Table 1.

Personal exposure to benzene and 1,3-butadiene (µg/m³) among refinery workers during a complete turnaround at Refinery 1

Exposure group	n	N	% > LOD	µ Y	σ 2Y	µ X	95 % CI	σ 2bY (%)	σ 2wY (%)
Benzene
Refinery workersa	24	43	91	4.6	3.7	610	230–1600	0	100
Refinery employees	15	27	93	4.5	3.1	430	140–1300	8	92
Contractorsa	9	16	88	4.7	4.9	1200	150–9500	0	100
1,3-Butadiene
Refinery workers	24	43	91	1.9	1.5	14	8.4–24	22	78
Refinery employees	15	27	96	1.9	1.4	13	7.1–24	11	89
Contractors	9	16	81	1.9	2.2	20	4.7–80	79	21

n number of workers, N number of measurements, % > LOD percentage of samples above limit of detection (LOD). LODs were 5 µg/m³ for benzene and 1 µg/m³ for 1,3-butadiene, µ _Y = mean (log scale) exposure, σ ²_Y = the total variance (log scale), µ _X = arithmetic mean exposure (µ _X = exp(µ _Y + σ ²_Y/2)), CI confidence intervals for the arithmetic mean exposure, σ ²_bY = between-individual variance component (log scale), σ ²_wY = within-individual variance component (log scale)

^aOne measurement of 2500 µg/m³ included