Provetaking av inhalerbart melstov

Abstract

Summary Kruse K & Eduard W. Sampling of inhalable flour dust. Arbete och Hälsa, 2009;43(5) In 2000 the Norwegian Labour Inspection Authority established an occupational exposure limit (OEL) for inhalable flour dust at 3 mg/m³. This is the first OEL in Norway to define inhalable dust instead of total dust. Because of inconsistencies between wind tunnel experiments and field studies a comparative study of aerosol samplers was performed in bakeries. Four inhalable samplers (PAS6, IOM, GSP and Button) and a 25 mm standard aerosol cassette (StK) were included in the study. Initial results with the Button sampler showed that the holes in the screen became clogged and this cassette was therefore excluded. Personal measurements were carried out in pairs with PAS6 as reference in a large and a small bakery. The samplers were attached on each shoulder and their position interchanged between measurements. The sampling was done for approximately 1-1½ h. Dust was collected on 2 μm Teflon filters which were analysed by gravimetry. SAC underestimated the exposure level compared to PAS6 (STK = 0,67⋅PAS60.95, r2 = 0.90, n = 25). GSP estimated higher exposure levels than PAS6 (GSP = 1,4⋅PAS60.92, r2 = 0.87, n = 27), while IOM estimated even higher dust levels especially for lower exposure levels as the power of PAS6 was significantly lower than 1 (IOM=2,4⋅PAS60.71 , r2 = 0.80, n = 27). The precision of the GSP and IOM was probably inferior to PAS6 and SAC because the ratios GSP/PAS6 and IOM/PAS6 had 3-4 times higher standard deviations than SAC/PAS6 (p<<0.001). The ranking of the other aerosol samplers was in agreement with earlier laboratory tests in wind tunnel. Laboratory tests have shown that the GSP sampler had the best fit to the inhalable CEN/ISO convention at en air velocity of 0.5 m/s. This convention assumes, however, that the exposure level is independent from the direction of the air stream. This assumption seems unrealistic for bakers who often have the dust source in front of them. Furthermore, a larger aerosol fraction is inhalable at air velocities that are more realistic for indoor air (0.1-0.3 m/s) than used in laboratory tests. The best estimate for inhalable dust sampling in bakeries seems therefore to lie between the GSP and the PAS6. The larger variability of GSP measurements and its need for a more powerful sampling pump (3.5 l/min) favour the use of PAS6 for sampling of inhalable flour dust. Because of considerable uncertainty about criteria for sampling of inhalableaerosol a valid alternative is to use those cassettes that were applied in key studies in the occupational exposure limit documentation. Then the PAS6 cassette should be used in Norway and the IOM cassette in Sweden. A consequence of a pragmatic choice of sampling cassette is, however, that an approximately 80 % higher flour dust exposure level would be accepted in Norway than in Sweden even though the occupational exposure limit values are the same in the two countries.