Exposure to inhalable flour dust in Canadian flour mills

Area of Science:

• Occupational hygiene
• Industrial toxicology
• Environmental health

Background:

• The American Conference of Governmental Industrial Hygienists (ACGIH) proposed a Threshold Limit Value (TLV) of 0.5 mg/m³ for flour dust in 1999, noting its sensitization potential.
• The Canadian Labour Program (HRDC) investigated flour dust exposure levels in Canadian flour mills to assess the feasibility of adopting this TLV.

Purpose of the Study:

• To evaluate current flour dust exposure levels in Canadian flour mills.
• To determine if the proposed ACGIH TLV of 0.5 mg/m³ is achievable in the industry.
• To compare the efficacy of different sampling methods for airborne flour dust.

Main Methods:

• Conducted an 8-hour work shift exposure study involving 104 workers across 14 Canadian flour mills.
• Utilized Institute of Occupational Medicine (IOM) samplers for dust concentration measurements.
• Reviewed existing literature on the health effects of flour dust exposure.
• Compared IOM sampler data with measurements from closed-face 37-mm cassettes.
• Included measurements from a highly automated mill with advanced technology.

Main Results:

• A significant majority of workers (97.1%) exceeded the 0.5 mg/m³ TLV.
• High exposure levels were recorded, with 67.3% exceeding 5 mg/m³ and 42.3% exceeding 10 mg/m³.
• The IOM sampler demonstrated greater efficiency in collecting inhalable particles compared to 37-mm cassettes.
• Even modern facilities and cleaning practices could not consistently maintain dust levels below the proposed TLV.

Conclusions:

• Flour dust exposure in Canadian mills frequently surpasses recommended occupational limits.
• Achieving the 0.5 mg/m³ TLV may be challenging for the flour milling industry, even with advanced technology.
• The findings highlight the need for continued monitoring and potential re-evaluation of exposure control strategies for flour dust.