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Final Progress Reports: University of California-Davis: Immunoassays for Human and Environmental Health Monitoring

Superfund Research Program

Immunoassays for Human and Environmental Health Monitoring

Project Leader: Bruce D. Hammock
Grant Number: P42ES004699
Funding Period: 1995-2023
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Final Progress Reports

Year:   2014  2009  2004  1999 

The analytical chemist continues to need an array of tools to support human and environmental monitoring studies. The goal of this project is to develop, validate and implement immunochemical methods as one of these tools. At the same time the goal is to improve these techniques by speeding up, making simpler and increasing throughput by development and evaluation of new methods. Project investigators have a library of assays for triazine herbicides, indicators of agricultural activity. One of the triazine metabolites, atrazine mercapturate was found to be an abundant biomarker in a human exposure study that used accelerator mass spectrometry for detection of radiolabel, at least at early time points (first 48 hours). Other mercapturates are also present in abundance. Although atrazine mercapturate itself is a viable marker, it may be more useful to have an assay that can detect the class of mercapturates. Toward this end researchers have developed antibodies that detect non-polar substituted S-mercapturates such as benzyl mercapturate, phenyl mercapturate, hexyl mercapturate, etc. These antibodies could be used to purify mercapturates from urine that could later be speciated by mass spectrometry. Another important class of compounds is the pyrethroid insecticides. With the phase out of organophosphates by the EPA, the use of pyrethroids will increase and concerns exist regarding the toxicity to non-target organisms in the ecosystem. Researchers have developed assays for permethrin and fenvalerate (some of the most heavily used pyrethroids), as well as for metabolites of esfenvalerate, as potential biomarkers of human exposure. In environmental monitoring or exposure studies, the pyrethroid used may not be known or may be present as mixtures of pyrethroids. Assays to distinguish type I and type II pyrethroids (those that differ structurally by an alpha cyano group) have also been developed. The other major class of conjugate found in urine is glucuronides. In spite of the phase out, monitoring of humans for exposure to organophosphates continues to be needed. For several organophosphates, 4-nitrophenol is the primary leaving group. It is found in human urine as the glucuronide conjugate. An assay for 4-nitrophenyl glucuronide has been developed that can be used as a screening method in human urine at an action level of 100 ppb. Similar to the mercapturate work, the development of a class-selective glucuronide assay has been developed for phenolic glucuronides. Validation and application of immunoassays that we have developed is moving forward with the assays for 2,3,7,8-tetrachlorodibenzodioxin. Comparing immunoassay results with results obtained by GC/MS for soil and biota samples has validated the previously developed assay. Lastly, researchers are evaluating new formats such as the use of polyelectrolytes to speed up the assay, and examining fluorescent labels as a step toward developing higher throughput assays.

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