Case-cohort analysis of brain cancer and leukemia in electric utility workers using a refined magnetic field job-exposure matrix.
BACKGROUND
The potential association between occupational electric and magnetic field exposure and cancer is well documented in the literature, but there is uncertainty regarding a causal relation.


METHODS
Using data from a completed cohort study, we sought to refine the job-exposure matrix in a case-cohort analysis by regrouping jobs into more homogeneous groups, but without making additional measurements. From the original cohort, we selected the 164 men who died of leukemia, 145 men who died of brain cancer, and a random subcohort of 800 men (0.6% of the cohort). Erroneous job assignments were corrected and job groups were subdivided based on differences in work environments or tasks performed.


RESULTS
Magnetic field exposure remained unrelated to leukemia mortality and positively associated with brain cancer mortality based on both cumulative and average magnetic field indices. Although not monotonic across the middle intervals, increased risk of brain cancer was found in relation to career exposure, with risk ratios of 1.8 (95% CI = 0.7-4.7) and 2.5 (95% CI = 1.0-6.3) in the uppermost categories for cumulative and average exposure, stronger for exposure 2-10 years past.


CONCLUSIONS
Improvements in exposure assignment based only on reassignment of job titles to occupational categories had little impact on the measured associations of magnetic fields with leukemia or brain cancer.
Savitz
D A
DA
Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill 27599-7400, USA. david.savitz@unc.edu
Cai
J
J
van Wijngaarden
E
E
Loomis
D
D
Mihlan
G
G
Dufort
V
V
Kleckner
R C
RC
Nylander-French
L
L
Kromhout
H
H
Zhou
H
H
D001932:Brain Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D015984:Causality; D004574:Electromagnetic Fields; D006801:Humans; D007938:Leukemia / Q000453:epidemiology*; D008297:Male; D009784:Occupational Diseases / Q000453:epidemiology*; D013997:Time Factors