Residential magnetic fields exposure and childhood leukemia: a population-based case–control study in California

Abstract

Purpose Studies have reported an increased risk of childhood leukemia associated with exposure to magnetic fields. We conducted a large records-based case-control study of childhood leukemia risk and exposure to magnetic fields from power lines in California. Methods The study included 5,788 childhood leukemia cases (born in and diagnosed in California 1986-2008) matched to population-based controls on age and sex. We calculated magnetic fields at birth addresses using geographic information systems, aerial imagery, historical information on load and phasing, and site visits. Results Based on unconditional logistic regression controlling for age, sex, race/ethnicity and socioeconomic status using subjects geocoded to a basic standard of accuracy, we report a slight risk deficit in two intermediate exposure groups and a small excess risk in the highest exposure group (odds ratio of 1.50 (95% confidence interval [0.70, 3.23]). Subgroup and sensitivity analyses as well as matched analyses gave similar results. All estimates had wide confidence intervals. Conclusion Our large, statewide, record-based case-control study of childhood leukemia in California does not in itself provide clear evidence of risk associated with greater exposure to magnetic fields from power lines, but could be viewed as consistent with previous findings of increased risk.

The sensitivity of reported effects of EMF on childhood leukemia to uncontrolled confounding by residential mobility: a hybrid simulation study and an empirical analysis using CAPS data

“…Naturally, as the effect of mobility increased, so did the amount of bias generated by leaving it out of the model. A similar trend was seen for calculated fields, where again, previously observed associations (such as OR of 1.50) were not reached [20].…”

“…It appeared as though mobility might play a role in the observed association between both EMF exposures and childhood leukemia. The 'unadjusted' ORs, however, were also lower than previously observed in CAPS analyses [20,21]. Even with our "strongest mobility" scenario, neither bias-adjusted association of EMF exposure with leukemia appeared to be null, although the confidence intervals were relatively wider than before bias-adjustment.…”

“…We used CAPS to estimate odds ratios (ORs) between the variables used in previous analyses [20,21] and distance to high-voltage overhead powerlines, calculated magnetic fields, and childhood leukemia to the extent possible with the available data using both cases and controls. Table 1 lists the ORs and prevalences of our selected characteristics to both exposures of interest as well as to leukemia.…”

Residential mobility and childhood leukemia

“…As reported previously, using all leukemia cases and controls, we found an OR for childhood leukemia of 1.44 (95% CI 0.74-2.77) for those whose birth residence was within 50 m of a 200 + kV line, (Crespi et al, 2016) and an OR (95% CI) of 1.50 (0.70-3.21) for the highest exposure of calculated fields (≥0.4 μT) (Kheifets et al, 2017a). The results of analyses stratified by the mobility status of the cases are presented in Table 2. Among non-movers, moderate associations for childhood leukemia and both living within 50 m of voltage 200 + kV power line (OR: 1.62, 95% CI: 0.72-3.65) and living in higher calculated fields (OR: 1.71, 95% CI: 0.65-4.52) at birth home were observed.…”

“…Controls were excluded if they were diagnosed with any type of cancer in California before the matched case's date of diagnosis. Detailed descriptions of the study design and methods have been previously published (Kheifets et al, 2015), as have the results of the calculated magnetic fields and distance analyses (Crespi et al, 2016;Kheifets et al, 2017a).…”