Comparison of Risks from Use of Traditional and Recycled Road Construction Materials: Accounting for Variability in Contaminant Release Estimates

Recycled materials, such as recovered materials from the transportation sector or secondary or by-product materials from the industrial, municipal, or mining sectors can be used as substitutes for natural materials in the construction of highway infrastructure. Trace metals in these recycled materials may leach out and contaminate the groundwater and soil posing a long-term environmental problem. Environmental risk assessments are necessary to evaluate which recycled material applications are acceptable. The first step for determining the environmental risk of using recycled materials is to characterize the source term. Estimates of contaminant release fluxes can then be used in a comparative risk assessment. This paper will give an example of a comparative, probabilistic approach for exposure assessment. Existing deterministic models for estimating contaminant release will be presented and incorporation of variability in these models will be discussed.