3.7. International Workshop on the current state of research on the aetiology of childhood leukaemia

Project management: Federal Office for Radiation protection
Organisation: Valentum Kommunikation GmbH
Start: 20 November 2019
End: 23 November 2019

Background

The epidemiological findings of an increased risk of childhood leukaemia upon exposure to low magnetic fields led to the evaluation of magnetic fields as "possibly carcinogenic" by the WHO / IARC. No satisfactory scientific explanation has been found for this observation. Only high doses of ionising radiation have so far been scientifically proven to cause childhood leukaemia. Many other factors are suspected to trigger childhood leukaemia; these include both environmental and genetic factors. Whether and how these factors ultimately affect the risk of leukaemia or whether an interaction of the individual factors leads to an increase in the risk of leukaemia is largely unknown.

In order to clarify the question of the correlation between low-frequency magnetic fields and the development of childhood leukaemia, a better understanding of the aetiology and pathogenesis of the disease is required.

The BfS regularly organises international workshops on the status of research into the causes of childhood leukaemia in order to continuously monitor scientific progress in this field.

Objective

A 6th International Workshop was held in order to: determine the scientific progress of research into the causes of childhood leukaemia, present and discuss the latest findings, techniques, and possibilities, and, if necessary, adapt the ongoing BfS research programme "Radiation protection in power grid expansion".

Implementation

The public workshop took place from 20 to 22 November in Freising. It was aimed at interested scientists such as biologists, medical doctors, and epidemiologists as well as scientists from other disciplines. In total, 52 guests from 13 different countries took part in the workshop. In 26 lectures, invited experts spoke on the following topics:

1. The influence of environmental factors on the development of disease
2. The influence of genetic and epigenetic factors on the development of disease
3. The influence of the immune system on the development of disease
4. Animal models in leukaemia research
5. Natural background radiation as a risk factor for childhood leukaemia

Results

The workshop provided a comprehensive overview of the current state of research on the causes of childhood leukaemia. This showed that the development of leukaemia is highly complex and can be influenced by many factors. For example, epidemiological studies have observed that exposure to pesticides, low-level ionising radiation, or infections during pregnancy can increase the risk of leukaemia. On the other hand, factors such as taking folic acid or vitamins reduce the risk of contracting leukaemia. In addition to such environmental factors, genetic factors play a role in the development of the disease. For example, germline mutations in certain genes, including PAX5, can increase the risk of developing the disease. Syndromes such as Rubinstein-Taybi syndrome or Cornelia De Lange syndrome have also been associated with childhood leukaemia. In up to 5 % of healthy newborns, pre-leukaemic clones (i.e. cells with a leukaemia-specific mutation such as the ETV6-RUNX1 translocation) have been detected. Such pre-leukaemic cells are more sensitive to environmental factors.

Magnetic fields (MF) as an environmental risk factor for the development of childhood leukaemia have also been discussed. The correlation between MF and an increased risk of leukaemia observed in epidemiological studies has decreased over the years. However, an overall review of high-quality epidemiological studies still shows a weak but significant association. Most epidemiological studies have low case numbers in the high exposure groups (i.e. at magnetic flux densities above 0.3–0.4 microtesla). Future studies should therefore focus on groups of people in which a high proportion is exposed to a high magnetic flux density. Other environmental risk factors should also be taken into account in order to prevent these confounding factors from influencing the results.

The observations of an increased risk of leukaemia with magnetic field exposures above 0.3–0.4 microtesla are so far based only on epidemiological studies. In order to further investigate the relationship between MF and childhood leukaemia, additional experimental studies in animal models are necessary. To this end, existing animal models for leukaemia research were presented and discussed in a special session. The Sca1-ETV6-RUNX1 mouse model reflects the situation in humans quite well. With the help of this model, not only the influence of magnetic fields on the development of leukaemia but also the interaction between environmental and genetic risk factors can be studied in greater depth.

The report on the workshop with the agenda and the abstracts of the individual contributions has been published in DORIS, the online repository of the BfS. A detailed summary and discussion of the workshop results, also in the context of other international literature, was published in the journal Frontiers in Public Health (J.A. Schmidt et al. Front Public Health 2021).