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The U.S. Environmental Protection Agency (EPA) and other federal, state and local agencies have collected extensive environmental monitoring data from the World Trade Center site and nearby areas in Manhattan, Brooklyn and New Jersey. Since September 11, EPA has taken samples of the air, dust, water, river sediments and drinking water and analyzed them for the presence of pollutants that might pose a health risk to response workers at the World Trade Center site and the public. The samples are evaluated against a variety of benchmarks, standards and guidelines established to protect public health under various conditions. EPA is collecting data from 19 fixed air monitors in and around ground zero and is using portable sampling equipment to collect data from a range of locations.
Ambient Air Sampling:
PM 2.5 - Monitoring for fine particulate matter (particles less than 2.5 micrometers in diameter) was conducted on October 19 and October 20 at Pace University, the Borough of Manhattan Community College and the U.S. Coast Guard building located in Battery Park. All 24-hour averages were below the National Ambient Air Quality Standards (65 ug/m3) for all stations.
Particulate Monitoring - Samples collected on October 20 and October 21 using personal monitors at fixed air monitoring map locations L (north east side of Stuyvesant High School), R (north west side of Stuyvesant) and N (south side of Pier 25) were all below the OSHA time weighted average for particulates.
VOCs - Sampling for volatile organic compounds (VOCs) was conducted on October 19, 20 and 21 in the plume on the debris pile. For each of the days, benzene exceeded the OSHA time weighted permissible exposure level at one debris pile location in the smoke plume at ground level.
Direct Readings - Direct readings were taken October 19, 20 and 21. On October 19 and 20, there were no significant readings noted. On October 21, there was an overall increase in carbon monoxide readings taken throughout the monitoring area in lower Manhattan. Several direct readings of carbon monoxide were detected above the National Ambient Air Quality Standard (NAAQS) 8-hour average of 9 parts per million (ppm), but below the NAAQS 1-hour average of 35 ppm and the OSHA permissible level of 50 ppm.
PAHs - Two dust samples were collected on October 10 from rooftops in the vicinity of the World Trade Center and analyzed. Both samples showed elevated levels of polyaromatic hydrocarbons (PAHs) above EPA action guidelines, which are based on a 30-year exposure. Neither sample was above the action guideline adjusted to a one-year exposure. The rooftop location limits the potential for exposure. Roofing material may also have contributed to these results. Dust samples collected on September 16 at street-level locations had significantly lower PAH levels.
U.S. Government Website