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   WTC OSHA Silica Sampling Data for Northwest 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?
05/29/02 AREA SAMPLE  Personal 455 0.100 ND 5.000   
05/29/02 AREA SAMPLE  Area 465 0.100 ND 5.000   
05/13/02 AREA SAMPLE  Area 450 0.026 ND 5.000   
05/04/02 DOCKBUILDER  Personal 390 0.430 6.40 1.190   
05/04/02 LABORER  Personal 420 0.190 ND 5.000   
05/03/02   Area 414 0.043 ND 5.000   
05/03/02   Personal 412 0.410 13.00 0.667   
05/03/02   Area 444 1.300 4.00 1.667   
05/01/02   Personal 445 0.160 ND 5.000   
04/27/02 NY FIRE DEPARTMENT  Personal 420 0.065 ND 5.000   
04/27/02 NY FIRE DEPARTMENT  Personal 420 0.082 ND 5.000   
04/27/02 AREA SAMPLE  Area 375 0.058 ND 5.000   
04/27/02 NY POLICE DEPARTMENT  Personal 410 0.077 ND 5.000   
04/27/02 AREA SAMPLE  Area 373 0.063 ND 5.000   
04/24/02 NY FIRE DEPARTMENT  Personal 435 0.150 ND 5.000   
04/24/02 NY FIRE DEPARTMENT  Personal 437 0.110 13.00 0.667   
04/24/02 NY FIRE DEPARTMENT  Personal 435 0.160 18.00 0.500   
04/24/02 AREA SAMPLE  Personal 475 0.110 16.00 0.556   
04/24/02 AREA SAMPLE  Area 470 0.096 ND 5.000   
04/24/02 DOCKBUILDER  Personal 299 0.420 11.00 0.769   
04/24/02 DOCKBUILDER  Personal 267 0.150 ND 5.000   
04/23/02 NY FIRE DEPARTMENT  Personal 463 0.160 ND 5.000   
04/23/02 NY FIRE DEPARTMENT  Personal 470 0.061 ND 5.000   
04/23/02 NY FIRE DEPARTMENT  Personal 472 0.070 ND 5.000   
04/23/02 NY FIRE DEPARTMENT  Personal 461 0.099 ND 5.000   
04/23/02   Personal 444 0.083 ND 5.000   
04/23/02   Personal 232 0.380 ND 0.627   
04/23/02   Personal 124 0.380 26.00 0.627   
04/23/02   Personal 423 0.310 ND 5.000   
04/23/02   Personal 516 0.150 17.00 0.526   
04/21/02 AREA SAMPLE  Area 485 0.052 ND 5.000   
04/21/02 AREA SAMPLE  Area 19 0.000 ND 5.000   
04/21/02 AREA SAMPLE  Area 475 0.130 22.00 0.417   
04/21/02 AREA SAMPLE  Area 514 0.034 ND 5.000   
04/21/02 AREA SAMPLE  Area 513 0.015 ND 5.000   
04/21/02 AREA SAMPLE  Area 480 0.000 ND 5.000   
04/20/02   Personal 419 0.074 22.00 0.417   
04/19/02   Area 462 0.330 4.90 1.449   
04/19/02   Personal 462 0.740 3.60 1.786   
04/19/02   Area 460 0.270 9.60 0.862   
04/18/02   Area 497 0.057 ND 5.000   
04/18/02   Area 446 0.059 ND 5.000   
04/18/02   Area 466 0.041 ND 5.000   
04/18/02   Personal 477 0.100 ND 5.000   
04/16/02 AREA SAMPLE  Personal 507 0.120 ND 5.000   
04/16/02 DOCKBUILDER   Personal 90 0.072 ND 5.000   
04/16/02 DOCKBUILDER  Personal 440 0.150 8.60 0.943   
04/09/02 GRAPPLER  Personal 472 0.035 ND 5.000   
04/09/02 GRAPPLER  Personal 479 0.025 ND 5.000   
04/06/02 AREA SAMPLE  Area 375 0.035 72.00 0.135   
04/06/02 AREA SAMPLE  Area 405 0.059 34.00 0.278   
04/05/02 DOCKBUILDER  Personal 422 0.280 ND 5.000   
04/05/02 DOCKBUILDER  Area 422 0.110 ND 5.000   
04/04/02 NY FIRE DEPARTMENT  Personal 457 0.100 ND 5.000   
04/04/02 NY FIRE DEPARTMENT  Personal 450 0.050 ND 5.000   
