EFFECT OF NITROGEN-DIOXIDE ON HUMAN NASAL EPITHELIUM

The nasal epithelium of young adult white men in good health was evalu ated by electron microscopy in a condition blind fashion relative to e xposures of 2 ppm nitrogen dioxide (NO2) or clean air for 4 h. The exp osure protocol involved two separate exposures of the same individuals to NO2 or clean air approximately 3 wk apart. We found qualitative an d quantitative evidence that luminal border membranes of ciliated cell s were ultrastructurally altered in six of seven samples of nasal epit helium obtained following NO2 exposures, although subsequent morphomet ric statistical analyses were not significant. This alteration was cha racterized by cilia containing excess matrix in which individual or, m ore commonly, multiple ciliary axonemes were embedded, and by vesicula tions of luminal border ciliary membranes, a pattern less common in cl ean air-exposed control specimens. Although these patterns were not wi despread, their morphology was consistent with findings of previous an imal studies involving acute and chronic exposure to NO2. Our findings suggest that adverse effects on mucociliary function in normal humans due to acute exposure to low levels of NO2 are most likely minimal. H owever, in view of other reports of NO2 exposure in laboratory animals documenting ciliary injury, our observations support a view that simi lar patterns might appear more prominently with higher NO2 levels and/ or more extended exposure intervals.