HEALTH IMPACT ASSESSMENT: THE INFLUENCE OF BIAS IN EPA’S DECISION TO DREDGE PCB FROM HUDSON RIVER SEDIMENTS
Robert A. Michaels, RAM TRAC Corporation; Schenectady, NY*
ABSTRACT. The Hudson River has been impacted over the years by massive disposal of PCBs. The largest contributor has been reported to be the General Electric Company (GE). Before requiring GE to dredge the Hudson River bottom to remove PCBs, the US EPA perennially debated the question for decades. The protracted debate spanned issues of science and values. The decision to dredge clearly and unavoidably was influenced by values as expressed via the political process. Recent postponement of dredging until 2007 at the earliest undermines EPA’s declaration of the finality of its ‘decision’. The present study addresses the question of whether, despite political influence, dredging is justifiable by science, most notably by the science of health risk assessment (HRA), or should be reconsidered, especially given the opportunity afforded by the dredging postponement. Health impact assessment (HIA) assesses project impacts, whereas HRA predicts them. HIA therefore can reveal the degree to which actual impacts accord with predicted impacts. The present study compares health impacts predicted by EPA, which considered scientific and political factors, vs. health impacts that are ‘actual’ in the sense that science alone would predict them. I acknowledge the impossibility of fully excluding political and other biases, even from purely scientific studies. This study, however, adopts the premise, reasonable in the current context, that such biases can be excluded to a relatively complete degree, that is, compared with regulatory agency deliberations on which political factors impinge. If EPA’s analysis was duly insulated from political input, the present study should reveal no significant differences from EPA’s findings. The combination of politics and science inherent in regulatory decision making is a viable paradigm only to the degree that scientific analysis can be insulated from politics. Two criteria were used to determine whether effective insulation was attained with respect to the Hudson River dredging decision: 1. whether the values of parameters influencing the decision were estimated accurately and, 2. if inaccurate, whether documentable errors favorable to the Agency decision were made systematically, or whether the errors were distributed randomly, some favoring and some opposing the actual Agency decision. My four conclusions are: 1. US EPA evaluation of parameters determining human exposure to PCBs systematically understated concentrations of PCBs that can, and presumably will, become airborne under dredging scenarios. 2. These spurious parameter values were used by EPA to justify exclusion of PCBs from the list of substances of potential concern whose risks were required to be quantified in the dredging HRA. 3. PCB risks and their acceptability remain unassessed and unknown, as does the degree to which dredging would exacerbate them. 4. Without credible resolutions of these issues, the dredging decision should be reconsidered because it currently lacks scientific merit. Figuratively, the emperor who loves clothes in fact has no clothes.
__________________________________ *Robert A. Michaels, PhD, CEP; President, RAM TRAC Corporation, www.ramtrac.com, 3100 Rosendale Road; Schenectady, NY 12309; (518) 785-0976, ram@ramtrac.com
INTRODUCTION ----------------------------------------------------------------------------------------------------------------------
Once lived an emperor who thought so much of new clothes that he spent all his money to obtain them. When swindlers presented the emperor with an imaginary new suit, his courtiers admired it. No one wished to let others know that he saw nothing. “But he has nothing on at all,” said a little child at last… “But he has nothing on at all,” cried the whole people at last.
Hans Christian Andersen. Aesop's Fables: The Emperor’s New Suit, 1837.
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For decades the U. S. EPA has considered dredging the Hudson River bottom to remove PCBs. The largest contributor to PCB contamination of the Hudson River has been reported to be the General Electric Company (GE), and GE would pay the lion's share of the restoration cost. The cost indeed would constitute a lion's share, measured in hundreds of millions of dollars initially and probably over a billion dollars cumulatively for limited PCB 'hotspot' dredging. This cost far exceeds median 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 (5). 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 numbers impart urgency to the task of revealing any bias, or resolving any appearance of bias, in the scientific analyses used as inputs to the dredging decision. Adding to the urgency of evaluating possible bias in the dredging decision, PCBs have been associated with numerous adverse human health effects (see, for example: 3, 6-12, 14, 16, 19-21). These include higher rates of low-birth-weight infants among residents of zip codes where PCB disposal sites are located (4) and, more recently, higher hospitalization rates for coronary heart disease in PCB zip codes (9). PCBs are known to cause cancer in animals and, therefore, they are deemed probable human carcinogens (3). The dredging issue has become confounded with the equity issue, essentially, how much GE should pay for damaging the Hudson River and its environs. A proper separation of the equity issue from other dredging issues is essential to unbiased, objective, and otherwise competent scientific decision making. As a former consultant to GE, I recuse myself from consideration of the equity issue. 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 for its role in damaging the Hudson River and environs should be unaffected by this paper, which addresses only the issue of whether the technical justification offered for dredging has been influenced by bias and, if dredging ultimately is not found to be justified, how the amount of the assessment against GE might otherwise be spent toward maximum public benefit. EPA now has postponed dredging, probably to 2007, affording an opportunity to consider whether dredging constitutes the best use of funds that will enter the public coffers. For example, could greater health benefits be obtained more inexpensively by presenting each household along the Hudson River with a treadmill? Could greater benefits be obtained from the GE funds by using them to establish a research institute focusing on local epidemiological issues? Resolution of these important issues is secondary to the primary task of the present paper, which is to investigate and evaluate the possible role of bias in scientific analyses undertaken to decide whether or not dredging PCB-laden sediments from the Hudson River should be undertaken.
