Feasibility of granular bed filtration of an aerosol of ultrafine metallic particles including a pressure drop regeneration system.

UNLABELLED: A process for filtering an aerosol of ultrafine metallic particles (UFP) has been designed and tested, based on the principle of a multistage granular bed. The filtration system comprised a succession of granular beds of varying thickness composed of glass beads of different diameters. This system allows the pressure drop to be regenerated during filtration ("on-line" mode) using a vibrating probe. Tests monitoring the pressure drop were conducted on a "10-L/min" low airflow rate device and on a "100-m(3)/hr" prototype. Granular bed unclogging is automated on the latter. The cyclic operation and filtration performances are similar to that of filter medium-based industrial dust collectors. IMPLICATIONS: Filtration of ultrafine metallic particles generated by different industrial processes such as arc welding, metal cutting, or spraying constitutes a difficult problem due to the high filter clogging properties of these particles and to the high temperatures generally encountered. Granular beds represent an advantageous means of filtering these aerosols with difficult properties.

Methods for measuring performance of vehicle cab air cleaning systems against aerosols and vapours.

Vehicle cabs equipped with an effective air cleaning and pressurization system, fitted to agricultural and off-road machineries, isolate drivers from the polluted environment, in which they are likely to work. These cabs provide protection against particulate and gaseous pollutants generated by these types of work activities. Two laboratory methods have been applied to determining the performance characteristics of two cabs of different design, namely, optical counting-based measurement of a potassium chloride (KCl) aerosol and fluorescein aerosol-based tracing. Results of cab confinement efficiency measurements agreed closely for these two methods implemented in the study. Measurements showed that high confinement efficiencies can be achieved with cabs, which are properly designed in ventilation/cleaning/airtightness terms. We also noted the importance of filter mounting airtightness, in which the smallest defect is reflected by significant degradation in cab performance. Determination of clean airflow rate by monitoring the decrease in test aerosol concentration in the test chamber gave excellent results. This method could represent an attractive alternative to methods involving gas tracing or air velocity measurement at blowing inlets.

Simultaneous sampling of peroxyacetic acid and hydrogen peroxide in workplace atmospheres.

The use of peroxyacetic acid (PAA) in the disinfection processes in the food industry or for medical purposes is increasing. As it is the product of the reaction of acetic acid (AA) and hydrogen peroxide (HP) and coexists with them, and given the fact that the chemical properties of these two substances are not very different from PAA, the sampling and analysis of this substance in working atmospheres is difficult. A specific sampling device was developed. It is composed of: (i) a cassette with quartz fibre filters impregnated with titanium oxysulfate hydrate for the sampling of HP followed by; (ii) a tube filled with silica gel soaked with methyl p-tolylsulfoxide for the sampling of PAA. The analysis of this silica gel was performed by liquid chromatography with UV detection of the methyl p-sulfone generated by the sampling of PAA. The conservation of the sampling media (before and after sampling) and its efficiency were also checked. From the results of sampling campaigns performed in various workplaces, the relative contributions of PAA, AA and HP to an exposure index, taking into account the atmospheric concentrations and the threshold limit values, were established. This calculation shows that the simultaneous determination of PAA and HP, which the method presented in this paper allows, provides a fairly good estimation of the exposure.

Determination of short-term exposure with a direct reading photoionization detector.

The use of a direct reading photoionization detector (PID) to determine short-term solvent exposures is described in the present paper. To assess the relevance of such a total exposure evaluation it was necessary to compare it with the real concentration of pollutants. This comparison was made by measuring in parallel with the PID determination the concentration of each pollutant using a standard technique, i.e. sampling on charcoal tubes and subsequent analysis by gas chromatography. Laboratory tests showed that the linearity of the answer of the PID is good for many compounds and for a mixture of these compounds. Similar tests were carried out for painters in workplaces with the same good correlations (determination coefficient r2 close to 1) between the PID response and the real concentration of the pollutants measured on the sampling tubes. The use of PID also allowed determination of the exposure profile of the workers and comparison of the short-term exposure to the corresponding limit values. Many cases of the short-term limit values being exceeded were revealed by use of the PID, although very few cases of the long-term limit values have been found by the usual sampling (charcoal tube) and analytical (gas chromatography) methods.

Development of a continuous aerosol mass concentration measurement device.

A dynamic aerosol mass concentration measurement device has been developed for personal sampling. Its principle consists in sampling the aerosol on a filter and monitoring the change of pressure drop over time (Delta P). Ensuring that the linearity of the Delta P = f(mass of particles per unit area of filter) relationship has been well established, the change of concentration can be deduced. The response of the system was validated in the laboratory with a 3.5 microm alumina aerosol (mass median diameter) generated inside a 1-m(3) ventilated enclosure. As the theory predicted that the mass sensitivity of the system would vary inversely with the square of the particle diameter, only sufficiently fine aerosols were able to be measured. The system was tested in the field in a mechanical workshop in the vicinity of an arc-welding station. The aerosol produced by welding is indeed particularly well-adapted due to the sub-micronic size of the particles. The device developed, despite this limitation, has numerous advantages over other techniques: robustness, compactness, reliability of calibration, and ease of use.

Estimation of the percutaneous absorption of styrene in an industrial situation.

