Site Specific Health Risk Assessment – A Case Study For Hydrocarbon Contaminated Soils

The results of an innovative risk assessment procedure for a hydrocarbon contaminated site are presented and discussed. The study was carried out for a dismissed oil refinery area, considering clean-up workers as the unique receptors exposed to the contaminated media and selecting for the analysis 5 carcinogenic and 2 not-carcinogenic chemicals, after having applied the concentration toxicity screen. The first part of the paper is focused on constructing empirical probability density functions for the Exposure Point Concentration (EPC) by using recent site-specific procedures. Probabilistic Risk Assessment was performed with a Monte Carlo algorithm using the calculated empirical distribution for EPC and distributions suggested in the recent literature for other exposure parameters. The cumulative distribution for Cancer Risk and Hazard Index for all contaminants of concern and all exposure pathways defined during site characterization were thus determined. In order to assess the influence of uncertainty and spatial variability in risk analysis, the study was also carried out in the deterministic framework and the input point values for the EPC were chosen as 95% percentiles of empirical distributions calculated according to the different methods presented here. Considering spatial contamination patterns leads to more correct risk estimates and, in some cases, this would result in avoiding unnecessary cleanup. Keywords: health risk assessment, exposure point concentration, contaminated soils.