Changes over time in the reported risk for childhood leukaemia and magnetic fields

Abstract

There have been many studies from 1979 to the present reporting raised risks for childhood leukaemia with exposure to power-frequency magnetic fields. There are also suggestions that the reported risk has been decreasing. We examine trends in the risk over time from all available studies. For 41 studies, we combine reported risks using inverse-variance weighting, drawing risk estimates from previous pooled analyses where possible for greater consistency. We examine the cumulative risk for studies published up to each successive calendar year for all studies and for various subsets, and test for a trend over the period. The cumulative relative risk has indeed declined, for our most rigorous analysis from a maximum 2.44 in 1997 to 1.58 in 2017, but not statistically significantly when tested as a linear trend. We find suggestions of higher risks in studies looking at higher exposures and in studies with better quality exposure assessment. We conclude that there is a decline in reported risk from the mid 1990s to now, which is unlikely to be solely explained by improving study quality but may be due to chance, and an elevated risk remains.

Exposure to magnetic fields and childhood leukemia: a systematic review and meta-analysis of case-control and cohort studies

“…We have found a pooled OR of 1.51 (95% CI 1.26-1.80) for the association between ELF-MF and childhood leukemia in the earlier studies performed before 2000 and a pooled OR of 1.04 (95% CI 0.84-1.29) for the recent studies. These results are in agreement with the study performed by Swanson and colleagues [62] who found a decline in the risk for childhood leukemia and ELF-MF from the mid-1990s to 2017. Furthermore, the test for subgroup differences based on the method to assess magnetic field exposure indicates a Q value (df=3) of 6.16 (p=0.10) and an I 2 of 51.3% (Table 4).…”

Risk Factors for Childhood Leukemia: Radiation and Beyond

“…However, how ELF-MF may cause leukemia is unknown -until today, no plausible biological mechanism has been found, and experimental in vitro and in vivo studies do not confirm the results of the epidemiological studies. Besides, it was shown that newer epidemiological findings point to a decline in the reported relative risk (RR) since the 1990's to now (115): In their analysis, Swanson et al (115) calculated the cumulative RR from 32 studies published up to each successive calendar year, showing that the RR settled around 2 in the mid-1990s before declining to a current value of 1.44 in 2017, though the decline is not statistically significant. Improvement of study quality was not considered an explanation for the decline by the authors.…”

Evaluation of the Effects of Exposure to Power‐Frequency Magnetic Fields on the Differentiation of Hematopoietic Stem/Progenitor Cells Using Human‐Induced Pluripotent Stem Cells

“…Epidemiological studies have suggested that exposure to ≥0.4 μT residential MFs increases the risk of childhood leukemia [Ahlbom et al, 2000 ; Kheifets et al, 2010 ; Swanson et al, 2019 ]. In this study, we evaluated the effects of up to 300 mT (rms) of 50‐Hz MFs, which is considerably higher than the levels mentioned above, on the efficiency of differentiation from human mesodermal cells into HSPCs.…”

“…Since first shown in 1979 [Wertheimer and Leeper, 1979 ], the association between exposure to power‐frequency magnetic fields (MFs) and the development of childhood leukemia has been discussed, while the findings of epidemiological studies have been influential [Ahlbom et al, 2000 ; Kheifets et al, 2010 ; Swanson et al, 2019 ]. Based on these findings, the International Agency for Research on Cancer (IARC) classified that extremely low‐frequency MFs (ELF‐MFs; up to 3 kHz) are possibly carcinogenic to humans (Group 2B) [IARC, 2002 ].…”