Nasal epithelium as a sentinel for airborne environmental pollution

A wide range of chemicals, particulate matter, and gaseous air pollutants a re present in urban atmospheres and may pose a significant health risk for human populations. Nasal passages are the first site of contact of the resp iratory tract with the environment and offer significant protection to the lower respiratory tract by conditioning the inspired air. This activity, wh ich includes removal of certain pollutants, places the nose at risk of path ological changes, including cancer, Mexico City residents are exposed to a complex mixture of air pollutants. Based on predicted nasal air how charact eristics, four nasal biopsy sites were selected for study in adult male vol unteers from a control low polluted town (n = 12) and southwest metropolita n Mexico City permanent residents (n = 54). Clinical data with emphasis on nasal symptoms and histopathological changes including basal and goblet cel l hyperplasia, squamous metaplasia, epithelial dysplasia, and neovasculariz ation were evaluated. Immunohistochemical staining was used to assess accum ulation of p53 protein. Control individuals had no respiratory symptoms and their biopsies were unremarkable. Mexico City residents complained of epis taxis, rhinorrea, nasal crusting, dryness, and nasal obstruction. Their bio psies showed patchy shortening of cilia, deciliated areas, basal cell hyper plasia, and squamous metaplasia. Dysplastic lesions were predominantly loca ted on antral squamous epithelium and in squamous metaplastic epithelium of the posterior inferior turbinates and they exhibited p53 nuclear accumulat ion. Individuals with > 10 h of daily outdoor exposure for 5 years or more had the highest rate of dysplasia. Subjects with epistaxis were more likely to have dysplasias and neovascularization. Results of this study suggest: (a) Nasal lesions in Mexico City residents are likely the result of many po tentially toxic and/or carcinogenic pollutants, including ozone, aldehydes, particulate matter, and unmeasured pollutants; (b) the alteration of the n asal mucociliary defense mechanisms and the effects of reactive and/or wate r-soluble materials and particulates could be playing a major role in the n asal pathology; (c) the accumulation of p53 protein in dysplastic nasal les ions in the context of prolonged exposure to air pollutants raises the poss ibility that p53 mutations are already present and are providing the squamo us cells with a selective advantage for clonal expansion; and (d) the nasal passages provide a valuable sentinel tissue for the detection of toxic air pollutants. (C) 1998 Society of Toxicology.