more severe in nonallergic rhinitis (NAR) patients during pollen season than in other seasons. Little is known about the role of pollen and air pollutants on the severity of NAR.
Objective: The aim of this study is to assess the cross-sectional effects of both pollen and air pollutants on NAR patients during the pollen and non-pollen seasons, and to further explore the possible relationship among these triggers.
Methods: A total of 2411 clinically diagnosed NAR outpatients from 2018 to 2019 were recruited for this study. The severity of NAR was measured using rhinoconjunctivitis symptom scores. Associations of daily exposure to pollen, PM2.5, PM10, NO2, SO2, CO, O-3, and rhinoconjunctivitis symptom scores were evaluated using Logistic regression models. Distributed Lag Nonlinear models were used to explore single-day and accumulative Lag effects of environmental factors mentioned above.
Results: During the pollen season, pollen concentration, higher exposure levels of PM10, PM2.5, NO2, and SO2 increased the severity of NAR group when compared with the low-moderate severity group. The high severity group was associated with lower exposure levels of O-3. However, during non-pollen seasons, no significant association was found in air pollutant metrics, pollen concentration, and severity of NAR. The exposure-severity effects of pollen were different when different ambient pollutants were stratified.
Conclusion: Synergistic effect of pollen and air pollutants, including PM2.5, PM10, SO2, NO2, and O-3, might be responsible for aggravating the symptoms of NAR patients during pollen seasons.