AgMask - Evaluation of the types, efficient use and health risks of application of silver-based biocides to provide antimicrobial properties to face masks applied during the COVID-19 crisis

Last updated on 3-5-2023 by Wesley Van Dessel
Project duration:
January 10, 2020
September 30, 2022

In short

The Belgian population will have to wear face masks for a long period of time. Many of these commercial face masks contain silver-based biocides that give antimicrobial properties. To answer the uprising questions about which masks are safe and which are the best (stability, durability, …), we examine if the silver-based biocides applied in face masks are in accordance with the legal standards. During the AgMask COVID-19 project, we verify if small silver particles (in the form of ions and / or nanoparticles) are released from the face masks. These particles can then result in exposure to silver through inhalation, which can be unhealthy. The project evaluates and optimizes government instructions on the practical use of face masks and assesses possible health risks.

Project description

The AgMask COVID-19 project evaluates the types, efficiency and potential health risks of silver-based biocides that gives antimicrobial properties to face masks. It is important to know whether silver is released from face masks in the form of ions and/or nanoparticles, which can result in exposure to silver through inhalation. This information is essential to check the quality of such face masks and to monitor any risks

During this project we combine our expertise in analytical electron microscopy, heavy metal analysis and risk analysis with VITO’s breathing simulation and air sampling infrastructure. This unique collaboration allows us to:

  • characterise the silver-based biocides in face masks in situ
  • estimate the exposure by inhalation to silver ions and to silver (nano) particles
  • assess the main external factors that determine the release of silver-based biocide
  • determine the risk of the application of silver-based biocides in different types of face masks available on the Belgian market. 

The results allow us to: 

  • verify that the silver-based biocides used are in accordance with the legal standards
  • measure the extent to which wearers are exposed to the silver biocides used in mouth mask
  • evaluate and optimize government instructions on the practical use of face masks
  • check possible health risks: Which masks are safe? Which are the best (stability, durability, …)?


Final results and conclusions

In this project we have demonstrated that face masks can contain (nano)particles of silver biocides (and titanium dioxide) and we have also measured the amount of particles present.

Based on these data, we developed a methodology to define a safe ceiling (acceptable exposure limit) that would allow the production of intrinsically safe (safe-by-design) face masks.

In addition to this theoretical estimate, we tried, in collaboration with Ghent University and VITO, to measure the actual exposure to these (nano)particles while wearing a face mask. However, no available method gave a conclusive answer to this question. The current results therefore do not allow to draw any final conclusions on the actual health risks to the wearer, nor does the current scientific knowledge permit to draw general conclusions on possible health risks to the population from wearing face masks containing silver biocide (or TiO2) (nano)particles.

Based on these findings, we advised the competent authorities to anchor the safe-by-design concept more strongly in legislation. Further research and development is also needed with regard to the safety of products containing (nano)particles. More specifically in these three areas:

  • Verify what risks the use of face masks (and other consumer goods) containing nanoparticles entails in practice, and study their possible impact on health.
  • Regulate and control the quality of such consumer goods.
  • Investigate the health and environmental risks associated with the life cycle of products containing (nano)particles.

Download the final report:

Silver-based biocides and titanium dioxide particles in face masks for general use. Final report of the TiO2Mask and AgMask COVID-19 projects.

Intermediate results at the end of phase 1 — 2022:
The results of the analysis show that the silver values measured in 15 of the 20 masks examined were below the strict limit value. In 4 masks the threshold was slightly exceeded and in 1 mask the threshold was very much exceeded. 

More details can be found in the interim report on the first phase of the project.

Frequently asked questions about the AgMask-project

Early results from phase 1 (in situ characterisation) — February 2021:

In a first phase, we’ve analysed the Avrox face mask. Later in the study, we will also investigate other masks treated with silver-based biocides sold on the European market and, as a control, masks not containing silver.  

  • The first results indicate that the fibres of the Avrox masks do indeed contain a silver ion biocide as an active component, as stated by the manufacturer. We also found silver nanoparticles.
  • We also found titanium dioxide nanoparticles. 
  • The titanium dioxide particles are mainly bound within the matrix of the fibres. The silver particles are found on the surface of the fibres. Some nanoparticles are known in literature to potentially pose a health risk. However, the current results do not allow us to estimate whether these nanoparticles are actually released from the masks and to what extent the users are exposed. The methodology for this is still being developed in cooperation with colleagues at VITO. The results will not be available in the short term, as we are also entering new scientific territory here

PDF icon Download the analysis report of the Avrox face masks

If it turns out that the wearer of the mask may be exposed to nanoparticles, further investigation will be required to assess whether this poses any risk to the wearer’s health.  A product is not necessarily harmful because it contains certain substances. Everything depends on the actual exposure and the effects of those substances. This is another area where more study is needed.

Conclusion: at the moment we have early results from the first phase of the study. There are many unknown elements and it is therefore not certain whether there are any possible risks and how big they are.

In accordance with our duty to identify possible health risks, Sciensano has transferred these initial results to the competent authorities.

Frequently asked questions about the AgMask project

Frequently asked questions about the TiO2Mask project

Sciensano's project investigator(s):


Evelien Frijns
Kristof Tirez

Financial Source

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