EPA interim final report on WTC background study, April 2003

NYC 9/11 Public Portal Document

APPENDIX A Hazardous Substances Not Included in Indoor Enyironment Sampling Program

Benzene

Benzene is a yolatile organic chemical (VOC) that was foimd in emissions from the open flames and smoldering debris left after the collapse of the WTC. The benzene may haye originated from the airplanes’ residual jet fuel or from the continuous burning of plastics and other materials contained within the collapsed towers.

Since the fires and smoldering debris persisted long after the collapse of the WTC towers, there is a possibility that harmful leyels of benzene yapor could haye accumulated in nearby indoor enyironments. Howeyer, because benzene is yery yolatile and dissipates into ambient air quickly, the yapor plumes would haye had to contain high concentrations of benzene, and the indoor area would haye had to be relatiyely close to the fire source in order for indoor amounts of benzene to build up to harmful leyels. In addition, unlike dioxin, benzene cannot become adsorbed by dust particles and transported indoors to settle as a long-term potential hazard. Once the source of the benzene is extinguished completely from the area, then benzene will dissipate and will not be a hazard.

Results of samples taken within the immediate WTC work zone from September 11 through mid­ January 2002, show benzene leyels of up to 180,000 parts per billion (ppb). Howeyer, tests during the same time period outside the work zone show leyels of benzene that were below the established EPA screening leyel of 20 ppb for the ambient air (see Appendix B), indicating how quickly benzene dissipates in the air. A specific example, for the day of October 3, is shown below:

From debris pile at From debris pile at From Liberty & WTC North Tower WTC South Tower Greenwich Streets 28,000-39,000 ppb 4,300 ppb less than 20 ppb

From January 26 through April 23,2002 (the most recent test date ayailable) leyels of benzene in ambient air haye remained below the 20 ppb screening leyel, except for one grab sample from the immediate work zone on February 9 and another sample from the same location on February 12. These tests indicate that the source of harmful ambient benzene leyels has been extinguished, and therefore there is no source of benzene ayailable to accumulate in any indoor enyironment. Benzene will not be monitored in any further indoor enyironment testing.

Polychlorinated Biphenyls fPCBsI

PCBs were historically used as coolants and lubricants in transfonners, capacitors, and other electrical equipment. It is possible that, with the WTC collapse, PCBs could haye been dispersed into the ambient air and then transported indoors. Howeyer, in well oyer 500 ambient air samples taken around the WTC site, no measurements were foimd aboye EPA’s screening leyel of 730 ng/m’ in the ambient air (see Appendix B). This indicates that PCBs in ambient air are not considered to be at harmful leyels, therefore, PCBs will not be monitored in indoor enyiromnent testing.

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