VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

Section VII. Comments and Future Studies Ambient concentrations of monitored substances of concern have generally decreased to background concentrations in the aftermath of the September 11 disaster. Most substances were at these backgrounds during 2002, although some exceptions were noted. Concentrations of benzene and other VOCs at the North Tower site were considerably above typical urban background as recently as early January, and air concentrations of dioxin were considerably elevated above urban background at monitors close to the WTC site through early December. The average daily benzene concentration at the North Tower was also above the OSHA PEL in early January. Concentrations of asbestos above the AHERA standard were detected in February and March.

Although the general trend of decreasing ambient concentrations for the measured pollutants is reassuring, there are limitations in the interpretation of the data. For example, very little data are available for exposures in the few days to a week immediately after September 11, and there is very little information on exposures inside residences or offices where people spend most of their time. Sampling of air and dust within residences has been conducted by ATSDR, and the results of that study are provided. This study showed very little asbestos in the air in apartments near the WTC and in the comparison apartments. However, a small number of apartments near the WTC had asbetsos detected in the dust samples while none were detected in the comparison apartments. Air and dust within 2 apartments located near the WTC were sampled on September 18. Very low concentrations of dioxin, PCBs and metals were found. However, asbestos readings were elevated in both air and dust in both apartments. EPA is now conducting extensive indoor air monitoring, and the results will be evaluated in future EPA reports.

Data do exist for reactive VOCs such as formaldehyde, acetaldehyde, or acrolein, all of which are irritants and might have been produced by the fires at WTC, but to date, these data have not been evaluated. Although the press reported the fires to be out at the WTC site on December 20, there are reports that the fires flared up on occasion in January.

From interpretation of photographs taken during the hours following the collapse of the WTC Towers, it is speculated that some people may have been exposed to the extremely high levels of ambient PM and its constituents were likely to be at risk for immediate acute respiratory and other symptoms. Fine particles or metals such as chromium and nickel in the initial dust cloud could have been irritating or sensitized individuals to further response. The cumulative risk from so many different exposures at high concentrations may well have produced effects that cannot be fully discerned by examination of exposure to individual substances. The potential for multiple chemical sensitivities is of potential concern. Also, even though data may suggest that a substance is associated with a particular effect, a quantitative guidance value may not have been developed. Thus, simply comparing ambient concentrations against known health guidance values may overlook some effects.

Further studies of potential health effects resulting from the WTC disaster are being conducted by a variety of agencies and institutions. These should help in evaluating some of the remaining uncertainties regarding exposure and human health impacts resulting from the

DRAFT-DO NOT QUOTE OR CITE 135 October 2002

NYC-WTC_000148976