Eighth Symposium on the Urban Environment


Issues with use of toxicity values for emergency response

Timothy J. Bauer, NSWCDD, Dahlgren, VA

In the event of an airborne release of Toxic Industrial Chemical (TIC) by accidental or intentional means, emergency responders must have a reasonable estimate of the location and size of the resulting hazard area. Emergency responders are responsible for warning persons downwind of the hazard to evacuate or shelter-in-place and must know where to look for casualties after the hazard has passed or dissipated. Given the same source characterization, modern hazard assessment models provide comparable concentration versus location and time estimates. Even urban hazard assessment models often provide similar predictions. There is a major shortcoming, though, in applying model output to estimating human toxicity effects. There exist a variety of toxicity values for non-lethal effects ranging from short-term to occupational to lifetime exposures. For health and safety purposes, these estimates are all safe-sided in converting animal data to human effects and in addressing the most sensitive subset of the population. In addition, these values are usually based on an assumed 1 hour exposure duration at constant concentration and do not reflect either a passing cloud's concentration profile or duration. Emergency responders need expected value toxicity parameters rather than the existing safe-sided ones. This presentation will specify the types of toxicity values needed to provide appropriate TIC hazard estimates to emergency responders and will demonstrate how dramatically their use changes the hazard area.

wrf recording  Recorded presentation

Joint Session 14, Dense Gas Dispersion (Joint with the Meteorological Aspects of Air Pollution Committee)
Tuesday, 13 January 2009, 1:30 PM-3:00 PM, Room 124B

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