03/09/02 NY FIRE DEPARTMENT  Personal 440 0.080 ND 5.000   
03/09/02 NY FIRE DEPARTMENT  Personal 439 0.280 5.90 1.266   
03/09/02 NY FIRE DEPARTMENT  Personal 437 0.059 ND 5.000   
03/08/02 DRILLER  Personal 410 2.200 9.90 0.840  YES 
03/08/02 DRILLER  Personal 370 0.530 4.60 1.515   
02/25/02   Personal 450 0.240 ND 5.000   
02/24/02   Personal 410 0.065 ND 5.000   
02/24/02   Area 480 0.210 14.00 0.625   
02/24/02   Area 480 0.047 ND 5.000   
02/22/02   Personal 480 0.100 ND 5.000   
02/22/02   Area 435 0.046 ND 5.000   
02/21/02   Area 460 0.022 ND 5.000   
02/20/02 DOCKBUILDER  Personal 225 0.160 ND 5.000   
02/20/02 DOCKBUILDER  Personal 285 1.800 8.40 0.948  YES 
02/20/02 DOCKBUILDER  Personal 210 1.800 8.60 0.948  YES 
02/19/02 LABORER  Personal 86 3.100 7.60 1.042  YES 
02/19/02 LABORER  Personal 538 0.530 4.30 1.587   
02/01/02 GRAPPLER   Personal 450 0.035 ND 5.000   
01/29/02   Personal 495 0.140 ND 5.000   
01/18/02 LABORER  Personal 433 0.300 8.70 0.935   
01/18/02 AREA SAMPLE  Area 431 0.050 ND 5.000   
01/18/02 LABORER  Personal 430 0.066 ND 5.000   
01/12/02 SURVEY ENGINEER  Area 489 0.028 ND 5.000   
11/17/01 AREA SAMPLE  Area 292 0.130 ND 5.000   
11/17/01 AREA SAMPLE  Area 24 0.049 ND 5.000   
10/26/01   Area 402 0.610 ND 5.000   
10/26/01 CAT OPERATOR  Personal 403 0.000 ND 5.000   
10/23/01 OPERATING ENGINEER  Personal 285 0.063 ND 5.000   
10/21/01 "BOBCAT" OPERATOR  Personal 260 0.250 ND 5.000   
10/19/01 KEEPING ROADWAY CLEAR ON NORTH SIDE OF #7 WTC.  Personal 386 0.110 ND 5.000   
10/18/01 BOBCAT OPERATOR  Personal 378 0.057 ND 5.000   
10/16/01 POLICE OFFICER  Personal 354 0.028 ND 5.000   
10/14/01 CSHO  Personal 355 0.037 ND 5.000   
10/14/01 LABORER  Personal 345 0.000 ND 5.000   
10/11/01   Area 324 0.086 ND 5.000   
10/10/01 OPERATING ENGINEER  Personal 343 0.250 ND 5.000   
10/10/01 GRAPPLER OPERATOR  Personal 435 0.180 ND 5.000   
10/10/01 IRONWORKER-BURNER/CUTTER  Personal 111 2.300 ND 5.000   
10/10/01 "BOBCAT" OPERATOR  Personal 152 0.230 ND 5.000   
10/10/01 LABORER  Personal 140 0.970 ND 5.000   
10/09/01 GRAPPLER/CLAW OPERATOR/OPERATING ENGINEER  Personal 336 0.033 ND 5.000   
10/09/01 GRAPPLER/CLAW OPERATOR/OPERATING ENGINEER  Personal 296 0.016 ND 5.000   
10/07/01 EXCAVATOR OPERATOR/OPERATING ENGINEER  Personal 210 0.220 ND 5.000   
10/05/01   Area 357 0.073 ND 5.000   
10/04/01   Area 349 0.210 ND 5.000   
10/04/01   Area 325 0.110 ND 5.000   
10/02/01 GENERAL LABORER  Personal 345 0.210 ND 5.000   
10/02/01 TORCH CUTTER/BURNING  Personal 335 0.160 ND 5.000   
09/30/01 TORCH CUTTER/BURNING  Personal 335 0.310 ND 5.000   
09/30/01 EXCAVATOR OPERATOR/OPERATING ENGINEER  Personal 74 0.000 ND 5.000   
09/30/01 LABORER  Personal 290 0.063 ND 5.000   
09/27/01 GRAPPLER OPERATOR  Personal 285 0.056 ND 5.000   
09/27/01   Area 200 0.120 ND 5.000   
09/22/01 BLDG 7, EAST CORNER  Area 269 2.900 < 1.00 3.333   
 
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