METHODS
This investigation adopts the methods of health risk assessment (HRA) and health impact assessment (HIA) toward achieving just one primary task. The primary task is to identify multiple parameters that were used to determine the safety and efficacy of dredging and, essentially, to peer review their quantification based upon Agency documentation. Two criteria were used to determine whether effective insulation of science from politics was attained with respect to the Hudson River dredging decision: 1. whether the values of parameters influencing the decision were estimated accurately and, 2. if inaccurate, whether documentable errors favorable to the Agency decision were made systematically, or whether the errors were distributed randomly, some favoring and some opposing the actual Agency decision. The null hypothesis is random distribution of errors (not the absence of errors), which would be expected if decision making was unbiased. Any finding of significant systematic error in either direction would constitute evidence of bias, that is, evidence for rejecting the null hypothesis of the absence of bias. Secondary methods also were used. They are not a priori methods, and they are not described in detail here. Rather, they are the diverse methods typical of peer review, which most essentially consists of considering the scientific merit with which numerous methods were selected for use and applied in the original analyses supporting the dredging decision. Readers can judge for themselves whether or not I applied the methods of HRA, HIA, and peer review objectively.
FINDINGS
EPA identification of parameters used in dredging decision making
The number of parameters on which the dynamics of PCBs entering the water column from sediments and entering the air from the water column are diverse and numerous, numbering in the hundreds or thousands. The number that are visible in any scientific explication of this issue depends upon the degree of detail with which the analysis is conducted. The parameters include initial concentrations of over two hundred PCB congeners, from monochlorinated to decachlorinated biphenyls, in each medium, bulk amounts, areas involved, depths of sediments, as well as parameters describing the physical, chemical, and environmental degradation (such as half life), transformation (such as dechlorination), and other environmental dynamics (such as solubility, boiling point, volatilization, and vapor density) of these numerous congeners. The safety issue also encompasses the toxicological parameters of the PCB congeners. The full list of such parameters is far too long to elucidate in great detail here. Fortunately, the present analysis requires no such highly detailed elucidation. The parameters that are of greatest concern here are those that are most susceptible to being overestimated or underestimated, especially if by a wide margin of error, or overlooked entirely. These are the parameters (unlike, say, molecular weights, which are known to a high degree of accuracy) whose estimated values substantially may depend upon who is doing the estimating. Quantification of these parameters can vary from liberal to conservative, depending upon whether the estimator has a (conscious or unconscious) agenda other than to conduct a purely scientific analysis… in short, a bias. Nine such estimated, determinative parameters that were (or should have been) used for technical justification of the dredging decision were identified, as follows: --1. Mobilization of sediment-borne PCBs in dredging. Sediment-borne PCBs that normally would not enter the water column, and therefore also would not enter the atmosphere, will become mobilized by dredging. Such PCB mobilization must be considered in assessing the potential public health significance of PCB dredging; --2. PCB congeners to be included in the analysis. All 209 PCB congeners should be included;
--3. Phases of PCBs to be included in the analysis. All phases should be included, most notably including molecular PCBs that are dissolved and particulate PCBs that are colloidal; --4. Precipitation of PCB-bearing sediment particles from the water column. Precipitation rates should be quantified realistically, as this parameter is important in determining the rate of PCB removal from the water column (to the sediments); --5. Electrostatic charges on PCB-bearing sediment particles in the water column. Electrostatic charges tend to agglomerate particles if they are attractive (plus near minus) or separate particles if they are the same (in the extreme case, all plus or all minus). Sediment-bearing particles in a common environment carrying the same adsorbed substances typically would have a predominance of similar charges. They should be modeled because they potentially might be important in preventing agglomeration, and thereby important in inhibiting precipitation and PCB removal from the water column by limiting evolutionary increases in waterborne particle mass; --6. Reflection coefficient of precipitating PCB-bearing sediment particles. The reflection coefficient quantifies the tendency of particles, once settled out of the water column, to return to the water column as a result of ‘bouncing’. The reflection coefficient should be quantified and is important for particles that are of relatively low mass;
--7. PCB codistillation. Codistillation is an obscure chemical process that happens to be well documented for PCBs, that results from molecular attraction to surfaces. For PCBs these surfaces include glass containers in the laboratory, but also the air-water interface in lakes and rivers. Entry of PCBs into the air from the water is known to be significantly faster and more extensive in a given interval than would be the case if the same mass of waterborne PCBs were assumed to be distributed evenly throughout the water column (the ‘bulk concentration’). Accurate estimation of waterborne PCB entry into the air that people will breathe requires quantification of PCB codistillation; --8. Empirical measurement of airborne PCBs over PCB-contaminated waters. Empirical measurements, to the extent available, should be used for validating modeled relationships, such as models of PCB entry into the air from Hudson River water; --9. Warm water sources of Hudson River PCB entry into the atmosphere. Warm water occurs in the Hudson River at near-shore locations where cooling water is discharged from industrial facilities and, before discharge, in cooling towers supplied by Hudson River water. These sources of potential entry of Hudson River PCBs into the atmosphere near population centers must be accounted for in assessments of the potential public health significance of PCBs, and the possibly increased significance to public health if PCB dredging is undertaken.
