Scientists and regulators nationwide who assess the health risks of contaminated soils and develop cleanup plans have a new tool: a UC Davis-developed computer program that shows pathways that hazardous industrial substances may have taken through soil. The computer model, begun at Lawrence Livermore National Lab and developed at UC Davis, "helps you find out where you want to look carefully," when contamination has occurred, says Tom McKone, a UC Davis research engineer and lecturer who worked on the model and also does research at LLNL. "It's like a map. This helps you find the main pathways to determine the human exposures to hazards in soil." The model is based on the U. S. Environmental Protection Agency's risk assessment methods, but has two innovations. First, the program incorporates more information on the fate and transport of chemicals, enabling the user to predict chemical concentrations that people might ingest or absorb through their skin. And second, the program can express risk as a range of values, rather than one specific number, which can more accurately reflect the uncertainty and variability about estimates of chemical movement in the environment and the nature of potential human exposures.