Micro-organisms and dust exposure in an Italian grain mill

In order to assess possible occupational risk for workers in a grain mill, we evaluated aerial microbiological contamination in different areas of the mill and at different points of the production line. We also measured the concentration of aerodispersed dust particles.

An assessment of microbiological contamination levels based on a Global Index of Microbial Contamination per cubic metre (GIMC per m3), an Index of Mesophilic Bacterial Contamination, and an Amplification Index is proposed. The indices were obtained from total and fungal counts. The cleaning sector is the most contaminated area of the mill: the mean GIMC per m3 was 17,213.6. In this area, the average microbial contamination was 11.41 times higher than that in the external environment. The highest concentrations of aerodispersed dust (inhalable 2.763 mg m(-3); respirable 1.400 mg m(-3)) were found in the cleaning area.

The proposed microbiological indices and the concentrations of aerodispersed dust particles show that the most hazardous section of the mill is the cleaning area. The large variation in the data does not depend on seasonal factors, but rather on not easily identifiable conditions of the internal environment which facilitate diffusion and/or proliferation of the micro-organisms.

The proposed microbiological contamination indices and the evaluation of the concentration of dust particles allow the identification of critical positions during the production cycle so that suitable measures to prevent the aerial contamination can be taken.