Wednesday, June 10, 2009

FIRESIDE CHAT: Hudson River PCB Dredging (d)

Bias in the US Environmental Protection Agency’s Baseline Health Risk Assessment Supporting the Decision to Require Dredging of PCB-Bearing Sediments from the Hudson River

Robert A. Michaels, Uriel M. Oko


Purpose, Scope, and Overview

Administrative procedure under Superfund involves interested parties (‘stakeholders’), by design introducing politics into EPA administrative procedure. The present study addresses the question of whether, despite political influence, dredging is justifiable by the science of health risk assessment (HRA). The EPA apparently justified its decision to require dredging based upon a baseline assessment of PCB risks, not an assessment quantifying PCB risks potentially posed under dredging scenarios ~US Environmental Protection Agency, 1999, 2000a, 2000b!. An HRA should compare potential risks under specific dredging scenarios with baseline risks following completion of the demonstration dredging project. For this comparison process to be valid, baseline risks potentially posed by all relevant exposure routes, including PCB inhalation, should have been estimated in a valid and unbiased manner. The present study addresses this issue.

Selection of Parameters

The issue of bias must be addressed via evaluation of a fair, rather than a biased, selection of EPA’s parameters. A random selection of parameters is neither required nor appropriate; we focus narrowly upon mis-estimated parameters. Accordingly, our procedure was to evaluate EPA’s analysis and systematically ignore all parameters whose use by EPA was technically justified. Parameters of interest to us are not those of greatest a priori concern ~quantitatively most important in determining risk!. In our investigation, parameters that were accurately estimated were dropped from concern, no matter how important they might have been quantitatively in determining risk. We identified nine parameters whose evaluation by EPA was found to be technically deficient. In short, we did not“cherry-pick”parameters to bias our analysis in a particular direction. Our analysis, of course, is verifiable against cited EPA documents.


or see:

Michaels, RA.; and UM Oko. Bias in the US EPA baseline health risk assessment supporting the decision to require dredging of PCB-bearing sediments from the Hudson River. Environmental Practice (Cambridge University Press), 9(2):96-111, June 2007.