Table 1.
Summary statistics of primary manufacturers by process and instrument.
| Summary statistic by instrument | |||||||||||||||||
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| Sample characteristics | CPC | DustTrak | DC | ||||||||||||||
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| Particle concentration | Mass concentration | Surface area | |||||||||||||||
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| particles cm−3 | mg m−3 | μm2 cm−3 | |||||||||||||||
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| Site | Material, quantity handled |
Process | n | GM | GSD | Max | Adjusted P-valuea |
n | GM | GSD | Max | Adjusted P-valuea |
n | GM | GSD | Max | Adjusted P-valuea |
| A | MWCNT, DWCNT 40–50 g day−1, powder form(15 nm diameter; 100 μm length) | Outdoor backgroundb | 510 | 2.9E+03 | 1.54 | 3.07E+04 | — | 513 | 0.035 | 1.35 | 0.330 | — | — | — | — | — | — |
| MWCNT production-A | 132 | 1.01E+04 | 1.55 | 2.69E+04 | 0.000 | 131 | 0.026 | 1.15 | 0.053 | 0.000 | 182 | 8.8 | 2.00 | 45 | — | ||
| MWCNT production-B | 52 | 2.1E+03 | 1.14 | 2.8E+03 | 0.000c | 52 | 0.019 | 1.07 | 0.022 | 0.000c | — | — | — | — | — | ||
| Harvesting DWCNTs | 6 | 3.18E+04 | 1.04 | 3.32E+04 | 0.000 | 6 | 0.032 | 1.04 | 0.035 | 0.008 | 6 | 33.5 | 1.28 | 47 | — | ||
| Harvesting MWCNTs | 45 | 3.18E+04 | 1.04 | 3.44E+04 | 0.000 | 45 | 0.032 | 1.07 | 0.037 | 0.001 | 45 | 24.7 | 1.39 | 42 | — | ||
| Harvesting MWCNTs (second batch) | 17 | 8.7E+03 | 1.02 | 8.9E+03 | 0.000 | 17 | 0.036 | 1.04 | 0.040 | 0.000 | 17 | 38.3 | 1.18 | 59 | — | ||
| B | SWCNT 5–15 g day−1, powder form(1.1 nm diameter; 2 μm length) | Outdoor backgroundb | 283 | 5.8E+03 | 1.35 | 4.02E+04 | — | 289 | 0.037 | 1.14 | 0.083 | — | — | — | — | — | — |
| SWCNT production | 30 | 1.12E+04 | 1.87 | 4.36E+04 | 0.315 | 41 | 0.023 | 1.19 | 0.046 | 0.000 | 41 | 23.0 | 1.65 | 64 | — | ||
| harvesting SWCNTs | 8 | 5.9E+03 | 1.09 | 6.9E+03 | 0.142 | 8 | 0.017 | 1.03 | 0.018 | 0.000 | 8 | 15.6 | 1.37 | 26 | — | ||
| Reactor clean-out | 20 | 1.43E+04 | 2.43 | 7.69E+04 | 0.275 | 17 | 0.022 | 1.04 | 0.026 | 0.000 | 17 | 21.4 | 3.03 | 69 | — | ||
| Outdoor background (Day 2) | 113 | 8.9E+03 | 1.55 | 5.35E+04 | — | 299 | 0.046 | 1.40 | 0.077 | — | — | — | — | — | — | ||
| Indoor background (Day 2) | 38 | 8.5E+03 | 1.35 | 1.72E+04 | 1.00d | 38 | 0.033 | 1.09 | 0.043 | 0.434d | 38 | 7.4 | 2.01 | 24 | — | ||
| SWCNT production-A (Day 2) | 113 | 9.0E+03 | 1.46 | 2.92E+04 | 1.000 | 159 | 0.040 | 1.27 | 0.067 | 0.431 | 161 | 13.8 | 1.73 | 43 | 0.001e | ||
| SWCNT production-B (Day 2) | 48 | 6.0E+03 | 1.28 | 1.17E+04 | 0.181c | — | — | — | — | — | — | — | — | — | — | ||
