Nasal Epithelium as a Sentinel for Airborne Environmental Pollution

Abstract

A wide range of chemicals, particulate matter, and gaseous airpollutants are present in urban atmospheres and may pose a significanthealth risk for human populations. Nasal passages are the first site ofcontact of the respiratory tract with the environment and offersignificant protection to the lower respiratory tract by conditioningthe inspired air. This activity, which includes removal of certainpollutants, places the nose at risk of pathological changes, includingcancer, Mexico City residents are exposed to a complex mixture of airpollutants. Based on predicted nasal air how characteristics, four nasalbiopsy sites were selected for study in adult male volunteers from acontrol low polluted town (n = 12) and southwest metropolitan MexicoCity permanent residents (n = 54). Clinical data with emphasis on nasalsymptoms and histopathological changes including basal and goblet cellhyperplasia, squamous metaplasia, epithelial dysplasia, andneovascularization were evaluated. Immunohistochemical staining was usedto assess accumulation of p53 protein. Control individuals had norespiratory symptoms and their biopsies were unremarkable. Mexico Cityresidents complained of epistaxis, rhinorrea, nasal crusting, dryness,and nasal obstruction. Their biopsies showed patchy shortening of cilia,deciliated areas, basal cell hyperplasia, and squamous metaplasia.Dysplastic lesions were predominantly located on antral squamousepithelium and in squamous metaplastic epithelium of the posteriorinferior turbinates and they exhibited p53 nuclear accumulation.Individuals with > 10 h of daily outdoor exposure for 5 years or morehad the highest rate of dysplasia. Subjects with epistaxis were morelikely to have dysplasias and neovascularization. Results of this studysuggest: (a) Nasal lesions in Mexico City residents are likely theresult of many potentially toxic and/or carcinogenic pollutants,including ozone, aldehydes, particulate matter, and unmeasuredpollutants; (b) the alteration of the nasal mucociliary defensemechanisms and the effects of reactive and/or water-soluble materialsand particulates could be playing a major role in the nasal pathology;(c) the accumulation of p53 protein in dysplastic nasal lesions in thecontext of prolonged exposure to air pollutants raises the possibilitythat p53 mutations are already present and are providing the squamouscells with a selective advantage for clonal expansion; and (d) the nasalpassages provide a valuable sentinel tissue for the detection of toxicair pollutants. (C) 1998 Society of Toxicology.