Nasal cytology in Southwest metropolitan Mexico City inhabitants: A pilot intervention study

Southwest metropolitan Mexico City (SWMMC) inhabitants have been exposed several hours per day for the last 6 years to photochemical smog, ozone being the most important oxidant pollutant. Subjects exposed to the SWMMC atmosphere develop several histopathological changes in their nasal mucosa: dysplasia is the most significant, affecting 78.2% of adult individuals within 60 or more days of residence in SWMMC. This study was originally designed to explore whether chemical intervention could modify nasal dysplasia as determined by nasal cytology in a defined adult population. In a placebo-controlled, randomized, double-blind trial, 177 health male subjects were divided into 5 groups to whom 5000 IU of vitamin A, 100 IU of vitamin E (5000 IU + 100 IU), 16 mg of β-carotene, or placebo were administered daily for 4 months, Sixteen clinical and cytological variables were monitored. No effect on dysplasia was seen at the end of the 4-month trial; however, an apparent reversibility as well as progression of the dysplastic nasal legions and high correlation coefficients between dysplasia and nasal cytology of polymorphonuclear leukocytes (PMNs; 0.85) squamous metaplasia (SM; 0.50), and nasal mucosa atrophy (NMA;0.41) were found. A mathematical theoretical nasal dysplasia (tD) predictor equation for SWMMC adult male inhabitants is proposed (tD=0.85 Δ PMNs + 0.50 ΔSM + 0.41 ΔNMA + 0.98), in which PMNs are the best single dysplasia predictor, and all variables are independent. We suggest that the nasal cytological changes in SWMMC inhabitants may constitute an adaptative response to environmental pollutants and long-term follow-up of these subjects will be necessary to establish the possible outcomes of the nasal abnormalities.