Efficacy Testing for Preservatives (PT7, PT9) – Challenges and Goals

Efficacy Testing for Preservatives (PT7, PT9) – Challenges and Goals

During the 2024 Dublin Biocides Symposium in March, Trine Østergaard Jensen, Berit Lindegaard and Dr Jonas Stenbæk from the Danish Technological Institute (DTI), gave a presentation about the challenges and goals of efficacy testing for preservatives (PT7 & PT9).

The DTI performs various accredited tests including testing of biocides according to the Biocidal Products Regulation (EU) No. 528/2012 (the BPR). In order to determine what efficacy testing is required for PT7 and PT9, the interested party must share first information regarding the label claims and Summary Product Characteristic (SPC) with the test centre. It is essential to determine first what needs to be protected, what biology needs to be controlled, how it is going to be used or applied and in which situations, if it is used on/in a material and which one, and whether it is preventative or curative.

Berit explained that efficacy testing is considered core data since according to the BPR, biocidal products are necessary for the control of organisms that cause damage to natural or manufactured materials. The Tier 1 approach includes screening laboratory testing which does not always provide sufficient documentation, and in this case Tier 2 testing which includes realistic life testing is needed.

Berit warned that efficacy testing can take a while to perform as the applicant must take into consideration the time needed to prepare the material (i.e., incorporation of the product into the textile) and potential ageing requirements. Reference samples without biocide and with a known biocide are often included.

Furthermore, Berit explained the importance of determining the minimum inhibition concentration (MIC) and testing the product at different concentrations as there is often a maximum concentration restraint of the biocidal product to minimize any adverse effects to human health or the environment. Following the Guidance documents (Volume II Efficacy, Assessment + Evaluation, Parts B+C) is common practice. However, in certain cases for some product groups like PT9, there is a need to modify the tests. The value entered in IUCLID for the reliability index of the test method should be 1, as 2 or 3 is usually considered only as additional information, and a certified institute should be used.

Dr Jonas showed some examples of the PT7 testing performed at DTI such as BS 3900 testing which is a screening method. Dr Jonas explained some of the deficiencies of this testing and showed a more realistic modified test method developed at DTI where a more natural mold environment in the chamber was employed. Artificial ageing such as QUV can also be applied. Graphs showing tropical testing with results within only 60 days were also shared, performed as alternative to Tier 2.

Trine presented some examples of PT9 testing performed at DTI explaining the differences between Phase 1 which is a laboratory/ screening test and a Phase 2 test where the same matrix was tested, and ageing could be assessed. Trine explained the importance of showing first that the target organism, e.g. bacteria can grow in/on the untreated material as under normal conditions most bacteria are not able to grow in most articles.

If you need support with efficacy testing or any other aspects of the registration of your biocidal products, please contact Kerona’s Biocide Team at info@kerona.ie

If you missed the symposium, you can download the slides here: Dublin Biocides Symposium 2024 – Speakers Presentations – Kerona Scientific Ltd.