Lateral flow tests are not unsafe

In England, secondary school and college students and staff, and their households, are being asked to regularly take a lateral flow test to check for Covid-19. We’ve seen a large number of posts on social media warning people not to use Covid-19 lateral flow tests, as the swabs are sterilised with ethylene oxide, which can cause cancer. Our readers have also asked us to check these claims.

Ethylene oxide is a colourless gas which is used to sterilise medical equipment around the world and, although overexposure can be dangerous, its use does not make medical products like lateral flow tests unsafe. 

It is correct that too much exposure to ethylene oxide can carry health risks, including cancer. 

Ethylene oxide for sterilisation

As the posts on social media claim, lateral flow tests are sterilised using ethylene oxide. Sterilisation of medical devices is very important to ensure infections do not spread.

A spokesperson for the DHSC told Full Fact: “Lateral flow tests used in schools have been rigorously tested and are safe to use on a regular basis.

“Any suggestion otherwise is inaccurate and harmful misinformation.”

The DHSC also confirmed that a minimal amount of ethylene oxide is used for sterilisation of the swabs—just 1-2μg (millionths of a gram) per gram.

The UK regulator, the Medicines and Healthcare products Regulatory Agency, also confirmed to Full Fact that ethylene oxide is a highly controlled and safe method of sterilisation, which is assessed and evaluated through the sterilisation process to ensure it meets agreed safety standards. 

The US Food and Drug Administration (FDA) suggests around half of all sterile medical devices in the US are sterilised with ethylene oxide, including equipment used in general healthcare practices like wound dressings and more specialised equipment like stents (small tubes that can help keep blocked arteries open). The FDA says that, for many medical devices, sterilisation with ethylene oxide may be the only effective method that does not cause any damage to the object being sterilised. 

Is ethylene oxide harmful?

Exposure to large amounts of ethylene oxide can have serious health consequences. However, there is no suggestion that using something that has been sterilised by ethylene oxide will be harmful. 

Many of the misleading Facebook posts we have seen have quoted from the National Cancer Institute in the US, which sets out the risks from ethylene oxide. Although the health risks set out by the page are genuine, this is not to say that anyone who uses a medical device that has been sterilised with a small amount of ethylene oxide will suffer them.

The Centers for Disease Control and Prevention in the US says that “acute exposure” can result in irritation and central nervous system depression, while “chronic inhalation” of the gas has been linked to cataracts, cognitive impairment and neurologic dysfunction. It also notes that in some cases, burns in patients have been associated with ethylene oxide residues in implants used in surgical procedures. 

Chronic exposure to ethylene oxide has been associated with an increased risk of leukemia, stomach cancer, pancreatic cancer and non-Hodgkin lymphoma. As some of the Facebook posts suggest, over exposure to ethylene oxide can alter the DNA in a cell. There has been recent controversy in America over the health concerns of people living near sterilising factories using ethylene oxide. 

In the UK, there are exposure limits set by the Health and Safety Executive to protect workers who may interact with the chemical.

Professor Andrea Sella, professor of inorganic chemistry at University College London, told Full Fact that ethylene oxide has been used as a sterilising agent in the medical industry “for decades”. 

“When ethylene oxide is used in large quantities, being an alkylating agent, it will cause damage and disrupt DNA and protein in a cell. Indeed that is the basis of its use as a sterilizing agent,” she said.

“However, the sterilization process involves exposing a material to ethylene oxide for a few seconds or minutes, and then removing the gas entirely before the now sterile item is packaged. There is nothing left of the ethylene oxide once it is packaged, and there is no conceivable harm that can come from using an item sterilized in this way. 

“Using ethylene oxide is far safer than using, say, bleach, that is much less discriminating in its chemistry and leaves residues that may be undesirable.”