Fact Check-Lateral flow tests do not cause cancer; ethylene oxide sterilisation is a widely-used process that is regulated by international safety standards

A live video broadcast to Facebook about the methods used to sterilise medical equipment has falsely suggested “ethylene oxide-coated” swabs in lateral flow tests cause cancer. This claim reveals the user’s lack of understanding about the sterilisation process.

The 11-minute video was streamed on March 19 and has since been viewed tens of thousands of times (here, here). In it, the Facebook user presents an NHS lateral flow test for COVID-19, which includes a note on the packaging to say it has been sterilised using ethylene oxide.

“If you’re testing your children with this, you’re taking a piece of plastic with fibres on the end that’s been sterilised using ethylene oxide, which has the ability to cause cancer by damaging DNA,” the user says. “It states that on a government website. It also states that on the packaging that I just took out of this sealed box… This is important stuff, guys.”

The user also reads the harmful effects of ethylene oxide from a webpage by the National Cancer Institute in the United States (here). He adds: “You’re putting this inside your head. Ethylene oxide is a cancer-causing chemical used for sterilisation. It damages DNA and some people are allowing this to be put inside their children’s head, so it touches the membrane that separates the nasal passage from the brain. Not only is that in danger of causing encephalitis, it can cause problems with the endocrine system […]

“I’m begging you to not test your children. It can cause leukaemia. It can cause lymphoma. It can cause breast cancer […] They’re literally telling us it causes cancer and people are going: ‘You’re a fucking conspiracy theorist.’ Maybe so. But it’s not a theory when there’s evidence on a government website stating something that’s written on the back of the document of the PCR test.”

While the Facebook user is correct to say ethylene oxide is considered a carcinogen (here, here) and that its gaseous form is used to sterilise swabs (here), it is not accurate to say the swabs are “coated” in the substance when they are eventually used. A major part of the sterilisation process ensures the gas is removed from the product (here) and that any leftover residue is below that of the safety levels set by national and international standards (here, here, here, here, here).

Ethylene oxide (EO) gas is an extremely common feature when sterilising medical equipment (here). Used for decades, EO-sterilised equipment is said to make up around 50% of all sterile medical devices in the U.S. (here, here).

A basic process for sterilising products includes a number of steps: preconditioning and humidification, gas introduction, exposure, evacuation, and air washes. Afterwards, time is set aside for aeration to further rid devices of residual EO (here, here). A 2017 study on rayon and cotton swabs used to collect DNA samples found residuals dropped below measurable levels three weeks after being treated with EO (here, here).

In a statement to Reuters, the Department for Health and Social Care addressed claims that COVID-19 test swabs pose a danger to humans. It said: “Lateral flow tests have been rigorously tested and are safe to use on a regular basis. Any suggestion otherwise is inaccurate and harmful misinformation.

“Ethylene oxide is only used in the sterilisation of swabs and it is one of the most commonly used sterilisation tools in the healthcare industry, principally applied by manufacturers to keep medical devices safe.

“We are working in lockstep with social media platforms to ensure they are identifying and taking action to remove incorrect claims, such as this, about the pandemic, including deliberately false information that could endanger people’s health.” 


False. While ethylene oxide is a carcinogen widely used to sterilise medical equipment, the sterilisation process is tightly controlled to ensure any residue left over is negligible – and to ensure medical devices are safe to use.

This article was produced by the Reuters Fact Check team. Read more about our work to fact-check social media posts here.