WTC OSHA Silica Sampling Data for Staten Island Area

Please Note:

The PEL for Respirable Dust containing crystalline silica (quartz) is determined individually for each sample, using the following formula:

PEL = 10mg/m3 ÷ (%SiO2+2), where %SiO2 refers to the amount of crystalline silica measured in that sample.

This calculated PEL is compared with the Respirable Dust sample result to determine whether there is an overexposure. According to this formula, if there is no crystalline silica found in a sample, the PEL for that Respirable Dust sample is 5.0 mg/m3. As the formula implies, the PEL for respirable dust containing crystalline silica varies depending on the concentration of crystalline silica in the sample. The higher the concentration of crystalline silica the lower the PEL. (Click here for more information on the crystalline silica and the OSHA PEL.)

The Particulates not otherwise regulated (Respirable Fraction) OSHA permissible exposure limit (PEL) is 5.0 mg/m3.

aOther forms of crystalline silica (cristobalite) have not been detected in WTC samples. bResults are averaged and reported for the time duration stated. cND = Crystalline Silica None Detected.
Date Taken Operation Sample Type Duration (min) Respirable Dust TWAb mg/m3 Crystalline Silicaa (Quartz)c %b PEL mg/m3 (based on formula) Respirable Dust TWAb >PEL?
06/27/02 GRAPPLER  Personal 308 0.200 ND 5.000   
06/27/02 LABORER  Personal 295 0.120 ND 5.000   
06/06/02   Personal 335 0.120 ND 5.000   
06/06/02   Personal 300 0.030 ND 5.000   
05/22/02   Area 340 0.061 ND 5.000   
05/16/02 AREA SAMPLE  Area 297 0.120 21.00 0.435   
05/10/02   Personal 335 0.074 ND 5.000   
04/26/02   Personal 340 0.043 ND 5.000   
04/26/02   Area 368 0.017 ND 5.000   
04/19/02 AREA SAMPLE   Area 300 0.170 ND 5.000   
04/19/02 AREA SAMPLE  Area 292 0.062 ND 5.000   
04/05/02   Area 438 0.110 ND 5.000   
03/27/02 AREA SAMPLE  Area 290 0.033 ND 5.000   
03/14/02   Area 232 0.055 ND 5.000   
03/14/02   Personal 224 0.130 ND 5.000   
03/06/02 AREA SAMPLE  Area 302 0.054 ND 5.000   
03/06/02 NY FIRE DEPARTMENT  Personal 283 0.000 ND 5.000   
11/07/01   Area 311 0.081 ND 5.000   
10/23/01   Area 323 0.037 ND 5.000   
10/23/01   Area 241 0.130 ND 5.000   
10/18/01   Area 409 0.087 ND 5.000   
10/11/01 RAKER  Personal 114 0.260 ND 5.000   
10/11/01 CONVEYOR OPERATOR  Personal 127 1.000 ND 5.000