Phase I of GE’s EPA-mandated Hudson River PCB dredging project involves about 90 acres of river divided into 18 five-acre work areas (‘units’). Up to 12 dredging platforms were deployed at any given time, though usually fewer, with only one platform working in any unit. The obvious parameters relevant to this effort included waterborne and airborne PCB levels, as well as employees’ personal exposure to airborne PCB. None of these parameters was measured, or measured adequately.
Personal exposure. According to EPA, employees’ personal exposure was measured. As of my data request, on 16 September 2009, 143 days into Phase I, EPA indicated that GE had generated 243 samples among employees in the dredging corridor and those in the dredge spoils processing facility combined. The figure below shows that this number is significantly less than one percent of the number of samples that would be expected. Indeed, GE had reported that over 500 employees were involved in the dredging project. Assuming conservatively that only 300 employees were potentially exposed to airborne PCB in three eight-hour shifts per day with 100 employees per shift, one would expect GE to have generated 34,200 personal monitoring samples, more than 100 times the number actually reported.
Waterborne PCB. Waterborne PCB in the Hudson River is the primary source of airborne PCB. Indeed, EPA studied the relationship of waterborne PCB in a cold river to airborne PCB a meter above the river surface. That produced the EPA Level of Concern (LOC) for airborne PCB of 0.08 ug/M3, associated with EPA’s Maximum Contaminant Level (MCL) for PCB of 500 ppt in water. Generated primarily by dredging, waterborne PCB therefore should be measured where dredging occurs… but that was not done. Instead of sampling at Rogers Island, water was sampled, and waterborne PCB measured, about five miles downstream of Rogers Island. As a result, waterborne PCB concentrations at dredging sites are anyone’s guess, specifically determined by anyone’s guess about the applicable dilution factor that occurs as dredge-mobilized material travels five miles downstream.
Airborne PCB. Just as waterborne PCB concentrations at dredging locations are anyone’s guess, airborne PCB concentrations at dredge sites also are anyone’s guess, because airborne PCB was not routinely measured (and might not have been measured at all) at dredging platforms. As mentioned above, EPA reported that GE had generated 243 personal monitoring samples for personnel engaged in dredging. These samples might seem to be useful as indicators of community airborne PCB concentrations, but EPA was unable to indicate how many of the 243 personal monitoring samples originated from the dredging corridor or, for that matter, whether any of them originated from the dredging corridor. They all could have originated from the dredge spoils processing facility and, indeed, blown-up photographs of personnel on a dredge platform revealed no sign of air samplers worn on their person. (Further, EPA indicated that the personal samples are the property of GE, and therefore not subject to a requirement of public disclosure. The samples were reported all to be negative, but the threshold detection limit was the OSHA occupational limit for PCB of 1000 ug/M3, which is far higher than airborne concentrations that would be of concern relative to EPA’s residential and commercial limits.)
Airborne PCB was monitored by two portable air samplers set up adjacent to each dredge platform, on opposite shores of the river. These samplers recorded 24-hour average concentrations of airborne PCB. Three problems undermine the usefulness of these monitors. First, personnel engaged in dredging are exposed to aerosols generated at the dredge platform, which reasonably would be expected to fall back to the river surface before reaching monitors on shore, except when wind speed is adequate to transport them as far as the shore, and when wind direction is aimed at the portable monitor. In those cases, of course, only one monitor would record the PCB, as the wind would be blowing away from the monitor on the opposite shore. Second, wind direction varies, so each air monitor would be pumping air originating from 360 degrees, not primarily from the direction of the dredge platform to which it is adjacent. This is illustrated in the figure below, in which red arrows represent air originating from the dredge platform, and the preponderance of black arrows represent air originating from other directions.
The figure above also illustrates how, as the dredge platform moves downstream, the angle from which PCB might impinge on the portable monitor increases. Thus, a time series should show increasing airborne PCB concentrations as the surface area of dredged river increases. This observation cannot actually be made, however, because GE procedures call for moving each portable air monitor downstream with the dredge platform, so no monitor remains to record evolving airborne PCB concentrations at any former dredge site. Indeed, as the area of dredged river surface increases to its maximum, the concentration of airborne monitors per acre of dredged river declines in direct proportion, because no monitors are added to cover the increased area of dredged river.
This gives rise to the third problem: that PCB volatilization might not reach a steady state until long after the portable air monitors are withdrawn downstream with the dredge platforms. Indeed, PCB release from the river surface might not reach steady state rates until long after Phase I is complete. By then, portable monitors would have been withdrawn, not only to points downstream, but altogether.
One strategy to rectify this egregious situation, at least partially, might be effective: examining meteorology data to determine the fraction of time when wind direction was toward a portable air sampler on shore. If the fraction of time was, say, one percent, then the airborne concentration from the point of origin (the dredge platform) would have been at least 100 times higher than the concentration reported by the sampling unit (“at least,” because the sampling unit would not have recorded PCB-bearing aerosols that had precipitated back to the river surface before reaching shore). I do not know if the required meteorology data are available.
The observations reported above give rise to several conclusions and recommendations, as follows:
Conclusion 1: Water monitoring miles downstream of dredging is inadequate to characterize PCB mobilization.
Conclusion 2: Air monitoring using portable air samplers on shore is inadequate to quantify either residential or commercial exposure to airborne PCB.
Conclusion 3: Personal monitoring of GE dredging personnel as implemented in Phase I is inadequate to quantify occupational exposure to airborne PCB.
Conclusion 4: Levels of airborne PCB probably are higher than suggested by available data, and possibly unsafe.
Conclusion 5: Hudson River PCB dredging is making exposed people into experimental subjects, and riverfront communities into the subjects of epidemiology studies that will continue for generations to come.
Recommendation 1: Water and air monitoring, including personal monitoring, should occur together at dredge platforms.
Recommendation 2: Permanent arrays of air and water samplers are needed to confirm or refute EPA safety claims, and to protect public and environmental health.
Recommendation 3: Dredging Project Phase I evaluation should consider all issues, most notably including possible cessation of dredging.
Copyright © 2009 by The Center for Health Risk Assessment and Management, a Division of RAM TRAC Corporation