DAMAGE TO THE NASOPHARYNGEAL MUCOSA INDUCED BY CURRENT LEVELS OF URBAN AIR-POLLUTION - A FIELD-STUDY IN LAMBS

This study concerns the effects of urban air pollution on the nasophar yngeal epithelium, with the aim of evaluating the possible harmful act ivity of levels of atmospheric pollution which are not currently consi dered to be dangerous. Over a 3 month period, 10 lambs kept in a zone characterized by numerous vehicles were sacrificed at regular interval s, and their nasopharyngeal mucosa was examined by scanning electron m icroscopy and image analysis. Two lambs kept in a rural area were used as controls. The local levels of some airborne contaminants (NOx, NO2 , NO, SO2, CO and particulate matter with aerodynamic diameter less th an or equal to 10 mu m (Ph10)) were monitored throughout the experimen t. The urban air had an irritating effect, inducing hypersecretion of mucus and morphological damage to the ciliated epithelium. These alter ations increased with the duration of exposure to urban air and with i ncreasing pollution levels, although the levels remained below current legal levels. We conclude that the harmful effects of airborne contam inants are probably underestimated. Moreover, physicochemical evaluati on of pollution parameters should be complemented by morphological stu dy of upper respiratory epithelium in exposed animals, since this muco sa is a sensitive target for irritating agents.