EPA quantification of parameters used in dredging decision making
U. S. EPA evaluation of each of the nine parameters described above appears systematically to have underestimated concentrations of PCBs that could, and presumably would, become airborne under a dredging scenario. These parameters include the following:
--1. Mobilization of sediment-borne PCBs in dredging,
--2. PCB congeners to be included in the analysis, --3. Phases of PCBs to be included in the analysis,
--4. Precipitation of PCB-bearing sediment particles from the water column,
--5. Electrostatic charges on PCB-bearing sediment particles in the water column,
--6. Reflection coefficient of precipitating PCB-bearing sediment particles, --7. PCB codistillation,
--8. Empirical measurement of airborne PCBs over PCB-contaminated waters,
--9. Warm water sources of Hudson River PCB entry into the atmosphere,
Adoption of simplifying assumptions in modeling river flow, precipitation of suspended particles, and PCB dynamics can result in omission and/or unreliable quantification of important parameters contributing to overall PCB-associated risk. I believe that this indeed has occurred. It is hinted at in Section 5 (Assessment of Water Quality Impacts) of Appendix E of the U. S. EPA’s revised HRA for the Hudson River (24): “A complete evaluation of water quality impacts requires integrating a calibrated hydrodynamic model of the system with a water quality model capable of predicting changes due to advection, turbulent diffusion, and settling of the suspended particles. Such a model is beyond the scope of this evaluation” (24, Section 5, page 12; emphasis added). The technical merit of EPA quantification of each parameter listed above is evaluated sequentially in the subsections below:
Mobilization of sediment-borne PCBs in dredging
PCB mobilization must be considered in assessing the potential public health significance of PCB dredging. Its consideration by EPA, however, was inadequate. Research undertaken by Joel Baker at the Chesapeake Biological Laboratory in Maryland simulating Hudson River PCB dredging revealed that EPA underestimated PCB mobilization (2). The degree to which this underestimation occurred itself may have been underestimated, because EPA now has proposed to return to the more primitive, once-repudiated ‘clamshell’ method of dredging. This was done because the high-tech suction method of dredging initially proposed for use by GE was deemed to be infeasible. In short, EPA has underestimated PCB mobilization likely to be caused by dredging, thereby underestimating sediment-borne PCBs subject to becoming waterborne, and thereby also underestimating waterborne PCBs subject to becoming airborne.
