Short-term association between air pollutants and outpatient visits for conjunctivitis in an arid industrial city of Northwest China: A time-series study

Purpose : This study aims to quantify the short-term association between ambient air pollutants and outpatient visits for conjunctivitis using empirical data. Methods : This study collected daily outpatient visits for conjunctivitis in Jiayuguan City from January 1, 2023 to December 31, 2024, as well as meteorological and air pollutant data during the same period. We used a quasi-Poisson generalized linear regression model that incorporates a distributed lag nonlinear model to analyze the nonlinear relationship and lag effect between pollutant exposure and the risk of outpatient visits for conjunctivitis, and conducted stratified analysis by gender, age and season to identify susceptible populations. Results : A total of 14,598 cases of conjunctivitis were included during the study. The results showed that particulate matter (PM _2.5 and PM ₁₀ ) was not statistically significantly associated with outpatients for conjunctivitis, and the exposure-response curve showed a downward trend. Conversely, gaseous pollutants (NO ₂ and CO) showed a significant positive linear correlation with outpatients for conjunctivitis, with the effect being stronger in the cold season. NO ₂ was significant at lag1-3, lag5 days and lag02–07 days, with each 10 μg/m ³ increase corresponding to an RR of 1.126 (95%CI: 1.050, 1.208), corresponding to a 12.60% increase in patient visits. CO had the strongest effect at lag07 days (RR =1.836, 95% CI: 1.126, 2.991). Furthermore, NO ₂ primarily increases conjunctivitis visits in women and children (0-14 years), while CO exposure is significantly associated with conjunctivitis visits in men and older adults (≥65 years). Conclusions : In this arid, industrial city in Northwest China, gaseous pollutants (rather than particulate matter) are the key environmental factor driving the increase in conjunctivitis outpatient visits. This study reveals the differentiated effects of specific pollutants on populations with different demographic characteristics, highlighting the public health significance of strengthening ocular surface health protection for specific vulnerable subgroups during the cold season.