FIRESIDE CHAT: Liquid PCB Oils and Hudson River PCB Dredging

further info: www.ramtrac.com

The U. S. Environmental Protection Agency (EPA) reported at a public meeting in the Hudson River town of Fort Edward, New York on 19 August that GE clamshell dredges recently have started to encounter liquid PCB oils in dredging ‘prisms’. I attended that meeting along with my colleague, Dr. Uriel M. Oko. EPA's revelation constituted a virtually silent bombshell, as apparently none of the many media representatives in attendance took special note of it. It is worthy of note, however, because pure PCB oils must be viewed in an entirely different, more ominous context than river sediments harboring PCBs in the parts-per-million (ppm) concentration range. Pure liquid PCB oil concentrations can be expressed in ppm if necessary: 1,000,000 ppm. Mobilizing PCB oils via dredging is commensurately more serious than mobilizing sediments bearing PCBs in the low ppm range as originally anticipated.

As reported in a 28-August CNS News article published online (for which I also was interviewed; 1), EPA acknowledged that the project recently had discovered “sheens” of liquid PCB oil on the river surface, “an indication, the EPA said, that the river floor contained not only contaminated silt, but more potent pockets of pure PCB oil – and that the dredging is releasing the oil into the river water.” EPA, however, placed a relatively benign spin on this news: “It’s not really affecting dredging, that’s why we’ve taken those mitigation measures to, you know, to counteract the sheens.” Counteracting microscopically thin PCB ‘sheens’ visible on the river surface is very different from the real challenge: counteracting pools of liquid PCB oils of unknown, potentially large volume in trenches beneath.

PCB sheens on the river surface constitute yet another source of airborne PCBs not addressed in any EPA assessment of risks to health potentially posed by sediment dredging at PCB hotspots in the Hudson River. (See previous blog posts to learn of other potentially risk-posing sources of airborne PCBs associated with dredging.) Observation of these PCB sheens raises the question of whether they might be expected to arise from underlying sediments bearing PCBs in merely the ppm range, or whether they must originate from more massive pools of liquid PCB oils at the river bottom as suggested by EPA.

Can bottom sediments form surface sheens via some upward PCB migration process? Three factors suggest not:

--1. PCBs chemically bound to sediments for decades are unlikely to become unbound,

--2. If they did become unbound, they also would have to become concentrated from the low-ppm range at the river bottom to near purity at the surface, which is unlikely to occur in a flowing, turbulent river, and

–3. PCB oils are denser than water, so they would be expected to sink, not to rise from the bottom, unless physically forced upward, or lifted.

PCB liquids include more than 200 types, or congeners, varying in their degree and pattern of chlorination (with from one to 10 chlorine atoms per PCB molecule). Each congener has a unique density, but bulk density of commercial PCBs of the types disposed to the Hudson River (known as Aroclors) are reported to have a density of about 1.5 grams per milliliter (g/ml; 2), which is 1.5 times the density of water.

The most probable origin of PCB liquids forming surface sheens, in my view and apparently in EPA's view, is that they are being massively disrupted from pools of liquid PCB oils formed in sediment low points (depressions) following original disposal from land-based facilities or ships. These bottom pools gradually might have become covered over with debris and sediments. The onset of dredging may be forcing the liquids upward toward the surface as dredge jaws expose them and close around them. This process is visible for sediments (which have tightly-bound PCBs that would not be expected to form sheens), and reasonably would apply as well to liquid pools (which would be expected to form surface sheens).

Sediments and PCB oils that are not forced upward by closing dredge jaws might be retained within the dredge buckets, and physically lifted. These materials would be subject to leakage during their ascent to the surface and beyond. These dual processes of disruption by squishing and by lifting reasonably would be expected to generate PCB liquids and PCB sheens at the surface, as PCBs are chemically attracted to surfaces, including to the air-water interface in rivers.

EPA’s report of encountering PCB liquids seems, at least in retrospect, unsurprising given the history of past PCB disposal into the river in the form of liquid PCB oils from land-based facilities and from ships. Given this history, why did EPA adopt the clamshell method of dredging, thereby failing to prepare for this seemingly expectable eventuality? Its sobering actuality now casts further doubt on the wisdom of specifying clamshell dredging rather than vacuum dredging, or no dredging.