PCB congeners to be included in the analysis
All PCB congeners should be included. Mono- and dichlorinated PCBs, however, were excluded from the inventory of PCBs in Hudson River water, thereby underestimating waterborne PCBs subject to becoming airborne. Figures 4 through 7 of the revised Hudson River health risk assessment (HRA; 22-24) depict a precipitous fall-off of “total tri+ PCB congener water column concentrations” within approximately 10 meters of the dredge site. PCB congeners can bind from one to 10 chlorine atoms. If each number of chlorines were represented equally, exclusion of the monochlorinated and dichlorinated PCBs would represent two of 10 (20 percent). The actual fraction (weight-percent) excluded is unclear because commercial PCBs were sold as Aroclors, such as Aroclor 1254, with 54 weight-percent chlorine, such that each Aroclor product sold had a distinctive distribution of mono- to deca- chlorinated PCB congeners (hence the ability to ‘fingerprint’ PCB sources). In addition, PCB degradation in sediments results in gradual dechlorination, which tends to deplete the high-chlorine congeners and enrich the low-chlorine congeners... precisely the congeners that were excluded from Figs. 4 to 7, and which apparently were excluded from consideration in quantifying PCB release from river water to air. The fraction of total PCB represented by the monochlorinated and dichlorinated PCBs would appear to be about one third, as suggested by an EPA estimate that is described below. The plan to dredge Hudson River sediments selected among several remediation options. The option favored by environmentalists, creatively named “Alternative no. 5,” would remove 155,000 pounds of PCBs, compared with 1.3 million pounds; which equals 650 tons, or approximately 600,000 kg or 60 tonnes. That is the amount that is reported to have been deposited into the Hudson by GE from its two upriver capacitor plants before PCBs were banned from U. S. commerce by the Toxic Substances Control Act of 1976. Responding to criticism of the plan to dredge only 100,000 pounds of PCB under a less ambitious option, GE provided ‘new data’ to the EPA that showed that the actual amount of PCBs that would be dredged from the river bottom under Alternative no. 5 would be 150,000 pounds, almost identical to the amount preferred by environmental groups (5). By way of explanation, EPA indicated that it simply had refined its PCB estimate of a year earlier. EPA did this by including previously-excluded monochlorinated and dichlorinated PCBs, on the rationale (according to EPA’s TAMS contractor) that “fish principally absorb (higher chlorinated) PCBs.” The Agency apparently assumed that the monochlorinated and dichlorinated PCBs constituted one third of total PCB (50,000 pounds out of 150,000 pounds of total PCB). Clearly, the Agency’s HRA of 1999 (22) and 2000 (23, 24) for Hudson River dredging therefore excluded approximately one third of total PCBs from the PCB inventory. This was done, notwithstanding that the scope of the Hudson River HRA included the airborne risks, not just fish consumption risks, that might be posed by PCBs that will be resuspended and mobilized by dredging. This exclusion, however, did not stop EPA from taking credit for inclusion in its dredging plan of the extra 50,000 pounds of PCB assumed to be accounted for by the monochlorinated and dichlorinated PCBs to augment the acceptability of its dredging plan in the face of criticism in 2001. The Agency actions described above highlight three issues relating to potential bias introduced by political interests into the scientific analysis: --1. whether EPA accurately inventoried the amount of PCBs that might pose risks to health, --2. whether EPA accurately assessed risks potentially posed by PCBs in its PCB inventory (addressed in greater detail later), and
--3. whether the PCB risks that were quantified in the HRA corresponded to the PCB amounts that would be dredged, and that would be subject to mobilization with the potential to pose health risks.
The findings indicate that EPA based its risk estimates on a smaller pool of PCBs. They indicate further that the Agency did this by excluding monochlorinated and dichlorinated PCB congeners from the HRA. EPA did this, notwithstanding that the excluded congeners would necessarily be included in sediments that would be dredged, and therefore would contribute to airborne PCB concentrations and health risks posed by dredging.
Phases of PCBs to be included in the analysis
All phases should be included, including dissolved and colloidal phases of PCBs. Instead these two phases were excluded from the inventory of PCBs in Hudson River water, thereby underestimating waterborne PCBs subject to becoming airborne. The mechanical action of dredging ‘hot spots’ will cause PCBs adsorbed to silt particles to enter the water column. Whereas most of the PCBs will remain adsorbed to the silt, a fraction will enter the water column, either in the dissolved (molecular) phase or in the colloidal phase (consisting of fine droplets). Exclusion of PCBs in these dissolved and colloidal phases from the revised Hudson River HRA is reported in Appendix E, Section 5.2, titled "TSS Plume Estimates.” In that section, only silt particles were used to estimate settling rates: "Since data on settling rates were not available, a -4 median value for settling velocity of 1.9 x 10 M/sec was used in the transport calculations” (24). Inasmuch as silt has specific gravity of about 2.5, this settling velocity is translated to particles of diameter exceeding 20 microns (uM). This size excludes the vastly more numerous colloidal particles, which are commonly recognized as being 1 uM and smaller. The excluded colloids would suspend in the water phase even beyond the dredge site perimeter of perhaps 20 M. PCBs can remain in the water, suspended as globules of pure PCBs that are smaller than 20 um. A U. S. EPA review of experience of dredging PCBs shows that dredging hot spots can disperse waterborne PCBs beyond the 20-meter envelope ('silt curtain') around a dredge site, with observed concentrations of 0.1 to 0.2 ppm (100,000 to 200,000 ng/L). This is approximately 3,000 to 6,000 times the PCB concentration assumed under a non-dredging scenario in the HRA prepared in support of another project (specifically, the PSEG NY proposal to site the Bethlehem Energy Center, or BEC, gas-fired power plant on the Hudson River at Bethlehem, New York; 17, 18). In this higher waterborne PCB concentration range, resulting airborne PCB concentrations were reported to have exceeded safe concentrations (24). Indeed, EPA’s HRA Appendix E (24) states the following: “While these estimates of total tri+ PCB congener concentrations represent cumulative concentrations, dissolved or particulate tri+ PCB congener concentrations may be of even greater interest. In particular, the dissolved water column concentrations tend to be of greater concern because of their increased bioavailability” (24, page 59).
