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However, it is not generally rec- ognized that subtle lesions can occur in the centriacinar zone of the lung in individuals exposed to ambient particles. Our results show a continuum of changes in the respiratory and membranous bronchi- oles, being most severe in individuals who smoke and in persons exposed to agricultural dusts, but also present to a lesser degree in the population in general. The latter is not sur- prising in view of the poor air quality in the region (Alexis et al. 1999). We do not have data on lifetime exposures, but both the agri- cultural workers and nonagricultural work- ers would likely have had similar exposure to ambient air pollutants. The high levels of ozone in this region may also be contribut- ing to the background levels of airway disease (Harkema et al. 1993). The physiologic effects of the small air- way lesions are uncertain, because subtle changes such as those shown in this study can be detected only by nonroutine tests for small airway function (Wright et al. 1992). However, the changes described here in these young farmworkers may not be trivial, as they can progress to clinically significant disease (Wright et al. 1992). Conclusion Agriculture dust exposure is associated with mineral dust small airway disease and pneu- moconiosis, independent of age and cigarette smoking. These changes were observed in young individuals with no known respiratory disease. The natural history of this lesion in agricultural workers is unknown but deserves further study in longitudinal investigations of agricultural workers, using techniques sensi- tive to detection of small airway disease and pneumoconiosis. Ref Rencs Adesina AM, Vallyathan V, McQuillen EN, Weaver SO, Craighead JE. 1991. Bronchiolar inflammation with fibrosis associated with smoking. 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