Uncertainty in Health Impact Assessment of Organic Air Toxics from Refinery – A Case Study in Taiwan

Abstract

Background Petroleum refinery is one of major sources of NMOGs in Taiwan which contributed 2.3% emissions among all stationary sources. Estimation of the toxic may affect significantly on health risk assessment due to the different emission factor selection. Aims This study investigates the procedure for health impact assessment organic air toxics released from a refinery in Taiwan. Six emission source categories, including stack, equipment component, storage tank, flare, loading/unloading, and wastewater treatment plant, in refinery were discussed. Methods NMOG emissions from each category were calculated by applying WebFIRE and SPECIATE 4.0. Facility priority for target air toxics was evaluated. The ISCST3 model was used to simulate the ambient concentration. Result Total of 31 VOC species were identified by using emission factors in WebFIRE and SPECIATE 4.0. The results show that the top air toxic is benzene. The results of facility priority of carcinogenic effect showed the highest score is flare. The scores of flare, equipment component, wastewater treatment plant, and storage tank are higher than 10 and will be classified as high priority facility. The ambient concentrations of four selected organic air toxics were simulated. The maximum annual concentration of benzene was 183 ?g/m3. The maximum total cancer risk for target air toxics is 7,120×10-6. Benzene is most important compound ( 6.91×10-3) and followed by ethylbenzene (2.10×10-4 ). Conclusions The case study in Taiwan indicates that air toxic emission profile selection causes the greatest variation on health impact assessment among those relevant factors in a refinery. .