Geographia Technica, Vol 22, Issue 1, 2027, pp. 94-105
ASSOCIATION BETWEEN SATELLITE-DERIVED PM2.5 AND CONJUNCTIVITIS CONSULTATION RATES IN A HAZE-PRONE AREA OF NORTHERN THAILAND: A LONGITUDINAL SPATIAL ANALYSIS
Supachai NAKAPAN 
, Vivat KEAWDOUNGLEK , Anuttara HONGTHONG
ABSTRACT: Ocular health may be impacted by air pollution, especially fine particulate matter (PM₂.₅), but evidence remains limited in the haze-prone area. This study investigated the spatiotemporal relationship between conjunctivitis consultation rates and satellite-derived PM₂.₅ in Chiang Rai Province, northern Thailand, from 2021 to 2023. Meteorological factors and satellite-derived Aerosol Optical Depth (AOD) were used to predict ground-level PM2.5. A linear mixed-effects model (LMM) with month and year as fixed effects and subdistrict as a random intercept evaluated relationships with predicted PM2.5, temperature, and planetary boundary layer height (PBL). Geographic Information Systems and Global Moran's I were used to characterize spatial patterns. Predicted PM2.5 was statistically significantly inversely associated with conjunctivitis consultation rate in the primary log-transformed LMM (β = −0.000420, 95% CI: −0.000806 to −0.000033, p = 0.033). While the untransformed sensitivity model showed the same direction but did not reach statistical significance (β = −0.000523, 95% CI: −0.001074 to 0.000028, p = 0.063), however. PBL was positively associated with conjunctivitis consultant rate (β = 0.000084, 95% CI: 0.000010 to 0.000158, p = 0.026). Significant regional clustering (Moran's I = 0.149, p < 0.001). Given potential exposure misclassification, healthcare utilization, reporting patterns, and residual confounding, the negative association should be interpreted as an ecological association rather than evidence of a protective or causal effect.
Keywords: Aerosol Optical Depth; Conjunctivitis consultation rate; Linear mixed-effects model; Satellite-derived PM2.5; Spatial epidemiology.
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