Risk of childhood acute lymphoblastic leukaemia following parental occupational exposure to extremely low frequency electromagnetic fields

Relationship between parental exposure to radiofrequency electromagnetic fields and primarily hematopoietic neoplasms (lymphoma, leukemia) and tumors in the central nervous system in children: a systematic review

Low-frequency electromagnetic fields have grown exponentially in recent years due to technological development and modernization. The World Health Organization (WHO)/International Agency for Research on Cancer (IARC) has classified radiofrequency electromagnetic fields (RF-EMFs) as possibly carcinogenic to humans (Group 2B), and recent studies have investigated the association between exposure to electromagnetic fields in parents and possible health effects in children, especially the development of tumours of the central nervous system (CNS). The objective of this systematic review was to collate all evidence on the relationship between parental occupational exposure to electromagnetic fields and the development of CNS cancer in children and to evaluate this association. This review was prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Embase, and Web of Science were searched from January 1990 to April 2021. The search was conducted using the following search string: "occupational" AND "child" AND "electromagnetic" AND "cancer". Seventeen articles met our inclusion criteria: 13 case-control studies, two cohort studies, and 2 meta-analyses. Most of the studies showed several methodological weaknesses that limited their results. Due to a lack of consistency regarding the outcome as well as the heterogeneity in the reviewed studies, the body of evidence for the effects of parental exposure to electromagnetic fields is not clear. Methodological heterogeneity in the way that studies were conducted could be responsible for the lack of consistency in the findings. Overall, the body of evidence allows no conclusion on the relationship between parental exposure to electromagnetic fields and the occurrence of CNS tumours in children.

Non-ionizing radiation as possible carcinogen

The advent of wireless technologies has revolutionized the way we communicate. The steady upsurge in the use of mobile phone all over the world in the last two decades, while triggered economic growth, has caused substantial damage to the environment, both directly and indirectly. The electromagnetic radiation generated from mobile phones, radio-based stations, and phone towers, high-voltage power lines have been reported which leads to the variety of health scares such as the risk of cancer in human beings and adverse effects in animals, birds, etc. Though the usage of such radiation emitting from mobile phones has risen steeply, there is a lack of proper knowledge about the associated risks. The review provides the latest research evidence based both on in vitro studies, in vivo studies, and possible gaps in our knowledge. Moreover, the present review also summarizes available literature in this subject, reports and studies which will help to form guidelines for its exposure limits to the public.Abbreviations: Continuous Wave: CW; Code Division Multiple Access: CDMA; Global System for Mobile Communications: GSM; Peripheral Blood Mononuclear Cell: PBMC; Radiofrequency: RF; Radiofrequency radiation: RFR; Universal Mobile Telecommunications System: UMTS; Wideband Code Division Multiple Access: WCDMA; Specific Absorption Rate: SAR; National Toxicology Program: NTP; amplitude-modulated or amplitude-modulation: AM; Electromagnetic frequencies: EMF; confidence interval: CI; Gigahertz: GHz; odds ratio: OR; incidence ratio: IR; reactive oxygen species: ROS; specific absorption rate: SAR; International Agency of Research on Cancer: IARC; single-strand breaks: SSB; double-strand breaks: DSB (7,12-Dimethylbenz[a]anthracene): DMBA; Hour: h; international commission on non-ionizing radiation protection: ICNIRP; extremely low frequency: ELFl; microtesla: mT; Gigahertz: GHz; hertz: Hz; decibel: dB; kilometer: Km; Watt per square meter: W/m²; Hour: h; positron emission tomography: PET.

Extremely low frequency electromagnetic fields and cancer: How source of funding affects results

While there has been evidence indicating that excessive exposure to magnetic fields from 50 to 60 Hz electricity increases risk of cancer, many argue that the evidence is inconsistent and inconclusive. This is particularly the case regarding magnetic field exposure and childhood leukemia. A major goal of this study is to examine how source of funding influences the reported results and conclusions. Several meta-analyses dating from about 2000 all report significant associations between exposure and risk of leukemia. By examining subsequent reports on childhood leukemia it is clear that almost all government or independent studies find either a statistically significant association between magnetic field exposure and childhood leukemia, or an elevated risk of at least OR = 1.5, while almost all industry supported studies fail to find any significant or even suggestive association. A secondary goal of this report is to examine the level of evidence for exposure and elevated risk of various adult cancers. Based on pooled or meta-analyses as well as subsequent peer-reviewed studies there is strong evidence that excessive exposure to magnetic fields increases risk of adult leukemia, male and female breast cancer and brain cancer. There is less convincing but suggestive evidence for elevations in several other cancer types. There is less clear evidence for bias based on source of funding in the adult cancer studies. There is also some evidence that both paternal and maternal prenatal exposure to magnetic fields results in an increased risk of leukemia and brain cancer in offspring. When one allows for bias reflected in source of funding, the evidence that magnetic fields increase risk of cancer is neither inconsistent nor inconclusive. Furthermore adults are also at risk, not just children, and there is strong evidence for cancers in addition to leukemia, particularly brain and breast cancer.