OBJECTIVE: This field study was designed to compare the level of styrene absorbed percutaneously with that absorbed by inhalation in a real situation in the fiberglass-reinforced polyester industry. METHODS: The study protocol consisted of comparisons of the patterns of urinary excretion of styrene metabolites by four groups of workers, all of whom performed the same task at the same time in the same workshop but wore the following different protective equipment: total protection with an insulating suit and mask, respiratory equipment only, percutaneous protection only, and no protection. RESULTS: The urinary excretion level of the group with total protection did not significantly differ from that of the group with respiratory protection only. CONCLUSIONS: Precutaneous absorption is not a particularly important pathway for styrene absorption during stratification work in the polyester industry. Completely insulating personal protective equipment provides no greater level of protection than does a respirator at positive pressure alone.

Exposure to chloramines in a green salad processing plant.

Acute eye and upper respiratory irritation was reported at an industrial facility that processes green salads in water containing hypochlorite. The irritant agents were chloramines resulting from the reaction of hypochlorite and nitrogen compounds coming from the sap proteins released when the vegetables were cut. Specific sampling and analytical methods were developed in order to assess the workers' exposure. Monochloramine, dichloramine and nitrogen trichloride were found in the atmosphere, which can explain the irritation phenomena of which the workers complained. In the washing room (where salads are processed), the total chloramine concentration ranged from 0.4 to 16 mg.m-3, depending on the day and the location of the area sampling points. The exposure of workers determined by personal sampling ranged from 0.2 to 5 mg.m-3. In a previous study, with swimming pool instructors exposed to the same pollutants, irritation phenomena generally appeared at chloramine values of around 0.5 mg.m-3.

Interactive effect of combined exposure to glycol ethers and alcohols on toxicodynamic and toxicokinetic parameters.

Ethylene glycol monomethyl ether (EGME) exhibits testicular toxicity and ethylene glycol monobutyl ether (EGBE) is a solvent with haemolytic effects in rats. The study of the interaction of two glycol ethers (EGME and EGBE) and three alcohols (ethanol, n-propanol and n-butanol, 10 or 30 mmol/kg), orally co-administered in male rats, was carried out from a toxicodynamic and toxicokinetic point of view. Administered alone, EGME (10 mmol/kg) caused a 30- and 5-fold increase in the urinary creatine/creatinine ratio at 24 and 48 h, respectively, and 24 h urinary excretion of methoxyacetic acid was of 0.71 +/- 0.042 mmol 24 h (mean +/- SE). The simultaneous administration of one of the three alcohols at either of the doses mentioned above did not significantly modify the urinary creatine/creatinine ration (24 and 48 h), or the 24 h urinary excretion of methoxyacetic acid. Administered alone, EGBE (5 mmol/kg) caused an average decrease of 26% in the number of circulating red blood cells and a strong (250 times) increase in the level of plasma haemoglobin 4 h after treatment. Urinary excretion of butoxyacetic acid in rats treated with EGBE (1 mmol/kg) was 0.083 +/- 0.0039 mmol/24 h (mean +/- SE). The simultaneous injection of 30 mmol/kg alcohol (ethanol, n-propanol or n-butanol) almost totally inhibits the haemolytic effect of EGBE, and decreases the urinary excretion of butoxyacetic acid by 43-31%. A strong dose of alcohol (30 mmol/kg) decreases the haemolytic effect due to EGBE, and reduces the urinary excretion of butoxyacetic acid. In contrast, the coadministration of alcohol did not modify the testicular toxicity of EGME, or the 24 h urinary excretion of methoxyacetic acid. It is possible that competitive inhibition of alcohol dehydrogenase by alcohols results in the diversion of EGBE metabolism.

Occupational exposure to organic solvents during paint stripping and painting operations in the aeronautical industry.

The exposure of workers to methylene chloride and phenol in an aeronautical workshop was measured during stripping of paint from a Boeing B 747. Methylene chloride exposure was measured during two work days by personal air sampling, while area sampling was used for phenol. During paint stripping operations, methylene chloride air concentrations ranged from 299.2 mg/m3 (83.1 ppm) to 1888.9 mg/m3 (524.7 ppm). The exposures to methylene chloride calculated for an 8-h work day ranged from 86 mg/m3 (23.9 ppm) to 1239.5 mg/m3 (344.3 ppm). In another aeronautical workshop, exposure to organic solvents, especially ethylene glycol monoethylether acetate (EGEEA), was controlled during the painting of an Airbus A 320. The external exposure to solvents and EGEEA was measured by means of individual air sampling. The estimation of internal exposure to EGEEA was made by measuring its urinary metabolite, ethoxyacetic acid (EAA). Both measurements were made during the course of 3 days. The biological samples were taken pre- and post-shift. During painting operations, methyl ethyl ketone, ethyl acetate, n-butyl alcohol, methyl isobutyl ketone, toluene, n-butyl acetate, ethylbenzene, xylenes and EGEEA were detected in working atmospheres. For these solvents, air concentrations ranged from 0.1 ppm to 69.1 ppm. EGEEA concentrations ranged from 29.2 mg/m3 (5.4 ppm) to 150.1 mg/m3 (27.8 ppm). For biological samples, the average concentrations of EAA were 108.4 mg/g creatinine in pre-shift and 139.4 mg/g creatinine in post-shift samples. Despite the fact that workers wore protective respiratory equipment during paint spraying operations, EEA urinary concentrations are high and suggest that percutaneous uptake is the main route of exposure for EGEEA.(ABSTRACT TRUNCATED AT 250 WORDS)