Grain Dust and Lung Health: Not Just a Nuisance Dust

The invitation to contribute to the present issue of the Journal, celebrating the 50th anniversary of the Canadian Thoracic Society (CTS), provides me with an opportunity to document what, in my view, is one of the most effective collective interventions in the field of epidemiology and occupational health. The present essay gives the reasons why the Society addressed the question of whether grain dust is not just a nuisance dust, and how it did so. My main source of information is from a 1978 report in the Canadian Lung Association Bulletin (1). Grain growing, handling and processing have long been major Canadian industries. In the 1971 census of Canada, there were in Canada approximately 253,000 farmers, farm managers and farm workers; approximately 5000 small elevator workers and 7200 large elevator workers; and approximately 15,000 workers in the flour, feed and seed mills. The dust to which grain workers are exposed is complex, whether it be wheat, barley, rye, oats or corn. It consists of the grain, hairs from the epicarp and the germ. Plant contaminants include weeds and pollens. Fungi grow in grain depending on its freshness. Rodents may infest it, leaving their spoor. Chemicals may be added to control fungi, arthropods and rodents. Free silica from the soil may be present or incorporated into the plant as phytoliths. Finally, grain workers often handle oil seeds such as sunflower, flax and mustard. Grain dust had been classified as a ‘nuisance’ dust; it does not, in the view of the influential American Conference of Government and Industrial Hygienists, require regulation because of its ill health effects on exposed workers. This, however, was contrary to the experience of several members of the CTS, who had been involved in an impressive number of epi-demiological research studies of workers in different branches of the grain handling industry before 1977.