Wildfire smoke induces eye surface inflammation and tear film changes in a human experimental model

This study investigated the short-term impact of exposure to smoke from vegetation burns on ocular surface symptoms and signs.

Woody bushfuels were burnt in an enclosed room (Flammability Laboratory, University of Tasmania, Australia) to generate particulate matter and monitored in real time (Dust Trak II). Eighteen participants (aged 20–63 years, 8 males and 10 females) fitted with respirators were seated 1.5 metres from the burn for 15 minutes. Clinical ocular surface measurements were conducted in the right eye. Tears were collected from the left eye and analysed for the cytokine interleukin-1β (enzyme-linked immunosorbent assay). Pre and postexposure differences were analysed using paired t tests or Wilcoxon signed rank tests. Associations between symptoms and signs were analysed using Spearman's correlation. Mean particulate matter with a diameter of 2.5 µm or smaller exposure was 1903 µg/m³. After smoke exposure, an increase in symptoms (median change, 2; interquartile range [IQR], 1–6; P = 0.001), ocular surface staining (median change, 1; IQR, 0–1; P = 0.007), limbal redness (mean change, 0.28 ± 0.36; P = 0.02), palpebral conjunctival redness (mean change, 0.35 ± 0.36; P = 0.009), palpebral conjunctival roughness (mean change, 0.3 ± 0.4; P = 0.046), and decrease in tear breakup time (mean change. 1.4 ± 2.6 seconds; P = 0.03) occurred. The change in bulbar conjunctival redness correlated with the change in dryness symptoms (r = 0.70; P = 0.001). The interleukin-1β concentration increased in the majority of participants post exposure (median change, 6.6 pg/mL; IQR, 2.2–21.1 pg/mL; P = 0.01).

This study demonstrated that short-term wildfire smoke directly and adversely affects the ocular surface and induces symptoms. It demonstrates the need to elucidate the role of anti-inflammatory therapies in mitigating the impact of smoke on the ocular surface.