On November 5, the Section on Risk Assessment organized a meeting with the intriguing title: Everything you always wanted to know about PFAS. This meeting was originally scheduled for April 7th, 2020, but was postponed to November due to COVID. More than 90 participants attended this virtual meeting. Fenneke Linker from the Risk Assessment Section chaired the meeting.
As a short introduction, Professor Annemarie van Wezel, University of Amsterdam, gave a general overview on PFAS. PFAS use is really wide-spread, in almost all industry branches and in many consumer products. OECD list contains >4700 PFAS substances. Only 107 substances are currently registered under REACH. PFAS are also called ‘forever chemicals’ because of their persistence. They are widespread, and present in 99 of 100 environmental samples.
The main health effects are effects on the immune system, on the liver failure, on renal function and on thyroid hormone levels. Because of the heterogeneity it is difficult to derive general health levels.
For humans, dietary intake is the main route of exposure.
In 2020 EFSA has proposed a single group Tolerable Weekly Intake (TWI) of 4.4 ng/kg bw per week for the sum of PFOA, PFNA, PFHxS and PFOS. Europeans partly exceed this TWI.
Worldwide PFAS is found in environmental organisms. Most reported PFAS concentrations in the environment are below their predicted no effect concentration. However, our understanding of the toxicity is incomplete, due to lack of information on new PFAS, precursors and degradation products and mixture toxicity.
Annemarie illustrated that both in the Green Deal and in the EU Chemical Strategy, essential use and benign by design (or safe and sustainable) are important issues, that need to be further worked out. She advertised an EU project, PERFORCE, that started in January 2020, that is an innovative training network to train a new generation of innovative early stage researchers, so that they will be able to face current and future challenges and to convert knowledge and ideas into products and services for economic and social benefit.
Statement: The EFSA opinion for 4 PFAS should be summed to 4000+PFAS.
30 out of 90 people voted in favour.
A few remarks were made via the chat: what are the advantages /disadvantages of creating a single limit on all 4000+ PFAS when the group of chemicals is so diverse? An advantage would be a more inclusive risk assessment, but a disadvantage is that a lot of tox data has to be available.
Another question was whether it would be possible to use toxic equivalence like the TEQ for dioxins Instead of gathering all tox data, or are the adverse effects too different? Another participant referred to an RIVM paper on relative potency factors .
A third question was whether background levels only originate from pollution? The other sources are one of the big unknows. There are several activities related to pollution (e.g. at airports where fire fighter foams were used). Also paper mills might have a relevant contribution, according to a recent exploratory study by RWS. Different investigations are going on to further map the sources.
Statement: Research focus should be on possibilities how to replace PFAS by benign alternatives. A majority, 60 of 90, raised their hand. It was also indicated that also non-chemical alternatives should be considered.
Determination of PFAS limits in soil
Arjan Wintersen of the Dutch National Institute for Public Health and the Environment (RIVM) presented the determination of PFAS limits in soil, prepared together with his colleague Piet Otte. There are three building blocks used in setting Environmental Quality Criteria for soil: Human health risk limits, ecological risk limits (covering both direct and indirect (via food web) exposure) and “other” (risk) limits, which may be, e.g., background levels. RIVM is responsible for preparing science-based advisory limit value, the Ministry of Environment subsequently decides on the legal limit values.
Depending on the use of the soil, differently criteria are developed. When used for agriculture or designated as “nature”, a stricter limit value applies than for residential use; for industrial use the least strict value is applied.
At the moment, only two PFAS are significantly present in Dutch soil: PFOS at 1.4 µg/kg dry soil and PFOA at 1.9 µg/kg (95th percentiles). Higher concentrations are found in top soil than in subsoil and predominantly in built areas, not in rural areas or areas designated as nature. For PFOA, there is a clear link with its source, Nemours in Dordrecht, as its concentration decreases exponentially with the distance for the plant. There are no indications other PFAS like GenX are structurally present in Dutch soil.
The current soil standards addressing human health effects were based on Tolerable Daily Intakes (TDI’s) derived by the RIVM some three to five years ago. They vary between 6-21 ng/kg bodyweight/day for PFOS, PFOA and GenX. These are well above the current background values in soil. However, this year EFSA has derived a Tolerable Weekly Intake (TWI) of 4.4 ng/kg bodyweight for the sum of PFOS, PFOA, PFNA & PFHxS, which corresponds to 0.63 ng/kg bodyweight/day. Point of Departure was a Benchmark Dose Level (BMDL) of 17.5 ng/mL in blood serum of breast of children, associated with a reduced immune response.
