Magnetic fields affect DNA
Magnetic fields from the electrical network can not only damage the DNA of brain cells, but the effects can be cumulative.
These are some of the findings of recent studies by US researchers Drs Henry Lai and Narendra Singh.
The Lai and Singh team first showed that magnetic fields from electricity could have genetic effects in 1997 when they found that a 60 Hz field of 0.1 - 0.5 mT produced single-strand and double-strand breaks in the DNA of rats’ brain cells.
Shortly afterwards they showed that this DNA damage could be prevented by pretreating the rats with free radical scavenging drugs. The results of these and other experiments indicated that free radicals may play a role in the DNA damage produced by exposure to magnetic fields.
The present study expands on this work.Magnetic fields
In the first of the current experiments Lai and Singh exposed rats to a magnetic field of 0.01 mT for either 24 or 48 hours. They found that exposure increased the number of single-strand and double-strand breaks in rats’ brains.
Rats exposed for 48 hours had significantly more DNA strand breaks of both types, as shown by the graph below, and this suggests, say the researchers, that effects are cumulative.
In this study DNA single– and
double-strand breaks occurred at an exposure of 0.01 mT for 24 hours. However, the team’s 1997 research found no double-strand breaks at an exposure of 0.1 mT for 2 hours. This suggests that as well as signal strength, duration is an important factor for the occurrence of effects.Magnetic fields and drugs
In a related series of experiments, Lai and Singh tested the effects of exposure to the free-radical scavenging drugs trolox and 7-nitroindazole. Different groups were exposed to either:
drug + magnetic field
drug + sham exposure
magnetic field + injection without drug (vehicle)
sham exposure and injection without drug (vehicle).
The results showed that both drugs prevented the occurrence of single– and double-strand DNA breaks. This provides further evidence that free radicals play a role in the damage caused by magnetic field exposure.
Lai and Singh also treated some rats before exposure with deferiprone, a drug that decreases the amount of free iron present in cells. They found that this treatment prevented DNA damage occurring.
This finding suggests that iron may play a role in magnetic field damage. It is consistent with the free-radical hypothesis because iron is involved in the formation of free radicals.Magnetic fields and cell death
In this experiment Lai and Singh exposed (or sham exposed) rats to a magnetic field of 0.5 mT for 2 hours. They found that exposure significantly increased the incidence of cell death by apoptosis (sham 0.28%;exposure 0.61%) and necrosis (sham 0.99%; exposure 1.88%).
The researchers hypothesise that these effects could also be the result of free radical action.How does damage occur?
Lai and Singh propose that magnetic fields initiate an iron-dependent process that generates free radicals and leads to cell death.
“We propose that the effects of magnetic fields act through a two-stage process. Magnetic field exposure first affects iron homeostasis in certain cells, leading to an increase in free iron in the cytoplasm and nucleus. This in turn leads to an increase in hydroxy radicals … which damage DNA, lipids, and proteins. Damage to lipids … in cellular membrane in turn leads to an increase in calcium leakage from internal storage sites in the cell. This will trigger the second step, which is an increase in nitric oxide synthesis.”
The two researchers speculate that magnetic fields will affect different cells - and therefore people - differently. “Cells with high rates of iron intake, e.g., proliferating cells, cells infected by virus, and cells with high metabolic rates such as brain cells, would be more susceptible to the effects of magnetic fields.”
Further, brain cells with high iron content, such as glial cells and myelin, may be more vulnerable to damage by magnetic fields. Damage to either glial cells or myelin could contribute to an increased risk of neurodegenerative disease, which has been associated with exposure to magnetic fields in a number of studies.
The study will be published in the May issue of Environmental Health Perspectives and can be found at http://ehp.niehs.nih.gov/members/2004/6355/6355.pdf.
EMR Focus, Vol 1 no 1, Mar 2004