NYC-WTC_000199636

NYC 9/11 Public Portal Document

Data Limitations

These VOCs were selected for analysis because they are commonly found at low levels in outdoor and indoor air, routine analytical procedures were readily available and many have been shown to be constituents of fires. Other VOCs and semivolatile organic compounds have been found in the smoke from fires and can be expected near the site and in the smoke plume as well. Different sampling techniques are required for these compounds.

Public Health Implications

Although the highest levels of VOCs were found in samples from the plume at the WTC debris pile, these results are not likely to represent the potential exposure of the residents. Residents are unlikely to be in the plume at the debris pile where they could be exposed to these levels for any length of time. Therefore, the sampling results for areas potentially affected by the plume (i.e., at downwind locations) but not at the debris pile are more relevant for evaluating potential exposure to the residents. The levels of some of the chemicals in the plume measured at the debris are elevated and exceed typical background ranges, and recovery and emergency workers should take precautions to limit their exposure to emissions from the plume.

The levels of VOCs at the upwind sites (75 Park Place and 225 Rector) are within the range of typical background levels.

The air concentrations of VOCs at the downwind site (140 Broadway) were generally greater than those measured upwind (75 Park Place and 225 Rector) and typical background concentrations. However, none of the WTC-related chemicals measured at 140 Broadway exceed both typical background levels and air comparison values except benzene, chloromethane and styrene. Based on the available information, exposures to these chemicals from the plume are unlikely to last more than one year. Thus, in addition to typical background levels, the concentrations of the chemicals measured at 140 Broadway are evaluated with health comparison values for air based on noncancer effects and exposure durations of less than one year (e.g., acute (up to two weeks) and intermediate (up to one year) air comparison values).

None of the chemicals detected above background at 140 Broadway exceed intermediate or short-term air comparison values except benzene. The average and highest levels of benzene at 140 Broadway are slightly above typical background and are near the intermediate comparison value for this chemical. This comparison value for benzene is about 90 times lower than the exposure level that caused mild neurological effects in mice exposed regularly for 30 days.

The benzene air concentrations at 140 Broadway (as well as typical background concentrations of benzene) exceed the health comparison value for benzene in air based on carcinogenic effects following long-term exposure. The cancer comparison value is the air concentration associated with an increased lifetime cancer risk of one-in-one million (10’^). Because tjie estimated duration of exposure is at most one year, and because elevated levels are unlikely to persist for extended periods of time (e.g. the fires will be put out and the wind direction will periodically change), community exposures are not expected to result in cancer risks that are appreciably

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NYC-WTC_000199636