Precipitation of PCB-bearing sediment particles from the water column
Precipitation rates should be quantified realistically, as they in turn quantify the rate of removal from the water column of PCBs that had been resuspended and mobilized by dredging. Instead the residence time of flat, PCB-bearing clay particles in river water was quantified unrealistically, based upon the more rapid precipitation of spherically shaped particles acting in accordance with Stokes Law. This procedure underestimated waterborne PCBs, and thereby also the underestimated amount of PCB that would become airborne. Mathematical treatment is simplified when a spherical shape for fine particulates is assumed, which is the case in Stoke’s Law. This assumption, however, predicts faster than natural settling rates because, in nature, spherical particles are rare. Disk, rod shapes, and irregular random shapes are more common, and these shapes settle more slowly than spheres. Mathematical predictions of settling rates that do not account for irregular shapes can predict 100 percent faster settling rate at the >20-uM particle size range, and more than 1,000
percent faster at the <10-uM size range. Clay is abundant in the Hudson River region, and would constitute a significant if not the preponderant fraction of PCB-contaminated sediment particles that will be resuspended and mobilized during dredging. Flat clay particles settle via a side-to-side oscillation during descent, greatly increasing their path length and residence time in the water column. That is why they settle more slowly than predicted by Stokes Law. Such delay in exiting the water column reasonably would be expected to increase the concentration of PCB-laden particles in the water column markedly, much as delays at highway exits markedly increase traffic on the highway.
Electrostatic charges on PCB-bearing sediment particles in the water column
Electrostatic charges should be modeled, but instead they were ignored. By this omission EPA failed to account for prolonged suspension in the water column of charge-separated PCB-bearing clays, and it thereby also underestimated waterborne PCBs subject to becoming airborne. Most fine particles, because of their high surface-area-to-volume ratio, become electrostatically charged in water. The charges cause the particles to repel one another, increasing their residence times in the water column. Often the particles will not settle at all. Excluding this factor from the analysis of precipitation of suspended particles in the Hudson River results in decreased PCB-laden particles in the water column as a result of increased settling velocity. EPA’s assumption of rapid exiting of PCB-laden particles suspended in the Hudson River cannot materialize.
Reflection coefficient of precipitating PCB-bearing sediment particles
The reflection coefficient should be quantified because it constitutes a potentially significant source of return to the water column of PCB-bearing silt particles that are of relatively low mass. Instead no reflection coefficient (or, equivalently, a reflection coefficient of zero) was included in calculating PCB removal rates from the water column. This procedure thereby underestimated waterborne PCBs subject to becoming airborne. The rate of free settling in water of silt particles influenced by earth’s gravity can be predicted from particle size and the specific gravity of discrete particles. At the bottom of settling columns where the particles compact, however, other mechanisms take over. One of these processes is reflection, which refers to the fact that particles of low mass may bounce off the substrate on which they land. Similarly, colloids may remain in suspension longer as a result of bouncing off water molecules with which they collide (in a well-documented phenomenon termed Brownian motion). These phenomena of reflection and bounce occur in a zone of activity termed the 'hindered zone' of settling. Failure to incorporate a reflection coefficient when calculating deposition of PCB-laden particles in the Hudson River water column tends to underestimate particle and PCB concentrations in the water, just as traffic could be underestimated on a highway if the model used fails to count a high fraction of exiting vehicles that immediately reenter the highway. PCB codistillation
Empirical measurements should be used for validating model assumptions that are used in quantifying PCB entry into the air. Instead, available empirical measurements were suppressed (see below), thereby underestimating the water-to-air transfer coefficient. Accurate estimation of waterborne PCB entry into the air requires quantification via accounting for PCB codistillation. By ignoring PCB codistillation in quantifying the water-to-air PCB transfer coefficient, EPA underestimated waterborne PCBs subject to becoming airborne. A recent news item (1) based upon Research conducted by the Integrated Atmospheric Deposition Network (15) reveals that codistillation has transferred nearly two tons of PCBs from Lake Ontario to the atmosphere between 1992 and 1996. According to a news report (1) describing this startling finding:
"The Great Lakes have begun to 'exhale' significant quantities of chemicals, including ...PCBs..., releasing them into the atmosphere... Researchers say ... the lakes begin naturally cleansing themselves through the volatilization process (i. e., evaporating pollution off the water surface). The latest figures from the Integrated Atmospheric Deposition Network (IADN) show a net release from Lake Ontario alone of almost two tons of PCBs into the air... from 1992 through 1996..." (1, page 9, emphasis added). That's a half ton (nearly 500 kg) of PCBs each year codistilling from the surface of a cold lake. Codistillation, however, also is temperature-dependent. Thus it would occur at a greater rate, and to a greater degree, in warm water, such as in Hudson River water heated during industrial use as a cooling fluid, and then itself cooled in cooling towers before return to the river. EPA’s failure to account for codistillation might be explained by unfamiliarity with the phenomenon, as well as by an unwillingness to give appropriate credence to empirical data arising from credible reports. The issue of EPA’s treatment of empirical data is addressed below.
