FOI release

Freedom of Information request about safe thresholds of ethylene oxide residue on NHS Covid Lateral Flow (LFT) test swabs currently distributed by the NHS (FOI-21-300)

Published 28 May 2021

Thank you for your email of 25 March 2021 with the following requests:

“I am requesting a copy of all and any documentation concerning and/or determining safe thresholds of ethylene oxide residue on NHS Covid Lateral Flow (LFT) test swabs currently distributed by the NHS.

I request any and all studies, independent tests, risk assessments and/or independent reviews in relation to the safety and ‘safe frequency of use’ of Covid Lateral Flow tests treated with ethylene oxide for the detection of SARS-Cov2. 

I request the name and address of all manufactures of Covid Lateral Flow Tests that have been treated with ethylene oxide distributed by the NHS to the public in the UK.”

The MHRA does not hold the information you have requested.

The manufacturer is responsible for testing the amount of ethylene oxide left on the device after sterilisation to ensure that the residue is below the allowable limit. The allowable limit of residual EO is set by the international standard ISO 10993-7:2008.

The sterilisation process, including residual testing, is documented by the manufacturer. This documentation is reviewed by an independent third-party body called an ‘Approved Body’ (in Europe these are called ‘Notified Bodies’), before the manufacturer is allowed to manufacture swabs for the UK market. Testing on random samples of swabs by the approved body once market approval has been given is unusual. However, the ‘Approved body’ carries out periodic audits of the manufacturer’s process to ensure continued compliance.   

Each approved body has a unique identifying number that appears next to the CE (or UKCA) mark symbol on the packaging of the swab. An internet search using this number with the words ‘notified body’ should give the name and contacts for the Notified or Approved body. The MHRA audits these Approved Bodies to make sure they are fulfilling their obligations. European Notified Bodies are audited by their relevant Competent Authority.

We understand that there is concern about the use of ethylene oxide, a known carcinogen, to sterilise swabs used in Covid-19 tests. We would like to reassure you that this is a safe method of sterilising swabs. It is used to sterilise a wide range of medical devices.

The sterilisation process consists of a number of highly controlled and monitored stages, including removing ethylene oxide after treating the swabs. The amount of residual EO that is allowed on medical devices is set by the international standard ISO 10993-7:2008. As part of the sterilisation process the manufacturer must confirm, and document, that the residual EO level on a medical device is below the specified allowable limit before the device is packaged ready for use.

These allowable limits were selected to ensure that any residual levels present on the medical device after sterilisation pose a minimal risk of causing cancer to the person using the device.

The amount of residual ethylene oxide that is allowed on any medical device, including test swabs, has been set according to the time that the device (swab) is in contact with the person. This contact time is divided into 3 categories: limited, prolonged, and permanent duration.

The swabs used in lateral flow test kits fall into the category of limited contact time.

These limits apply to adults and children.

These allowable limits were selected to ensure that any residues on the medical device after sterilisation pose a minimal risk of causing cancer to the person using the device.

The average time of contact for a single test (around 20 seconds) and the current testing regime (twice a week), means that each person is exposed to any residue on the swab for around 40 seconds per week.

Calculating from the allowed residues, even with this increased use of the swabs, the contact time still falls within the ‘limited contact’ level originally set by the manufacturer.

A person would need to be tested twice a week for over 40 years for the total contact time to be in a higher contact category.

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.

If you disagree with how we have interpreted the Freedom of Information Act 2000 with regards to your request, you can ask for an internal review. It will be carried out by a senior member of the Agency who was not involved with the original decision. Internal review requests should be submitted within two months of the date you receive this response and addressed to: [email protected].

If you were to remain dissatisfied with the outcome of the internal review, you would have the right to apply directly to the Information Commissioner for a decision. Please bear in mind that the Information Commissioner will not normally review our handling of your request unless you have first contacted us to conduct an internal review.

The Information Commissioner can be contacted online: https://ico.org.uk/make-a-complaint/official-information-concerns-report/official-information-concern/ 

Yours sincerely

MHRA Customer Service Centre

Medicines and Healthcare products Regulatory Agency

10 South Colonnade, Canary Wharf, London E14 4PU