Low magnetic fields leave mouse DNA undamaged
| 27 Aug 2016Cells in brain, kidney and liver shown to withstand sustained exposure to magnetic fields
The 19th-century works of Hans Christian Ørsted, Michael Faraday, James Clerk Maxwell and others demonstrated that electricity and magnetism are in fact two sides of the same coin: a magnet moving near a coil of wires induces a current in the coil and circulating electric current generates magnetic fields. We have since harnessed this unified electromagnetism to provide for the energy needs of billions around the globe. However, it is thought that prolonged exposure to electromagnetic (EM) fields produced by everything from household appliances to the electrical lines that power them can affect certain cells in the body, causing a variety of cancers. For this reason, several countries have adopted limits for EM exposure, with most European countries limiting ambient magnetic fields to 0.1 mT (milliteslas). It should be noted that medical devices such as MRI machines generate fields of up to 3 T, but patients typically are in the vicinity of such high fields for brief durations only.
To test the effects of EM fields on biological cells in a controlled environment, researchers exposed two groups of mice to fields of 0.1 mT and 1.0 mT respectively over eight weeks, while a third group of mice living in similar conditions but without the EM exposure served as a control. The EM fields in the experiment were generated at a frequency of 50 Hz, which is the frequency in most countries of the transmission of electricity via power lines. The same researchers previously found that an eight-week exposure to a higher field of 1.5 mT caused unrepaired DNA damage in mice. In both these studies, the scientists used breaks in the DNA strands in the cell nuclei as a measure of DNA damage. In the latest study, they also looked at whether DNA inside mitochondria was being produced regularly, a part of the normal DNA repair process in cells.
Previous research has suggested that extended exposure to EM fields damages cells that are involved in the transport, reabsorption or storage of iron. The researchers therefore studied how cells involved in these activities in the brain, the kidney and the liver were affected by EM exposure.
An artistic representation of DNA. Image by Nogas1974 / CC BY-SA 4.0
Three sets of mice were kept in otherwise identical conditions but were exposed to different EM fields: the first group to 0.1 mT, the second to 1.0 mT and the third group to no EM fields other than the Earth’s natural magnetic field. After eight weeks, cells from mice randomly selected from each group were analysed for signs of DNA damage.
The researchers performed a so-called “blind” analysis, which means they didn’t know which mice the cells came from, so that they didn’t bias the results in any way with knowledge about the EM-exposure levels involved. They looked for signs of DNA damage in the cells that could be tied to the EM-field levels each group of mice was exposed to. The tests showed that exposure to EM fields of 0.1 mT and 1.0 mT did not result in unrepaired damage to DNA in the nuclei of cells. Exposure to 1.0 mT, however, was linked to a reduction in synthesis of DNA in the mitochondria, the structures that make energy for the cell. DNA synthesis is a part of the normal DNA repair process, so lower levels of synthesis may indicate some irregularity in DNA repair possibly linked to the EM exposure.
From these experiments, it doesn’t appear that continuous exposure to low-intensity magnetic fields causes more unrepaired damage to DNA than might occur from natural causes. The small number of cell types analysed, however, doesn’t make this the final word on the effects of EM radiation on organisms and their DNA, though it does support the European safety limit of 0.1 mT.
Citation:
Korr, H., Angstman, N.B., Born, T.B., Bosse, K., Brauns, B., Demmler, M., Fueller, K., Kántor, O., Kever, B.M., Rahimyar, N., Salimi, S., Silny, J., & Schmitz, C. (2014). No evidence of persisting unrepaired nuclear DNA single strand breaks in distinct types of cells in the brain, kidney, and liver of adult mice after continuous eight-week 50 Hz magnetic field exposure with flux density of 0.1 mT or 1.0 mT. PLOS One, 9(10), e109774. DOI: 10.1371/journal.pone.0109774