Ecological risk limits were based on the relative number of species affected at certain soil concentrations of PFOS, PFOA or GenX, either directly or indirectly via the wood web. Due to the biocumulative properties of PFAS, the indirect limit values are up to nearly two orders of magnitude lower, and thus determine the limit to be used. These are still above the background valuers, but less than one order of magnitude.
Arjen concluded by summing up what we still do not know, e.g. the transfer and accumulation of PFAS from soil to crops and farm animals. After his presentation quite a number of questions were asked, e.g.:
- Are there other sources than man-made PFAS in the soil background levels?
- Unknown, but RIVM will look into this issue
- What about levels in groundwater?
- Nation-wide Research is on-going, will be published beginning of next year
- Has intake of PFAS via supermarket bought food been taken into account in PFAS exposure calculations?
- No, that is not in the RIVM model (valid for any substance exposure via the environment)
To conclude Arjen put a statement to the vote: “The PFAS that we measure in the environment are only the top of the iceberg.” It was supported by 40 of the 80 odd attendants of the symposium. Arjan himself left the answer open and stated PFOS and PFOA are the main PFAS in soil, but that it might be different for other compartments, depending on the mobility and the affinity of the PFAS (for components in the compartment concerned).
Marije Schouwstra, policy coordinator at the Ministry of Infrastructure and Water management (IenW) introduced us to 50 years of soil policy. In soil policy there is a balance between protection of the soil and the use for economic and social purposes. The basic principles are prevention and remediation. The approach in policy was that all contamination should be eliminated; remediated sites should be fit for all possible future functions. With PFAS a new kind of pollution was introduced: omnipresent despite a prevention policy. Such a wide dispersive use was not addressed in the policy.
Within the soil policy, according to the Standstill principle it has to be prevented that cleaner sites are polluted as well; if you want to transport soil, you have to be sure that you do not contaminate another site. You need a risk based limit value (risicogrenswaarde) to be able to set a norm, and that takes time.
Marije shared a few lessons learned: Communication in extremely important. The Framework was experienced as tightning the rules. And our regulations have to be adapted to diffuse pollution, there is a need for development of a new methodology to cope with diffuse emerging contaminants.
Statement: I make a conscious choice and try to buy products without PFAS.
30 out of the 90 participants raised their hand. As a consumer it is hard to know if products contain PFAS. But for some products, like rain coats and cooking utensils, you can buy PFAS-free products. It might be indicated on the label. But for a large number of products it is impossible to make a well informed choice.
Statement: We have to phase-out all PFAS, also in essential uses. Only 15 participants of the 90 raised their hand .
Statement: before introducing new substances in production processes, you should proof its non-toxic an non -persistence character.
The majority of the participants agreed: 54 of 90
From soil to (drinking) water
Frederic Béen from the KWR Water Research Institute presented the analytical methods available for determining PFAS in drinking water as well as ways to remove them from drinking water. At the EU-level two limit values have been set for PFAS, established in December 2019: 0.1 µg/L for the sum of the 20 most important PFAS and 0.5 µg/L for the sum of the 4700 known PFAS. The latter value is not yet in vigour, awaiting the development of a suitable analytical method by the EU over the next three years. The new TWI for four PFAS developed by EFSA has not yet been used to derive a drinking water limit, but preliminary calculations using a simplistic approach lead to a value of about 4 ng/L.
Frederic presented the following analytical methods:
- Total organic/extractable fluorine methods: these are useful for rapid screening, yet not ideal for testing drinking water as their Limit of Detection (LoD) is 0.5 µg/L.
- Total oxidizable precursors assay (TOPA): only useable for known PFAS, requires further validation and standardization, needs to be adapted to accommodate emerging PFAS as well
- Broad screening methods: do not need reference standards, will also identify unknowns, but mainly qualitative although more quantitative applications are being developed based on machine learning
- Comprehensive workflows: including a step-wise combination of available analytical methods to analyse water quality in the Netherlands and develop a monitoring programme targeted at locally important PFAS, a research project of KWR in collaboration with WFSR, RIWA, Water Boards and Dutch drinking water companies.
PFAS are extremely persistent and difficult to remove from drinking water. There is a well-developed method (Granular Activated Carbon (GAC)), that works well for long-chain PFAS but is less effective for the short-chain ones. For the latter PFAS various technologies are in development, but not ready yet.