Parental occupational exposure to low-frequency magnetic fields and risk of leukaemia in the offspring: findings from the Childhood Leukaemia International Consortium (CLIC)

OBJECTIVES

Previously published studies on parental occupational exposure to extremely low-frequency magnetic fields (ELF-MF) and risk of acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML) in their offspring were inconsistent. We therefore evaluated this question within the Childhood Leukemia International Consortium.

METHODS

We pooled 11 case-control studies including 9723 childhood leukaemia cases and 17 099 controls. Parental occupational ELF-MF exposure was estimated by linking jobs to an ELF-MF job-exposure matrix (JEM). Logistic regression models were used to estimate ORs and 95% CIs in pooled analyses and meta-analyses.

RESULTS

ORs from pooled analyses for paternal ELF-MF exposure >0.2 microtesla (µT) at conception were 1.04 (95% CI 0.95 to 1.13) for ALL and 1.06 (95% CI 0.87 to 1.29) for AML, compared with ≤0.2 µT. Corresponding ORs for maternal ELF-MF exposure during pregnancy were 1.00 (95% CI 0.89 to 1.12) for ALL and 0.85 (95% CI 0.61 to 1.16) for AML. No trends of increasing ORs with increasing exposure level were evident. Furthermore, no associations were observed in the meta-analyses.

CONCLUSIONS

In this large international dataset applying a comprehensive quantitative JEM, we did not find any associations between parental occupational ELF-MF exposure and childhood leukaemia.

Residential exposure to electromagnetic fields during pregnancy and risk of child cancer: A longitudinal cohort study

OBJECTIVE

We assessed whether exposure to electromagnetic fields during pregnancy increases the risk of childhood cancer.

METHODS

We studied a retrospective cohort of 784,944 newborns in Quebec, Canada between 2006 and 2016 who were followed for cancer one decade after birth. The exposures were residential distance to the nearest high voltage power transformer station and transmission line. We determined the incidence of childhood cancer, and estimated hazard ratios and 95% confidence intervals (CI) in Cox proportional hazards regression models adjusted for maternal and birth characteristics.

RESULTS

There were 1114 incident cases of cancer during 4,647,472 person-years of follow-up. Residential proximity to transformer stations was associated with a somewhat greater risk of cancer, but there was no association with transmission lines. Compared with 200 m, a distance of 80 m from a transformer station was associated with a hazard ratio of 1.08 (95% CI 0.98, 1.20) for any cancer, 1.04 (95% CI 0.88, 1.23) for hematopoietic cancer, and 1.11 (95% CI 0.99, 1.25) for solid tumours.

CONCLUSIONS

Residential proximity to transformer stations is associated with a borderline risk of childhood cancer, but the absence of an association with transmission lines suggests no causal link.

Biological effects of non-ionizing electromagnetic fields: Two sides of a coin

Controversial, sensational and often contradictory scientific reports have triggered active debates over the biological effects of electromagnetic fields (EMFs) in literature and mass media the last few decades. This could lead to confusion and distraction, subsequently hampering the development of a univocal conclusion on the real hazards caused by EMFs on humans. For example, there are lots of publications indicating that EMF can induce apoptosis and DNA strand-breaks in cells. On the other hand, these effects could rather be beneficial, in that they could be effectively harnessed for treatment of various disorders, including cancer. This review discusses and analyzes the results of various in vitro, in vivo and epidemiological studies on the effects of non-ionizing EMFs on cells and organs, including the consequences of exposure to the low and high frequencies EM spectrum. Emphasis is laid on the analysis of recent data on the role of EMF in the induction of oxidative stress and DNA damage. Additionally, the impact of EMF on the reproductive system has been discussed, as well as the relationship between EM radiation and blood cancer. Apart from adverse effects, the therapeutic potential of EMFs for clinical use in different pathologies is also highlighted.

Parental Occupational Exposures and Risk of Childhood Acute Leukemia

Introduction:

Acute leukemia, accounting for 20% of all cancers diagnosed in individuals younger than 19 years old, is the most prevalent childhood malignancy. Among environmental risk factors, parental occupational exposures have attracted scientific interest as potential predisposing factors for childhood leukemia. The role of parental occupational exposure to social contacts, harmful chemicals, electromagnetic fields and ionizing radiation has been investigated with conflicting and inconsistent results.

Aim:

A case-control study aiming to assess the association between parental occupational exposures to social contacts, chemicals and electromagnetic fields and the risk of offspring acute leukemia.

