Modeling occupational exposure to solvent vapors using the Two-Zone (near-field/far-field) model: A literature review

Source avec lien : Journal of Occupational and Environmental Hygiene, Prépublication, . 10.1080/15459624.2020.1861283

Le modèle à deux zones est utilisé en hygiène du travail pour prédire les concentrations de contaminants atmosphériques en champ proche et en champ lointain. Une revue de la littérature a été effectuée sur 21 publications scientifiques dans lesquelles le modèle à deux zones a été utilisé pour évaluer l’exposition professionnelle aux vapeurs de solvants. Des données sur les scénarios d’exposition, les solvants, les taux de production/émission, les paramètres en champ proche et en champ lointain, et les performances du modèle ont été recueillies et analysées.

The Two-Zone model is used in occupational hygiene to predict both near-field and far-field airborne contaminant concentrations. A literature review was carried out on 21 scientific publications in which the Two-Zone model was used to assess occupational exposure to solvent vapors. Data on exposure scenarios, solvents, generation/emission rates, near- and far-field parameters, and model performance were collected and analyzed. Over the 24 exposure scenarios identified, 18 were evaluated under controlled conditions, 5 under normal workplace activities, and 1 was reported based on literature data. The scenarios involved a variety of tasks which consisted, mostly, of cleaning metal parts, spraying solvents onto surfaces, spilling liquids, and filling containers with volatile substances. Twenty-eight different solvents were modeled and the most commonly tested were benzene, toluene, and acetone. Emission rates were considered constant in 16 scenarios, exponentially decreasing in 6 scenarios, and intermittent in 2 scenarios. Four-hundred-and-forty-six (446) predicted-to-measured concentration ratios were calculated across the 21 studies; 441 were obtained in controlled conditions, 4 under normal workplace activities, and 1 was calculated based on the literature data. For controlled studies, the Two-Zone model predictive performance was within a factor of 0.3–3.7 times the measured concentrations with 93% of the values between 0.5 and 2. The model overestimated the measured concentrations in 63% of the evaluations. The median predicted concentration for the near-field was 1.38 vs. 1.02 for the far-field. Results suggest that the model might be a useful tool for predicting occupational exposure to vapors of solvents by providing a conservative approach. Harmonization in model testing strategies and data presentation is needed in future studies to improve the assessment of the predictability of the Two-Zone model. Moreover, this review has provided a database of exposure scenarios, input parameter values, and model predictive performances which can be useful to occupational hygienists in their future modeling activities.

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