Performance assessment of mixed wastes using the PATHRAE-EPA model

The development of standards for low-level waste and below regulatory concern waste disposal by the U.S. Environmental Protection Agency has led to the development of the performance assessment code PATHRAE. The PATHRAE code is used to provide estimates of the magnitude of health effects to critical population groups which could potentially occur from disposed radioactive wastes. The PATHRAE code has been extended to include the transport and health effects assessments for non-radiological contaminants. Thus, PATHRAE is a useful tool for performing multiscenario, multipathway analyses of mixed wastes. It has been applied to radiologically and non-radiologically contaminated CERCLA (Superfund) sites and to DOE contractor-operated disposal facilities. The EPA-approved approach of using the linear, non-threshold theory for non-radiological carcinogens facilitates the calculation of the cancer risk for these contaminants. A standard methodology is also applied to non-radiological contaminants that are not carcinogenic. The acceptable daily intake is input into the code instead of the cancer risk conversion factors. PATHRAE then calculates and prints the ratio of the expected daily intake of contaminants to the acceptable daily intake. The code prints out the risks and fractions of acceptable daily intakes for each contaminant and for each pathway/scenario combination. It also sums over all carcinogens for each pathway/scenario, and then sums over all pathways/scenarios to obtain total risk to the critical population group