Characterization of airborne mineral dusts associated with farming activities in rural Alberta, Canada.

The dry and windy climate of the Western Canadian prairie provinces, combined with large scale agricultural activities, results in aerosolization or organic and mineral dusts. The purpose of this study was to conduct an environmental and minerological analysis of these dusts in order to estimate the risk for pneumoconiosis in exposed farmer populations. Two districts in central/southern Alberta were chosen for study. One of these regions was representative of a predominantly grain growing district with minimal use of irrigation; the other region was largely devoted to forage and irrigated crop production. Air pollution statistics showed a bi-modal distribution of total suspended particulates (TSP) with peaks corresponding with maximal farm activities in the spring and early fall. Analysis of bulk dust samples obtained from tractor cab filters showed that the majority of particles from both districts were within the respirable range (less than 5 microns). Samples from the forage-crop region contained more organic material, a greater water soluble fraction and had particles that were, on average, smaller and rounder than particles from the grain district. These differences were thought to reflect differences in irrigation patterns and use of fertilizers between the two districts. Free silica (quartz) content was also very variable and ranged from 1 to 17% on a mass basis. Respirable fibrous minerals were occasionally identified, however, no asbestos fibres, fibrous tremolite, or fibrous zeolites were identified. The results indicate that there is potential risk for mineral dust pneumoconiosis in heavily exposed farmer populations and that this risk will be influenced by local and regional factors.