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P. Novaes, M. Matsuda, A. Berra, U. P. Santos, M. Peres Rangel, R. Santo, N. Kara-Jose, P. H. N. Saldiva; Clinical and Histological Ocular Surface Alterations in Workers Involved in Sugar Cane Burning. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2605.
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Investigate the impact of sugar cane burning on the ocular surface of cane workers and compare clinical and histological parameters during the burning and the non-burning periods.
Thirty healthy sugar cane workers were recruited from the rural city of Cerquilho, located in the State of São Paulo, Brazil. Measurements of the daily average concentrations of particulate matter 2.5 were done during the burning and the non-burning periods. Schirmer's I test, biomicroscopy, tear film break-up time (TBUT), eye irritation symptoms, fluorescein and rose bengal staining, and impression cytology of the inferior tarsal conjunctiva (PAS positive areas) were evaluated during the two periods. The subject’s PAS positive areas were classified into three categories according to the total years of labor in sugarcane harvesting.
PM2.5 exposure levels during sugarcane harvesting were 3.5-fold higher than the established limit of 25µg/m3 (WHO 2006). Mean TBUT values were lower in the burning period (mean 6.48s; SD 3.47) than in the non-burning period (mean 10.16s; SD 7.79; p=0.05). There was a decrease in PAS positive areas during the burning period (p=0.014). A non-linear regression model reveals a strong relationship between PAS positive areas and years working in sugar cane harvesting (Figure 1; r=0.99, p=0.015). Concerning the other clinical tests, there was no difference between periods .
These findings indicate there is an increase in mucus production and goblet cell hyperplasia, as an adaptive response to chronic occupational exposure to air pollution. However, the decrease in PAS positive areas during exposure to acute episodes of higher concentrations of air pollution generated by sugar cane burning suggest a toxic effect on the ocular surface. A tendency towards greater tear film instability was also detected during the burning period.
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