NYC-WTC_000204899

NYC 9/11 Public Portal Document

PM 2.5 Air Monitoring Data Summary for NYC WTC Sampling

Totals (for sampling through 02/05/02, in ug/m3) Total Samples____________ 53754 Samples above 40 ug/m3 673 Samples below 40 ug/m3 54399 Samples above 65 ug/m3 28 .vark J Samples below 65 ug/m3 54427 L 'Nrf/Vojt Percent Above 40 ug/m3 1.24 Q\..a % Above 65 ug/m3________ 0.05 Maximum Value (09/13/01 at 165.63 PS64)_________ Minimum Value___________ -50.04* Levels of Concern*________ 40.65 Average All 13.82

1% Airborne particles like smoke and dust are solids and \ C]S4iii[.hs '4jum ■ liquid droplets of Mugfru: different sizes nrunirb*. h/ilfTw • f susjoended in the air. EPA sets the level of concern s <

9S% to caution sensitive groups, including children, the elderly, and people with heart or lung disease. For fine particles, that level is 40 ug/m3 for 24-hour average exposure. This level is based on EPA's Air Quality Index . Above this level, we recommend that sensitive groups reduce their exposure. Shorter term peaks are also of potential concern for sensitive groups. The level of concern for the general population is 65 ug/m3 over a 24 hour period. Most healthy adults and children are expected to recover quickly from any symptoms of short-term exposure like coughing, wheezing, or eye and throat irritation. EPA expects the long­ term risk from these short-term exposures to be low.

*'The information contained in this database should be considered provisional and may be subject to adjustment upon final analysis. Viewers of this data are advised that changes in atmospheric conditions, particularly humidity, can affect reported hourly particulate concentrations. Changes in humidity can increase or decrease reported concentrations and in the extreme, result in negative reported values. While these effects do not invalidate daily average concentrations, viewers are cautioned that hour to hour comparisons may not always be appropriate.

CITY_21MC100_008980691

NYC-WTC_000204899