Table 3.
Comparison of total aerosol measurements by decade and sampling and analytical method
| Classification | <1970s |
1970s |
1980s |
1990s |
2000s |
P-valuea | |||||
| N (n) | WAM (SD) (mg m−3) | N (n) | WAM (SD) (mg m−3) | N (n) | WAM (SD) (mg m−3) | N (n) | WAM (SD) (mg m−3) | N (n) | WAM (SD) (mg m−3) | ||
| Sampling duration (N = 7654, overall P-valueb = ***) | |||||||||||
| <2 h | 270 (2) | 3.97 (1.0) | - | - | - | - | - | - | - | NA | |
| 1–7 h | - | - | 157 (1) | 5.14 (1.97) | 221 (3) | 1.64 (1.0) | - | - | 386 (2) | 0.55 (0.28) | *** |
| Full shift | - | - | - | - | 473 (2) | 0.27 (0.13) | 5531 (6) | 0.51 (0.31) | 548 (5) | 0.56 (0.23) | *** |
| 24 h | - | - | - | - | - | - | 68 (1) | 0.46 (NA) | - | - | NA |
| P-valuea | NA | NA | *** | NS | NS | ||||||
| Sample type (N = 9379, overall P-value = ***) | |||||||||||
| Personal | 13 (1) | 15.9 (NA) | 52 (2) | 0.96 (1.21) | 434 (2) | 0.26 (0.24) | 5854 (8) | 0.50 (0.31) | 299 (5) | 0.57 (0.30) | *** |
| Area | 294 (3) | 4.93 (3.71) | 184 (3) | 4.46 (2.51) | 260 (3) | 1.45 (1.0) | 89 (2) | 0.45 (0.04) | 517 (3) | 0.55 (0.16) | *** |
| Both | - | - | 603 (1) | 2.19 (0.96) | 411 (1) | 1.87 (0.38) | 75 (1) | 0.77 (1.33) | 294 (1) | 0.63 (0.35) | *** |
| P-value | NS | NS | *** | NS | NS | ||||||
| Sampling device (N = 7957, overall P-value = NS) | |||||||||||
| Filter cassette | 270 (2) | 3.97 (1.0) | 209 (2) | 4.10 (2.58) | 173 (3) | 1.74 (1.04) | 5015 (5) | 0.49 (0.23) | 984 (6) | 0.55 (0.23) | *** |
| Impactorc | - | - | - | - | 521 (2) | 0.37 (0.44) | 659 (4) | 0.67 (0.75) | 126 (3) | 0.78 (0.12) | *** |
| P-value | NA | NA | *** | NS | * | ||||||
| Filter type (N = 7957, overall P-value = NS) | |||||||||||
| GF | 270 (2) | 3.97 (1.0) | 170 (2) | 4.88 (2.11) | 602 (4) | 0.67 (0.88) | 970 (1) | 0.52 (0.30) | - | - | *** |
| PVC | - | - | 39 (2) | 0.72 (1.46) | - | - | 34 (1) | 0.14 (0.06) | 377 (3) | 0.56 (0.18) | *** |
| PTFE | - | - | - | - | - | - | 4633 (6) | 0.51 (0.35) | 733 (5) | 0.58 (0.26) | NS |
| MCE | - | - | - | - | 92 (1) | 0.96 (0.83) | 37 (1) | 0.52 (NA) | - | - | NS |
| P-value | NA | ** | NS | NS | NS | ||||||
| Analytical method (N = 9379, overall P-value = **) | |||||||||||
| Gravimetric | 285 (2) | 5.62 (4.58) | 643 (3) | 2.12 (1.04) | 932 (3) | 1.02 (0.86) | 3191 (10) | 0.56 (0.31) | 755 (8) | 0.59 (0.21) | *** |
| Extraction | 22 (1) | 2.39 (0.72) | 196 (3) | 4.23 (2.62) | 173 (3) | 1.74 (1.04) | 2827 (5) | 0.44 (0.29) | 355 (2) | 0.54 (0.31) | *** |
| P-value | NS | NS | NS | *** | NS | ||||||
P-value = ANOVA (dependent variable = log-transformed level), *0.05 < P < 0.10; **0.01 < P < 0.05; ***P < 0.01; NS, not statistically significant; NA, not applicable because category of studies = 1; N (n), number of measurements, (no. of studies); ‘-’, no measurements.
a
P-values of multiple comparison t-test in the classification within decade or among decades.
b
P-value of ANOVA evaluating differences in the classification across decades.
c
Includes open-filter cassette.