Canada Raises Exposure Limit for Flour Dust, Lowers OEL for Grain Dust

Published August 8, 2018

In July, Canada adopted new exposure limits for flour dust and grain dust in federally regulated workplaces.

The new limit for flour dust of 3 mg/m3 is a six-fold increase from the previous limit of 0.5 mg/m3, which the Canadian government characterized as “impracticable” because it required workers in wheat flour mills, where exposures above 0.5 mg/m3 are constant, to wear respiratory protection their entire work shifts. According to a June 2017 notice published in the Canada Gazette, the wearing of respiratory protection at these facilities interferes with work tasks and can introduce other health risks such as heat exhaustion and breathing difficulties. The OEL of 3 mg/m3 would protect workers against asthma and reduce the risk of respiratory sensitization, which are two possible health effects of occupational exposure to flour dust.

The ACGIH threshold limit value for flour dust is 0.5 mg/m3. Occupational exposure limits for flour dust in other countries range from 3 mg/m3 to 10 mg/m3, while some of Canada’s provinces have adopted the 0.5 mg/m3 limit. In the United States, OSHA does not have an exposure limit for flour dust.

The previous federal limit for grain dust in Canada was 10 mg/m3. The new limit of 4 mg/m3 aligns the federal regulation with those of Canadian provinces, all of which adopted the 4 mg/m3 limit more than twenty years ago. The new limit takes into consideration the available scientific evidence for protecting workers as well as the economic feasibility of achieving the OEL. Exposure to grain dust can cause acute irritation of the eyes, the upper respiratory tract, and sometimes the skin.

In the U.S., OSHA’s permissible exposure limit for grain dust is 10 mg/m3. Both the TLV and the NIOSH recommended exposure limit are 4 mg/m3.

For more information, see the Canadian government’s news release. The government website also provides general information on controls and sampling for flour dust and grain dust.