NYC-WTC_000199088

NYC 9/11 Public Portal Document

Mr. Bernard P. Orlan June 18, 2002 Air Sampling for Silica Page 2 P.S. 234M ATC Project No. 15-19125-0279

Results

On both days, silica was detected in one of the seven samples as follows:

Sample #ATC-0423-234M-S5 (Room 315): 0.0172 mg/m^ Sample #ATC-0430-234M-S3 (Cafeteria): 0.0118 mg/m3

The Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) is the only regulatory standard for silica exposure, however it is intended for occupational exposure in settings such as foundries, sandblasting, rock drilling, etc. The Environmental Protection Agency (EPA) does not have an ambient-air quality standard or guideline for silica.

The OSHA PEL for silica-containing dust is based on the percent of quartz (SiO2) found in the dust, the higher the percentage of quartz, the lower the PEL. The formula for calculating the PEL is found in 29 CFR 1910.1000, Table Z-3. The formula is:

10mg/m3 %SiO2 + 2

The PELs for the silica in these samples are shown in the table:

OSHA PELS for SILICA DETECTED

April 23 Room 315 14.0 <28 0.0172 0.333 S5 April 30 Cafeteria 12.0 <24 0.0118 0.385 S3

The silica concentrations detected are well below the calculated OSHA PELs.

It is our pleasure to provide these indoor air consultative services to the New York City Board of Education. If you have any questions about this report, please contact me at (212) 353-8280, extension 212.

Sincerely, ATC Associates, I

James R. Cohn, CIH, CSP Regional Manager, Industrial Hygiene Division

Attachment

CITY_21MC100_003031260

NYC-WTC_000199089