Occupational exposure limit values for chemicals

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A general comment on the concept of occupational exposure limit values for chemicals is made, and several topics related to these limit values are reviewed: the scientific basis for their establishment, the main lists of limit values, the limit values in the European Union and in Spain, the comparison of exposure with limit values and the exposure to several substances.

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... Steps for an effective risk assessment and management in tunnelling operations 1. Hazards Identification: Forecasting the presence of hazardous substances in the rock mass to be excavated; the prediction should be completed with the best estimate of its uncertainty 2. Risk Analysis: Correlating the result of the Hazard Identification with workers exposure models. The latter should be defined with the best possible detail, taking into account, however, that the diversification of tasks is often quite blurred in spite of the formal job descriptions (in a real case of use of TBM we found 11 official job descriptions, but identified only 3 typologies of actual job) 3. Risk Assessment: The results of the Risk Analysis are here used for decision making, through direct comparison with minimized risk targets (e.g., Occupational Exposure Limits (OELs) values if available (Skowroń, 2013), or relative ranking of effectiveness and cost of different risk reduction measures based on different techniques and technologies 4. Risk Management: Selection of both the most appropriate technologies and techniques for winning, mucking, ventilation, etc. and the management policies, procedures and practices, to grant along the time Occupational Safety and Health, neighboring areas environmental quality and economic effectiveness ...
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In tunnelling operations, Occupational Safety and Health (OS&H) and Environmental Protection of the areas close to the tunnel portal become even more critical in case of rock formations potentially containing asbestos, quartz, radioactive elements, etc. In order to limit the workers’ exposure and the environmental impact becomes in these cases of paramount importance to preliminarily analyze and quantify the possible presence of the pollutants in the rock and, if necessary, to implement suitable measures to avoid/minimize their emission from the winning and mucking operations. However, in case of asbestos minerals, to obtain reliable results from the preliminary analysis is a challenging task, due to the complex patterns of occurrence of asbestos within the host rock. Consequently, the definition of special monitoring, alarm and control systems is essential during the tunnel excavation. The paper summarizes the results of a thorough study aimed at defining the most suitable monitoring techniques in uncertain situations and the residual criticalities, essentially due to the delay between the beginning of the pollutant release at the tunnel face and its detection. The final part of the work deals with the possible innovative prevention solutions suitable to minimize the previously mentioned delay and ensure the safety of the workers along the time necessary to stop the activities and evacuate the tunnel, on hold of the activation of a special “asbestos” organization.
Solvent mixture concentrations in paint and resin manufacture were on-line monitored using a portable open path Fourier transform infrared (OP-FTIR) analyser in order to determine solvent emission rates into workspaces. The mean solvent emission rate was 0.46 kg/h in paint production and 0.35 kg/h in resin manufacture. Expressed as emission factor, i.e. evaporated portion of the total solvent mass used, the corresponding values were 0.01% for paint production and 0.1% for resin manufacture. The OP-FTIR instrument together with advanced spectra analysis software facilitated a rapid identification of solvent mixtures and on-line concentration monitoring with good temporal resolution. The analyser seems to be particularly useful in industrial hygiene applications where spatial average concentrations are needed. The further benefit of the open path instrument is that no sampling lines, pumps or sample cells are needed.
Isocyanates, aminoisocyanates and amines were quantified from the combustion of 24 different materials or products typically found in buildings. Small-scale combustion experiments were conducted in the cone calorimeter, where generally well-ventilated combustion conditions are attained. Measurements were further made in two different full-scale experiments.Isocyanates and amino-compounds were sampled using an impinger-filter sampling system with a reagent solution of di-n-butylamine in toluene. Filter and impinger solution were analysed separately using LC-MS technique. Further the particulate distribution in the smoke gases was determined by impactor technique, and selected gaseous compounds quantified by FTIR.It was found in the small-scale that isocyanates were produced from the majority of the materials tested. The highest concentration was found for glass wool insulation, and further high concentrations were found for PUR products, particleboard, nitrile rubber and melamine. Lower concentrations were found for wood and cable-products. Amino-isocyanates and amines were generally found from PUR products only.The distribution of isocyanates between the particulate- and fluid phases varied for the different materials and a tendency to enrichment of particles was seen for some of the materials. Further, when comparing the potential health hazard between isocyanates and other major fire gases (based on NIOSH IDLH-values) it was found that isocyanates in several cases represented the greatest hazard. Copyright © 2003 John Wiley & Sons, Ltd.
Biomonitoring of chemicals in the workplace provides an integrated characterization of exposure that accounts for uptake through multiple pathways and physiological parameters influencing the toxicokinetics. We used the case of styrene to (i) determine the best times to sample venous blood and end-exhaled air, (ii) characterize the inter-individual variability in biological levels following occupational exposure and (iii) propose biological limit values using a population physiologically based pharmacokinetic (PBPK) model. We performed Monte Carlo simulations with various physiological, exposure and workload scenarios. Optimal sampling times were identified through regression analyses between levels in biological samples and 24-h area under the arterial blood concentration vs. time curve. We characterized the variability in levels of styrene in biological samples for exposures to a time weighted average (TWA) of 20ppm. Simulations suggest that the best times to sample venous blood are at the end of shift in poorly ventilated workplaces and 15min after the shift in highly ventilated workplaces. Exhaled air samples are most informative 15min after the shift. For a light workload, simulated styrene levels have a median (5th-95th percentiles) of 0.4mg/l (0.2-0.6) in venous blood at the end of shift and 0.5ppm (0.3-0.8) in exhaled air 15min after the end of shift. This study supports the current BEI(®) of the ACGIH of 0.2mg/l of styrene in venous blood at the end of shift and indicates a biological limit value of 0.3ppm in end-exhaled air 15min after the end of shift.
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