The world's largest salt mine has temporarily laid off 50 workers.

Goderich's Sifto salt mine says air quality issues underground have forced the layoff.

Sources suggest the layoff may be as long as seven weeks, but the company says workers will be recalled once the air issues have been resolved.

More bad news for Sifto as shipping in the great lakes has ended.

Over 75 per cent ice cover on the great lakes means all of Sifto's road salt will be traveling by truck for the time being.