Real-Time Ozone Sensor Based on Selective Oxidation of Methylene Blue in Mesoporous Silica Films.

Sensitive and selective personal exposure monitors are needed to assess ozone (O3) concentrations in the workplace atmosphere in real time for the analysis and prevention of health risks. Here, a cumulative gas sensor using visible spectroscopy for real-time O3 determination is described. The sensing chip is a mesoporous silica thin film deposited on transparent glass and impregnated with methylene blue (MB). The sensor is reproducible, stable for at least 50 days, sensitive to 10 ppb O3 (one-tenth of the occupational exposure limit value in France, Swiss, Canada, U.K., Japan, and the USA) with a measurement range tested up to 500 ppb, and insensitive to NO2 and to large variation in relative humidity. A model and its derivative as a function of time are proposed to convert in real time the sensor response to concentrations, and an excellent correlation was obtained between those data and reference O3 concentrations. This sensor is based on a relatively cheap sensing material and a robust detection system, and its analytical performance makes it suitable for monitoring real-time O3 concentrations in workplaces to promote a safer environment for workers.

Sampling and Analysis of Bitumen Fumes: Comparison of German and French Methods to Determine a Conversion Formula.

Bitumen is classed as possibly carcinogenic to humans according to the International Agency for Research on Cancer. Data on individual exposure to bitumen fumes is therefore required to highlight the exposing situations and develop methods to prevent them. The Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA) and the French National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS) have both developed methods to measure individual exposure. The objective of this study was to determine a conversion factor to allow interconversion of data acquired by the two methods. To develop this conversion factor, comparative laboratory and workplace tests were performed according to both the IFA method (No. 6305) and the INRS method (MetroPol M-2). The amounts of organic material collected on the filters and XAD-2 beds were compared. The results revealed differences between the sampling and analytical methods that could be linked to sampler design, extraction solvent, and the detection method used. The total quantification returned by the two methods-the sum of the masses quantified on filter and XAD-2 bed for each sampler-were correlated in both controlled and real-life tests. A conversion equation was therefore determined, based on field tests: CIFA = 1.76 CINRS ± 0.39 (R2 = 0.99) that is applicable to total quantification data. This formula can be applied to data acquired by the two institutes to increase the number of data points available on exposure to bitumen fumes in various conditions, and thus increase the statistical power of studies into occupational prevention.

Alternatives for Benzene in the Extraction of Bitumen Fume from Exposure Sample Media.

Benzene is frequently used to extract collected bitumen fumes from personal sampler substrates. However, this solvent is particularly dangerous because of its carcinogenicity (group 1 of the International Agency for Research on Cancer classification). Therefore, to prevent the exposure of laboratory technicians to benzene during the fume extraction step from samplers, a compromise had to be found to identify a less toxic solvent with the same extraction capacity. To compare the extraction capacities of selected solvents, bitumen fumes were generated in the laboratory from three different batches of road surfacing bitumen collected on dedicated bitumen fume samplers. The samplers were then extracted by benzene and the solvents tested. Of 11 selected solvents less toxic than benzene and used in studies on bitumen and bitumen fume analyses, n-hexane and n-heptane were identified as alternatives to benzene. In particular, the results demonstrated that n-heptane was the best candidate solvent for benzene replacement, due to its extraction efficiency comparable to benzene for the three bitumen fumes tested and its low toxicity, which is highly compatible with benzene replacement.

Developing a new simplified method to determine diffusive uptake rates of volatile organic compounds in workplaces based on a fractional factorial designs approach.

Exposure to organic vapors in the workplace is a source of occupational risk. Admissible exposure levels are tightly regulated and must be closely monitored. However, the complexity and slowness of the existing complete protocols to determine diffusive uptake rates through passive sampling have limited the use of this tool despite obvious advantages. In this study, we experimentally validate two simplified protocols to determine diffusive uptake rates with passive sampling. The proposed 2(6-3) and 2(6-2) fractional factorial designs were validated for toluene sampling using a (Gas Adsorbent Badge for Individual Exposure) GABIE-activated charcoal sampler in a controlled atmosphere. The uptake rate for this sampler had been determined previously using a full protocol. The uptake rates for all three protocols were similar, indicating that the proposed new designs can be substituted for classical full protocols. After validation of our protocols, uptake rates for new substances used as fuel additives (methyl and ethyl tert-butyl ethers, MTBE and ETBE) were determined on the same sampler using the 2(6-2) design. In these experiments, temperature appears to have a non-negligible influence on the uptake rates measured for these compounds. With some precautions of usage (ambient temperature below a determined limit temperature or at least exposure time ≥4 h) and storage (storage temperature = 4°C) of the sampler, the experimental diffusive uptake rates determined by this method can be used with good confidence. Field experiments confirmed the experimental results, showing good agreement between active and passive sampling using the experimentally determined uptake rates.

ALASCA proficiency testing scheme for occupational hygiene laboratories.

Nowadays, quality assurance is an important part in the environment of analytical laboratories, who need to prove their ability to perform analysis as well to handle routine control as research and development analysis. A proficiency testing scheme (PTS) is one of the possible and powerful tools to evaluate both bias and dispersion of the analysis. As far as industrial hygiene is concerned, since analytical uncertainty is insignificant with regard to sampling strategy uncertainty, laboratories could be tempted to neglect analytical uncertainty assessment as well. The department 'Métrologie des Polluants' (part of INRS) has been organising a proficiency testing scheme since 2002 with the intention of giving the most reliable performance assessment to the participant. The original features, which are also the strong points of the scheme, are: the determination of the assigned value by a method that is independent from the analytical method to be tested; the development of original tools for the fabrication of samples; the strength of the statistic model, which is based on the WASP HSL scheme model; a tool to visualize the results of participants in bias and dispersion contribution; communication with the participants; a completely computerized system to handle the participant database, the sample database, results treatment and report edition; and the use of internet facilities to allow the participant to submit the results via a secured website. All these technical and organisational points are detailed in this paper.

GABIE and Perkin Elmer passive sampler performance under fluctuating concentration conditions.

Passive sampling is an approved and accurate method for the assessment of organic compound exposure over long sampling time. This method could be very convenient for the short-time exposure assessment, but passive samplers have to be validated for this use. In this article, the behaviour of two commercial passive samplers (GABIE and Perkin Elmer) under fluctuant concentration conditions is studied. Artificial atmospheres were produced in the laboratory and passive samplers were exposed to different concentration profiles. Both theoretical and experimental results detailed in the paper underline the capability of these two samplers to assess pollutant exposure either when the concentration is unsteady or when the sampling time is short. Then, a suitable sampling strategy is proposed for the assessment of short-term exposure, based on the association of a direct reading photoionization device and passive sampler.