Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2004
Publication Date: 1/1/2005
Citation: Kester, G.B., Brobst, R.B., Carpenter, A., Chaney, R.L., Rubin, A.B., Schoof, R.A., Taylor, D.S. 2005. Risk characterization, assessment, and management of organic pollutants in beneficially used residual products. Journal of Environmental Quality. 34(1):80-90. Interpretive Summary: Biosolids and many other organic amendments and byproducts are being considered for application on farmland to recycle nutrients and improve soils. The presence of anthropogenic organic compounds in these soil amendments has raised concerns regarding protection of humans and the environment. Risk assessment for land application has been conducted during development of the present US-EPA regulations for land application of biosolids by detailed calculation of potential transfer and risk from example organic compounds based on deterministic models. Risk assessment was often not possible because valid measurement of concentrations of compounds in biosolids were not detected. After ten years further research, analytical methods for lipophilic organics have been dramatically improved by evaluation of standard methods. Only by specification of methods of extraction and clean-up of extraction solutions, and methods of analysis and detection limits required can useful results be obtained. The most significant potential transfer routes are by soil ingestion by children or grazing livestock, followed by garden crops. Information for probablistic risk calcuations are favored for risk assessment, but the details for statistical distributions of soil ingestion and bioavailability from soil in diets are seldom available. Important progress has been made in reduction of potentially toxic organic compounds in biosolids by industrial pretreatment, and changes in manufacturing processes. Identified hazardous compounds are handled separately from sewage processing so that only traces of PCBs, dioxins, and other persistent chlorinated hydrocarbons are currently present in biosolids. Some other compounds of recent concern, including polybrominated diphenyl ethers, are also present in biosolids only at very low concentrations, and land application does not promote dispersal in the environment. Continuing data needs are discussed for improved risk assessment.
Technical Abstract: A wide array of organic chemicals occur in biosolids and other residuals recycled to land. The extent of our knowledge about the chemicals and the impact on recycling programs varies from high to very low. Two significant challenges in regulating these materials are to accurately determine the concentrations of the organic compounds in residuals, and to appropriately estimate the risk that the chemicals present from land application or public distribution. This paper examines both challenges and offers strategies for assessing the risks related to the occurrence of organic compounds in residuals used as soil amendments. Important attributes that must be understood to appropriately characterize and manage the potential risks for organic chemicals in biosolids include: toxicity and dose response; transport potential; chemical structure and environmental stability; analytical capability in the matrix of interest; concentrations and persistence in waste streams; plant uptake; availability from surface application versus incorporation; solubility factors; and environmental fate. This information is complete for only a few chemicals. Questions persist about the far greater number of chemicals for which toxicity and environmental behavior are less well understood. This paper provides a synopsis of analytical issues, risk assessment methodologies, and risk management screening alternatives for organic constituents in biosolids. Examples from experience in Wisconsin are emphasized but can be extrapolated for broader application.