RECOMMENDATIONS FOR REDUCING THE EFFECT OF GRAIN DUST ON THE LUNGS

Objective: To assess the appropriateness of the current Canadian stand ards for exposure to grain dust in the workplace. Options: The current permissible exposure limit of 10 mg of total grain dust per cubic met re of air (expressed as mg/m(3)) as an 8-hour time-weighted average ex posure, or a lower permissible exposure limit. Outcomes: Acute symptom s of grain-dust exposure, such as cough, phlegm production, wheezing a nd dyspnea, similar chronic symptoms, and spirometric deficits reveali ng obstructive or restrictive disease. Evidence: Articles published fr om 1924 to December 1993 were identified from Index Medicus and the bi bliographies of pertinent articles. Subsequent articles published from 1994 (when the recommendations were approved by the Canadian Thoracic Society Standards Committee) to June 1996 were retrieved through a se arch of MEDLINE, and modification of the recommendations was riot foun d to be necessary. Studies of interest were those that linked measurem ents of total grain dust levels to the development of acute and chroni c respiratory symptoms and changes in lung function in exposed workers . Papers on the effects of grain dust on workers in feed mills were no t included because other nutrients such as animal products may have be en added to the grain. Unpublished reports (e.g., to Labour Canada) we re included as sources of information. Values: A high value was placed on minimizing the biological harm that grain dust has on the lungs of grain workers. Benefits, harms and costs: A permissible exposure limi t of 5 mg/m(3) would control the short-term effects of exposure to gra in dust on workers. Evidence is insufficent to determine what level is needed to prevent long-term effects. The economic implications of imp lementing a lower permissible exposure limit have not been evaluated. Recommendations: The current Canadian standards for grain-dust exposur e should be reviewed by Labour Canada and the grain industry. A permis sible exposure level of 5 mg/m(3) is recommended to control short-term effects. Further measurements that link the levels of exposure to res piratory health effects in workers across Canada should be collected t o establish an exposure-response relation and possible regional differ ences in the effects of grain dust. Validation: There has been no exte rnal review of these recommendations. However, the American Conference of Governmental Industrial Hygienists has recommended an 8-hour avera ge exposure limit of 4 mg/m(3) for wheat, oats and barley. Sponsor: Th e recommendations were approved by the Standards Committee of the Cana dian Thoracic Society.