Can Medical Swabs Sterilised With Ethylene Oxide Cause Cancer as Claimed?

By Naomi Wanjiku

An Instagram post claims that medical swabs sterilised with ethylene oxide can cause cancer.

The post notes that nasal swabs are made of nylon, rayon or plastic fibres, and plastic rods which are then sterilised in ethylene oxide.

Ethylene oxide is an effective pesticide and sterilising agent which makes it a preferred agent for decontaminating medical equipment, the post adds. Some of the devices that are sterilised using ethylene oxide include PCR/LFT swabs and SMEAR tests.

The post then raises the alarm that the chemical puts patients at risk of developing lymphoma, leukaemia, stomach, and breast cancers, and cautions users against taking tests that are conducted using swabs.

So, do swabs sterilised with ethylene oxide cause cancer? PesaCheck investigated.

According to the National Cancer Institute, ethylene oxide is a colourless flammable gas with a sweet odour. It is used in small amounts as a pesticide and, because it effectively damages DNA, it is also useful as a sterilising agent.

It is preferred as a sterilising agent because it is the only agent that can decontaminate a variety of medical devices, including those made of plastic, resin, metals, glass, and catheters without damaging them.

Medical swabs such as those used to perform polymerase chain reaction (PCR) and lateral flow tests (LFTs) are also sterilised using ethylene oxide.

Indeed, long-term and occupational exposure to ethylene oxide can result in lymphoma, leukaemia, stomach and breast cancers, as claimed in the post.

But how likely is it to get cancer from a medical swab?

PesaCheck reached out to a specialist in infectious diseases at Kenya National Hospital, Dr Samuel Njenga, who clarified that ethylene oxide does not remain on medical swabs after sterilization.

“Ethylene oxide is a gas. So it’s one of the gases used to sterilize anything that can be destroyed by heat. For the medical swabs, you cannot use heat so the best method to sterilize them is ethylene oxide. Once the gas passes through the swabs it kills any microorganisms but it does not persist on the swab because it is a gas,” Dr Njenga told PesaCheck.

Dr Njenga added that the only people who face the danger of getting exposed to cancer are the ones doing the sterilization.

“But if let’s say you are living in a place where you are being exposed to ethylene oxide, maybe you are the staff (the person doing the sterilization using ethylene oxide). If the equipment is faulty and ethylene oxide is leaking and you are not using the right protective gear, you can be prone to cancer after several years,” the infectious diseases specialist told PesaCheck.

Another expert in genetics and infectious diseases from the Australian National University, Dr Gaetan Burgio, also told AAP FactCheck that ethylene oxide is only used to kill microorganisms in medical swabs but is not part of the PCR test itself.

“The amount of ethylene oxide delivered in the chamber and the residual quantity after sterilisation is tightly monitored as a work health and safety procedure to ensure there is no residual substance left after sterilisation procedure,” Dr Burgio told AAP FactCheck.

A senior medical virologist from UNSW, Professor Bill Rawlinson, also told the fact-checking publication that if there are any residual amounts of ethylene oxide on the PCR swabs, the quantity would be negligible.

“There’s just not enough left over; and if it were leftover, time and exposure means that any residual ethylene oxide becomes denatured and becomes non-reactive,” Professor Rawlinson noted.

The Food and Drug Administration reviews premarket submissions of all the sterile medical devices in the United States of America before they are released into the market. The body ensures the medical devices meet all the requirements listed in the internationally agreed-upon voluntary consensus standards.

There are two voluntary consensus standards for ethylene oxide sterilisation which are ANSI AAMI ISO 11135:2014 and ANSI AAMI ISO 10993–7:2008(R)2012. These two standards contain guidelines on how to develop, validate, and control ethylene oxide sterilisation processes for medical devices.

The two standards also stipulate the acceptable levels of residual ethylene oxide and ethylene chlorohydrin left on a device after it has undergone ethylene oxide sterilisation. The two voluntary consensus standards also ensure levels of ethylene oxide on medical devices are within safe limits.


PesaCheck has looked into an Instagram post claiming that medical swabs sterilised with ethylene oxide can cause cancer and finds it to be FALSE.

This story was produced by Africa Uncensored in partnership with Code for Africa with support from Deutsche Welle Akademie.

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