The effects of chronic exposure to traffic derived air pollution on the ocular surface

The purpose of this study was to explore the clinical relevance of chronic exposure to ambient levels of traffic derived air pollution on the ocular surface. A panel study involving 55 volunteers was carried out in São Paulo, Brazil. We measured the mean individual levels of nitrogen dioxide (NO2) exposure for 7 days. All subjects answered the Ocular Symptom Disease Index (OSDI) and a symptoms inventory. Subsequently, subjects underwent Schirmer I test, biomicroscopy, vital staining and tear breakup time (TBUT) assessment. Subject's mean daily exposure to NO2 was categorized in quartiles. Statistical analysis was performed using one-way ANOVA, Tukey HSD and Chi-Square tests. A dose–response pattern was detected between OSDI scores and NO2 quartiles (p<0.05). There was a significant association between NO2 quartiles and reported ocular irritation (Χ2=9.2, p<0.05) and a significant negative association between TBUT and NO2 exposure (p<0.05, R=−0.316, Spearman's correlation). There was a significant increase in the frequency of meibomitis in subjects exposed to higher levels of NO2 (p<0.05). Subjects exposed to higher levels of traffic derived air pollution reported more ocular discomfort symptoms and presented greater tear film instability, suggesting that the ocular discomfort symptoms and tear breakup time could be used as convenient bioindicators of the adverse health effects of traffic derived air pollution exposure.