All electrical household appliances — including heating pads, electric blankets and mattress covers, plug-in hair dryers, computers, and coffeemakers — generate electromagnetic fields (EMFs). These invisible lines of force exist in nature (they are what make a compass needle point north) and they also surround electrical equipment, power cords, and power lines. As our daily lives fill up with more and more electronic devices, there has been increasing concern about the health effects of exposure to EMFs. There is no definitive proof that these fields cause cancer, but since exposure is greatest at short distances and heating pads are held very close to your body, I would suggest you find a different way to warm up before exercising.
For the past several decades, researchers have been investigating whether EMFs can disrupt internal body control systems and increase the risk of cancer or weaken the immune system. So far, no studies have confirmed that EMFs increase the risk of cancer among adults. The bad news is that the possibility of an EMF/cancer connection hasn’t been definitively ruled out.
Some early studies suggested a link between EMFs and childhood leukemia, but they looked at populations that lived in close proximity to power lines, not at the risk of using household appliances. Later studies have found only weak associations between power lines and childhood leukemia.
Although researchers have found no convincing evidence that EMFs directly damage biological structures, including DNA, or otherwise increase the likelihood of malignant transformation of cells, ongoing studies are looking at whether EMFs can promote cancer that already exists or disrupt normal cellular function, including the activity of the immune system.
Some research has suggested that exposure to low-level magnetic fields emitted by such appliances as hairdryers, electric blankets and electric razors can damage DNA in brain cells. The data come from a study in rats at the University of Washington, which found DNA damage in animals exposed to a 60 hertz field for 24 hours; more damage was found after 48 hours. Henry Lai, Ph.D., the study leader, said that data from this and a previous study suggest that the effects of exposure are cumulative and may build up in humans over time as a result of repeated brief use of common plug-in appliances. He suggests limiting exposure to as little time as possible, particularly with devices used close to the body. The strength of EMFs falls off exponentially as distance from the source increases. So, move plug-in clock radios away from your head and hold the hairdryers farther away.
Some non-EMF heating pads now on the market use infrared heat instead of EMFs. There have been some studies on their effectiveness, and many of them claim to be safer than electric versions that emit EMFs, but they have not been subjected to the long-term studies that electrical appliances have been. I think it’s better to wait for more rigorous studies on infrared heating pads before using one on a daily basis. (RH-This seems logical since Infared, non-eMF heating pads are newer so I’ll STET. GN)
Because we can’t say for sure that daily use of a heating pad poses no risk, I would advise you to limber up before your daily workout without using one. Try a good old-fashioned hot water bottle if you want a safer source of heat to apply. (RH-these last two points are new, but since they are suggestions, I’m fine with it. GN)
Andrew Weil, M.D.
Ervolino F, Gazze R. “Far infrared wavelength treatment for low back pain: Evaluation of a non-invasive device.” Work. 2015;53(1):157-62. doi: 10.3233/WOR-152152. PMID: 26409395. https://pubmed.ncbi.nlm.nih.gov/26409395/
Gale, George D et al. “Infrared therapy for chronic low back pain: a randomized, controlled trial.” Pain research & management vol. 11,3 (2006): 193-6. doi:10.1155/2006/876920 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2539004/
Originally Published June 2007. Updated January 2022.