Mediaroom

EFCTC COMMENT ON STUDY ON TFA IN RIVERS IN GERMANY AND RIVERS AS SOURCE OF DRINKING WATER

EFCTC COMMENT ON STUDY ON TFA IN RIVERS IN GERMANY AND RIVERS AS SOURCE OF DRINKING WATER

27.08.2018

A recent scientific paper [1] describes a comprehensive study on the quantities of trifluoroacetate (TFA) found in major rivers across Germany. Following this study, it has been claimed that HFO-1234yf has possible negative consequences for the production of drinking water. However, currently HFO-1234yf is at most an insignificant contributor to the quantities of TFA found. Furthermore, based on a recent study on Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe [2], the projected growth in use of HFO-1234yf and resulting emissions of TFA is expected to have only a small contribution to the quantities of TFA found in German rivers.

Even after a complete conversion of the European vehicle fleet, HFO-1234yf is calculated to result in expected average values of 0.6 – 0.8 µg/L of TFA in European rain water. This is well below the (HRIV) of 3 µg/L for TFA in tap water, which in turn provides an extremely small contribution to the acceptable daily intake (ADI) of TFA according to the European Food Safety Authority (EFSA). This is consistent with 2015 UNEP Ozone Secretariat Informal Brief on Ecological Issues on HFCs [3] which states ‘Projected future increased loadings of TFA to playas, land-locked lakes, and the oceans due to continued use of HCFCs, HFCs, and replacement products such as HFOs are still judged to present negligible risks for aquatic organisms and humans.’

HFO-1234yf is being used for mobile air-conditioning because it has an extremely low GWP (<1), less than the GWP of CO2, and a very short atmospheric lifetime (10.5 days) and a good balance of safety and technical properties. It has only recently been introduced into mobile air-conditioning in the EU and HFC-134a could be used in some new vehicles until the end of 2016. To date emissions of HFO-1234yf will be very low. Emissions during vehicle manufacture are extremely low, and new vehicles and servicing standards have much improved refrigerant containment compared to previous generations of vehicles resulting in lower emissions. In addition, very few vehicles containing HFO-1234yf will have reached end-of-life.

HFO-1234yf breaks down in the atmosphere to form TFA, which is removed by dry deposition or rained out as it is very water soluble. It is well established that TFA is a ubiquitous natural component in rivers, lakes, and other surface water bodies. More than 95% of the salts of TFA found in the oceans are naturally produced. These salts are inert and not of toxicological or environmental concern in the small concentrations that are present in the oceans, playas, and lakes. [3]

Salts of TFA are essentially non-toxic to mammals with acute LD50 values of greater than 5 g/kg (5 g per kg of body weight; to help put this in context the LD50 for common salt is 3.5 g/kg [5]). Because of their high solubility in water and their very small octanol-water partition coefficient, they do not bioconcentrate in aquatic organisms, and do not biomagnify in the food chain. Thus, they present negligible risk to organisms higher on the food chain, including humans. [3]

In addition to natural TFA, the paper [1] on the quantities of trifluoroacetate (TFA) found in major rivers across Germany, discussed the variety of TFA sources that can lead to elevated levels of TFA being found in surface waters. The paper noted that at two sampling points at the upper Rhine (Basel and Karlsruhe), the mean concentration of TFA salts was below 0.5 µg/L, with similar levels in the in the upper Alz river, with significantly higher concentrations in other parts of the river system.

The study on Future emissions and atmospheric fate of HFC-1234yf from mobile air conditioners in Europe [2], reports that TFA rain water concentrations in southern Germany in 1995/96 were 0.11 µg/L, and in Switzerland in 1996/97 average surface water TFA concentrations were 0.08 µg/L in rivers and 0.12 µg/L in lakes. Concentrations in the oceans are typically in the range 0.15 to 0.2 µg/L. The study assessed the future emissions of HFO-1234yf after a complete conversion of the European vehicle fleet and calculated that the use of HFO-1234yf would result in expected average values of 0.6 – 0.8 µg/L of TFA in European rain water.

