|Lung injury and fibrogenic response to dusts from citrus and grape harvests
Rajini, P., J.A. Last, S.A. McCurdy, R. Lawson, R.J. Southard, K.P. Allamneni and H.P. Witschi
Inhalation Toxicology. 1995. 7:363-376.
Epidemiologic studies on a population of agricultural workers in California involved in citrus and grape harvesting have shown that in vineyard workers, but not in citrus orchard workers, there appears to be an increased prevalence of signs of restrictive lung function (Gamsky et al., 1992). The etiologic agent(s) causing these pulmonary changes have not been identified. Case reports of farm workers have identified mineral particles, particularly silica or silicates, as possible causative agents (Sherwin et al., 1979; Fennerty et al., 1983; Glyseth et al., 1.984). The observations are consistent with silica or silicates causing restrictive pulmonary disease. However, other agents such as pesticides or pesticide residues found commonly in soil in grape-growing regions cannot be excluded as potential additional causative agent(s). We decided to study mechanisms that might underlie the lung function changes observed in farm workers. Particularly we wanted to characterize the in vivo biological activity of the agricultural dusts generated in harvesting operations. We specifically tested the hypothesis that vineyard and citrus orchard dusts collected from leaf surfaces in the area where harvest operations were ongoing would differ in their potential to cause fibrotic changes in the lung. To accomplish this goal, rats were treated with single or repeated instillations of actual dust samples collected in the field. Responses of the lung were evaluated by analysis of lung lavage fluid, lung collagen content, histopathology, and cell kinetic studies. We found that dusts collected in vineyards have fibrogenic potential, whereas dusts collected in citrus groves are biologically less active.