One objection to the liquid-pool hypothesis that must be addressed is the fact that PCB concentrations in downstream water samples have not revealed PCB oils or concentrations high enough to suggest their presence upstream. The heavier-than water density of PCBs, however, would be expected to cause them to hug the river bottom as they move downstream. They would not be expected to register in surface water samples taken five miles downstream.

EPA now appears to be faced with the quandary of whether to:

--1. mobilize PCB oils by continuing clamshell dredging, even though the dredge buckets cannot retain the oils efficiently,

--2. allow the PCB oils to be mobilized by river currents washing over the now-exposed pools,

--3. institute vacuum dredging, or

--4. stabilize the oils by covering them over again.

I wish I had the answer to this quandary, but for now suffice it to bring this issue to the light of public scrutiny… which EPA’s silent bombshell on 19 August did not seem to do.

Literature Cited

1. Brickley, Adam. EPA river clean-up uncovers pools of cancer-causing PCBs. Alexandria, Virginia; CNS News, http://www.cnsnews.com, 28 August 2009;

2. UN EP. Training manual for the preparation of a national environmentally sound management plan for PCBs and PCB-contaminated equipment in the framework of the implementation of the Basel Convention. Châtelaine, Switzerland, United Nations Environment Programme; Basel Convention Series/SBC No. 2003/01, ISBN : 92-1-158674-7, 103 pages, March 2003.

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

FIRESIDE CHAT: Health Risks and Hudson River PCB Dredging

further info: www.ramtrac.com

In recent days the U.S. Environmental Protection Agency (EPA) twice ordered the General Electric Company (GE) to cease dredging Hudson River sediments at Fort Edward after measured PCB levels in water and air exceeded acceptable levels. On Monday EPA ordered GE to resume dredging after PCB levels had returned to within acceptable limits. EPA insisted that dredging has been safe, but EPA’s sampling stations are remote. Specifically, they are further from the dredge buckets than are employees working on dredging platforms, and they are further than residents are at some riverfront homes. This raises the question of whether the Hudson River dredging project as currently implemented has exposed these employees and residents, protected by neither respirators nor masks, to unacceptable PCB levels.

I can offer two answers to this question. The first is ‘apparently yes’, and the second is that documentation is problematic because the nearest EPA sampling stations are five miles downstream for water and a difficult-to-determine distance (perhaps hundreds of yards) for air. Acceptability for water samples is defined by the applicable drinking water quality standard (500 ppt) which, EPA asserts, will protect municipal drinking water supplies located downstream.

This might or might not be true. The Maximum Contaminant Level (MCL) established under the Federal Safe Drinking Water Act is, indeed, 500 ppt. MCLs however, are set as enforceable limits that are as close as possible to health goals. As a known cancer-causing agent (carcinogen) in animals, and as a probable human carcinogen, PCBs are subject to an MCL Goal (MCLG) of zero ppt under the Safe Drinking Water Act. That is, EPA has the onus of enforcement when PCB levels reach 500 ppt, and of prohibiting projects that would generate PCB levels even below 500 ppt.

Unquestionably, PCB levels in water are significantly (many times) higher at the point where they are mobilized from sediments at dredge locations, before being diluted with river water during five miles of transport downstream to EPA’s water sampling stations. EPA’s data collection protocols exclude water sampling at dredge locations, so we cannot know for sure just how diluted PCBs are five miles downstream, or how many times more concentrated they are at dredge locations. A reasonable, order-of-magnitude guess would seem to be that PCBs would be transported in turbulent flow, undergoing at least a 10-fold dilution, and possibly 100-fold or maybe even 1000-fold, depending upon river flow volume and flow rate. This might not pose a problem for people drinking water nearby, if they do not drink Hudson River water.

PCBs, however, enter the air from the water, especially when they are introduced near the surface of the water. EPA quantified the relationship between PCBs in cold river water and in air a meter above the river surface. Specifically, for each ug/L (that is, for each 1000 ppt) of PCB in river water, PCB levels in air (in ug/M3) were reported to be: a minimum of 0.02, a median of 0.09, a mean of 0.15, and a maximum of 0.40 ug/M3. These values are explained and cited in a fully peer-reviewed article by myself and co-author Dr. Uriel Oko, published in the Cambridge University Press journal Environmental Practice. This article is available for download in its entirety, for free, at www.ramtrac.com/publications.

