Table 2.

Personal exposures to benzene (µg/m³) at Refinery 1 and 2

Exposure group	n/N	% >LOD	µX	95% CI	Max	µ Y	${\mathit{\sigma }}_Y^2$	${\mathit{\sigma }}_{bY}^2$ (%)	${\mathit{\sigma }}_{wY}^2$ (%)
Refinery 1
Refinery process technicians	68/132	42	15.3	10.4–22.5	3775	1.6	2.2	18	82
Outdoor process techniciansa,b	59/108	48	20.7	12.7–33.6	3775	1.7	2.6	22	78
Process area	40/71	44	9.6	6.4–15.5	144.1	1.5	1.6	9	91
Harbour and tank park	19/37	57	74.5	34.6–160.5	3775	2.2	4.1	20	80
Indoor process techniciansa	14/24	17	3.7	3.0–4.5	7.9	1.2	0.2	19	81
Maintenance workersb	34/67	22	5.9	3.7–9.4	1324	0.9	1.8	14	86
Process area	21/41	20	3.6	2.7–4.9	16.7	1.0	0.6	15	85
Harbour and tank park	10/20	25	13.3	5.9–30.3	1324	1.1	3.1	11	89
Laboratory workers	13/25	32	4.6	3.4–6.2	15.4	1.3	0.4	16	84
Engineers	21/41	27	4.5	3.0–6.7	45.6	1.0	0.9	25	75
Safety and emergency staff	7/14	43	5.1	3.9–6.6	9.9	1.5	0.2	24	76
Refinery 2
Outdoor process technicians	45/66	47	13.7	8.3–22.7	273.6	1.6	2.1	11	89
Process area	35/51	45	13.3	7.5–23.8	159.4	1.6	2.1	18	82
Tank park	10/15	53	15.8	5.1–48.4	273.6	1.7	2.2	3	97
Laboratory workers	6/11	45	8.4	3.4–20.7	20.0	1.7	0.9	77	23
Engineers	9/17	29	5.0	2.5–9.7	29.9	1.1	1.0	37	63

n number of workers, N number of measurements, % >LOD percentage of samples above the limit of detection (LOD), µ _X arithmetic mean (AM), calculated as exp(µ _Y + ${\mathit{\sigma }}_Y^2$/2) where µ _Y and ${\mathit{\sigma }}_Y^2$ are the mean and the variance of the log-transformed observations, CI confidence interval for the AM, Max maximum level detected, µ _Y and ${\mathit{\sigma }}_Y^2$ mean and variance of the log-transformed observations, ${\mathit{\sigma }}_{bY}^2$ and ${\mathit{\sigma }}_{wY}^2$ between- and within-individual variance of the log-transformed observations

^aSignificant difference in geometric mean (GM) between outdoor and indoor process technicians, p < 0.05, at Refinery 1

^bSignificant difference in GM between outdoor process technicians and maintenance workers, p < 0.01, at Refinery 1