Flour dust – aspiration fraction Documentation of proposed values of occupational exposure limits (OELs

The term "flour dust" refers to particles derived from finely ground cereal grains and "non-cereal" grains. Flour flour usually also contains ingredients that play an important role in improving dough quality, such as enzymes, additives such as baker's yeast, flavors, spices and chemical ingredients such as preservatives. Flour is one of the basic raw materials used in the food industry and in the production of animal feed. Taking into account the nature of the production activities in mentioned industries, the highest occupational exposure to flour dust is usually observed in bakeries and grain mills. Significant exposure to flour dust is also found in factories of pasta, pizzeria and pastry, restaurant kitchens, malt factories, animal feed factories and agriculture. The main route of exposure to flour dust in occupational conditions is respiratory and skin. The main effect of repeated or long-lasting human exposure to flour dust is irritation and allergy. Epidemiological reports have shown that asthma, conjunctivitis, rhinitis and skin reactions are the main adverse health effects of flour dust exposure. Currently in Poland for flour dust the maximum admissible value (MAC, NDS) is the same as for organic dust (plant and animal origin). The MAC values are: for inhalable fraction 2 mg/m3 and for respirable fraction 1 mg/m3 when dust contains 10% or more crystalline silica and when dust contains less than 10% of crystalline silica, 4 mg/m3 for inhalable fraction and 2 mg/m3 for respirable fraction. The need to prepare documentation for flour dust resulted from the fact that existing documentation and MAC values mainly concern the effects of farmers' exposure to organic dust of plant and animal origin. It did not refer to flour dust for which the sensitization effect is critical. The basic mechanism of action of the flour dust on the body is the reaction of hypersensitivity with stimulation antibodies type E (IgE) developing shortly after exposure to the antigen. The value of hygienic norms for flour dust in Poland has not been established, yet. There is no data regarding animal experiments and in vitro studies with flour dust. On the basis of epidemiological studies, the risk of nasal symptoms has been found to increase with dust concentrations of 1 mg/m3 and the risk of asthma at concentrations above 3 mg/m3. The SCOEL assumes that exposure to the inhalable fraction of flour at a concentration of ≤ 1 mg/m3 protects most exposed workers from nasal mucositis and that the predicted symptoms, if present, are mild. However, the concentration of flour dust <1 mg/m3 may cause symptoms in already sensitized workers. The results of the study show that the full protection against allergens present in the flour dust in the air at low concentrations is difficult to achieve. At the same time, ACGIH's recommended TLV value for the inhalable flour dust fraction at 0.5 mg/m3 (8-h TWA). The "dose-response" results suggest that the symptoms of exposure to flour, especially from the lower respiratory tract, asthma, as well as the risk of sensitization, are rare in the inhalable fraction concentration in the range 0.5  1 mg/m3. Considering the above, the Interdepartmental Commission for MAC and MAI at the 84th meeting of 4.11.2016 adopted the TLV value for the inhalable fraction of flour dust at the level of 2 mg/m3, that is, at the level of the current MAC value for inhalable fraction of dust containing > 10% of the crystalline silica. No grounds for determining the short-term limit MAC(STEL) and the limit value in biological material. The standard is marked with "A" (sensitizing substance).