Material and Methods:

108 children with acute leukemia and equal number of matched controls were included. Data on parental occupations before conception, during pregnancy, during breastfeeding and after birth, and on potential risk factors was recorded. Associations between parental exposure and risk of childhood leukemia were estimated.

Results:

Parental occupational exposure during the four periods of exposure was not associated with childhood leukemia. High birth weight and family history of cancer were associated with the development of childhood acute leukemia. A weak association of maternal medication use during pregnancy and leukemia risk emerged.

Conclusions:

Since the causative factors of childhood leukemia remain unknown, further investigation is mandatory for the reduction of disease burden.

The associations between maternal factors during pregnancy and the risk of childhood acute lymphoblastic leukemia: A meta-analysis

BACKGROUND

Although genetic and environmental factors are considered to be the main causes of acute lymphoblastic leukemia, the associations between maternal factors during pregnancy and the childhood ALL is still unclear.

PROCEDURE

In this study, meta-analysis was used. Medline, PubMed, and Web of Science were searched. The result was assessed based on pooled odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

The pooled ORs showed that there were associations between childhood ALL and the birth order (The first vs others, OR = 1.08, 95%CI = 1.00-1.16), the education of pregnant woman (>high school vs ≤ high school, OR = 0.82, 95%CI = 0.77-0.86), smoking (Ever vs never, OR = 1.10, 95%CI = 1.02-1.19).

CONCLUSIONS

Our meta-analysis showed that there were important associations between childhood ALL and the birth order, the education of pregnant woman, smoking.

Effects of long-term 50Hz power-line frequency electromagnetic field on cell behavior in Balb/c 3T3 cells

Power-line frequency electromagnetic field (PF-EMF) was reported as a human carcinogen by some epidemiological research, but the conclusion is lack of robust experiment evidence. To identify the effects of long-term PF-EMF exposure on cell behavior, Balb/c 3T3 cells in exponential growth phase were exposed or sham-exposed to 50 Hertz (Hz) PF-EMF at 2.3 mT for 2 hours (h) one day, 5 days every week. After 11 weeks exposure, cells were collected instantly. Cell morphology was observed under invert microscope and Giemsa staining, cell viability was detected by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, cell cycle and apoptosis was examined by flow cytometry, the protein level of Proliferating Cell Nuclear Antigen (PCNA) and CyclinD1 was detected by western blot, cell transformation was examined by soft agar clone assay and plate clone forming test, and cell migration ability was observed by scratch adhesion test. It was found that after PF-EMF exposure, cell morphology, apoptosis, cell migration ability and cell transformation didn't change. However, compared with sham group, cell viability obviously decreased and cell cycle distribution also changed after 11 weeks PF-EMF exposure. Meanwhile, the protein level of PCNA and CyclinD1 significantly decreased after PF-EMF exposure. These data suggested that although long-term 50Hz PF-EMF exposure under this experimental condition had no effects on apoptosis, cell migration ability and cell transformation, it could affect cell proliferation and cell cycle by down-regulation the expression of PCNA and CyclinD1 protein.

Comparison of the genotoxic effects induced by 50 Hz extremely low-frequency electromagnetic fields and 1800 MHz radiofrequency electromagnetic fields in GC-2 cells

Extremely low-frequency electromagnetic fields (ELF-EMF) and radiofrequency electromagnetic fields (RF-EMF) have been considered to be possibly carcinogenic to humans. However, their genotoxic effects remain controversial. To make experiments controllable and results comparable, we standardized exposure conditions and explored the potential genotoxicity of 50 Hz ELF-EMF and 1800 MHz RF-EMF. A mouse spermatocyte-derived GC-2 cell line was intermittently (5 min on and 10 min off) exposed to 50 Hz ELF-EMF at an intensity of 1, 2 or 3 mT or to RF-EMF in GSM-Talk mode at the specific absorption rates (SAR) of 1, 2 or 4 W/kg. After exposure for 24 h, we found that neither ELF-EMF nor RF-EMF affected cell viability using Cell Counting Kit-8. Through the use of an alkaline comet assay and immunofluorescence against γ-H2AX foci, we found that ELF-EMF exposure resulted in a significant increase of DNA strand breaks at 3 mT, whereas RF-EMF exposure had insufficient energy to induce such effects. Using a formamidopyrimidine DNA glycosylase (FPG)-modified alkaline comet assay, we observed that RF-EMF exposure significantly induced oxidative DNA base damage at a SAR value of 4 W/kg, whereas ELF-EMF exposure did not. Our results suggest that both ELF-EMF and RF-EMF under the same experimental conditions may produce genotoxicity at relative high intensities, but they create different patterns of DNA damage. Therefore, the potential mechanisms underlying the genotoxicity of different frequency electromagnetic fields may be different.