What are the Health Effects of Flour Dust Exposure
The health risk associated with inhalation of grain dust including wheat, rye, millet, barley, oats or corn cereals or a combination of these which have been processed by milling and commonly referred to as flour dust include:
- Changes in lung function
- Increased prevalence of chronic bronchitis; and
- Occupational Asthma (OA) and respiratory symptoms.
Symptoms from flour dust exposure include cough, wheeze, shortness of breath (dyspnoea), hoarseness, asthma, eye problems, conjunctivitis, rhinitis and sinusitis. The most serious appears to be from occupational asthma which may occur after even after 30 years of exposure. The majority of workers in the baking industry appear to have the onset of symptoms approximately 8 years after initial exposure. Compared with the general population the increased prevalence of occupational asthma attributable to bakers appears to be 2-3 cases per 1000 person-years.
Grain dust with elevated levels of alpha-amylase, a dough improver derived from fungal organisms such as Aspergillus oryzae or Aspergillus niger, acts as an allergen, along with wheat or flour dust which may sensitise workers leading them more likely to show symptoms.
Symptoms of exposure are through to occur through two mechanisms:
- Total inhalable flour dust acting as an irritant (between 4 – 10 mg/m3); and/or
- Atopic or sensitised (due to previous exposures) having an allergic response at lower levels.
Sensitisation to flour dust has been estimated to occur in to non-atopic individuals at the lower range of 1 – 2.5 mg/m3.
What is the Australian Standard for Exposure to Flour Dust
The NSW Work Health and Safety Regulation 2011 (WHS Reg) prescribe specific duties in relation to exposure standards for specific chemicals and mixtures at Chapter 3, Part 3.2 Division 7 Managing risks from airborne contaminants. WHS Regulation 49 requires a Person Conducting a Business or Undertaking (PCBU) at a workplace to ensure that the airborne concentration of a flour dust does not exceed the exposure standard. WHS Regulation 50 requires that atmospheric testing is carried out to confirm the compliance with the exposure standard for flour dust.
The exposure standard refers to the publication by Work Safe Australia “Workplace Exposure Standard for Airborne Contaminants” with the Date of Effect being 22 December 2011. The exposure standard for grain and flour dust (oats, wheat, barley) is a Time Weighted Average (TWA) of 4mg/m3.
Work Safe Australia note that “exposure standards do not represent a fine dividing line between a healthy and unhealthy work environment. Natural biological variation and the range of individual susceptibilities mean that a small number of people might experience adverse health effects below the exposure standard”.
What are Exposure Standards to Flour Dust in Other Parts of the World
By reviewing the literature it appears Safe Work Australia have set the exposure standard to reduce the effect of symptoms rather than eliminating sensitisation to grain and flour dust. The Australian exposure standard for flour dust is consistent with the German exposure standards. The UK Control of Substances Hazardous to Health Regulations (COSHH)) Workplace Exposure Limit (WEL) is set at 10 mg/m3 which also takes into account socio-economic factors rather than solely health based outcomes.
The UK HSE recommends health monitoring to assess symptoms of occupational asthma, atopy and lung function and note that a recent draft recommendation from the European Commission’s Scientific Committee on Occupational Exposure Limits concluded that there would be only a low risk of developing respiratory symptoms, including asthma, with exposures to inhalable flour dust in the region of 0.5 – 1mg/m3.
In summary compliance with the TWA of 4mg/m3 for grain and flour dust as outlined by Work Safe Australia “Workplace Exposure Standard for Airborne Contaminants” as referenced by the NSW WHS regulation will reduce the effect of respiratory symptoms; however in the longer term there is a significant risk of workers, who are constantly exposed, to acquire sensitisation and develop occupational asthma for dust levels greater than 1 mg/m3.
How is Flour Dust Tested and Measured
Personal and static air monitoring should be taken over the full shift to Australian Standard AS 3640-2009 Workplace atmospheres – Method for sampling and gravimetric determination of inhalable dust using IOM sampling heads, 25 mm PVC filters with flow rate of 2.0 L/min.
Samples for inhalable dust monitoring should then be analysed by a laboratory accredited by the National Association of Testing Authorities (NATA) for gravimetric analysis.
In addition to monitoring flour dust levels, health monitoring individuals exposed to flour dust should be considered.