The inhalation of dust at work remains, in the 21st century, one of the most important causes of illness related to work. In the industrialised nations several million workers (including retired workers) have been killed or injured by dust at work. In order to get reliable data of worker's exposure, a measurement system ideally needs to be able to determine the three particle size fractions according the standard EN 481 'Workplace atmospheres: Size fraction definitions for measurement of airborne particles' (CEN, 1993).
A new reference method for the simultaneous measurement of hazardous particulate matter according EN 481 had to be developed, which will provide a better assessment of occupational health risks than methods which are currently available. This included the design and testing of two three stage personal air samplers based on the existing IOM and GSP samplers for the inhalable dust fraction incorporating additional porous plastic foams. Two foam plugs with different porosity are used to select the thoracic and respirable dust fraction, which reach the lower parts of the lung.
The porosity of polyurethane foams can be best determined by measuring the cell diameters with optical means. The cell diameter is more precise than the value pores per inch (ppi). The particle penetration tests using polydisperse dusts (glass microspheres) in wind tunnel (velocity: 0.15 m/s) and calm air chamber tests (Görner et al. 2001) indicate that selected foams with predicted geometry and porosity comply with the required penetration curves sufficiently well. Standard chemical analysis procedures as used for membrane filters can similarly be applied for analysis of elements, except for impurities in polyurethane foam like tin and calcium. Even organic compounds can be sampled on foams when preparing the foams in a special way. Prototype samplers have been constructed and further field tests gave information on the handling. By appropriate choice of foam selection characteristics, a sampler of this type can collect the respirable fraction on the filter, the thoracic fraction on the filter plus the adjacent foam plug and the inhalable fraction on the filter plus both plugs. Two new types of three-stage personal air samplers (IOM-ITR, PGP-ITR) will be available on the market in the future. It is expected to extend this sampling principle onto other air samplers. Recommendations for a later use in different national air sampling systems shall be given in order to reach a higher degree of European harmonisation in occupational exposure measurement.
Görner P, Wrobel R, Fabriès J-F, Aitken RJ, Kenny LC, Moehlmann C:
Measurement of sampling efficiency of porous foam aerosol sampler prototypes. Journal of Aerosol Science Vol.32 (2001), Suppl. 1, 1063-1064.
Kenny LC, Aitken RJ, Görner P: Investigation and application of a model for porous foam aerosol penetration. Journal of Aerosol Science 32 (2001) 271-285.
Möhlmann C, Aitken RJ, Kenny LC, Görner P, VuDuc T, Zambelli G:
Size-selective personal air sampling: A new approach using porous foams.
Ann occup. Hyg., Vol. 46, Supplement 1, pp. 386-389, 2002.
Contact: Carsten Möhlmann, BIA, D-53754 Sankt Augustin;
Polyurethane foam has been found to serve well as a sampling and selection medium for particles. The physical and chemical behaviour of porous foams was investigated using microscopy (optical, SEM), elemental and organic chemical analyses. A semi-empirical model was developed and used to predict the particle penetration and foam plug geometries (Kenny et al. 2001), suitable as good starting points for particle penetration tests. The foam characteristics were to be determined in detail; and a three stage personal air sampler using such foams was to be prototyped and adopted to existing national personal air samplers in order to get a simple, easy to handle sampling technique.
Besides the development of a sampler, special attention is paid to the development of suitable analysis procedures to determine the mass and chemical composition of the sampled dust collected in each stage.
Funding SchemeCSC - Cost-sharing contracts
S3 7HQ Sheffield
EH8 9SU Edinburgh