Exposure Research Focuses On Toxic Pollutants In Water

On Oct. 17, EPA's National Exposure Research Laboratory announced the release of three separate reports related toxic pollutants in water. Topics include organophosphate pesticides, lead and cadmium (from Superfund sites), and fecal contamination. All three documents can be accessed in PDF format from the laboratory's Web site (http://www.epa.gov/nerl/index.html -- click on "Recent Additions").

Organophosphate Pesticide Degradation Under Drinking Water Treatment Conditions. This research project seeks to provide evaluated methods, tools, and databases for forecasting the fate of pesticides and other toxic chemicals in drinking water treatment systems. These products will be useful to EPA Program Offices and others who must evaluate the ultimate fate of chemicals that occur in drinking water sources. This report describes the development and testing of experimental methods and computational models to characterize and simulate chlorination and hydrolysis of organophosphate pesticides under drinking water treatment conditions. Chlorpyrifos and its degradates were used as model compounds for the study. This work is the first step in developing screening-level tools for forecasting chemical transformations in drinking water treatment scenarios that ultimately will make assessment of risk from consuming drinking water more accurate.

Empirical Models Of PB And CD Partitioning Using Data From 13 Soils, Sediments And Aquifer Materials. Lead (Pb) and cadmium (Cd) are two of the most commonly found contaminants of concern at Superfund National Priorities List (NPL) sites. Because these contaminants are elements, they do not degrade, and hence when present at elevated concentrations in soils, sediments and aquifer materials, may pose a risk to the biological community over geological time periods. The risk posed by an environmental toxicant is dependent upon its fate in the environment. Among the properties governing the environmental fate of a metal toxicant, the solid/water partition coefficient (Kd) is perhaps the most significant. Unfortunately, in common with many other toxicants existing as ions in aqueous solution, theoretical models for predicting Kds for Pb and Cd that are applicable to all environmental systems do not exist. This document develops improved, default, empirical partitioning models for Pb and Cd that assist in achieving this objective.

Temporal And Spatial Variability Of Fecal Indicator Bacteria: Implications For The Application Of MST Methodologies To Differentiate Sources Of Fecal Contamination. Temporal variability in the gastrointestinal flora of animals impacting water resources with fecal material can be one of the factors producing low source identification rates when applying microbial source tracking (MST) methods. Understanding how bacterial species and genotypes vary over time is highly relevant when the fecal material used to create a source library is collected under very different seasonal conditions than the environmental sample. EPA's objective was to identify and compare the temporal and spatial variability of fecal indicator bacteria from a specific host in manure and water samples and evaluate the implications of such variability on microbial source tracking approaches and applications. This study suggests that, in order to increase the validity of MST methods, it is necessary to consider temporal variability when designing the sampling scheme of the source material and constructing source libraries, and increase the specificity and field testing of DNA-based markers.

This article originally appeared in the 10/01/2005 issue of Environmental Protection.

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