Empirical measurement of airborne PCBs over PCB-contaminated waters
The degree to which EPA was familiar with codistillation cannot be known with certainty. However, such familiarity was not necessary for enabling the Agency accurately to quantify PCB water-to-air transfer coefficients, inasmuch as empirical measurements cited by EPA had been made to quantify this parameter. Indeed, the revised Hudson River HRA (23, 24) Appendix B cites nine empirical measurements of airborne PCB concentrations (4.5) contributing toward estimating the transfer coefficient of PCBs from water to air (24, Table B-1). These and possibly other measurements were used by EPA to produce PCB water-to-air transfer coefficients (summarized in 24, Table B-2; and see original data source, 13) as follows:
“These data can be used to estimate an empirical water to air transfer coefficient, representing the ratio of the PCB concentration in air divided by the PCB concentration in water. Using the detected PCB concentrations in air and water summarized in Table B-2, empirical air-water transfer coefficients range from 0.02 to 0.4 ug/M3 per ug/L, with a median value of 0.09, and an average value of 0.15 (ug/M3 per ug/L)” (23, page 18). These measured values, however, were found to be surprisingly high, possibly because EPA was unfamiliar with codistillation, in which case the Agency would not have expected the transfer coefficients to be as high as suggested by the measurements. Further investigation could have elucidated the explanation for the higherthan-expected PCB water-to-air transfer coefficients, but further investigation apparently was not undertaken. Instead, the measured values described above were suppressed or, more specifically, they were assigned a low weighting. This was accomplished via adulteration of the nine empirically derived transfer coefficients with two lower transfer coefficients that were derived via two modeling approaches. The two modeling approaches, which did not incorporate codistillation, produced transfer coefficients that were expressed in units of ng/M2 sec per ng/L. These units cannot be compared directly with the empirical values, which were expressed in ug/M3 per ug/L. The units were brought into line, and the comparison made, via use of the average PCB concentration in the river (24 ng/L = 0.024 ug/L; 23, page 18). EPA used this concentration to produce a flux (13 ug/sec; 23, page 19) which, using the median empirical transfer coefficient (0.09), generated a modeled airborne concentration of 0.00012 to 0.00021 ug/M3 (23, page 20, compared with 0.002 to 0.53 ug/M3 detected empirically (23, page 20). This corresponds to a factor of 10 to 4,400 difference between the modeled vs. empirical data (0.53/0.00012 = 4417; 0.002/0.00021 = 10). That is, the modeled water-to-air transport factors downwardly biased the estimated transfer of PCBs from Hudson River water to the atmosphere by a factor ranging from as 1/4400th to 1/10th of the empirically determined values. EPA’s preference for modeled transfer coefficient values biased the expected concentration of airborne PCBs over the river surface in a direction favorable to EPA’s dredging proposal and, in this sense, was selfserving. It was sufficiently self-serving to reduce airborne PCB estimates to below levels of concern (requiring
quantitative risk assessment) to the EPA and the New York State Department of Environmental Conservation (NYS DEC). Contrary to EPA’s routine procedure of validating its air models against reality via use of dyes or other markers, in this case EPA invalidated reality based upon reality’s failure to conform to EPA’s air model.
Warm water sources of Hudson River PCB entry into the atmosphere
Potential warm-water sources of must be accounted for in assessing the potential public health significance of airborne PCBs under any dredging scenario. Instead the high temperature of cooling tower water was ignored in predicting PCB volatilization, thereby underestimating waterborne PCBs subject to becoming airborne. Water in cooling towers may be heated by up to 100° F (56° C) above ambient river water temperature. According to the revised HRA for the Upper Hudson and Mid-Hudson River (22): "The concentrations of PCBs in air were calculated from a combination of historical monitoring data and modeled emissions from the river…" (22, page ES-4; emphasis added).
For every 10° C rise in water temperature, the rate of a chemical reaction, such as the rate of PCB codistillation, is approximately doubled. Consequently, the rate of PCB transfer from water to air occurring with a 40° C water temperature increase would be expected to undergo four doublings. Thus, the rate at which PCBs in cooling tower water at 45° C (113° F) would escape to the air would be approximately 16 times greater than that in Hudson River water at 5° C (41° F). If only 1 mg/L (ppm) of suspended colloidal PCBs remain in the water column, the calculated weight of PCBs entering the cooling tower under one project proposal (the PSEG NY proposal to site the Bethlehem Energy Center gas-fired power plant on the Hudson River at Bethlehem, New York; 17, 18), based on 4,500 gallon/minute uptake, would be 2.25 lb/hour (1 kg/h; or 54 lbs/day, which is equal to 25 kg/d). Examination of studies forming the basis for the passage quoted above pertaining to transfer of PCBs from river water to air, however, reveal none addressing PCB release from cooling towers. DISCUSSION AND CONCLUSIONS
Implications for risk
Given the relatively low transfer coefficient of PCBs from cold ambient river water compared with relatively hot cooling tower water, the HRA states that :
"the calculated cancer risks from inhalation of volatilized PCBs [from ambient river water] are de minimis (i.e., insignificant)" (22, section 2.3.4, page 41).
