2022
Screening PMT properties with RIVM method
Screening PMT properties with RIVM method
Substances that are persistent, mobile and toxic (PMT substances) are listed for the first time in the European CLP Regulation. It will take some time before manufacturers have this information on the labels, but RIVM has in the interim developed a method for screening potential PMT substances. "We hope that this will help to identify harmful substances as early as possible," says Julia Hartmann.
Drinking water provision is one of the subjects that occupies the Netherlands National Institute for Public Health and the Environment (RIVM). As a scientific staff member in the drinking water team, Julia Hartmann works on diverse subjects concerned with the quality and quantity of drinking water in the Netherlands. She conducts research for the Dutch government for example, as well asinternationally. "Water flows freely and does not stop at countries’ borders, so it's very important that we also collaborate and exchange knowledge internationally," she says.
For example, on substances with PMT properties. Persistent means that a substance does not break down (or only does so a little) in the environment and remains present there for a long time. Mobile designates substances that are highly soluble in water and are therefore easily distributed. Toxic substances are poisonous to humans and ecosystems. Plants and animals become sick because of these or even die. "It's the combination of these properties in substances about which we are most concerned," says Hartmann.
The Dutch and European governments aim to keep these substances out of the environment and to keep the concentrations already present as low as possible. "Substances that are both persistent and mobile cannot be purified out of the water by the drinking water companies using current purification techniques, or can only be purified out with great difficulty," explains Hartmann. Some poly and perfluoroalkyl substances, i.e. PFAS, have PMT properties. PFAS are man-made chemical substances. They do not arise in the environment naturally. Examples of PFAS are GenX and PFOA (perfluorooctanic acid). PFAS are used in applications including nonstick coatings on cooking utensils (Teflon).
Some substances are non-toxic and yet very persistent and very mobile (vPvM) and their concentrations in the environment can increase rapidly. "This category is formally non-toxic, but if you are exposed to them for long enough, these substances can still lead to undesirable effects in humans and ecosystems," says Hartmann.
Recently, PMT substances have been included as a hazard category in the European CLP Regulation (Classification, Labelling and Packaging) that has existed since 2008 and was updated on 20 April 2023. These rules oblige businesses in the European Union to state on product labels what chemical substances they contain. And also in which hazard category they come, so we know whether we should be concerned about them.
Hartmann: "This ensures that everyone in a substance’s production chain knows that it has hazardous properties, and this includes consumers." This could be a manufacturer of clothing who knows exactly what substances are in the dye or the textile, or a consumer who knows what is in the bottle of cleaning product in the kitchen cabinet.
In 2023, the hazard categories endocrine-disrupting chemicals, PBT/vPvB and PMT/vPvM were added to the Regulation. PBT stands for persistent, bio-accumulating and toxic, and the substances with bio-accumulating properties accumulate in the food chain.
Hartmann calls the fact that the PMT substances are now also in the Regulation "a real milestone." "Until this update, there was still a lot of discussion about what a PMT substance formally is. To include this in legislation, you must of course have criteria. And now the first step has been taken for this."
The information will however not appear immediately on the labels this year, because businesses get the opportunity to modify their production process during a transition period. From 1 May 2025, businesses must comply with the CLP Regulation for substances that are new on the European market. For substances that are already on the European market, the obligation applies from 1 November2026. Until these dates, businesses may state the information voluntarily.
To nonetheless start making some progress here, RIVM has developed a method to screen substances for PMT or vPvM using automated means. This research, which Hartmann collaborated in, originates from the PMT thematic group, an association that comes under the working group 'Approach to Upcoming Substances.' In this, experts from the Ministry of Infrastructure and Water Management, the RIVM, Rijkswaterstaat, the Provinces, Vewin, drinking water companies and RIWA have discussed the approach to and possible harmfulness of new and unknown substances since 2015.
The RIVM translated the results of the research into the PMT screening tool that has been on the Institute's website since 1 July 2023. Here, permit issuers can in an accessible way look up to what extent a substance is possibly persistent, mobile and toxic. "We hope that this will help in the assessment of the permits for wastewater discharges, so that PMT substances can be identified as early as possible," says Hartmann.
At this time, the RIVM has screened around 6000 substances: there PMT scores may be looked up on the website. Each substance receives a score between 0 and 1: 0 means a substance probably has no PMT properties, while 1 means the probability is very high that the substance does have these properties. The intention is to screen and even more substances.
The point therefore is to estimate the properties of the substance. "The screening is based on models and not on experimental data," explains Hartmann. "We try to make a prediction based on substances with similar structures." The exact PMT properties have in fact only been measured and recorded for a limited number of substances, so the screening is therefore a first step. After this, the exact properties of suspect substances can be investigated in a laboratory. This is a lot of work and so was not mandatory until recently.
Hartmann opens the RIVM website and enters as an example 1,4-dioxane, a substance that has applications including a solvent in the paper, cotton and textile industry, and which is now categorised in Europe as a Substance of Very High Concern due to its PMT properties. The substance has a PMT score of 0.38. You can also see that the substance is expected to be 0.09 persistent, 0.73 mobile and 0.84 toxic. Below 0.33, the PMT score is low to average, between 0.33 and 0.5 it is high, and the researchers consider a score exceeding 0.5 to be very high.
“1,4-dioxane is a good example of the fact that alongside general PMT score, the user of the screening method also has to look carefully at the separate scores for P, M and T," says Hartmann. "Once experimental data is available, this overrules the scores in the screening method. This is the case for 1,4-dioxane. We know that this substance is very persistent; the score of 0.09 for persistence is this an underestimate."
Considering alternatives
If the PMT score of a substance in a permit application emerges as high, the permit issuer could for example ask for more information about the substance before a discharge permit is issued, explains Hartmann. Or an alternative to the use of the substance could perhaps be considered. Discussion is still underway in the European Union, she reports, about exactly what experimental data companies should have to supply about how mobile a substance is.
Besides the CLP Regulation about the classification, labelling and packaging of substances, the European REACH Regulation about the registration, assessment, authorisation and restriction of chemical substances exists. REACH contains a list of substances of very high concern which is a different classification from CLP. "If a substance is classified as hazardous in the CLP Regulation this can be a warning to look at it in more detail in REACH," explains Hartmann. "So is this a substance of very high concern, yes or no?"
Confronting PMT in Europe and worldwide
There is currently a lot of attention to PMT substances in the Netherlands and Europe. Various European research projects are working on the issue, states Hartmann. The PROMISCES project for example, which the RIVM is also involved with, concerns preventing PMT substances in the groundwater system. "This study revolves around the questions: will the circular economy be held back by the presence of PMT substances, and if so, what solutions can we come up with for this?"
ZeroPM is another European Union-financed project about PMT substances that RIWA is also involved with. Hartmann: "The aim of this project is no more pollution by PMT substances. And what you can do if they are present in the environment and what substances then have priority."
Ultimately of course PMT substances are a worldwide problem emphasises Hartmann. This is why the European Union will chair a new United Nations workgroup with the aim of developing worldwide criteria for PMT and vPvM substances. Hartmann: "It is very important to keep these substances out of the environment as far as possible, and for this worldwide attention is crucial."