NYC-WTC_000205194

NYC 9/11 Public Portal Document

• Respirable Silica: The overwhelming majority of 835 silica samples (excluding bulk and blank samples) show no detectable levels of airborne silica. However, 54 exposures exceeded the PEL. The highest sample result was approximately twenty-one times the OSHA limit (jack hammering concrete 16 feet below grade). The other elevated exposures were approximately one to fourteen times the OSHA limit. These exposures occurred during; 1) pre-drilling/slurry wall 2) jack hammering, 3) rubble removal and loading operations near the Winter Garden; 4) during the breaking up of concrete in the pit; 5) while drilling the concrete slurry wall, 6) flagging operations in pit, and 7) while chipping concrete with power tools during demolition activities at 7 WTC’s parking garage. Most of the work areas where apparent overexposures to silica occurred were in the rubble pile/pit; an area where OSHA continues to encourage the use of respiratory protection. Organic Compounds: OSHA has taken a total of 650 samples (excluding bulk and blank samples) for organic compounds such as acetaldehyde, acrolein, acrylonitrile, benzene, 2-butanone, carbofurans, dioxin, PCBs, ethyl benzene, formaldehyde. Freon R-22 (chlorodiflouromethane), hexone, isocyanates (e.g. MDI, TDI), perchloroethylene, polynuclear aromatics, phosgene, styrene, toluene, 1-3 butadiene, trichloroethylene, vinyl chloride, glutaraldehyde, and xylene. Screening samples initially showed elevated levels of some organic chemicals resulting from the fires burning in the rubble pile. Subsequent personal and area samples show worker exposure levels to be below OSHA limits. However, one personal sample result for a benzene sample taken was found to be at the 8-hr. OSHA Allowable Limit concentration of 1 ppm. This was found on a backhoe operator moving debris on 10/7/01. See information below for the specific counts in regards to polynuclear aromatics, Freon R-22, phosgene and dioxin.

Dioxins: OSHA has taken 10 dioxin samples (excluding blanks) in the plume over hot spots in (and around the perimeter of) the rubble pile. Dioxin levels detected

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NYC-WTC_000205195