Table 4

Relative risks of mortality from brain tumours and all other causes by levels of estimated exposure to magnetic fields received in preceding 5 years (four separate analyses), study of United Kingdom electricity generation and transmission workers, 1973–94

Exposure to magnetic field received in preceding 5 years (μT.y)4-151 n RR4-152  (95% CI) RR4-153  (95% CI)
Brain tumours:4-154
 Zero861.01.0
 0.01–0.49170.94 (0.56 to 1.59)0.99 (0.58 to 1.69)
 0.5–1.9130.95 (0.53 to 1.72)0.98 (0.54 to 1.81)
 2.0–4.960.63 (0.27 to 1.45)0.64 (0.28 to 1.50)
 ⩾5.020.40 (0.10 to 1.63)0.42 (0.10 to 1.74)
RR/μT.y4-164 0.91 (0.81 to 1.03)0.92 (0.82 to 1.03)
All other causes:4-161
 Zero75031.01.0
 0.01–0.4911591.04 (0.97 to 1.10)0.94 (0.88 to 1.00)
 0.5–1.96680.93 (0.86 to 1.01)0.824-165 (0.75 to 0.89)
 2.0–4.93740.824-165 (0.74 to 0.91)0.724-165 (0.65 to 0.81)
 ⩾5.01870.824-160  (0.71 to 0.95)0.724-165 (0.62 to 0.83)
RR/μT.y4-164 0.984-165 (0.96 to 0.99)0.964-165 (0.95 to 0.97)
  • 4-150 p<0.05;

  • 4-160 p<0.01;

  • 4-165 p<0.001.

  • 4-151 1 Year refers to a working year, about 250 8 hour shifts.

  • 4-152 Analysed simultaneously with sex and attained age.

  • 4-153 Analysed simultaneously with sex, attained age, calendar period, year of starting employment, and negotiating body. For levels, see table 1.

  • 4-154 Any part of death certificate coded to ICD-9 191,192, 225, 237.5, or 237.6.

  • 4-164 Five exposure categories scored by the mean value in each category—namely, 0.0, 0.19, 1.14, 3.16, and 11.40 μT.y. See text for details.

  • 4-161 No part of death certificate coded to ICD-9 191,192, 225, 237.5, or 237.6.