Introduction to Biocidal Testing

What are biocidal products?

Biocides are a chemical substance designed to destroy any harmful organisms. A biocidal product is a product containing one or more biocidal active substances, often alongside co-formulants. An active substance is a chemical compound, or a microorganism itself, used within a biocidal product that is responsible for making the product effective. A co-formulant is a substance that is not considered biocidal, but may help a product be more effective, such as stabilisers, preservatives, colourants, or fragrances.

Examples of biocidal products include:

• Disinfectants
• Preservatives
• Pest control
• Antiseptics
• Hand sanitisers
• Wipes
• Anti-bacterial handwashes and hand rubs
• Insecticides

Biocidal products are strictly regulated. Within the UK, products are regulated by the Health & Safety Executive (HSE), under the Great British Biocidal Product Regulation (GB BPR). In the European Union (EU), they are governed by the Biocidal Products Regulation (EC) No. 528/2012 (EU BPR), via the European Chemicals Agency (ECHA).

To market a product, it must comply with the regulation; including the use of active substances and list of suppliers approved by the relevant BPR.

Since Brexit, the person responsible for the biocidal product (authorisation holder) or the supplier must be established in the UK for a product to legally be sold within the GB markets.

Any product sold must contain sufficient information so that it can be used effectively and safely. This information is usually relayed primarily through the product label.

Biocidal products that wish to make a label claim must be supported by relevant efficacy test data.

Tests are categorised into 3 phases:

Phase 1: Mostly used in the development stages of products, either to prove an active substance within a product could be biocidal (for BPR submission to the list of approved active substances), or to prove that a co-formulant within a product has no biocidal activity – e.g., some essential oils have antimicrobial products, so if these are used to fragrance a product, they may wish to be screened to ensure that they are not contributing to reducing the number of organisms. In addition, sometimes several co-formulants mixed may react with one another to produce additional compounds that could also do the same thing.

For these tests, NO interfering substance is used, and instead, water is used.

A standard contact time of 5 minutes (bacteria), 15 minutes (fungi/yeasts) and 30, 60 or 120 minutes (bacterial spores) is used for testing. For bacterial spores, results are compared to reference test solutions.

As Phase 1 testing does NOT take into consideration specific applications, therefore CANNOT be used to make a biocidal claim.

Phase 2: Phase 2 biocidal testing is broken down into 2 steps:

 Step 1 (2/1) refers to quantitative suspension tests to establish that a product has biocidal activity (e.g., bactericidal, fungicidal, sporicidal, virucidal etc.) within a liquid suspension under simulated practical conditions appropriate for use.

Step 2 (2/2) refers to quantitative laboratory tests to establish biocidal activity (e.g., bactericidal, fungicidal, sporicidal, virucidal etc.) when applied to a surface or skin under simulated practical conditions.

Phase 2, step 1, and phase 2, step 2 biocidal tests are generally needed in combination to support efficacy claims for chemical disinfectants or antiseptics. This is because dried-out (desiccated) microorganisms may be stressed and therefore offer different challenges to biocides, in comparison to those within a liquid suspension.

Phase 3: Phase 3 testing includes tests under actual conditions, rather than laboratory conditions (field tests or on-site tests). Guidelines are in place for the scope of the testing requirements; however no current standards are in use for phase 3 testing, but they may be developed in the future. For phase 3 testing, bespoke methods related to specific applications can be created by Melbec to aid product efficacy claims.

All biocidal testing can be carried out using standard organisms or can be adapted to include alternative organisms required to support individual product claims. If these standards are not appropriate to support a product claim, we have the technical knowledge and expertise to develop and validate a bespoke method relevant to your requirements.

To discover our full range of testing, please use the ‘Understanding Test Requirements’ page to discover which standard tests you may require to complete your biocidal product claim.

There are many different types of disinfectants used within biocidal products, including:

• Alcohols
• Chlorine and chlorine compounds
• Hydrogen Peroxide
• Quaternary Ammonium Compounds (QACs)

Alcohols:

The mode of action for alcohols is by denaturation of proteins. Alcohols are commonly found in products including hand sanitisers, wipes, and disinfection liquids. Alcohols are generally a good biocidal choice for bacteria, fungi, and viruses. Generally, they are slightly more effective against Gram-negative bacteria than Gram-positive. Alcohols are ineffective against bacterial spores, and for fungi, alcohols are sometimes inconsistent, and higher concentrations are generally required compared to bacteria.

Did you know, 100% ethanol is less bactericidal than 70% (when the alcohol is diluted using water). This is because the ethanol takes longer to evaporate, and this longer contact time means that it can penetrate cells more effectively.

Chlorine and chlorine compounds:

For these types of disinfectants, the exact mode of action is unclear, however several modes of action, including oxidation of enzymes and amino acids and DNA breakdown are associated with chlorine compounds. Hypochlorites are the most widely used of the chlorine disinfectants, usually as liquid (Sodium hypochlorite). Household bleach is a common example of a disinfectant containing chlorine. It is a broad-spectrum disinfectant against bacteria, fungi and viruses. Often at concentrations considered biocidal, hypochlorites are often corrosive and can cause skin irritation and burns, therefore care should be taken with use.

Hydrogen Peroxide:

Hydrogen Peroxide works by producing hydroxy free radicals that attack membrane lipids, DNA, and other vital cell components. They show good germicidal activity for bacteria, fungi, spores, and viruses.

Most frequent concentrations used generally range from 6-25% within products.

Hydrogen peroxide is very stable when stored but can cause chemical irritation when used and can also cause cosmetic changes on surfaces, so care must be taken.

Quaternary Ammonium Compounds (QAC):

This type of disinfectant is widely used, with bactericidal action from inactivation of energy-producing enzymes and cell membrane disruption. Generally, it shows good fungicidal, bactericidal and virucidal activity against enveloped viruses. However, QAC’s are not sporicidal, and generally not tuberculocidal or virucidal against non-enveloped viruses. QAC’s are often used in general hygiene products.