Saturday, October 3, 2009

FIRESIDE CHAT: Hudson River PCB Dredging and Personnel Monitoring

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Numerous General Electric Company (GE) personnel are engaged in EPA-mandated dredging of PCBs from selected ‘hotspots’ in the Hudson River. They may be exposed to PCBs occupationally if assigned, most notably, to either of two general locations: --1. on the water, including any of 12 dredging platforms or numerous supporting barges and tugboats deployed in the dredging corridor, or --2. on the land, primarily including a large dredge spoils ‘processing facility’. These two groups include at least 100 people potentially exposed occupationally, and probably closer to 200. Yet as of 17 September, after 114 days into the project, according to EPA spokesperson Kristin Skopeck, only 243 work-day personal monitoring samples for possible exposure to airborne PCB had been collected for these personnel working at the processing facility and in the dredging corridor combined.

By comparison, if 100 people instead worked in a radiation area, each person would be required to wear a radiation badge all day, every day. Personal exposure would have been monitored daily for each person on all 114 days, producing 11,400 samples. The dredging project, judged by this personal monitoring regimen, generated only two percent of the number of samples that might be expected (calculation: 100 x 243/11,400 = 2.1 percent). Further, EPA has been unable to provide a breakdown of the 243 samples to report what percent were taken in the processing facility vs. the dredging corridor, claiming that such personnel monitoring data are GE property. Thus, at this stage, available information fails to assure that any personal monitoring of dredging corridor personnel has been undertaken at all.

Even if all 243 samples were taken in the dredging corridor, monitoring two percent of workers, workdays, and work locations combined can hardly be deemed to constitute a reliable program, either for personnel protection or for air monitoring at dredge platform locations over the dredged area and project period covered. Available data could represent, at the extremes, inclusion of 100 employees on two percent of 114 days, or one employee on all 114 days. If the number of employees is closer to 200, then the personal monitoring commitment falls from just two percent to even less, closer to one percent.

The argument that personnel monitoring data, as GE property, need not be disclosed by EPA ignores an important public interest in having this information. Specifically, water sampling routinely has occurred approximately five to 6.5 miles downriver from active dredging locations. Levels of airborne PCB arise from PCB in the water: higher waterborne concentrations generate higher airborne concentrations. PCB concentrations in Hudson River water, however, have not been measured anywhere near the dredge platform locations, where concentrations must be most elevated, so PCB concentrations in air at those presumably most-contaminated locations can be known only from direct air monitoring. The public therefore, has a legitimate interest in knowing where and when airborne PCB was measured onboard dredging platforms, and whether air sampling within the dredging corridor has been adequate to characterize PCB levels in air each day and at each dredging location. Moreover, employees on the dredging platforms have a personal health interest in being protected adequately from exposure to airborne PCB, and in knowing whether or not exposure levels were excessive (and to what degree) at any time(s) during their period of duty.

EPA indicated to me that, according to GE, all personal monitors so far have reported non-detect for airborne PCB. The detection levels, however, were reported to correspond to the relatively high occupational exposure limit of 1000 ppm as a time-weighted average over an eight-hour exposure period. Thus, even if air sampling had occurred every day at every dredging location, levels might have exceeded the commercial-zone airborne PCB limit of 21 ppm and the residential-zone limit of 11 ppm as a 24-hour time-weighted average. Exceedances of these benchmark airborne PCB concentrations would be undetected unless they also exceed the occupational standard. Whether they have exceeded the occupational standard can be known only if monitoring has been adequate. The small number of personal monitors, however, strongly suggests that monitoring has not been adequate, and that airborne PCB levels at dredging platform locations are completely or nearly completely unknown.

This lack of information seems potentially serious, because EPA data relating PCB in water to PCB in air suggest that air levels must be excessive at dredging platform locations. Specifically, EPA quantified the relationship between PCB concentrations in water from a cold river and in air a meter above the river surface. For each ug/L (that is, for each 1000 ppt) of PCB in river water, PCB concentrations 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 2007 in the Cambridge University Press journal Environmental Practice. This article is available for download in its entirety, for free, at

The bottom line is that, when waterborne PCB reaches EPA’s 500-ppt stop-dredging benchmark, airborne PCB a meter above the river would be expected to be at about the mean observed value, 0.08 ug/M3. Significantly, that concentration also is EPA’s airborne PCB Level of Concern (LOC). This seems technical and maybe esoteric, until one considers that measurements of waterborne PCB have been taken five to 6.5 miles downstream of dredging locations. Waterborne PCB concentrations at locations of dredge platforms may be thousands of times higher than at locations miles away (ppm rather than ppt), or even millions of times higher (parts per thousand rather than ppt) where liquid PCB oils have been encountered (five locations, I am told by EPA). These massively higher waterborne concentrations imply massively higher airborne concentrations at dredge platform locations… nothing too esoteric about that.

Potential occupational exposure at dredging platform locations may be significantly greater than that implied by EPA’s published relationship of waterborne PCB to airborne PCB. 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 then lifting sediments and water above the surface, where leakage drops sediments and water violently onto the river surface. These processes must produce abundant droplets (aerosols) of various sizes, all containing PCBs, whereas air samples above river water in EPA’s original data did not include this source of airborne 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 near dredge platform personnel.

Though airborne PCB concentrations in the dredging corridor would seem to be higher than EPA’s stop-dredging standards as explained above, the nearest measurements are taken onshore rather than on location. EPA established a stop-dredging standard of 0.11 ug/M3 for airborne PCB in residential zones, and of 0.26 ug/M3 for airborne PCB in commercial zones. EPA also orders GE to stop dredging when the waterborne level is 500 ppt, and presumably the air level is about 0.08 ug/M3, and that has happened on multiple occasions… but the stop-dredging conditions presumptively would exist often if not perpetually at active dredging locations based upon the relationship between PCB concentrations in water vs. air above the water as elucidated by EPA and explained above.

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 preponderance of PCB entering the air. Indeed, air monitors are moved to follow dredging platforms as they move downstream, so they are relatively close to ongoing dredging. As the recently-dredged area of Hudson River surface expands, however, each onshore monitor becomes less capable of characterizing airborne PCB concentrations area-wide, as they are positioned only to capture airborne PCB from active dredges. As the recently-dredged area increases, the number of onshore monitors must increase commensurately to quantify PCB entry into air from the increasing area of affected river surface.

Onshore airborne PCB monitors also are unlikely to capture the preponderance of PCB entering the air even at the nearest active dredging platform. A major problem with EPA’s airborne PCB sampling procedure is that samples are taken at significant distance from the dredge platform, whereas employees are right there, at virtually zero distance away. Onshore sampling is inadequately protective for dredging personnel. By the time air reaches sampling units on shore, much of the PCB already 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. Further, wind speed and wind direction are variable. Only a fraction of PCBs entering the air at the location of dredge platforms (and of people working on them) will reach the sampling units. 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 four qualitative conclusions from the above observations. The first is that airborne PCB levels to which dredgers and possibly some residents at the riverfront 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 reliably 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. Finally, the fourth conclusion is that the public has an interest in having all of GE’s airborne PCB personal monitoring data made public, especially data taken in the dredging corridor.

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