River water five miles downstream of dredge platforms, where PCB levels in water exceeded 500 ppt and forced cessation of dredging, reasonably might be expected to produce airborne levels of PCB that exceed half of the values associated with 1000 ppt, reported by EPA (above): a minimum of 0.01, a median of 0.05, a mean of 0.08, and a maximum of 0.20 ug/M3. Among the four values, as EPA knows, the mean value is the most significant, being the airborne concentration that captures the variability of PCB levels in time and over space in and above river surface waters. Indeed, the reported mean value of 0.08 ug/M3 in air a meter above the river is equal to EPA’s Level of Concern (LOC) for airborne PCB in residential settings, as reported in EPA’s Quality Assurance Project Protocol (QAPP) for the Hudson River dredging project.

Upstream, at dredging platforms where levels of PCB in water reasonably might be expected to be 10 to 100 or maybe even 1000 times higher than five miles downstream, resulting airborne levels on average might reasonably be expected to be 10 to 100 or maybe even 1000 times higher than EPA’s LOC. EPA also has set a stop-dredging standard of 0.11 ug/M3 for airborne PCB in residential settings, and of 0.26 ug/M3 for airborne PCB in commercial or industrial (occupational) settings (as also reported in the QAPP). Both of these standards would be exceeded if airborne PCB is 10 times higher at dredge sites than at water sampling sites five miles downstream where PCB levels reach 500 ppt in water. Indeed, a 10-fold increase of the air levels over downstream sampling points would amount to 0.8 ug/M3, exceeding the residential standard of 0.11 ug/M3 by a factor of more than seven-fold, and the occupational standard of 0.26 ug/M3 by a factor of more than three-fold.

The values estimated above represent airborne levels at dredge sites occurring when downstream PCB levels in water reach the 500-ppt stop-dredging threshold, but the problem is worse than that. When values are more typical, say about a third of the stop-dredging threshold, air levels still would be predicted to exceed the airborne acceptability limit at the dredge buckets by somewhat smaller factors (one third of the factors estimated above). That is, airborne PCB levels apparently exceed EPA acceptability limits pervasively, not just occasionally during brief intervals when levels are high enough to cause EPA to order cessation of dredging.

This problem is only the tip of the iceberg, however, because it also assumes that downstream PCB levels in water were diluted only by a factor of 10-fold compared with levels at the source, at dredging platforms. In turbulent river flow, dredged PCB would mix into a much larger general river flow over a distance of five miles, probably producing dilution factors more in the range of 100-fold or maybe even 1000-fold. In that case, airborne PCB levels at dredge sites, where unprotected employees are working, would be 10-fold or maybe even 100-fold higher.

The factors estimated above represent gross exceedances of acceptability limits. The acceptability limits are not my limits; they are EPA’s limits. The problem, however, might be worse even than the exceedance factors estimated above. This is because the original EPA data relating airborne levels of PCB over a cold river to the source PCB levels in the river water do not account for dredge buckets in the Hudson River billowing sediments to the river surface as they close, and lifting sediments and water above the surface, where leakage drops sediments and water violently onto the river surface. This process must produce abundant droplets (aerosols) of various sizes, all containing PCBs, whereas air samples above river water in EPA’s original data set did not include this source of PCB. So, for occupationally exposed individuals, the relationship of PCB levels in water to levels in air must be much worse, exposing them to inhalable PCBs that are volatilized as well as to PCBs that are aerosolized. That unhealthy process happens yet again when the dredges swing their retained load over the barges, and drop them again, this time in their entirety, producing yet another burst of PCB entry into the air in the form of vapors and aerosols.

The obvious question is: why are such troubling airborne PCB levels not captured in EPA air samples to either side of the river at dredge sites? The answer is either that I am wrong, which I don’t believe, or that EPA’s sampling process is flawed in a way that causes it to miss the levels to which employees on dredge platforms actually are exposed. One major problem with EPA’s airborne sampling procedure is that samples are taken at significant distance from the dredge platform, maybe hundreds of yards away, whereas employees are right there, at zero distance away. The sampling distance is not discernible from maps of air sampling locations that EPA gave to me when I visited the Hudson River Field Office recently.

Remote sampling generally is not protective. If you work in a radioactive area, you must wear a personal radioactivity monitor that reports your personal exposure. If you work in a coal mine, you wear a personal airborne particle monitor to report your personal exposure to airborne particles (coal dust). In general, monitors are placed where they reliably capture the levels of toxic substances to which employees are potentially exposed. This is not EPA’s practice in the Hudson River PCB dredging project… and one must wonder why it is not.