This means that risks to public health potentially posed by transfer of PCBs from the Hudson River surface to the air effectively were assessed as zero in the HRA, and risks posed by PCBs entering the air from cooling towers (with or without dredging) were unquantified and, indeed, unconsidered. Also unquantified, according to the HRA, are "the contribution of PCBs in air from contaminated sediment and floodplain soil" (22, section 2.3.4, page 20). If EPA had estimated accurately PCB transfer from Hudson River water to air, potential risks to people inhaling PCBs would have been required to be included in EPA's HRA. Both EPA and the New York State Department of Environmental Conservation (NYS DEC) use a threshold level of concern as a criterion for requiring quantification of health risks posed by an agent in an HRA. Specifically, if estimated PCB releases to the air are expected to produce a concentration equal to or exceeding one percent of NYS DEC's published Air Guide Concentration (AGC), those emissions must be included in the quantitative portion of the HRA.
Even the lowest of the five empirical measurements of PCB concentration in the air above the Hudson River surface (0.02 ug/M3) exceeded NYS DEC's published AGC value for airborne PCBs of 0.00045 ug/M3 by a factor of 44-fold. It exceeded by more than 4000-fold the trigger value (one percent of the AGC value) for including PCB inhalation as an exposure pathway to be quantified in the HRA. Use of the mean (0.15 ug/M3) or the median (0.09 ug/M3) of all five empirically measured values would, of course, exceed these critical benchmarks even more dramatically. EPA understatement of PCB release to air affects other projects besides the Hudson River dredging project. NYS DEC, for example, need not account for PCB emissions from cooling towers in approving permit applications for projects (such as power plants), even if those projects will use cooling towers. Indeed, citizen criticism of EPA's EIS value in NYS DEC permit review of project proposals has been rejected, not on technical grounds, but because the EPA values previously had undergone peer review. The net result is that HRAs prepared by project applicants may claim to account for public health risks potentially posed by waterborne PCBs becoming airborne. They ‘account’ for them, however, by quantifying them as zero, based upon the erroneous and unreviewable assumption that PCB emissions from water to air will be de minimis. Failure of EPA to quantify a non-zero risk to public health potentially posed by airborne PCBs that would be resuspended and mobilized by Hudson River dredging is a direct result of biasing (at least) each of the nine parameters addressed in the Findings section above in a direction permissive to adopting the dredging strategy. EPA's procedures, therefore, undermined public health protection by eroding the margin of safety that should be built into Agency standards of public health protection. A collateral effect was to eliminate the requirement to quantify these same risks in HRAs supporting other projects proposing to use cooling towers supplied by Hudson River water potentially affected by dredging. For example, the HRA for a recently approved proposal by PSEG NY to site the Bethlehem Energy Center (BEC) gas-fired power plant on the Hudson River at Bethlehem, New York (17, 18) was exempted from quantifying risks potentially posed by airborne PCBs on the authority of the EPA HRA for the Mid-Hudson River (22-24). Implications for decision making
In my opinion the most valuable reward for doing river restoration projects such as those listed in the NRRSS database, is that a river is in some sense 'fixed'. Although this reward would have to be especially large for the Hudson River to justify the enormous price of 'fixing' it, the reality seems different. Whereas we should be rewarded with clean sediments and water, EPA’s dredging program includes only PCB 'hotspots', leaving PCBs remaining in sediments, biota, and water elsewhere in the river; and also leaving virtually all non-PCB contaminants in sediments, biota, and water even after dredging is completed. Indeed, EPA’s dredging proposal addresses 150,000 pounds (68,000 kg) of sediment-borne PCB compared with 1.3 million pounds (591,000 kg) that GE concedes that it discharged into the Hudson from two capacitor plants. That amounts to less than 12 percent of the PCB amount known to have been discharged, and an even smaller fraction of the (unknown) total amount of PCBs discharged into the Hudson River. Whereas we should be rewarded with an uncontaminated sport fishery and safe-to-consume fish caught in the river, in fact the fish cannot possibly become edible. Even if every PCB molecule could be removed from the river, all other Hudson River pollutants will remain after PCB ‘hotspot’ dredging is completed, including heavy metals such as mercury. Whereas we should be rewarded with only de minimis air pollution arising from river water, in fact mobilization of PCBs by dredging will increase PCB release to the air for a period of years, and other pollutants also will continue to become airborne even after dredging is completed. Whereas Hudson River restoration should reward us with only a vanishingly low incidence of adverse health effects that might be caused by airborne PCBs, in fact such health effects (if really caused by PCBs) also would increase for many years before they begin to diminish under a dredging scenario. Some people see light at the end of the tunnel, when dredging really will reduce PCBs in sediment, biota, water, and air; and really will reduce PCB-associated human disease to de minimis levels. Others see the same light at the end of a different, somewhat longer tunnel, when continued natural burial of sediment-borne PCBs by sediment loading from runoff into the river likewise will sever the connection of PCBs to the
