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The use of Monte Carlo simulation to quantify the uncertainty in modeled estimates of toxic, radiation and overpressure impacts resulting from accidents in large chemical plantsAmsterdam, Heinrich Francois January 2004 (has links)
Thesis (MTech (Chemical Engineering))--Peninsula Technikon, Cape Town, 2004 / Current Risk Assessment procedures for the estimation of the acute health impacts
resulting from the accidental release of toxic chemicals into the atmosphere involve the
definition or construction of a representative accidental release scenario and the use of
one or other air quality or dispersion model to estimate ambient air concentrations and
exposure durations in the vicinity of the source. Legislation such as the South African
Occupational Health and Safety Act, 1993, Major Hazard Installation Regulations,
United States Risk Management Plan Rule and the European Union Seveso n, to prevent
and or minimize impacts of such events require owners of installations to perform a Risk
Assessment if they handle hazardous substances above specified threshold quantities.
Mathematical modeling has been widely used to assist with the Exposure Assessment to
perform off-site worst-case release analysis. Governmental departments, agencies and
local authorities increasingly (but not exclusively) rely on air pollution models for
making decisions related to air quality, traffic management, urban planning, and public
health. As a result, the model users' community is becoming larger and more diverse.
Most of the air quality modeling work has so far been based on the "deterministic"
approach of using only set input parameters and specific applications. The selected model
provides estimates of averaged concentrations using specific meteorological and emission
data sets.
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Effects of an industrial fire on a community of south Phoenix, ArizonaDegher, Alexandra B. 07 October 2003 (has links)
On August 31, 1992, Quality Printing Circuits, a circuit board manufacturing plant in
Phoenix, Arizona, burned to the ground. The fire lasted approximately eight hours, creating a thick,
black smoke that blew into the surrounding community. Emergency evacuation was erratic and
since no air samples were taken during the fire, community exposure levels were unknown.
Immediately afterwards, residents reported health problems but government studies on the
community were unable to link reported health problems and the fire.
Eight months after the fire, a local advocacy group performed a health study on the
community. The 690 people surveyed reported symptoms such as asthma, blurred vision, vomiting,
hair loss, rashes, and extremity numbness. The survey was never analyzed and the case was closed.
Community members continued to report health problems and five years after the fire, the US
Environmental Protection Agency reopened the case. They performed two sampling studies but
results found that chemical levels were below allowable exposure levels.
This thesis contains three chapters that investigate the political, health, and scientific issues
related to the QPC fire. The scientific chapter uses the EPA's ISCST3 dispersion model and a
mixed-box model, to approximate community exposure concentrations and compare them to
allowable human exposure levels. Results of the ISCST3 model show that four (hydrogen chloride,
polycyclic aromatic hydrocarbons, Acrolein, and naphthalene) of the twenty chemicals modeled
were above government allowable concentrations. Inhalation exposure to these chemicals causes
similar symptoms as those reported by residents.
The health-focused chapter characterized health symptoms reported in the 1993 health
survey. Results found that symptoms experienced by residents were similar to those documented in
other studies of exposure to chemical smoke. The study also found that residents living closest to
QPC reported a greater number of symptoms than residents living further away.
The political chapter analyzed the debate as to whether QPC officials and government
agencies took the steps needed to protect the exposed community during and after the QPC fire.
What became evident was that a significant conflict existed between the interests of residents
involved in the QPC fire and the government agencies responsible for protecting them. / Graduation date: 2004
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