Mean total dust exposure levels and FENO concentrations among controls, exposed and the exposed subgroups
| Total dust exposure (mg/m3) | FENO concentrations (ppb) | FENO categories (ppb) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Category | Ns | GM (GSD) | bw δ2 | ww δ2 | Nf | AM (SD) | Range | Median | GM (GSD) | p Value | <25 n (%) | 25–50 n (%) | >50 n (%) |
| Controls | 16 | 0.6 (1.3) | 0.000 | 0.775 | 28 | 20 (15) | 5–69 | 15 | 16 (1.9) | Ref | 21 (75) | 5 (18) | 2 (7) |
| All exposed | 126 | 5.0 (3.2) | 0.906 | 0.431 | 127 | 23 (25) | 5–168 | 15 | 16 (2.2) | 1.00* | 89 (70) | 27 (21) | 11 (9) |
| Stage I | 74 | 4.1 (3.2) | 0.951 | 0.407 | 65 | 26 (30) | 5–118 | 16 | 17 (2.4) | 1.00† | 45 (69) | 13 (20) | 7 (11) |
| Stage II | 52 | 6.3 (3.1) | 0.696 | 0.594 | 62 | 21 (19) | 5–121 | 14 | 16 (2.1) | 1.00† | 44 (71) | 14 (23) | 4 (6)‡ |
| Low exposure | 54 | 3.2 (2.7) | 0.645 | 0.400 | 63 | 25 (30) | 5–168 | 16 | 17 (2.3) | 1.00† | 44 (70) | 16 (25) | 6 (10) |
| High exposure | 72 | 8.9 (3.0)§ | 0.645 | 0.573 | 64 | 21 (20) | 5–114 | 14 | 16 (2.1) | 1.00† | 45 (70) | 14 (25) | 5 (8) |
*Independent t test for FENO between controls and all exposed.
†ANOVA test for FENO between controls and exposed subgroups.
‡χ2 Test (p=0.350).
§Mixed effects model between low and high exposure (p=0.001).
AM (SD), arithmetic mean (SD); bwδ2, between worker variance; FENO, fractional exhaled nitric oxide; GM (GSD), geometric mean (geometric SD); Nf, number of FENO measurements; ppb, parts per billion; Ref, reference group; ww δ2, within worker variance.