| Harvesting SWCNTs (Day 2) | 19 | 1.01E+04 | 1.69 | 2.17E+04 | 1.00d | 19 | 0.041 | 1.07 | 0.046 | 0.008 | 19 | 14.6 | 1.47 | 28 | 0.000e | ||
| Reactor clean-out (Day 2) | 25 | 6.6E+03 | 1.46 | 1.23E+04 | 1.00d | 25 | 0.016 | 1.12 | 0.028 | 0.000 | 25 | 13.5 | 1.79 | 72 | 0.004e | ||
| C | MWCNT 50–100 g day−1, powder and aqueous forms(15 nm diameter; 15 μm length) | Outdoor Backgroundb | 210 | 7.9E+03 | 1.43 | 2.58E+04 | — | — | — | — | — | — | — | — | — | — | — |
| Indoor Background | 22 | 1.23E+04 | 1.10 | 1.45E+04 | 0.000d | 26 | 0.038 | 1.02 | 0.041 | — | 25 | 61.8 | 1.11 | 72 | — | ||
| Harvesting MWCNTs | 20 | 1.21E+04 | 1.05 | 1.40E+04 | 0.000d | 20 | 0.037 | 1.02 | 0.047 | 0.113e | 20 | 55.2 | 1.27 | 86 | 0.197e | ||
| MWCNT Production-A | 204 | 1.53E+04 | 2.79 | 9.79E+04 | 0.161 | 319 | 0.044 | 1.08 | 0.050 | 0.000e | 319 | 63.4 | 1.53 | 159 | 1.000e | ||
| MWCNT Production-B | 91 | 1.13E+04 | 2.33 | 9.51E+04 | 0.000c | — | — | — | — | — | — | — | — | — | — | ||
| Harvesting second batch of MWCNTs | 23 | 4.4E+03 | 1.03 | 4.6E+03 | 0.000d | 20 | 0.032 | 1.04 | 0.035 | 0.000e | 20 | 44.3 | 1.63 | 104 | 0.232e | ||
| Outdoor background (Day 2)b | 240 | 5.5E+03 | 1.57 | 3.33E+04 | — | — | — | — | — | — | — | — | — | — | — | ||
| Indoor background (Day 2) | 26 | 3.2E+03 | 1.04 | 3.4E+03 | 0.00d | 7 | 0.011 | 1.02 | 0.012 | — | — | — | — | — | — | ||
| Sonication-A (Day 2) | 71 | 7.4E+03 | 1.30 | 1.44E+04 | 0.136 | 94 | 0.011 | 1.02 | 0.012 | 0.049e | 85 | 31.9 | 1.75 | 93 | — | ||
| Sonication-B (Day 2) | 23 | 3.5E+03 | 1.07 | 4.0E+03 | 0.041c | — | — | — | — | — | — | — | — | — | — | ||
| Spray coating and sieving-A (Day 2) | 150 | 3.21E+04 | 1.43 | 4.75E+04 | 0.000 | 166 | 0.012 | 1.08 | 0.017 | 0.002e | 165 | 30.4 | 1.61 | 66 | — | ||
| Spray coating and sieving-B (Day 2) | 16 | 4.26E+04 | 1.05 | 4.73E+04 | 0.000c | — | — | — | — | — | — | — | — | — | — | ||
Note: All P-values were adjusted using a Bonferroni adjustment for the number of subtasks in a given day.
Default P-values were computed using a paired analysis compared with either indoor or outdoor background; all statistical tests accounted for autocorrelation of data using a second-order autoregressive model.
Outdoor background used for paired analysis compared with process measurements.
No completely concurrent background sample collected, compared with averaged background measurements during concurrently sampled process.
Compared with entire day outdoor background since no concurrent outdoor background collected during entire process.
Compared with indoor background since no outdoor background samples were collected.