Occupational hygiene for airborne chemicals and other materials has mainly focused on the world as it is rather than how it might be changed. We have described as scientifically as possible workers’ exposure and its determinants, and the effectiveness of control equipment and control strategies. This has led to a long string of good tools such as occupational exposure limits, sampling strategies and devices, check-lists, product information sheets, communication to employers and employed, and more costeffective control equipment. All these tools have been continuously sharpened, and we have seen a very significant lowering of the exposure in the past 30–40 years. But we have looked much less at the production processes and the ways that materials are handled, and how these affect exposure. It is easy to say why. Production management is usually unwilling to let us make experimental changes with a process, so we must use good model experiments. One area that has been studied is dustiness testing of powdered, granular or pelletized materials. Dustiness, defined as the propensity of a material to generate airborne dust during its handling, can be tested by standardized techniques that involve applying a specified type and amount of mechanical energy to a specified amount of test material for a specified time in order to overcome adhesive binding forces within the test material (Plinke et al., 1992), and thus disperse/release existing particles from the test material into the air. The amount of dust released is then determined. One major problem, however, is that dustiness is not a well-defined physical or chemical property of a material. The particle size distribution, humidity and the nature of the adhesive forces binding the particles of the test material together are important for the dustiness. The material is conceived as consisting of agglomerates of varying strengths, which in turn are made up of primary particles. The intention behind dustiness testing is that the energy applied should not be enough to divide the primary particles, e.g. by grinding, cutting and crushing, only to a varying degree separate primary particles from other primary particles and agglomerates, and also agglomerates from the bulk material. A higher input of energy or power will overcome stronger binding forces, and thus the measured dustiness will be higher. The method for applying the mechanical energy is also important. The outcome is that the measured dustiness depends on the test method: for some materials the differences can be substantial and different test methods may not even rank materials of widely differing dustiness values in the same order. But the different tests may simulate different work situations, which means that there may be no single ‘right’ test. The result is that a number of test apparatuses and corresponding test protocols have been developed either for general use or within a certain technical application/industry. These methods may constitute formal or informal standards. So this conceptually simple problem turns out to be something of a morass. A BOHS Working Group discussed and experimented for over a decade. It described many methods, stretching back to before the Second World War (BOHS, 1985), but in the end did not reach its goal of a standard method. Partly in response to this failure, HSE produced an MDHS on the rotating drum method (Chung and Burdett, 1994; HSE, 1996), although this does not meet all needs. It must be remembered that dustiness values, stated as the ratio of the weight of the amount of released E-mail: Goran.Liden@itm.su.se
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Jan 1, 2014
Olivier Louis Claude Le Bihan + 4
Open Access
