Ambient Levels of Air Pollution Induce Goblet-Cell Hyperplasia in Human Conjunctival Epithelium

Article excerpt

Acute adverse health effects of ambient levels of air pollution have been demonstrated in humans, mostly in terms of respiratory and cardiovascular events (Barnett et al. 2006; Ito et al. 2005; Medina-Ramon et al. 2006; Pope et al. 2002; Samoli et al. 2003; Souza et al. 1998).

Ocular mucosa is exposed constantly to the external environment. Indeed individuals living in areas with high concentrations of pollutants frequently report ocular symptoms (Saxena et al. 2003; Versura et al. 1999), and previous studies have detected tear film abnormalities and subclinical changes of the ocular surface in individuals who lived in cities with high levels of air pollution (Gupta et al. 2002; Saxena et al. 2003). In such scenario, changes in ocular mucosa may indicate potential damage to the eyes and represent a convenient biomarker of the adverse health effects induced by air pollution if objective estimators of ocular surface changes in individuals living in urban areas are proportional to the degree of exposure. In the present study we explored this concept by conducting a panel study combining determinations of individual exposure to air pollution, expressed in terms of nitrogen dioxide ([NO.sub.2]) and measuring ocular surface changes by impression cytology.

Materials and Methods

Study population. The study involved 29 volunteers, who were recruited in two locations, with different pollution levels: Sao Paulo (n = 13) and Divinolandia (n = 16). Sao Paulo is the largest city in Latin America, with high levels of air pollution, mainly as a result of traffic emissions. Divinolandia is a small city in the countryside of the state of Sao Paulo, where half the population lives in rural settings and where there is no significant industrial activity. The volunteers were recruited among the employees of two public hospitals: at the General Clinics Hospital of the University of Sao Paulo Medical School and the Regional Hospital in Divinolandia. The hospital in Sao Paulo is located downtown at an intersection of broad avenues with heavy traffic, whereas in Divinolandia the hospital is located in a relatively isolated spot surrounded by farms. The research protocol was approved by the ethics committees of both institutions, and all subjects gave their informed consent before enrollment in the study. The following inclusion criteria were adopted: a) to be part of the fixed staff of the hospitals, b) to have been living in the study area for at least 5 years, and c) to accept participating in the study after reading and signing an informed consent form. The following parameters were adopted to exclude volunteers: a) smoking, b) possibility of traveling to other areas during the monitoring period (7 days), c) contact with chemical solutions such as organic solvents, sodium hypochloride, and formalin, and d)individuals with history of use of contact lenses, ophthalmic surgery, and preexisting ophthalmic conditions. All volunteers used gas cooking and no houses had home heating.

Exposure assessment. [NO.sub.2] was used as an indicator of exposure to air pollution. We employed a passive sampler that included a cellulose filter (Energetica, Rio de Janeiro, Brazil) impregnated with an absorbant solution--trietanolamine 2%, 0.05% [omicron]-methoxyphenol, and 0.025% sodium metabisulfite (Lodge 1989), which was enclosed within a small plastic tube with one of its extremities open to ambient air. The nitrite produced during sampling was determined colorimetrically by reacting the exposed absorbing reagent with sulfanilamide and 8-anilino-1-naphthalene-sulfonic acid (ANSA) at a wavelength of 550nm.

Before the study we evaluated the efficiency and sensitivity of this measuring system by placing the filters near an automatic chemi-luminescence monitor of the State Sanitation Agency of Sao Paulo (CETESB 2007). Our method has an accuracy of 98.6% and a precision of 80%. The lower detection limit is an accumulated exposure of 100 [mu]g/[m. …