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Every day, you use a variety of technologies that you probably take for granted: the microwave that cooks your meals, the lights that let you to see in the dark, the television that entertains you... What do all these technologies have in common? They all require electricity to operate. And as demand for electricity increases, so does the number of transmission towers and overhead wires. But what if long-term exposure to the electrical and magnetic energy produced by high-voltage wires caused health problems? Thankfully, research seems to indicate that it doesn’t—at least not in the case of childhood leukemia—although it may appear that way at first glance.
Did you know? Compared to electric fields, which are weakened by obstacles like walls, magnetic fields are hard to shield against and more likely to penetrate the body. As a result, magnetic fields are the component of electromagnetic fields (EMF) that is normally studied as a possible cause of cancer.
High-voltage overhead power lines conduct electricity from power generating stations to power source substations, which are located close to where the energy is actually used. These power lines produce two types of energy: electrical energy and magnetic energy, which are given off in a field that expands in all directions around the wires. The US National Cancer Institute (NCI) describes electromagnetic fields (EMF) as areas of energy that surround any electrical device. The NCI also explains that EMFs are produced by a variety of sources, including power lines, electrical wiring, and household appliances.
However, the EMF emitted from high-voltage power lines are much stronger than those surrounding household appliances, which typically produce fields measuring between 0.01 to 0.02 microtelsas. By contrast, the magnetic fields within a few metres of a transmission tower can be as high as 6 microtelsas, or 300 to 600 times higher than in the average home.
A key concern for those who live near high-voltage power lines is whether their children are at higher risk for cancer. The NCI explains that the most common childhood cancers are leukemia and brain cancer, which is why most research has focused on these two types. For example, a 2005 study looked at leukemia incidence in relation to how far children lived from a high-voltage power line. Researchers studied over 29,000 children living in England and Wales between 1962 and 1995, making the study one of the largest of its kind ever conducted. The study found that children living within 200 metres of a power line had a 70% higher risk of leukemia, whereas children living 200 to 600 metres away had a 20% higher risk, in comparison to the general population.
Did you know? The tesla (T) is a unit used to describe the strength of magnetic fields. Scientists normally report data in millionths of a tesla, or microteslas (µT).
At first glance, the study suggests that there is an increased risk of leukemia associated with living near high-voltage power lines. Indeed, the results are statistically significant. However, all the cases of leukemia in the study only account for around 1% of the total leukemia cases found in the surrounding area for each year of the 33 year-long study. Furthermore, there is also no obvious biological explanation for how EMF might cause leukemia, and this 1% of yearly cases could be due to other factors or even chance.
Another UK report from February 2014 studied 16,500 children who lived near high-voltage power lines in early life and who were also diagnosed with leukemia. In this case, researchers from the University of Oxford found that the children who lived near power lines did not have a greater risk of acquiring leukemia in comparison with the general population.
To sum up, there does not seem to be a strong link between leukemia and living near high-voltage power lines or transmission towers. Scientists have also been unable to identify a biological mechanism for the possible risk. Cancer Research UK suggests that “if there were strong links, they are likely to have shown up in the research that has been done so far”, which they haven’t.