Sampling Efficiency and Performance of Selected Thoracic Aerosol Samplers.

Measurement of worker exposure to a thoracic health-related aerosol fraction is necessary in a number of occupational situations. This is the case of workplaces with atmospheres polluted by fibrous particles, such as cotton dust or asbestos, and by particles inducing irritation or bronchoconstriction such as acid mists or flour dust. Three personal and two static thoracic aerosol samplers were tested under laboratory conditions. Sampling efficiency with respect to particle aerodynamic diameter was measured in a horizontal low wind tunnel and in a vertical calm air chamber. Sampling performance was evaluated against conventional thoracic penetration. Three of the tested samplers performed well, when sampling the thoracic aerosol at nominal flow rate and two others performed well at optimized flow rate. The limit of flow rate optimization was found when using cyclone samplers.

Workplace aerosol mass concentration measurement using optical particle counters.

Direct-reading aerosol measurement usually uses the optical properties of airborne particles to detect and measure particle concentration. In the case of occupational hygiene, mass concentration measurement is often required. Two aerosol monitoring methods are based on the principle of light scattering: optical particle counting (OPC) and photometry. The former analyses the light scattered by a single particle, the latter by a cloud of particles. Both methods need calibration to transform the quantity of scattered light detected into particle concentration. Photometers are simpler to use and can be directly calibrated to measure mass concentration. However, their response varies not only with aerosol concentration but also with particle size distribution, which frequently contributes to biased measurement. Optical particle counters directly measure the particle number concentration and particle size that allows assessment of the particle mass provided the particles are spherical and of known density. An integrating algorithm is used to calculate the mass concentration of any conventional health-related aerosol fraction. The concentrations calculated thus have been compared with simultaneous measurements by conventional gravimetric sampling to check the possibility of field OPC calibration with real workplace aerosols with a view to further monitoring particle mass concentration. Aerosol concentrations were measured in the food industry using the OPC GRIMM® 1.108 and the CIP 10-Inhalable and CIP 10-Respirable (ARELCO®) aerosol samplers while meat sausages were being brushed and coated with calcium carbonate. Previously, the original OPC inlet had been adapted to sample inhalable aerosol. A mixed aerosol of calcium carbonate and fungi spores was present in the workplace. The OPC particle-size distribution and an estimated average particle density of both aerosol components were used to calculate the mass concentration. The inhalable and respirable aerosol fractions calculated from the OPC data are closely correlated with the results of the particle size-selective sampling using the CIP 10. Furthermore, the OPC data allow calculation of the thoracic fraction of workplace aerosol (not measured by sampling), which is interesting in the presence of allergenic particles like fungi spores. The results also show that the modified COP inlet adequately samples inhalable aerosol in the range of workplace particle-size distribution.

Laboratory study of selected personal inhalable aerosol samplers.

Assessment of inhalable dust exposure requires reliable sampling methods in order to measure airborne inhalable particles' concentrations. Many inhalable aerosol samplers can be used but their performances widely vary and remain unknown in some cases. The sampling performance of inhalable samplers is strongly dependent on particle size and ambient air velocity. Five inhalable aerosol samplers have been studied in two laboratory wind tunnels using polydisperse glass-beads' test aerosol. Samplers tested were IOM sampler (UK), two versions of CIP 10-I sampler, v1 and v2 (F), 37-mm closed face cassette sampler (USA), 37-mm cassette fitted up with an ACCU-CAP insert (USA), and Button sampler (USA). Particle size-dependent sampling efficiencies were measured in a horizontal wind tunnel under a 1 m s(-1) wind velocity and in a vertical tunnel under calm air, using a specific method with Coulter(R) counter particle size number distribution determinations. Compared with CEN-ISO-ACGIH sampling criteria for inhalable dust, the experimental results show fairly high sampling efficiency for the IOM and CIP 10-I v2 samplers and slightly lower efficiencies for the Button and CIP 10-I v1 samplers. The closed face cassette (4-mm orifice) produced the poorest performances of all the tested samplers. This can be improved by using the ACCU-CAP internal capsule, which prevents inner wall losses inside the cassette. Significant differences between moving air and calm air sampling efficiency were observed for all the studied samplers.

Site comparison of selected aerosol samplers in the wood industry.

