Monte Carlo uncertainty analysis of a diffusion model for the assessment of halogen gas exposure during dosing of brominators.
Monte Carlo simulation was incorporated into a diffusion-based exposure assessment model for the estimation of worker exposure to halogen gases during dosing of 500-lb sacks of a bromine-based biocide (BCDMH) into brominators. Indoor and outdoor dosing scenarios were modeled for small and large brominators. The diffusion model used describes a concentration gradient of halogen as a function of distance and time from the source instead of ascribing worst-case single point value estimates to the variables used in the diffusion model. Monte Carlo simulation was used to describe a distribution of values for each appropriate model variable. Using a personal computer and Monte Carlo simulation software, 10,000 iterations of the diffusion model were performed for four different dosing scenarios using random and independent samples from the distributions entered. The corresponding output distributions of predicted exposures were then calculated and displayed graphically for each scenario. The results of the Monte Carlo simulation predict that outdoor dosing of either small or large brominators with BCDMH is highly unlikely to result in an exceedance of the working occupational exposure limit for total halogen. In most ambient wind speed conditions, diffusion prevents appreciable airborne exposure to workers in the immediate vicinity of the brominator. Although relatively uncommon, dosing of brominators indoors in the assumed absence of local exhaust ventilation may generate airborne concentrations of total halogen that exceed the working short-term occupational exposure limit. Although very limited and inconclusive, field trial monitoring of BCDMH transfer operations indoors resulted in halogen concentrations well within the distribution of concentrations predicted by the Monte Carlo simulation of the diffusion model.
Shade
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WD
Rohm and Haas Company, Toxicology Department, Spring House, PA 19477, USA.
Jayjock
M A
MA
D000397:Air Pollution / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis; D001966:Bromine / Q000032:analysis* / Q000633:toxicity; D002713:Chlorine / Q000032:analysis* / Q000633:toxicity; D003198:Computer Simulation; D004058:Diffusion; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D004869:Equipment Safety; D005544:Forecasting; D006801:Humans; D008954:Models, Biological; D009010:Monte Carlo Method; D011237:Predictive Value of Tests; D012308:Risk Management
D002713:Chlorine; D001966:Bromine