What is a disinfection product?

Disinfection products belong to the group of biocides and aim to reduce the number of (pathogenic) micro-organisms on a surface to an acceptable level. Acceptable in this sense means that there is no longer a risk of contamination. Disinfection is defined as killing micro-organisms. The European "Biocidal Products Regulation" even gives a broader definition: "Active substance and preparation which, in the form in which they are supplied to the user, contain one or more substances intended to destroy a harmful organism, deter them, render them harmless, prevent their effects or otherwise by chemical or biological means.“

Chemical, thermal or biological disinfection?

Broadly speaking, there are three main forms to disinfect: chemical, physical or biological.

Chemical disinfection products contain substances that, when in contact with the substance for a certain period of time, result in the death of micro-organisms. This can happen in various ways: destruction of the cell wall, dehydration of the cell wall or substances that disrupt the propagation process and/or metabolism of the micro-organism.

For a certain period of time, what does that mean?

Effective killing of the desired number of micro-organisms when using a disinfectant requires a certain time for the product to do what it must do. It is called the contact time. The contact time required for a particular disinfectant to do its job effectively must be proven by the product manufacturer according to standard procedures and indicated on the product information (label and product documentation). To be able to sell a disinfection product in healthcare proving the efficiency of a disinfection product is mandatory in most countries. Manufacturers or distributors must register the products with local health authorities before the products can be marketed. In Europe for instance, disinfectants need to be approved by the European BPR(1) and in the US by the EPA(2). In the Middle East disinfection products must meet specific requirements and regulations that can vary by country.

Databridge market research has published an interesting paper that provides more information(3).

Dry or wet?

If you moisten a surface with a disinfection product, the liquid film will air dry within a certain time. During this process, the product is effective. The question is whether it still works once the surface is dry? And is the contact time specified by the manufacturer, the time between the wet and dried surface (wet contact time) or does a certain time span also count as long as the dried product is effective, if at all. Because the latter is difficult to prove and there is very limited scientific research available. One of the few studies that has been done, is a study published in 2021(4) on the bactericidal effect of "ready-to-use" disposable disinfection wipes for example, concludes that there is no additional bactericidal effect after drying of the disinfectant liquid film.

Wet contact time is what counts

From the above, it is clear that the contact time specified by the manufacturer refers to the wet contact time. There are US and European guidelines that either do not mention contact time at all or talk about contact time but do not define the term. However, most organizations advising the pharmaceutical industry define the term as wet contact time: the time between the, visually observed, moist and dried surface.

What dries up first is decisive

When using a disinfectant, the contact time prescribed by the manufacturer should be adhered to. Slightly longer is not a problem, shorter should not be done. Otherwise, there is a risk not killing enough micro-organisms and the risk of contamination is not, or not sufficiently, eliminated. As mentioned above, the contact time is simply the drying time of the disinfectant liquid film applied to the surface. However, a surface is never completely dry in its entirety from one moment to the next, so you must use the contact time for the first piece that has dried up. Make sense I would say.

By the way

• The purpose of disinfecting is not the same as the purpose of cleaning. Cleaning aims to remove dirt so that the surface is optically clean. Disinfecting aims to kill micro-organisms on the surface so that it is hygienically clean.
• The standard procedure for surfaces to be disinfected recommended by most infection control experts is a 3-step procedure: 

1. Absorb the (body) fluid (if applicable)
2. Clean
3. Disinfect

This takes time and, among other reasons, there are also products on the market that allow cleaning and disinfection in one operation. Although the 3-step procedure is considered to be the most effective, most experts support the 1-step procedure, under certain conditions, as an alternative to the standard procedure. 

Just a small note on the 3-step procedure. After cleaning and before disinfecting, the surface must be completely dry. If it is not, you dilute the disinfectant and the efficacy may be less.

• Disinfection only gives the desired result if it is performed correctly. Think for example of the right dosage, touching the entire surface and respecting the prescribed contact time.

• Unnecessary disinfection, excessive disinfection or improperly performed disinfection can lead to major problems in the short and long term. There are indications that long-term consequences can be that certain micro-organisms become resistant to certain disinfectants. Worldwide scientists are increasingly concerned with this emerging problem. The Dutch Health Council published an interesting study with recommendations on this in 2016(5)

Disinfection is not always needed, cleaning is sufficient enough. And when cleaning is sufficient, using microfiber cloths/mops moistened with water only is in many times a better solution than using a cleaning detergent. Dutch and Belgium IPC experts promote plead for professional cleaning instead of unnecessary disinfection. Which means that we have to disinfect only when it is needed, which of course does not mean that we don’t have to disinfect anymore at all. 

Contact time is only one aspect that matters for proper disinfection. But it is not just that. Disinfection is a serious job that requires expertise, care and high quality tools. In cleaning as well as in disinfection, rushing off is not desirable. We also must realize that rushing off disinfection can have far greater consequences than rushing off cleaning. In the end, cleaning and disinfection is a profession. Stakeholders should realize that and go for quality instead of the lowest price.

Ing. P.B. (Paul) Harleman 

Global Application Manager Vileda Professional 

Chief editor Vileda Professional Hygiene Magazine

Member technical committee VSR (Dutch Association Cleaning Research)