Posts falsely link microwave usage to colon cancer

"Doctors say colon cancer is on the rise due to toxins absorbed while cooking food on the microwave," says an Instagram post from January 27, 2023 that garnered more than 24,000 likes.

"Cancer occurs when certain cells grow out of control and spread through the body. High-energy radiation, such as microwaves, can cause this damage and may lead to cancer over time."

Similar claims circulated on Twitter and TikTok, amplifying a long-running but unsubstantiated fear about microwaves and cancer.

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Screenshot of an Instagram post taken February 3, 2023

The more recent posts also have no scientific basis -- and they misrepresent colon cancer trends.

The overall incidence of colorectal cancer in the US, a leading cause of cancer deaths, has declined since the mid-1980s, according to data from the National Cancer Institute and the American Cancer Society. This is in part due to earlier detection and removal of polyps before they become cancerous.

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Screenshot of a chart from an American Cancer Society report

Despite the overall decline, cases among those 50 and younger are rising -- they comprised 11 percent of diagnoses in 2019 compared with six percent in 1990, according to the American Cancer Society's report.

"Reasons for the rise in young age groups are unknown but may reflect an increased sedentary lifestyle and a higher prevalence of obesity and/or unfavorable dietary patterns in children and young adults," the report said.

Unproven link to microwaves

Claims about radiation or other harms from microwave use are unproven, according to experts and public health authorities.

"There is no evidence linking microwave ovens to colon cancer," said Marcie Klein, senior vice president at the nonprofit Colorectal Cancer Alliance.

The National Cancer Institute says on its website that microwaves do produce electromagnetic fields, but they are the "non-ionizing radiation part of the electromagnetic spectrum and are not known to damage DNA or cells directly."

The US Food and Drug Administration (FDA) says there is no harmful radiation from microwave ovens "unless the door hinges, latch, or seals are damaged."

"The FDA also monitors appliances for radiation safety issues and has received reports of microwave ovens that appear to stay on -- and operate -- while the door is open," the agency says on its website. "When operating as intended, microwave ovens have safety features to prevent them from continuing to generate microwaves if the door is open."

The World Health Organization (WHO) offers similar guidance on its website: "The design of microwave ovens ensures that the microwaves are contained within the oven and can only be present when the oven is switched on and the door is shut. Leakage around and through the glass door is limited by design to a level well below that recommended by international standards."

The WHO adds that, despite some misconceptions, "it is important to realize that food cooked in a microwave oven does not become 'radioactive.' Nor does any microwave energy remain in the cavity or the food after the microwave oven is switched off."

"In this respect, microwaves act just like light; when the light bulb is turned off, no light remains," the agency says.

AFP has fact-checked other false and misleading claims about cancer here.