WTC environmental health assessment draft, May 2002

NYC 9/11 Public Portal Document

The following substances were either not detected in the ambient air sampling around the WTC or were detected in very few cases, usually below EPA screening levels of concern. A-strrrrmary of the reasons why some chemicals might not be found around the WTC is provided below. Full discussion of the reasons these substances were not recommended for monitoring in the indoor environment is provided in Appendix A.

Chemical Reason Benzene Benzene is very volatile and dissipates into ambient air quickly. This is confirmed by results of air monitoring around the WTC. PCBs All measurements of ambient PCB in ambient air around the WTC work zone have been well below EPA’s screening level of concern.

Chromium Eevcls All measurements of chromium measured in ambient air around the WTC work zone have aH been below the EPA’s screening level of concern. Cadmium & Cadmium was not detected in air sampling, except in one sample at Manganese a level equal to EPA’s screening level. Manganese was found in only three samples that were above EPA’s screening level.

Mercury Although mercury was found once in police officers’ blood tests, the cause was determined to be canned tuna fish, not ambient air. Mercury has not been detected in any air samples taken in the WTC area. A study of indoor and outdoor WTC dust samples showed that it is unlikely that harmful levels of mercury could ever be released to the air. Particulate Ambient monitoring in the WTC area has shown that, since late Matter (PM) October, levels of PM 10 and PM 2.5 (two comrnonly measured inhalable PM sizes) have been below the EPA’s level of concern, indicating that there is no continuing source PM entering homes and offices.

The health-effects of the remaining substances were studied so that clean-up levels could be established.

Setting Benchmarks for the Contaminants of Potential Concern (COPCs)

A tiered approach was used to evaluate the health risks posed by any contaminants that might be present in ±e indoor environment (air and dust). For each COPC, three levels were established:

Tier I Level above which aggressive clean-up action should be taken

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CONFIDENTIAL CITY_21MC100_003423790 SUBJECT TO PROTECTIVE ORDER NO. 2, SEPT. 2008

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