Toxic load modeling for naturally fluctuating concentration exposures

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Authors
  1. Yee, E.
Corporate Authors
Defence R&D Canada - Suffield, Ralston ALTA (CAN)
Abstract
The toxic load model is widely used in hazard assessment involving the release of toxic gases into the atmosphere. The underlying basis of this model consists of laboratory experiments in which various animal species are exposed to constant concentrations of a toxic gas for a fixed exposure duration. However, natural variability (fluctuations) in the concentration of a toxic gas at a point in a plume dispersing in the atmosphere is a ubiquitous feature that must be properly incorporated into the toxic load model for noxious gases which do not vary linearly with the concentration and exposure time. Towards this purpose, the statistical characteristics of the toxic load (or, equivalently, the toxic load ratio) have been explicitly derived from the statistical properties of the exposure concentration on which it depends for three different models. In particular, the ensemble average and variance of the toxic load (and the related toxic load ratio) have been determined assuming that the probability density function of either the exposure concentration or dosage is well characterised using a clipped-normal distribution. Although these three models give the same predictions of the toxic load for constant concentration exposures, it is shown that predictions of the statistical characteristics (ensemble average and variance) of the toxic load ratio appropriate for a naturally fluctuating concentration exposure differ for the three models over a wide range of combinations of parameter

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Keywords
concentration fluctuation;concentration probability distribution;hazard assessment;plume dispersion;toxic load
Report Number
DRDC-SUFFIELD-TR-2012-052 — Technical Report
Date of publication
01 Aug 2012
Number of Pages
52
DSTKIM No
CA043377
CANDIS No
804685
Format(s):
Electronic Document(PDF)

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