Several samplers (IOM, CIP 10-I v1, ACCU-CAP, and Button) were evaluated at various wood industry companies using the CALTOOL system. The results obtained show that compared to the CALTOOL mouth, which can be considered to be representative of the exposure of a person placed at the same location under the same experimental conditions, the concentrations measured by the IOM, CIP 10-I v1, and ACCU-CAP samplers are not significantly different (respectively, 1.12, 0.94, and 0.80 compared to 1.00), the Button sampler (0.86) being close to the ACCU-CAP sampler. Comparisons of dust concentrations measured using both a closed-face cassette (CFC) and one of the above samplers were also made. In all, 235 sampling pairs (sampler + CFC) taken at six companies provided us with a comparison of concentrations measured using IOM, CIP 10-I v1, ACCU-CAP, and Button samplers with concentrations measured using a CFC. All the studied samplers collected systematically more dust than the CFC (2.0 times more for the IOM sampler, 1.84 times more for the CIP 10-I v1 sampler, 1.68 times more for the ACCU-CAP sampler, and 1.46 times more for the Button sampler). The literature most frequently compares the IOM sampler with the CFC: published results generally show larger differences compared with the CFC than those found during our research. There are several explanations for this difference, one of which involves CFC orientation during sampling. It has been shown that concentrations measured using a CFC are dependent on its orientation. Different CFC positions from one sampling session to another are therefore likely to cause differences during CFC-IOM sampler comparisons.

Aerosol sampling by annular aspiration slots.

Annular aspiration slots were studied in laboratory conditions in order to investigate their performance in sampling airborne particles. The sampling efficiency was measured in a wind tunnel as a function of particle aerodynamic diameter in various conditions of external wind speed. The geometric parameters of the annular slot and the aerodynamic conditions of sampling were optimised in order to improve the sampling efficiency. Optimal selection of these parameters led to the sampling efficiency decreasing very slightly with increasing particle size. Two semi-empirical models of sampling efficiency--in moving and calm air conditions--were derived and experimentally checked. Omnidirectional annular sampling heads are less sensitive to the external wind and their inner particle losses can be minimised. A prototype of a personal aerosol sampler for exposure assessment in occupational safety and health was designed on the basis of these models. It broadly meets the conventional efficiency for inhalable aerosol sampling.

Physical and biochemical properties of airborne flour particles involved in occupational asthma.

Aerosol particles which deeply penetrate the human airways and which trigger baker's 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.

Bioaerosol sampling by a personal rotating cup sampler CIP 10-M.

High concentrations of bioaerosols containing bacterial, fungal and biotoxinic matter are encountered in many workplaces, e.g. solid waste treatment plants, waste water treatment plants and sewage networks. A personal bioaerosol sampler, the CIP 10-M (M-microbiologic), has been developed to measure worker exposure to airborne biological agents. This sampler is battery operated; it is light and easy to wear and offers full work shift autonomy. It can sample much higher concentrations than biological impactors and limits the mechanical stress on the microorganisms. Biological particles are collected in 2 ml of liquid medium inside a rotating cup fitted with radial vanes to maintain an air flow rate of 10 l min(-1) at a rotational speed of approximately 7,000 rpm. The rotating cup is made of sterilisable material. The sampled particles follow a helicoidal trajectory as they are pushed to the surface of the liquid by centrifugal force, which creates a thin vertical liquid layer. Sterile water or another collecting liquid can be used. Three particle size selectors allow health-related aerosol fractions to be sampled according to international conventions. The sampled microbiological particles can be easily recovered for counting, incubation or further biochemical analysis, e.g., for airborne endotoxins. Its physical sampling efficiency was laboratory tested and field trials were carried out in industrial waste management conditions. The results indicate satisfactory collection efficiency, whilst experimental application has demonstrated the usefulness of the CIP 10-M personal sampler for individual bioaerosol exposure monitoring.

Field comparison of 37-mm closed-face cassettes and IOM samplers.

On examining the published results of comparisons of sampling with Institute of Occupational Medicine (IOM) (Edinburgh, U.K.) samplers and 37-mm closed-face cassettes it was observed that they usually do not take into account the dust deposited on the walls of the cassettes. As the method used by the Institut National de Recherche et de Sécurité, France (INRS), to analyze metals includes the analysis of these deposits, it was decided to evaluate the differences obtained between these samplers when using this method. The essays were conducted in three different plants, and repetitive static samplings were carried out to compare 2 L/min, IOM cassettes and 1 or 2 L/min 37-mm closed-face cassettes. The airborne particles were also sampled simultaneously for granulometric analysis. Gravimetric determinations of sampled aerosol were obtained by weighing 37-mm filters and IOM cassettes, and the aerosol collected on the filters and the particles deposited on the walls were analyzed separately for both types of samplers by atomic spectrometry for metals content. The intra-sampler variability and inter-sampler ratios were then determined. Although results obtained for gravimetric analysis are comparable to those published elsewhere (ratio IOM/37-mm much higher than 1), the metal analysis revealed a close agreement between the results obtained with the three sampling methods tested when the wall deposits were taken into account. As published previously, the ratio of wall deposits to filter collected aerosol for 37-mm cassettes is variable, and it would appear to be very difficult to find an appropriate correction factor applicable when only the filter is analyzed. Were these results to be confirmed by further experiments, sampling with 37-mm closed-faced at 1 or 2 L/min or with an IOM sampler would be equivalent for all pollutants for which the analytical method allows the recovery of walls deposit.