A second major sampling problem is related to the first. That is, by the time air reaches the sampling units, much of the PCB has dropped out, because aerosols are heavier than vapors, and do not carry as far in air currents (wind). So, EPA samplers are capturing only a fraction of PCBs that dredge employees’ respiratory systems must be capturing. By resuming dredging with fewer dredge units, EPA will succeed at reducing PCB levels in water five miles downstream, and air levels at sampling units… but that ‘engineering control’ measure will not reduce airborne PCB levels to which employees of dredge platforms will be exposed, though it will reduce the number of exposed employees.

A third major sampling problem is that wind speed and wind direction are variable. Only a fraction of PCBs entering the air at the location of dredge platforms and employees working on them will reach the sampling units. Of course, dilution in air will have occurred even when the air blows directly toward the samplers. Air samples are 24-hour averages, however, virtually assuring that wind direction will shift, steering airborne PCBs away from sampling units.

I draw three qualitative conclusions from the above observations. The first is that airborne PCB levels to which employees and some riverfront residents are exposed via inhalation appear to exceed EPA acceptability limits significantly. The second is that the Hudson River PCB dredging project is being conducted in a manner that fails to capture and record such exceedances, if they are occurring. The third is that the burden of proof now rests with EPA to show that its pre-project predictions of no unacceptable health risks associated with PCB dredging are correct, in view of evidence clearly suggesting that they are incorrect based upon data from actual project experience elucidated here.

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

Fireside Chat: Carbon, Energy, and the U. S. Postal Service

further info: www.ramtrac.com

Achieving fiscal sustainability of U. S. Postal Service (USPS) operations may be achievable by correcting its business model and thereby also contributing to environmental sustainability. Traditionally, the USPS business model has included charging for services not delivered, and delivering services not charged. Specifically, USPS customers are charged for post office boxes, essentially for opting out of mail delivery to their home or business address. In contrast, close to 150 million home and business addresses receive mail delivery each day, at no charge, and at significant cost to the USPS for labor and energy, and to the U. S. (and planet) for the huge ‘carbon footprint’ associated with use of fossil fuel by postal vehicles.

USPS operations, despite rapidly increasing postal rates in recent years, now cost more than income generated from postage. This imbalance has resulted in fiscal losses, and stimulated proposals to cut USPS costs by reducing service, specifically by reducing the number of mail delivery days from six per week to five. This USPS fiscal problem will remain intrinsic to its business model as long as labor and energy costs are recovered by charging mail senders but not mail recipients. The energy cost of postal delivery operations can be and should be recovered via a USPS charge for home and business delivery of mail. This can be achieved via an incremental charge, or by reducing charges to senders while imposing charges on recipients to recover labor and energy costs for home and business delivery.

Accordingly, USPS need not cut home and business mail delivery from six days to five per week. Instead USPS may cut unpaid service from six days to zero days per week. Charging postal customers for home or business delivery potentially can go a long way toward balancing the USPS budget, essentially by requiring them to internalize labor and energy costs that they traditionally have externalized at USPS (and public) expense.

In this scenario, the charge to mail senders would cover the traditional service of USPS delivery of mail to addressees’ post office, where it typically is sorted to a box. Post offices would open all boxes to the public lobby, rather than just those boxes that are paid for by post office box customers opting for in-person pick-up of their mail. Post office boxes would be available for free to all customers. Instead of charging customers for box rentals, USPS would charge for home or business delivery, thereby recovering (at least) the labor and energy cost of delivery.

The resulting charge might be deemed unacceptably onerous for people in the lowest income brackets. Low-income customers also might be especially dependent upon USPS services, because they are least likely to have access to computers and e-mail. This regressive aspect of a home or business delivery charge can be addressed, for example via a tax credit granted annually to low-income customers in the amount of their annual postal delivery charge.

In this manner, USPS customers can decide whether or not the cost of home- or business-delivery is economical in their individual circumstance, or whether in-person mail pick-up is more economical. In-person pick-up might be preferred, for example by people who can walk to their post office, or by people who routinely drive by their post office on their way to or from work. Economics would be enlisted to optimize energy efficiency, in some cases by continuing home or business delivery, in other cases by discontinuing it in favor of in-person mail pick-up.

