Association Between Particulate Matter Pollutants and Ophthalmology Visits for Ocular Surface Irritation and Allergy.

Background: The World Health Organization has declared climate change to be "the single biggest health threat facing humanity", yet there are limited studies on the impact of climate change-related air pollution on ocular health.

Objective: To explore associations between ocular surface irritation and allergy-related daily outpatient office visits with daily ambient particulate matter (PM) levels in the Denver Metropolitan Area.

Methods: Daily visit counts of ophthalmology outpatient offices were obtained from an academic health center (October 1^st, 2015 to January 27^th, 2023). Daily ambient average concentrations of PM ≤ 10 µm in diameter (PM₁₀) and 2.5 micrometers or less in diameter (PM_2.5) were obtained. Data were analyzed using distributed lag nonlinear models while accounting for the cumulative lagged effects of PM₁₀ and PM_2.5 for visits. Modifications due to temperature were assessed using stratified models.

Results: There were 144,313 ocular surface irritation and allergy visits to ophthalmic clinics during the study period. Daily visit counts increased with increasing daily ambient PM₁₀ and PM_2.5 concentrations. Five-day cumulative ambient PM₁₀ concentrations at 80, 90, 100, and 110 µg/m³ showed higher rate ratios at each level from 1.77 (95% CI: 1.71, 1.84) at concentration of 80 to 2.20 (95% CI: 2.09, 2.30) for concentration of 110 µg/m³. Similarly, the visit rate ratios increased as the daily PM_2.5 concentration increased, but this gradient effect was not significantly higher as the concentration increased. The effect of PM₁₀ was higher on days when the temperature was below the average. Temperature did not affect the association between daily visit counts and PM_2.5.

Conclusion: This study found that ambient PM increased the rate of ophthalmology visits due to ocular surface irritation and allergies. Most importantly, this association increased in magnitude with higher ambient PM concentrations. Additional studies are required to fully understand the effects of climate change-related stressors on ocular health.