V. Prodi

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.

PERSPEC: A Personal Sampler with Size Characterization Capabilities

The recommendations recently proposed by the International Standards Organization (ISO) and the American Conference of Governmental Industrial Hygienists (ACGIH) on particle-size definitions have stressed the importance of gathering information on a larger size interval than previously used and, specifically, in three size fractions defined by smooth collection efficiency curves with 50% cut-points at 10 µm and 3.5 µm. A personal sampler is proposed based on the inertial size separation of airborne particles and on the subsequent deposition on a 47- or 50-mm diameter membrane filter. The sampler operates with a standard rechargeable battery personal pump in a sealed circuit with a suction flow rate of 4 Lpm through the filter. Of this, 2 Lpm are recirculated into the inlet nozzle on the axis as a filtered air core of 4-mm diameter. A flow rate of 2 Lpm of external air is drawn through the surrounding ring of equal area. While proceeding through the nozzle, larger particles penetrate deeper into the clean ...

Aerodynamic High-Temperature Particle Characterization

For the purpose of in situ sampling at high temperatures the INertial SPECtrometer (INSPEC) has been modified by the adoption of appropriate materials (stainless steel and mineral seals). Since membrane filters suitable for this environment are not easy to find, the INSPEC architecture has been changed in order to allow quartz fiber filters to be used: because of their surface roughness, they are used downstream of a grid that has the purpose of flow confinement; the filter mat captures the particles and controls the flow rate in each grid slot. The particles are separated with a resolution of 2%–6%, in the aerodynamic size range, 0.5–10 or 1–20 μm, according to the total flow rate. The sampling flow rate ranges from a few tens of milliliters per minute to 0.5 L/min, with some sacrifice in resolution at higher values. The relationship between deposition distance and size can be drawn with a confidence of above 3%. The filter can be subjected to scanning electron microscopic measurement of the geometric si...

Perspec, Personal Size Separating Sampler: Operational Experience and Comparison with other Field Devices

Abstract The basic information needed for a realistic evaluation of the inhalation risk to workers and the general population from particulates is the airborne mass concentration distribution over size. Proposed international standards define the inhalable (formerly called inspirable) fraction, those particles capable of entering the nose or mouth; the thoracic fraction, those capable of entering the lungs (da < about 10 μm); and the respirable fraction, those capable of entering the gas-exchange region of the lungs (da < about 3.5 μm). In addition, the extrathoracic fraction is defined as the difference between the inhalable and thoracic fractions, and the tracheobronchial fraction is defined as the difference between the thoracic and respirable fractions. The sampling efficiency of actual devices is expected to match that specified for ideal samplers within some tolerance, e.g., ±10 percent in the 50 percent cutpoint diameter and ±0.1 in the sharpness of the cut specified by a geometric standard deviati...

Indoor viable particles sampling with size separation

Abstract Airborne viable microorganisms may cause health problems in work and generally indoor environments. Since the ability of following air movements is related, also for these aerosols, to particle size, detailed informations of the size distribution is helpful in the assesment of inhalability (penetration into the airways) and subsequent infectious microorganisms dissemination (regional deposition) into the airways. A study on the application of a personal spectrometer is presented.

Aerodynamic Calibration of Optical Instruments

Abstract Optical instruments are very often used on populations of particles and on single particles because of the very fast, or real-time, response. Nevertheless, the response depends on optical size and properties that are not the parameters of interest. In industrial and environmental hygiene, the aerodynamic size, above approximately 0.5 μm, is generally the ruling parameter; it may therefore be of interest to calibrate the optical signal in terms of aerodynamic size distributions. In this work several light-scattering portable instruments have been operated as area monitors, connected with a data acquisition system and a personal computer to build an accurate statistical trend of the signal and averages. A PERSPEC (personal spectrometer) was also run to draw ambient air through the light-scattering cell and sample the same aerosol as the one generating the light-scattering signal, with the cell aperture becoming the system inlet, which is fairly close to an “inhalable” aperture. The PERSPEC collects...

A proposed multi-detector method for prompt 90Sr detection in post-accident environmental matrices.

Strontium-90 is of relevant biological importance among fission products released during a fission reactor accident. Rapid information on its concentration in environmental matrices is extremely valuable, yet this implies chemical separations and handling with a shift in daughter equilibrium and therefore the need to wait a sufficient time for the equilibrium to be reestablished. The work concerns a feasibility study of a multi-detector system for a prompt evaluation of the 90Sr activity or, at least, a prompt determination of its order of magnitude in the presence of other pure beta and beta-gamma emitters; their interferences are examined on the basis of the Chernobyl releases and their decay properties. The technique is based on a plastic scintillator beta detector and a guard ring of BGO counters which can be logically connected in coincidence and anticoincidence. The evaluations show that a few hours are sufficient to determine a specific activity comparable with the Maximum Permissible Concentration in air by sampling 10 m3.