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

FIRESIDE CHAT: Hudson River PCB Dredging

further info: www.ramtrac.com

PCB levels in Hudson River water in recent days exceeded the 500-part-per-trillion (ppt) stop-dredging benchmark at Thompson Island, the northernmost water sampling point, forcing EPA to halt dredging upstream in the most contaminated zone including the area of Rogers Island at Fort Edward. EPA, however, has applied a bizarre spin on the need to cease dredging, attributing it to elevated water flow rather than to elevated PCB levels. The reality is, the General Electric Company (GE) built a pebble dam near the dredge site to slow the rate of PCB flow downstream. The reality is, PCB flow, not river flow, caused EPA to halt dredging.

By the time PCB-laden water reaches the closest water sampling points some five miles downstream of the dredge buckets, and beyond, it’s been diluted so much that the water samples come in under the 500-ppt stop-dredging benchmark that was established to protect downstream drinking water supply intakes. When the rains came, river levels rose, apparently enough to breach the pebble dam, and PCBs therefore entered the general flow, increasing PCB loads so much that downstream dilution was inadequate to reduce levels to below the benchmark. The reality is, PCB levels above the dam at Rogers Island typically must be higher… a lot higher… than the stop-dredging benchmark, but that seems okay because that’s not where water measurements are made, and it’s not where the downstream water supply intakes are located… though it is where people and homes are located. The ‘river flow’ incident is a little reminder that PCBs significantly higher than the 500-ppt stop-dredging benchmark can flow downstream, just as the low rumble you might hear at a train track should warn you that a big train is approaching.

Placement of the nearest sampling points a great distance from dredge buckets assures that actual PCB levels in water where PCBs are disturbed are not measured. The decision to measure PCB levels in water remotely from where people will be exposed suggests that close-by measurements would not be reassuring… and that maybe someone knew it when the dredging project was designed. PCBs, however, are no less toxic for being unmeasured.

Though drinking water intakes may be absent from the areas currently being dredged, PCBs in water also are known to enter the air, to a degree that can be known definitively only if air and water both are monitored where and when the dredge buckets are working. Monitoring of PCBs in air, however, also is displaced from the dredge site, a variable distance away from each dredge bucket… maybe averaging hundreds of yards. You can imagine the degree to which PCB levels decline over that distance in air by comparing the intensity of odor where a skunk sprays vs. the odor intensity hundreds of yards from the skunk. That significant reduction of odor intensity occurs because airborne concentrations of the skunk spray are reduced by air mixing with increasing distance. The reduction of concentration occurs even if the wind is blowing toward your nose but, as everyone knows, the wind blows in all directions, dispersing skunk odors and PCBs both toward and away from the nearest nose or sampling instrument.

This past week I watched, and photographed, PCB dredging from two shores of the Hudson River at Rogers Island, and found that homes are all around. One home was about 100 feet from the dredge bucket, and its back yard was probably only 20 feet away. The dredge buckets clearly were closer to homes than to air samplers, suggesting that PCB levels in air must be higher at such residential locations than at the nearest air sampling locations. Levels also must be higher onboard the dredge platforms, where a good number of people were working, all without respirators.

Employees don’t wear respirators, apparently because EPA is not very concerned about human exposure via PCB volatilization… but it should be. Indeed, EPA clearly was concerned about air levels that recently approached acceptability limits at air monitoring stations near Rogers Island. EPA acted quickly to reduce the air levels, in part by having dredge spoils spread evenly along the bottoms of barges and covered with water to reduce volatilization to the air. EPA also stopped barges containing the highest PCB levels from waiting to offload dredge spoils at the dewatering facility, instead having them proceed to the head of the line of barges to minimize the time available for volatilization to occur, even from sediments covered by a layer of water in the barges.

Dredging, ironically, was justified in part because of the fear that weather incidents and the occasional sinking of a boat or barge might disturb PCB-laden sediments. The clamshell dredging solution disturbs the sediments much more extremely. Dredge buckets in use in the Hudson River come in two sizes, hauling out one cubic yard or five cubic yards of sediment with each ‘bite’. The jaws, operated hydraulically, open much more widely than the width of the load that is hauled once the jaws close. Five-yard buckets open to nearly 15 feet, and close to about three feet. They are targeted to penetrate 18 inches into the sediment. When they close, 15 feet of river bottom is compressed to about three feet, causing sediment and water to billow upward as the jaws close. So, about 80 percent (12/15ths) of material initially enclosed in dredge jaws is disturbed without being removed.

