Ambient levels of air pollution induce goblet-cell hyperplasia in human conjunctival epithelium

BACKGROUND: Ocular mucosa is exposed constantly to the external environment, and chronic exposure to air pollution may affect the ocular surface. OBJECTIVE: We assessed the effect of air pollution on the ocular surface by combining determinations of individual exposure and conjunctival impression cytology. METHODS: A panel study was conducted with 29 volunteers recruited in two locations with different pollution levels: Sao Paulo (n = 13) and Divinolandia (n = 16). We assessed mean individual levels of nitrogen dioxide (NO2) exposure for 7 days, using a passive sampler. Impression cytology samples were obtained from inferior tarsal conjunctiva. Comparisons between the two groups in terms of NO2 exposure and goblet-cell counts were performed using the Student t-test. Correlations between goblet-cells counts and corresponding individual NO2 exposure levels were determined using Spearman's correlation. RESULTS: Individuals living in Sao Paulo received a significantly (p = 0.005) higher dose of NO2 (mean 32.47; SD 9.83) than those living in Divinolandia (mean 19.33; SD 5.24). There was a steady increase in goblet-cell counts, proportional to NO2 exposure (Spearman's correlation 0.566, p = 0.001), with a dose-response pattern. CONCLUSIONS: A positive and significant association between exposure to air pollution and goblet-cell hyperplasia in human conjunctiva was detected. The combination of simple measurements of exposure and impression cytology was an effective and noninvasive approach for characterizing human response to ambient levels of air pollution.