After his presentation a number of questions were asked, e.g.:
- How do you avoid cross-contamination during sampling (e.g. when the samples wears a PFAS-treated rain coat)?
- This is above all an issue in the lab, as many equipment used contain PFAS. Therefore you have to be careful and make ample use of appropriate blanks
- Should we also use bio-assays to analyse for PFAS?
- Yes, indeed.
- Instead of removing PFAS from drinking water, shouldn’t we try to remove it somewhere else (probably meaning at the source)?
- This discussion is on-going, but there is no decision yet.
From water to livestock to consumers
Jacqueline Steenbergen-Biesterbos from the Netherlands Food and Consumer Product Safety Authority (NVWA) presented their study, in which NVWA investigated whether there is a possible risk for human health due to exposure to PFOA and GenX in food. In 2017 and 2018 PFOA and GenX were found in soil and water due to air deposition of these substances, in Dordrecht and Helmond. Livestock might be exposed if polluted soil, grass or water is consumed. Subsequently, consumers might be exposed via the consumption of products of animal origin. Dietary exposure of children and adults was determined by measuring PFOA and GenX levels in various food items and using consumption data from the Dutch National Food Consumption survey.
The exposure of children and adults to PFOA and GenX via the consumption of cow’s milk, meat (cow/sheep), cheese, yoghurt, egg and eel does not pose a risk for human health.
Despite the fact that the exposure of children and adults to PFOA via the consumption of carp exceeds the provisional EFSA-TDI of 0.8 ng/kg body weight per day, the risk for human health is expected to be low. A TDI is a health based guidance value based on long term exposure. The carp was caught in a fishing pond in the close vicinity of a factory in Helmond. Fish from this pond will probably only, on occasion, be eaten by specific consumers (sport fishermen) leading to short term exposure. Furthermore, the risk assessment of carp was based on one fish and this fish does not provide an overview of the PFOA distribution in fish from the fishing pond.
Based on a comparison with the provisional EFSA-TDI of 0.8 ng/kg body weight per day, the exposure of children and adults to PFOA via the consumption of sheep’s milk might pose a risk to human health. The risk assessment for sheep’s milk is based on experimental transfer data from two sheep that do not show the same kinetics. Compared to dairy cows, the transfer of PFOA to milk in sheep is higher than one might expect. Therefore, no firm conclusion about the human health risk can be drawn. The full report can be found via https://www.nvwa.nl/documenten/consument/eten-drinken-roken/overige-voedselveiligheid/risicobeoordelingen/advies-van-buro-over-de-chemische-stoffen-pfoa-en-genx-in-voedsel.
Krista Bouma from the NVWA stated that for the risk assessment of PFAS in food contact materials (FCM), paper and paperboard are the main concern since PFAS in water and grease repellent coatings of these materials are present as monomers and not as a polymer, meaning they may more easily migrate to the food contained in them. However, data are needed on migration into food (instead of data on food simulants) in order to perform a more precise risk assessment. The NVWA has developed an analytical screening method that they can use on paper and paperboard to identify PFAS’s present. 46 samples (paper and paperboard intended for hot and/or fatty contact) were screened. Significant amounts of PFCA’s C13 and C14 were found, other PFAS’s (PFOA, PFOS, GenX, fluorotelomers) were either not detectable or present in negligible amounts. Further development is also dependent on developments in legislation (maximum residue levels in food versus or migration limits). Further research is carried out by WFSR, PFAS will be determined in easy and fast-food, packaged in paper/paperboard. If significant amounts of PFAS are detected in the food, then also the food contact material will be investigated to establish if this was the source of the PFAS. The report is expected in Q1 of 2021.
Statement: a risk assessment based on exposure via food is not sufficient. Other exposure sources/routes should also be taken into account.
A majority, 50 of 90 participants, raised their hand and agreed with this statement.
Statement: Should PFASes also be banned from non-stick polymeric coatings? Of the 90 participants, 42 agreed.
Fenneke Linker closed the meeting with a final statement: I gained new insights today. The virtual hand of 65 of the of 90 participants was raised! The slides of the presentations will be made available in the Risk Assessment section of the NVT website.
Presentation 1: Annemarie van Wezel
Presentation 2: Arjan Wintersen
Presentation 3: Marije Schouwstra
Presentation 5: Jacqueline Steenbergen-Biesterbos en Krista Bouma