Agent | Non-Hodgkin's lymphoma | Chronic lymphocytic leukaemia | Multiple myeloma | |||
Cases | Controls | Cases | Controls | Cases | Controls | |
N (%) | N (%) | N (%) | N (%) | N (%) | N (%) | |
Extremely low frequency magnetic fields | ||||||
Highest level of exposure* | ||||||
Background level | 41 632 (60.4) | 205 054 (59.5) | 12 654 (61.4) | 62 874 (61.0) | 22 397 (63.1) | 110 680 (62.4) |
Low level | 23 063 (33.4) | 116 584 (33.8) | 6525 (31.4) | 32 768 (31.8) | 10 944 (30.9) | 55 344 (31.2) |
High level | 4283 (6.2) | 23 252 (6.7) | 1436 (7.0) | 7433 (7.2) | 2126 (6.0) | 11 311 (6.4) |
Cumulative exposure (tertiles of exposure†) | ||||||
0 unit-years‡ | 41 632 (60.4) | 205 054 (59.5) | 12 654 (61.4) | 62 874 (61.0) | 22 397 (63.1) | 110 680 (62.4) |
1–20 unit-years | 10 384 (15.1) | 52 127 (15.1) | 2490 (12.1) | 12 601 (12.2) | 4380 (12.3) | 21 672 (12.2) |
21–30 unit-years | 4091 (5.9) | 21 160 (6.1) | 1091 (5.3) | 5328 (5.2) | 1674 (4.7) | 8605 (4.9) |
31–164 unit-years | 12 871 (18.7) | 66 549 (19.3) | 4380 (21.2) | 22 272 (21.6) | 7016 (19.8) | 36 378 (20.5) |
Electric shocks | ||||||
Highest level of exposure* | ||||||
Background levels | 286 201 (69.1) | 237 808 (69.0) | 14 249 (69.1) | 69 896 (67.8) | 25 098 (70.8) | 124 835 (70.4) |
Low levels | 76 595 (18.5) | 64 195 (18.6) | 3731 (18.1) | 19 418 (18.8) | 6291 (17.7) | 31 478 (17.8) |
High levels | 51 072 (12.3) | 42 887 (12.4) | 2635 (12.8) | 13 761 (13.4) | 4078 (11.5) | 21 022 (11.9) |
Cumulative exposure (tertiles of exposure) | ||||||
0 unit-years‡ | 48 393 (70.2) | 237 808 (69.4) | 14 249 (69.1) | 69 896 (67.8) | 25 098 (70.8) | 124 835 (70.4) |
1–20 unit-years | 5795 (8.4) | 29 544 (8.6) | 1428 (6.9) | 7571 (7.3) | 2498 (7.0) | 12 219 (6.9) |
21–35 unit-years | 8094 (11.7) | 42 515 (12.4) | 2644 (12.8) | 13 873 (13.5) | 4422 (12.5) | 22 363 (12.6) |
36–164 unit-years | 6696 (9.7) | 35 023 (10.2) | 2294 (11.1) | 11 735 (11.4) | 3449 (9.7) | 17 918 (10.1) |
*The cut-off points were 0.15 µT and 0.30 µT; taking the highest exposure levels for each participant.
†Tertiles of exposure distribution among exposed controls used as cut-off points.
‡Job duration multiplied by weights based on the distribution of the intensity of extremely low frequency magnetic field exposure over the occupations to exposure rating (ie, background 0, low 1, high 4).