Submitted to: Sustainable Land Application Conference
Publication Type: Abstract Only
Publication Acceptance Date: 2/15/2003
Publication Date: 1/4/2004
Citation: Kester, G.B., Brobst, R.B., Carpenter, A., Chaney, R.L., Rubin, A.B., Schoof, R.A., Taylor, D. 2004. Risk characterization, assessment, and management of organic pollutants in beneficially used residual products [abstract]. Sustainable Land Application Conference, Buena Vista, Florida, January 4-8, 2004. p. 39. Interpretive Summary:
Technical Abstract: A wide array of organic chemicals may be present in residual products that are recycled to land. Knowledge about these chemicals fall generally into two categories: those for whom much is understood and those for whom little is known. A challenge in regulating these materials is to appropriately estimate the risk the chemicals may present from this activity. This paper will examine both categories and offer strategies for assessing that risk. Some of the important attributes that must be understood include: toxicity and dose response; transport potential; chemical structure and strength of bonds; analytical capability in the matrix of interest; concentrations and persistence in waste streams; plant uptake; solubility factors; and environmental fate. Those chemicals for which this knowledge exists make up a very small fraction of all potential chemicals. For these chemicals a quantitative risk assessment may be performed and PCB and dioxin examples will be presented. An explanation of how these models can or can't be used for similarly structured chemicals will also be presented. Models for both deterministic and probabilistic assessments will be presented. The difficulties with subjective assumptions will be illustrated with a case example on a PCB deterministic risk assessment. Information will be presented on analytical capability and difficulties and concentrations of select constituents in residual products. Questions persist about the far greater number of chemicals for which little of the above is understood, but must be addressed to ensure public safety and environmental protection. A model will be presented in which certain chemicals with known similar structural properties may be grouped together for assessment. Gaps will be identified to determine additional needed information for chemicals of concern. An evaluation will be attempted to predict potential impacts based on expected fate in soil once the chemicals are applied. The evaluation will review chemical, physical, and biological properties to predict: likely persistence; likely toxicity; chemical bond strength and fate; erodibility; and likely end products. A recommendation will be made regarding the integration and use of the soil assessment in determining the likely risk of a group of constituents for which little information is available that could be used in a more conventional risk assessment.