Study type: Epidemiological study (observational study)

Residential magnetic fields predicted from wiring configurations: II. Relationships To childhood leukemia. epidem.

Published in: Bioelectromagnetics 1999; 20 (7): 414-422

Aim of study (acc. to author)

The data of a case-control study on childhood leukemia in Los Angeles County, USA, were reanalyzed with residential magnetic fields predicted from the wire configurations of nearby power transmission lines.

Further details

The principal residence of a child was defined as the house within southern California where the child lived in for the longest portion of etiologic period, i.e., the time period from conception to 0-2 years before diagnosis of the case. If no single residence spanned at least 40 % of the etiologic period, but two homes each spanned at least 25 %, both were designated as principal residences. Measurements were carried out for 315 principal houses of 164 cases and 144 controls. Maps with the complete information about nearby transmission and distribution wiring were obtained for 709 residences. The measured and predicted fields were categorized by their 50th, 75th, and 90th percentiles.

Endpoint/type of risk estimation

Type of risk estimation: (odds ratio (OR))

Exposure

Assessment

Exposure groups

Group Description
Group 1 24-h geometric mean measurements, measured principal: percentiles 50-74 %
Group 2 24-h geometric mean measurements, measured principal: percentiles 75-89 %
Group 3 24-h geometric mean measurements, measured principal: percentiles 90-100 %
Group 4 24-h geometric mean measurements, corrected for measurement error, measured principal: percentiles 50-74 %
Group 5 24-h geometric mean measurements, corrected for measurement error, measured principal: percentiles 75-89 %
Group 6 24-h geometric mean measurements, corrected for measurement error, measured principal: percentiles 90-100 %
Group 7 Wertheimer-Leeper code, measured principal: ordinary low (OLCC)
Group 8 Wertheimer-Leeper code, measured principal: ordinary high (OHCC)
Group 9 Wertheimer-Leeper code, measured principal: very high (VHCC)
Group 10 Wertheimer-Leeper code, all principal: ordinary low (OLCC)
Group 11 Wertheimer-Leeper code, all principal: ordinary high (OHCC)
Group 12 Wertheimer-Leeper code, all principal: very high (VHCC)
Group 13 predicted fields, measured principals: percentiles 50-74 %
Group 14 predicted fields, measured principals: percentiles 75-89 %
Group 15 predicted fields, measured principals: percentiles 90-100 %
Group 16 predicted fields, all principals: percentiles 50-74 %
Group 17 predicted fields, all principals: percentiles 75-89 %
Group 18 predicted fields, all principals: percentiles 90-100 %
Group 19 predicted fields, all mapped: percentiles 50-74 %
Group 20 predicted fields, all mapped: percentiles 75-89 %
Group 21 predicted fields, all mapped: percentiles 90-100 %
Group 22 predicted fields, all residences: percentiles 50-74 %
Group 23 predicted fields, all residences: percentiles 75-89 %
Group 24 predicted fields, all residences: percentiles 90-100 %
Group 25 measurements and predictions combined: measured principal: percentiles 50-74 %
Group 26 measurements and predictions combined: measured principal: percentiles 75-89 %
Group 27 measurements and predictions combined: measured principal: percentiles 90-100 %
Group 28 measurements and predictions combined: all principal: percentiles 50-74 %
Group 29 measurements and predictions combined: all principal: percentiles 75-89 %
Group 30 measurements and predictions combined: all principal: percentiles 90-100 %
Group 31 measurements and predictions combined: all mapped: percentiles 50-74 %
Group 32 measurements and predictions combined: all mapped: percentiles 75-89 %
Group 33 measurements and predictions combined: all mapped: percentiles 90-100 %
Group 34 measurements and predictions combined: all residences: percentiles 50-74 %
Group 35 measurements and predictions combined: all residences: percentiles 75-89 %
Group 36 measurements and predictions combined: all residences: percentiles 90-100 %

Population

Case group

Control group

Study size

Cases Controls
Eligible 331 257
Participants 232 232
Statistical analysis method:

Conclusion (acc. to author)

No association between measured magnetic fields and childhood leukemia was observed, but the risks were significant for predicted magnetic fields above 0.125 µT (group 24: OR 2.0, CI 1.03-3.89, number of cases and controls not specified), and a significant dose response was seen (P for trend = .02). When exposure assessment was done by a combination of predictions and measurements with corrections for errors, the odds ratio (group 36: OR 2.19, CI 1.12-4.31) and the trend (p = .007) showed somewhat greater significance.
These findings support the hypothesis that magnetic fields from electrical lines are causally related to childhood leukemia but that this association has been inconsistent among epidemiologic studies due to different types of errors in exposure assessment.

Study funded by

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