Table 3.
Personal exposure to benzene and 1,3-butadiene (µg/m3) among oil harbour workers and sewage tanker drivers
| Exposure group | n | N | % > LOD | µ Y | σ 2Y | µ X | 95 % CI | σ 2bY (%) | σ 2wY (%) |
|---|---|---|---|---|---|---|---|---|---|
| Benzene exposure | |||||||||
| Oil harbour workers | 21 | 34 | 79 | 3.6 | 4.3 | 310 | 80–1200 | 32 | 68 |
| Jetty workers | 13 | 20 | 90 | 4.1 | 4.1 | 470 | 96–2300 | 0 | 100 |
| Dockworkers | 8 | 14 | 64 | 2.8 | 4.6 | 170 | 12–2400 | 77 | 23 |
| Sewage tanker driver | 5 | 16 | 88 | 4.0 | 3.8 | 360 | 68–1900 | 0 | 100 |
| 1,3-Butadiene exposure | |||||||||
| Oil harbour workers | 21 | 34 | 59 | 0.5 | 1.2 | 2.9 | 1.8–4.7 | 0 | 100 |
| Jetty workers | 13 | 20 | 60 | 0.6 | 1.4 | 3.7 | 1.9–7.5 | 0 | 100 |
| Dockworkers | 8 | 14 | 57 | 0.3 | 0.9 | 2.0 | 1.1–3.7 | 0 | 100 |
| Sewage tanker driver | 5 | 16 | 75 | 0.8 | 1.8 | 5.2 | 2.1–13 | 0 | 100 |
n number of workers, N number of measurements, % > LOD percentage of samples above limit of detection (LOD). LOD for benzene was 5 µg/m3 and for 1 µg/m3 1,3-butadiene, µ Y mean (log scale) exposure
σ 2Y the total variance (log scale), µ X arithmetic mean exposure (µ X = exp(µ Y + σ 2Y/2)), CI confidence intervals for the arithmetic mean exposure, σ 2bY between-individual variance component (log scale), σ 2wY within-individual variance component (log scale)