If all of the billowing sediment returned to the river bottom, approximately five dredge passes on average would be required to pick it all up, approximately 20 percent each time. Of course, the river flows, and the billowed sediment flows, so the sediment returns to the river bottom downstream of where it was dredged. Computers limit dredge operations to a ‘dredging prism’, so if sediments return to the river bottom outside a dredging prism, they are not dredged again. Dredging prisms are defined by past PCB levels, not by PCB levels that result from settling of PCB-hot sediments on the river bottom downstream after disturbance by dredge jaws. According to EPA, the preponderance of river bottom in the current dredging area falls within dredging prisms… but this is not the case in most other river areas where PCB hotspots are designated for dredging.

Dredging is deemed complete at a dredging prism when, according to the EPA’s Quality Assurance Project Protocol, or QAPP: “an arithmetic average Tri+ PCB concentration in residual sediments of ≤ 1 mg/kg” [≤1 ppm, is attained]. Tri-plus PCB is total PCB minus the mono- and di-chlorinated PCB congeners, which EPA has estimated at about a third of total PCB… so the target levels are higher than they might seem. Target levels can be attained in two ways. One way is to mobilize the sediment, causing it to flow downstream outside the dredging prism… so success at dredging one spot is attained by dispersing the contaminants downstream. The second, intended way to succeed at PCB dredging is by removing sediments and dumping the sediment into a barge. How much occurs via the intended way, however, is unknown, because another parameter that EPA does not measure is the concentration of PCBs in the barge that ultimately is shipped to Texas for disposal of the PCB-laden dredge spoils.

One might think that PCB concentrations in barged dredge spoils are known from sampling in the river undertaken to map PCB ‘hotspots’. Arguably, we know the PCB levels in such sediments, but what we don’t know (though EPA might know it) is the fraction of dredge spoils that consist of sediments vs. solid objects such as boards, tree branches, rocks, tires, bottles, cans, and other metal objects that would not harbor much PCB. The mass of PCB shipped to Texas must be significantly less than the mass that would be estimated from PCB concentrations in sediments alone.

Shipment of dredge spoils to Texas, and disposal to a hazardous waste landfill, are expensive, consuming a sizable fraction of project costs. So, dredging represents a method of transporting not only PCBs, but also money, from New York to Texas. Texas is the home state of two presidents who together occupied the White House for 16 years during the decades-long evolution of the dredging project. The US EPA Record of Decision finally requiring PCB dredging by GE was issued in 2002, during the younger George Bush’s Administration.

As my photographs show, during dredge jaw closing sediments billow to the surface, causing PCBs to enter the air in the immediate vicinity of dredge buckets, where PCBs are neither sampled nor quantified. The dredge buckets then lift the sediment load above the river surface, where they spill more sediment and water into the river at the surface. From the surface, volatilized and aerosolized PCBs (in droplet form) enter the air at an accelerated rate because of turbulence of the process, in which air and water mix before the water falls back to the river. Such spillage is not supposed to happen with ‘environmental’ dredges. It does happen though, as my photographs also show, because the riverbed is loaded with solid objects such as the boards, tree branches, rocks, tires, bottles, cans, and other metal objects mentioned above, all of which prevent the dredge jaws from closing to form a safe seal.

In 2007 Dr. Uriel Oko and I published a fully peer-reviewed article in the Cambridge University Press journal Environmental Practice that documents massive underestimation by EPA of PCB, river, and sediment dynamics that would result in PCB entry into the atmosphere at dredge sites. The article is available at no charge at www.ramtrac.com/publications. The concerns raised in the article apparently have materialized, perhaps more severely even than we had predicted. Of course, the safety of the Hudson River dredging project as implemented currently can be assessed reliably only if proper measurements are taken to elucidate PCB levels in water and in air at dredge sites, and the relationship of the air levels to the water levels. Likewise, the effectiveness of the dredging project can be assessed reliably only when proper measurements are taken to elucidate PCB levels in dredge spoils that are sent to Texas, thereby to determine the amount removed from the river as opposed to mobilized downstream in the river. Clearly, construction of the pebble dam at Rogers Island demonstrates prior knowledge that PCB levels during dredging would be unacceptably high at dredge locations just north of the dam. Clearly, measurement of PCB in water remotely, at a closest point some five miles south of the dam, assures that such high levels would not be measured, notwithstanding the presence and potential for exposure to waterborne and airborne PCBs of unprotected residents and dredge workers.

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