Lai, H and NP Singh. 2004. Magnetic-Field-Induced DNA Strand Breaks in Brain Cells of the Rat. Environmental Health Perspectives 112 (6): 687-694.

This study confirms the ability of low-level magnetic fields to cause DNA damage and brain cell death in rats, and proposes a mechanism that may explain both how the damage occurs as well as why some anti-oxidants work to prevent it. The results suggest a mechanism by which several degenerative diseases in people, like Alzheimer's, might be linked to exposures to magnetic fields.

What did they do?

Lai and Singh exposed rats to magnetic fields for 24 and 48 hours. The exposure levels were within the range that people encounter in the home and workplace. They compared the extent of DNA damage in exposed animals with control animals. The control animals were exposed to two opposing magnetic fields simultaneously (a process called 'bucking') in which the fields canceled each other out.

DNA damage was assessed by first extracting DNA strands from experimental and control animals' brains and then calculating the amount of DNA of different lengths in the samples, using gel electrophoresis. Shorter strands indicate greater damage.

Rats were tested both with and without injections of the drugs Trolox, deferiprone, and p7-nitroindazole.

Lai and Singh also compared experimental and control animals with respect to two different types of cell death in the brain, apoptosis and necrosis. To do this they extracted cells from the rats' brains after the experiment and examined them under a fluorescent miscroscope, using standard tools for assessing apoptosis and necrosis.

What did they find?

As expected, animals in the experimental group had more DNA damage compared to controls, as indicated by the average length of DNA migration (figure to right).

Animals with the longest exposure (48 hrs vs. 24 hrs) had the most damage to the DNA.     This is reflected in the histograms to the left. DNA was broken into smaller fragments by greater exposure, and thus in the electrophoresis experiments, a greater percentage of cells exposed to the magnetic field migrated farther.

Animals treated with the three drugs, Trolox, deferiprone, and 7-nitroindazole, all had less damage than untreated animals.

Brain cell death due to both apoptosis and necrosis increased significantly following magnetic field exposure.

What does this mean?

These new results confirm the fact that magnetic fields within the range experienced by people in their home and workplace can cause genetic damage and kill brain cells. They also reveal ways that damage can be reduced by using certain drugs.

The drug experiments not only show ways to reduce damage, they also provide insights into the mechanism by which magnetic fields may be causing its effect:

• One of the drugs used, Trolox, eliminates free radicals. The decrease in DNA damage which resulted with Trolox treatment indicates that the process is in some way reliant on free radicals as part of the DNA breaking mechanism.
• Another one of the drugs, deferione, reduces the amount of iron available for chemical reactions. This suggests that iron is also necessary for the damage to occur.
• The third drug, 7-nitroindazole, stops nitric acid from being synthesized. This implies that nitric acid synthesis is necessary for the damage to occur.

Lai and Singh knit these observations together to propose that low level magnetic radiation causes DNA damage and cell death through a multistep pathway:

First, the magnetic field increases the availability of iron which in turn, through a chemical process known as the Fenton Reaction, increases the availability of free radicals. The free radicals cause localized damage to lipids and proteins involved in the cell's structural integrity. This damage causes calcium to leak from storage sites, which in turn causes nitric acid synthesis to increase. The nitric acid then diffuses among cells, causing DNA damage and increasing both forms of cell death, apoptosis and necrosis.

Why is this important? Lai and Singh offer three observations:

• People are exposed every day to magnetic fields at levels used in this study (0.01-0.5 mT) by appliances and transmission wires. Magnetic fields near transmission lines can be a 50-100 times higher. Occupational exposures can be much higher.
• Certain types of human brain cells have relatively high amounts of iron, the starting point of the causal pathway that Lai and Singh propose. This could make these cells, notably myelinated nerve fibers, more susceptible to damage from magnetic fields.
• Several neurodegenerative diseases such as amyotropic lateral sclerosis, Alzheimer's and Parkinson's include biological events tied to neuronal death and/or demyelination. Epidemiological studies have noted increased risk to these conditions associated with occupational settings that involve exposure to magnetic fields.