Occupational Exposures to Air Contaminants at the World Trade Center Disaster Site—New York, September–October, 2001

Abstract

and Health (NIOSH) collected general area (GA) and personal breathing zone (PBZ) air samples for numerous potential air contaminants. This report summarizes the results of the assessment, which indicate that most exposures, including asbestos, did not exceed NIOSH recommended exposure limits (RELs) or Occupational Safety and Health Administration (OSHA) permissible exposure limits (PELs) (1,2). One torch cutter was overexposed to cadmium; another worker was overexposed to carbon monoxide (CO) while cutting metal beams with an oxyacetylene torch or a gasoline-powered saw, and two more were possibly overexposed to CO. NIOSH recommended that workers ensure adequate on-site ventilation when using gas-powered equipment and use rechargeable, battery-powered equipment when possible.Toxic substances of concern included asbestos (from insulation and fireproofing materials), concrete (made from Portland cement and used in the buildings' construction) and the crystalline silica it contained, CO (from fires and engine exhaust), diesel exhaust (from vehicles and equipment), mercury (from fluorescent lights), chlorodifluoromethane (Freon ™ -22, from air conditioning systems), heavy metals (from building materials), hydrogen sulfide (from sewers, anaerobically decomposing bodies, and spoiled food), inorganic acids, volatile organic compounds (VOCs), and polynuclear aromatic hydrocarbons (PAHs) (from fires and engine exhaust). Environmental sampling during September 18-October 4 focused on search-and-rescue personnel, heavy equipment operators, and workers cutting metal beams (Figure 1) but also included various other occupations. A total of 1,174 air samples was collected, including 804 for asbestos. NYCDOH contractors collected most of the asbestos samples; NIOSH personnel collected all other samples. In addition, NIOSH collected 33 bulk samples of dust, debris, and other materials. All samples were collected and analyzed according to the NIOSH Manual of Analytic Methods (3) with some modifications. A total of 29 bulk samples of undisturbed settled material from various locations was analyzed for asbestos; 27 of these also were analyzed for crystalline silica and metals. Of the 29 samples, 26 (90%) had <1% asbestos (by mass); the three others had 1%-3%. All but one of 27 samples had crystalline silica; concentrations (by mass) ranged from 0-18%, with a median (for all 27 samples) of 3.2%. The most abundant metals in the samples were calcium, magnesium, aluminum, iron, and zinc. Lead, arsenic, cadmium, and beryllium concentrations (by mass) were <0.1%. Three bulk samples of fireproofing material on I-beams from the main debris pile were analyzed for asbestos; one was negative, and two had <1% asbestos. A sample of paint from a metal beam had 0.3% lead.Phase contrast microscopy (PCM) revealed fibers in 358 (45%) of the 804 asbestos air samples. Excluding 30-minute samples, 25 samples had fiber concentrations that, if the fibers had been asbestos, would have exceeded the REL of 0.1 fibers per cubic centimeter of air (f/cc) (1)....