Effect of PCB’s on New York City’s Watersheds

Besides the direct movement of PCB’s through the Hudson River, another mode of transfer that needs to be considered is through the air. The ecological impact of airborne PCBs on the New York City watershed that the river emits into the air – which in 1997 amounted to about two-thirds of the PCBs dissolved in the river.

Results also show that the airborne PCBs that have been deposited on the watershed, chiefly the more highly chlorinated (and generally more toxic) congeners, tend to accumulate there in vegetation, soil and reservoir sediments. In warm summer temperatures the accumulated PCBs vaporize; re-emitted into the air, they give rise to the unusually high airborne PCB concentration that have been measured at Frost Valley in the Neversink watershed: 1740 picograms per cubic meter.

This reflects the long-term accumulation and revolatilization process that has been underway since the Hudson River was first heavily contaminated with PCBs in 1957. According to a recent EPA report airborne PCB congeners collected at the Hudson River represent the PCBs that volatilize from the river water.

The exposures of the different watershed reservoirs and basins to the airborne PCBs emitted from the Hudson River vary considerably. The following map (Figure 14A) shows projected levels of PCBs in two of New York City’s Water considering current levels of airborne PCBs being emitted.

It now appears that this ecological hazard extends beyond the river itself. The hazards of PCB contamination is a problem for a much greater area besides those immediately surrounding the contamination site. For New York City, it’s water source is in danger.

Levels of airborne PCBs can be determined by measuring the PCB content of reservoir sediments and tree bark (which is known to accumulate PCBs); in both cases dating techniques can be used to delineate the history of PCB accumulation (in sediments, by serial analysis of layers; in tree bark, by comparative analysis of bark from trees of different ages).

The map in Figure 11 shows that the airborne contamination found in the watersheds is not only from the contaminants of the upper Hudson but in fact the whole river. The numbers written along the river represent the amount in grams of airborne PCBs released.

Taking into Account this different form of PCB contamination, there is cause for concern not only for the area immediately surrounding the upper Hudson River area but also for areas in the lower Hudson area whose watersheds, which lie reasonably close to the contaminated Hudson River are also vulnerable to contamination by PCBs.

 * To see the pictures clearly visit these links: Volatilization of PCBs,

Figure 14A, Figure 11