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

CONTINUED FROM PREVIOUS POST

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.

TO BE CONTINUED

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.

FIRESIDE CHAT: Hudson River PCB Dredging (c)

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

CONTINUED FROM PREVIOUS POST

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.

TO BE CONTINUED

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.

FIRESIDE CHAT: Hudson River PCB Dredging (b)

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

The US Environmental Protection Agency’s (EPA) baseline Hudson River health risk assessment (HRA) is evaluated and found to be biased toward keeping polychlorinated biphenyls (PCBs) in sediments. The HRA systematically misquantified parameters, underestimating PCB movement from sediments to water and from water to air. The EPA excluded from its analysis all mono-and dichlorinated PCB congeners, which EPA subsequently estimated at one-third of total PCB mass in the river, and excluded dissolved and colloidal PCB.

The EPA included silt-adsorbed PCB, but overestimated the rate at which it would settle out of the water column by inappropriately basing the rate on Stokes’ Law for more massive spherical particles. Flat clay particles settle more slowly with a longer path length and residence time. The EPA omitted electrostatic charges on clay particles that separate them, preventing agglomeration and maintaining clay in suspension; they also assumed that particles never “reflect” back into the water column after settling, likewise underestimating PCB concentrations in water.

Also omitted was PCB codistillation, in which PCBs at low bulk concentrations preferentially distribute to the air-water interface, accelerating PCB transfer from water to air. Indeed, EPA cited empirical data showing more rapid PCB water-to-air transfer, but reduced its effect on the HRA, by reducing the transfer coefficient by averaging in lower modeled PCB transfer coefficients that ignored codistillation. Finally, EPA omitted PCB release to the atmosphere from hot water in cooling towers in communities along the Hudson River. Water at cooling tower temperatures may release PCB into the air more than 10 times faster than rates determined from the surface of cold water and multiple orders of magnitude more rapidly than in EPA’s models. Together, EPA’s procedures reduced airborne PCB concentrations from above to below de minimis concentrations. This, in turn, eliminated the requirement for EPA’s HRA to quantify inhalation risks posed by airborne PCBs; the HRA, therefore, 'considered' airborne PCBs, but attributed zero health risk to them.

TO BE CONTINUED

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.

Copyright © 2009 by The Center for Health Risk Assessment and Management, a Division of RAM TRAC Corporation

FIRESIDE CHAT: Hudson River PCB Dredging

Dredging PCBs from selected Hudson River sediment ‘hotspots’, the largest PCB dredging project yet undertaken, began recently at Fort Edward, New York. Its beginning has evoked various reactions, ranging from celebration about the prospect of an eventually clean Hudson River, to concern about project impacts of noise, health effects, and diminished recreational river use and quality of use. Though I celebrate the prospect of a clean Hudson River environment, dredging won’t produce it in my lifetime.

Dredging during more than a decade of project implementation instead will produce predominantly negative effects, including degradation of water quality, increased PCB residues in Hudson River biota, and possibly serious health effects in people living in Hudson River communities. Indeed, it already has restricted recreational use of the river, as river events have been canceled and river users advised to wash their bodies thoroughly after swimming. To illustrate with a personal example: I was invited to kayak at Spiers Falls in the Hudson and, before responding, checked to see if it was upstream or downstream of the dredging project.

Washing is inefficient at removing PCBs from skin, because dermal lipid (fat) binds PCBs tightly. The advice to wash off PCBs reminds me of Lady Macbeth’s efforts to wipe her hands of King Duncan’s blood: “Out, damned spot! out, I say!” Such advice seems dramatically emblematic of ineffective concern among health officials about river users contacting PCB.

Lawsuits demanding provision of alternative drinking water supplies have resulted in expensive concessions to river towns seeking to protect their residents against PCB’s health effects, most notably the high probability that ingested PCBs can cause human cancer. This concern is valid. Switching to an alternative drinking water supply when PCBs are detected at or above a trigger concentration might solve it, but only if sampling is extensive and results provided quickly. Switching to an alternative drinking water supply, however, cannot address the many short-term health effects exerted PCBs, for example, causation of birth defects in newborn babies whose mothers were exposed to PCBs during pregnancy.

The General Electric Company (GE) is paying big bucks for dredging, but ‘we the people’ eventually may pay more. If dredging had not been required by the U. S. Environmental Protection Agency (EPA), lawsuits claiming adverse health effects would have been (indeed, have been) directed at GE as the main polluter and main defendant. In the future, however, the preponderance of human exposure to PCBs buried under river sediments will be mediated by dredging, without which the PCBs would have remained buried and isolated from ecosystems leading to such exposure. EPA will join GE as eventual defendants in any lawsuits linking dredging with PCB-associated health impacts. So, EPA’s assessment of health risks potential posed by Hudson River PCBs had better be reliable… but it is not.

Instead, EPA’s baseline health risk assessment of PCB-mediated risks in the Hudson River was found to be biased consistently in the dredging-friendly direction with respect to nine out of nine parameters determining the degree of health risk. Effectively, risks that EPA deemed low enough to justify dredging effectively were in fact never accurately quantified. The dredging project therefore represents an experiment on humans who did not consent to participate. If health risks materialize as health effects, we the people will pay. If health effects emerge that are serious and widespread in Hudson River communities, we the people will pay a lot.

Copyright © 2009 by The Center for Health Risk Assessment and Management, a Division of RAM TRAC Corporation
Posted by The Center for Health Risk Assessment and Management, a Division of RAM TRAC Corporation