FULL CLAIM: Ethylene oxide in nasal swabs is harmful, changes DNA, and increases the risk of developing cancer.
Testing for COVID-19 infection is one pillar in the attempt to contain the pandemic. For many types of antigen and PCR tests, swabs are used to collect material from the nasal passage or the throat, which is then tested for the presence of SARS-CoV-2.
In a video shared on TikTok and Instagram, a man claimed that ethylene oxide on nasal swabs in COVID-19 testing kits used in Australia is harmful. The person in the TikTok video claimed that ethylene oxide on the swab alters DNA and increases a person’s risk of developing different types of cancer. He also claimed that dry ethylene oxide on the nasal swab is inhaled, leading to lethal after-effects. This led a social media user to also claim that ethylene oxide reacts chemically with various proteins and DNA, and damages or destroys cellular structures.
Similar claims have been made previously, including on Facebook about nasal swabs in PCR tests used in the UK (e.g. here and here). Over 300 people have signed a petition to the UK parliament to remove ethylene oxide from self-testing kits. These and similar claims have been fact-checked and found to be false, e.g. here, here, and here.
Ethylene oxide is used to sterilize medical products and devices. The U.S. Centers for Disease Control and Prevention states that about 50 percent of sterile medical devices are sterilized using ethylene oxide gas, especially devices that are sensitive to heat or moisture. Sterilization using ethylene oxide gas is one of two options for sterilizing nasal swabs used for COVID-19 tests, the other being radiation, as the U.K. Medical and Healthcare products Regulatory Agency (MHRA) explains.
During this sterilization procedure, the products are placed into a chamber, which is filled with ethylene oxide gas. As part of this sterilization process, the sterilized product is “aerated” so that residual ethylene oxide is removed.
According to a study conducted in 2017 on swabs used for collecting DNA, no amount of ethylene oxide left on the swabs was measurable four weeks after the swabs had been treated with ethylene oxide. And in a fact-check by FactCheck.org, Stuart Battermann, professor of environmental health sciences at the University of Michigan, stated
a “swab is briefly exposed to the gas, then removed and packed. The gas would rapidly disperse. There is no coating or liquid or anything like that on the swab. By the time the swab is used, there’s likely hardly a trace of EO remaining. It is true that this gas is hazardous when breathed in at high enough concentrations for long enough periods. This is not the scenario for the occasional use of a swab.”
Ethylene oxide is used for sterilization because it disrupts DNA, as Andrea Sella, professor of inorganic chemistry at University College London, stated in a fact-check by Full Fact:
“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.
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.”
According to the U.S. Environmental Protection Agency (EPA), evidence indicates that long-term exposure to ethylene oxide by inhalation increases the risk of some blood cancers as well as breast cancer. In 2016, ethylene oxide was classified as carcinogenic to humans by the EPA. However, the most common route of exposure to ethylene oxide for the general population is by smoking tobacco.
Guidelines have been developed setting out how much residual ethylene oxide can remain on a product sterilized using ethylene oxide after aeration. These guidelines take into account how a device is used, how often, and for how long, and ensure that any residues pose a minimal risk of causing cancer and apply to both adults and children, as the MHRA explains.
Responding to a Freedom of Information request about the safety of ethylene oxide used in nasal swab sterilization, the MHRA stated that contact time for ethylene oxide exposure is divided into the categories limited, prolonged, and permanent duration, while the type of contact is divided into surface contacting and implant. Swabs used for COVID-19 tests fall into the category of “limited contact time” and “surface contacting”.
The MHRA also explained that on average, contact time with a nasal swab for a single test is around 20 seconds. If a person is tested twice a week, this person is exposed to any residual ethylene oxide for around 40 seconds per week. This contact time still falls within the category of “limited contact”, and a person would have to be tested twice weekly for over 40 years in order for the total contact time to fall under the “higher contact” category. The MHRA also stated:
“In the highly unlikely event that a swab does contain a residual amount above the allowable limit, the risk to the user is still considered to be very low. This is because, to be on the safe side, the limits of residue were deliberately set to be much lower than the limit thought to be a risk of causing cancer.”
In a statement to Reuters, the U.S. Department for Health and Social Care addressed the claims that COVID-19 test swabs pose a danger to humans. In its statement, the Department 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.”
In summary, only residual ethylene oxide remains on nasal swabs after sterilization. The sterilization process is regulated, so that medical devices sterilized using ethylene oxide are safe to use.
- 1 – Wilson-Wilde et al. (2017) Investigation into ethylene oxide treatment and residuals on DNA and downstream DNA analysis. Science and Justice.
- 2 – Kirman et al. (2020) Ethylene oxide review: characterization of total exposure via endogenous and exogenous pathways and their implications to risk assessment and risk management. Journal of Toxicology and Environmental Health, Part B.