Comparison of RBCA and CalTOX for setting risk-based cleanup levels based on inhalation exposure.
Risk-based corrective action (RBCA) and CalTOX (California EPA) are often used to develop risk-based soil cleanup levels. The determination of the entry parameters, including slope factors, degradation assumption, methodologies, and dispersion models for these two approaches greatly affect the onsite/offsite cleanup levels, risk distribution, and ranking of the influential factors. The subsurface soil-to-ambient air was considered as the only significant exposure pathway in this study. RBCA and CalTOX apply analytical equations and multimedia fugacity model, respectively, to simulate the transport of contaminants from subsurface soil to ambient air. Nine carcinogenic organic contaminants were selected as the target compounds. Environmental monitoring data collected from a contaminated site in southern Taiwan was used as model inputs. In this study, degradation assumption had greater influence on CalTOX evaluation than slope factors. The cleanup soil levels of all target chemicals developed by both models were close under the same slope factors and degradation assumptions, except for vinyl chloride and hexachlorobenzene. Furthermore, RBCA generally had larger offsite dispersion ratios than CalTOX, especially for long distances. The risk distribution obtained by RBCA was much board than by CalTOX. When 95th percentile was considered as the starting point, the SSTLs derived by RBCA were much stricter than by CalTOX. The ranking of influential factors in the onsite risk assessment for these two models were completely different because of their distinct model methodologies.
Chang
Shih-Hsien
SH
Department of Public Health, Chung-Shan Medical University, Taichung 402, Taiwan, ROC.
Kuo
Chung-Yih
CY
Wang
Jiunn-Wen
JW
Wang
Kai-Sung
KS
D001835:Body Weight; D004058:Diffusion; D004782:Environmental Health; D004784:Environmental Monitoring / Q000379:methods* / Q000592:standards; D004787:Environmental Pollution / Q000517:prevention & control*; D006256:Hazardous Waste; D006801:Humans; D019570:Inhalation Exposure; D008956:Models, Chemical; D018570:Risk Assessment; D012308:Risk Management; D012989:Soil Pollutants / Q000032:analysis* / Q000378:metabolism; D013624:Taiwan; D013696:Temperature; D014867:Water / Q000032:analysis; D014919:Wind
D006256:Hazardous Waste; D012989:Soil Pollutants; D014867:Water