Jean-Francois Fabries

A COLLABORATIVE EUROPEAN STUDY OF PERSONAL INHALABLE AEROSOL SAMPLER PERFORMANCE

Following the adoption of new international sampling conventions for inhalable, thoracic and respirable aerosol fractions, a working group of Comité Européen de Normalisation (CEN) drafted a standard for the performance of workplace aerosol sampling instruments. The present study was set up to verify the experimental, statistical and mathematical procedures recommended in the draft performance standard and to check that they could be applied to inhalable aerosol samplers. This was achieved by applying the tests to eight types of personal inhalable aerosol sampler commonly used for workplace monitoring throughout Europe. The study led to recommendations for revising the CEN draft standard, in order to simplify the tests and reduce their cost. However, some further work will be needed to develop simpler test facilities and methods. Several of the samplers tested were found to perform adequately with respect to the inhalable sampling convention, at least over a limited range of typical workplace conditions. In general the samplers were found to perform best in low external wind speeds, which are the test conditions thought to be closest to those normally found in indoor workplaces. The practical implementation of the CEN aerosol sampling conventions requires decisions on which sampling instruments to use, estimation of the likely impact that changing sampling methods could have on apparent exposures, and adjustment where necessary of exposure limit values. The sampler performance data obtained in this project were affected by large experimental errors, but are nevertheless a useful input to decisions on how to incorporate the CEN inhalable sampling convention into regulation, guidance and occupational hygiene practice.

Study of fifteen respirable aerosol samplers used in occupational hygiene

European and international standards lay down criteria for the size-selective aerosol sampling in occupational hygiene. Aerosol samplers are supposed to match these target sampling criteria. This study focused on 15 aerosol samplers used to sample the conventional respirable fraction. An aerodynamic particle sizer (APS) method was used to measure the sampling efficiency of the samplers in a low-velocity wind tunnel. Polydisperse coal dust was generated as the test aerosol. The data were fitted by an appropriate mathematical model. For some instruments the results show serious deviations from the conventional target curve, whereas other devices meet the convention quite well. The flow rate of certain cyclone-separator-based instruments was optimized to adjust their sampling efficiency. The mass concentration bias and accuracy of the samplers were calculated for a number of ranges of particle size distributions of aerosols commonly found in industrial workplaces. Finally, the performance of each sampler was evaluated using bias and accuracy maps. Most of these samplers are suitable for sampling the CEN-ISO-ACGIH respirable fraction of aerosols, but several require modification of the flow rate. For real industrial situations, the rough knowledge of the aerosol size distribution can guide the choice of an appropriate sampling technique.

Physical and Biochemical Properties of Airborne Flour Particles Involved in Occupational Asthma

Aerosol particles which deeply penetrate the human airways and which trigger bakers asthma manifestations are known to represent only a part of flour and of airborne particles found in bakeries. They were a major focus of this study. To this end, aerosols were produced from different wheat and rye flours, using an automatic generator designed for bronchial challenge. Particles were characterized for their size distribution, their ability to be deposited in the airways, their protein content, their histological composition and their reactivity with immunoglobulin E (IgE) present in sera from asthmatic bakers. Like dust particles collected in the bakery, the aerosols produced showed increased protein content but decreased IgE reactive protein content when compared to the corresponding bulk flours. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of these particles showed a predominance of endosperm gluten proteins. Under scanning electron microscopy, flour particles displayed various tissue fragments with entrapped large A-starch and small B- or C-starch granules, whereas aerosol particles appeared primarily as a mixture of the endosperm intracellular interstitial protein matrix and small B- or C-starch granules free or still associated. These observations showed that aerosols supposed to penetrate deeply the airways, mainly correspond to intracellular fragments of endosperm cells enriched in gluten proteins but with lower amount of allergens belonging to albumins or globulins.

Annular aspiration slot entry efficiency of the CIP-10 aerosol sampler

The CIP-10 personal or static aerosol sampler is designed to sample the respirable, thoracic or inhalable aerosol fraction by using the appropriate selector. All these versions have the same downward-oriented annular aspiration slot. The annular slot entry efficiency at a flow rate of 10 l min–1 was studied as a static sampler in an experimental wind tunnel, at first for a 1 m s–1 wind velocity. Glass beads were generated as a test aerosol by a fluidized bed aerosol generator. A sharp-edged thin-walled isokinetic probe was used for reference sampling. The particle size-dependent efficiency was deduced from the particle size distributions of both reference and annular slot samples. Particle size distributions were measured as functions of the volume equivalent diameter Dv by the Coulter Multisizer technique. The aerodynamic particle diameter Dae was deduced from Dv by using particle density and Reynolds number. The entry efficiency of the CIP-10 annular aspiration slot at 1 m s–1 is between 0.9 and 0.4 for the whole range of particle aerodynamic diameters within the range 10–60 µm. By minimizing the inner particle deposit under the protecting cup of the selector, the instrument can meet the CEN sampling criteria for sampling of inhalable aerosol as shown on the bias and accuracy maps.