Table 1

Cumulative exposures* and observation time within job groups of tunnel construction workers

	Units	Drill and blast workers (n = 115)		Tunnel concrete workers (n = 69)		Shotcreting operators (n = 22)		TBM workers (n = 3)		Outdoor concrete workers (n = 220)		Foremen (n = 67)		Engineers (n = 155)
	Units	AM†	SD‡	AM	SD	AM	SD	AM	SD	AM	SD	AM	SD	AM	SD
*Cumulative exposure adjusted for sick leave.
†Arithmetic mean.
‡Arithmetic standard deviation.
§Not measured. Cumulative exposure was computed using the same AM exposure as drill and blast workers.
¶Not measured. Cumulative exposure was computed by assuming exposure the same as ambient air levels (15 ppb nitrogen dioxide, and 0.5 ppm carbon monoxide, Norwegian Institute for Air Research, Kjeller, Norway).
**Not measured. Assigned a mean concentration of the limit of detection of the electrochemical sensor (2 ppm).
Observation time	y	5.9	2.5	6.1	3.0	6.0	3.4	7.1	3.2	5.7	3.9	6.3	3.0	6.1	2.6
Cumulative exposures
Total dust	mg⋅y/m³	18	7.8	21	11	73	41	48	20	6.5	3.4	0.78	1.3	0.27	0.78
Respirable dust	mg⋅y/m³	6.3	2.8	6.1	3.1	19	11	16	6.6	1.4	0.73	0.28	0.48	0.09	0.28
α-quartz	mg⋅y/m³	0.23	0.10	0.35	0.18	0.10	0.057	3.6	1.5	0.019	0.010	0.010	0.018	0.003	0.010
VOC	mg⋅y/m³	25	11	3.4	1.7	98	55	12	4.9	9.6	5.1	1.1	1.9	0.37	1.1
Oil mist	mg⋅y/m³	1.9	0.82	2.7	1.4	3.0	1.7	0.55	0.23	0.99	0.52	0.082	0.14	0.028	0.081
Oil vapour	mg⋅y/m³	29	13	12	6.1	28	15	2.1	0.88	17	8.8	1.3	2.2	0.43	1.3
Formaldehyde	ppm⋅y	0.13	0.056	0.11	0.055	0.13§	0.072	0.16§	0.066	0.033	0.017	0.006	0.010	0.002	0.006
Nitrogen dioxide	ppm⋅y	4.1	1.8	4.8	2.4	3.3	1.8	1.3	0.55	0.083¶	0.044	0.18	0.31	0.062	0.18
Carbon monoxide	ppm⋅y	67	29	30	15	19	11	13**	5.5	2.7¶	1.5	2.9	5.1	1.0	2.9