Sunday, June 21, 2009

FIRESIDE CHAT: Hudson River PCB Dredging (e)

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 criterion of bias

The bias issue is addressed qualitatively as well as supported and augmented quantitatively (statistically). Both approaches rely on the simple premise that the direction of errors in analyses of independent (non-covariant) parameters approaches randomness as the number of parameters increases. Randomness of error direction, therefore, is the null hypothesis. Its rejection is justified technically if a low-probability pattern of error directions is observed, such as mis-estimation of a large number of independent parameters in a consistent direction, permissive to dredging or contraindicating dredging. Observing such a low-probability distribution of error directions, whether or not based upon quantitative (statistical) analysis, would support the conclusion of bias, though not necessarily of intentional bias.

The public policy issue

Under a consent decree GE would pay the lion's share of Hudson River restoration costs. The costs, measured in hundreds of millions of dollars initially and probably over a billion dollars cumulatively for limited PCB 'hotspot' dredging, make the Hudson River a sediment 'megasite'. Projected remedial costs far exceed median costs for sediment sites, and far exceed costs ranging from $19,000 to $812,000 per project paid for achieving the various goals of 37,099 river restoration projects listed in the National River Restoration Science Synthesis (NRRSS) database (Bernhardt et al. 2005). For example, median costs for instream habitat improvement projects were reported to be $20,000; for water quality management $19,000; and for channel reconfiguration $120,000. These costs impart urgency to the task of revealing any bias, or resolving any appearance of bias, in the scientific analyses informing the dredging decision.

The public health issue

Adding to the urgency of evaluating possible bias, PCBs have been associated with numerous adverse human health effects (ATSDR 2000, Buckley and Tofflemire 1983, Carpenter 1998, Carpenter 2005, Carpenter et al. 2003, Chase et al. 1982, Choi et al. 2003, Hennig et al. 2002, Lucier 1991, Slim et al. 1999, Stehr-Green et al. 1989; and Taylor, Stelma, and Lawrence 1989). Effects include higher incidence of low-birth-weight infants among residents of zip codes of PCB disposal sites (Baibergenova et al. 2003) and, more recently, higher hospitalization rates for coronary heart disease in zip codes with PCB-contamination (Carpenter 2005). PCBs are animal carcinogens and probable human carcinogens (ATSDR 2000).

Confounding issues

Dredging has become confounded with equity, essentially, how much GE should pay for damaging the Hudson River and environs. A proper separation of the equity issue from other dredging issues is essential to unbiased, objective, and otherwise competent scientific decision making. We omit consideration of equity issues*. Indeed, any penalty or finding of liability assessed against GE can be applied toward dredging and/or used for other purposes. Thus, the amount of any penalty that might be assessed against GE should be unaffected by this paper.

The opportunity to decide issues

EPA now has postponed dredging to 2009, affording an opportunity to consider whether dredging constitutes the best use of resources. For example, could possible adverse PCB health effects be offset more effectively via less expensive but more health-enhancing strategies, such as health club memberships for families residing along the Hudson River? More germane to PCBs, could greater health benefits be derived by using GE funds to establish a research institute focusing on local epidemiological issues? Resolution of these issues is outside our scope. We focus narrowly on evaluating the possible role of bias in EPA scientific analyses to decide whether or not Hudson River PCBs might pose unacceptable risks under a dredging and/or non-dredging (‘baseline’) scenario.


*One of us (Michaels) previously consulted to GE under the auspices of RAM TRAC Corporation, but neither Michaels nor RAM TRAC has done so for over five years. Neither author or corporation has a business relationship with GE, or financial interest in the dredging issue.


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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.