Areal location of hazardous atmospheres simulation on toxic chemical release: A scenario-based case study from Ray, Iran

Chemical accidents cause significant danger for residents living close to chemical facilities. For this reason, this study assessed the impacts of a simulated chemical accident on surrounding residents in the city of Ray, Iran.

In this scenario-based case study in 2015, the Areal Location of Hazardous Atmospheres (ALOHA) model was applied to simulate a toxic chemical release from a chlorine warehouse in Shourabad, Ray, Iran. The population of the area was calculated based on the latest census in Iran, 2011. The atmospheric variables included were wind speed, air temperature, and relative humidity. We also included data on pollution source such as diameter, length and volume, and condition of chemicals. The simulation was repeated for each seasonal period. The simulated threat zones were mapped using Geographical Information System. The percentage of residents sustaining injuries and death was calculated using probit.

The maximum and minimum simulated threat zones by chlorine release are during summer and winter at 8.8 and 6.4 kilometers respectively. The total affected population was estimated at approximately 30,000 people. The greater percent of injuries and death was estimated to occur in the winter and autumn, compared to summer and spring, because of greater climatic instability. The number of individuals affected by chlorine release in the spring, summer, autumn and winter at 8.3, 8.8, 7.6 and 6.4 kilometers, are estimated at 22,500, 25,000, 28,100 and 27,500, respectively. Populations located in hot and warm zones of toxic chemical releases should have access to medical resources.

The results showed that relevant factors impact human vulnerability, and these should be examined to mitigate the harmful consequences of chemical accidents. Establishing a multi-level Emergency Response Program is also recommended in the area under study.