sediment, biota, water, and air; and reduce PCB-associated human disease to de minimis levels. Continued natural dechlorination of buried PCBs; and their further degradation by physical, chemical, and biological processes acting beneath the sediments; will finish the job if we do not dredge. The dredging argument has revolved narrowly around the length of the two tunnels leading to de minimis PCB levels, and whether shortening one of the tunnels via dredging can be justified given the near-term environmental disruption that unarguably will be associated with dredging. As an objective scientist I cannot, and do not, claim expertise in resolving subjective issues associated with deciding which tunnel constitutes the better route to essentially the same destination. Objective science, however, is relevant to some aspects of this issue. Specifically, given the apparent biases identified above (in Findings), objective consideration of the following three issue areas continues to remain essential: --1. Are PCBs harming health now and, if so, are the effects sufficiently serious, and the risks sufficiently high, to justify urgent action? Recall that Love Canal decades ago was urgently evacuated under the Federal Emergency Management Act, whereas such precipitous action would be deemed inappropriate today. Indeed, that overreaction spawned the modern Superfund Act, and Love Canal became the first Superfund site. --2. If sediment-borne PCBs indeed are the source of PCBs in air and/or biota, and if such PCBs are harming people's health now, will dredging exacerbate their effects by further mobilizing sediment-borne PCBs? If PCB-mediated health effects are deemed unacceptable now, their prolonged exacerbation by dredging would be deemed unacceptable squared. Additional measures to protect populations clearly would have to be contemplated, presumably short of evacuation but, also presumably, expensive. Conversely, if PCB health risks are acceptable today, what would motivate dredging to remove them, when natural processes eventually will remove them anyway? --3. If the benefits of eliminating PCBs from Hudson River 'hotspots' are deemed worth the enormous price in a hypothetical, otherwise clean Hudson River, are they also deemed worth the price in the real Hudson River, that is, the Hudson River that really has pollutants other than PCBs, and PCBs in places other than where dredging will occur? Lost in the dredging debate seems to be the larger picture produced by dredging, which unarguably is that of a dredged river polluted as before but, for a time (probably decades), harboring a lower PCB burden in its sediments. How does one justify the narrow focus on hotspot PCBs amounting to roughly 10 percent of the total disposed into the river, if the river remains toxic with other pollutants and with non-hotspot PCBs? In short, the decision process seems to have focused narrowly on hotspot PCBs, as if the larger context of a still-polluted post-dredging river were irrelevant. In light of the above questions, the near-term price of dredging must be measured not only in money, but also in terms of potential ecological and public health impacts. The Findings and considerations addressed above justify three specific conclusions and one general conclusion. First, risks to public health potentially posed by inhalation of PCBs were grossly understated (effectively, estimated at zero). Second, even if all the PCBs could be removed from the river, or from the hotspots to be dredged, all other Hudson River pollutants would remain. Their continued presence after completion of dredging would continue to limit recreational and commercial use of the Hudson River. For example, they would limit the amount of fish that could be consumed safely, especially by populations such as pregnant women, young children, and other sensitive subpopulations. Third, PCB risks and their acceptability were unassessed and remain unknown, as is the degree to which dredging would exacerbate them, and for how long. Finally, most generally, without credible answers to these questions, the dredging decision lacks scientific merit, and the emperor who loves clothes in fact has no clothes.
LITERATURE CITED
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24. US EPA. Revised HRA, Mid- and Upper Hudson River, Appendix E. Hudson River PCBs Reassessment FS. Appendix E: Engineering Analysis. Section 6. Technical Memorandum: Semiquantitative Analysis of Water Quality Impacts Associated with Dredging Activities. Bloomfield, New Jersey, TAMS Consultants, pp. 33-67, November 2000.
Publication citation
Michaels, RA. Health impact assessment: the influence of bias in EPA’s decision to dredge PCB from Hudson River sediments. Conference presentation. Albuquerque, New Mexico; Proceedings of the National Association of Environmental Professionals Annual Meeting; 14 pages, 21 April 2006;