Based on estimates of current and future use of HFCs, HCFCs, and HFOs, additional inputs to the global oceans, salt lakes and playas will add only fractionally (estimated to be less than 0.1%) to amounts already present from natural sources such as undersea vents and volcanic activity [3]. If 0.2 µg/L is the average concentration of TFA in all ocean water, the oceans would contain around 300 million tonnes of TFA [6].

The German Federal Environment Agency specifies a health-related indication value (HRIV) of 3 µg/L for TFA in tap water (based on the classification of TFA as non-relevant metabolite of the herbicide flurtamonesee footnote a). The 2017 updated peer review of the pesticide risk assessment of the active substance flurtamone by the European Food Safety Authority (EFSA) states that for the metabolite trifluoroacetic acid (TFA), the acceptable daily intake (ADI) is 0.05 mg/kg bw per day. No acute reference dose (ARfD) is needed on the basis of the available toxicological studies. [4]. Using the WHO guidelines for bodyweight (see footnote b), the ADI for a 60 kg adult is 3 mg/day (3000 µg/day). The (HRIV) of 3 µg/L for TFA in tap water would contribute 0.2% to the acceptable daily intake (ADI) based on 6 µg/day from 2 litres of tap water.

In summary, HFO-1234yf, after a complete conversion of the European vehicle fleet, is calculated to result in expected average values of 0.6 – 0.8 µg/L of TFA in European rain water. This is well below the (HRIV) of 3 µg/L for TFA in tap water, which in turn provides an extremely small contribution to the acceptable daily intake (ADI) of TFA according to EFSA.

Finally, this is consistent with 2015 UNEP Ozone Secretariat Informal Brief on Ecological Issues on HFCs which states ‘Projected future increased loadings of TFA to playas, land-locked lakes, and the oceans due to continued use of HCFCs, HFCs, and replacement products such as HFOs are still judged to present negligible risks for aquatic organisms and humans.’

Footnotes
(a) The health-related indication value (HRIV) of 3 µg/L for TFA in tap water is based on the classification of TFA as non-relevant metabolite of the herbicide flurtamone. Non-relevant metabolites are compounds which do not have pesticidal properties and therefore should be regulated similarly to other chemicals, and differently from pesticides and their relevant metabolites. Their toxic potential can be judged as being either lower or better documented. This is why only the two higher HRIVs (1 µg/l and 3 µg/l) are needed to assess the presence of these new analytes for lifelong exposure from the point of drinking-water hygiene. The regulatory function of a HRIV is that of a placeholder for a possibly higher Threshold of Toxicological Concern (TTC)-based surrogate HRGVTTC or a highest possible science-based HRGV (Health Related Guide Value). See Health related guide values for drinking-water since 1993 as guidance to assess presence of new analytes in drinking-water, Hermann H. Dieter, International Journal of Hygiene and Environmental Health 217 (2014) 117– 132 and [1].
(b) WHO drinking water default assumptions: There is variation in both the volume of water consumed daily and the body weight of consumers. It is therefore necessary to apply some assumptions in order to determine a guideline value. The default assumption for consumption by an adult is 2 litres of water per day, whereas the default assumption for body weight is 60 kg. In some cases, the guideline value is based on children, where they are considered to be particularly vulnerable to a particular substance. In this event, a default intake of 1 litre is assumed for a body weight of 10 kg; where the most vulnerable group is considered to be bottle-fed infants, an intake of 0.75 litre is assumed for a body weight of 5 kg. From World Health Organization Guidelines for Drinking‑water Quality Fourth Edition 2017 Chapter 8 Chemical aspects.

References
[1] Marco Scheurer, Karsten Noedler, Finnian Freeling, Joachim Janda, Oliver Happel, Marcel Riegel, Uwe Müller, Florian RüdigerStorck, Michael Fleig, Frank Thomas Lange, Andrea Brunsch, Heinz-Jürgen Brauch (2017), Small, mobile, persistent: Trifluoroacetate in the water cycle – Overlooked sources, pathways, and consequences for drinking water supply, Water Research 126 (2017) pp 460-471
[2] Stephan Henne, Dudley E. Shallcross, Stefan Reimann, Ping Xiao, Dominik Brunner, Simon O’Doherty, and Brigitte Buchmann, Future Emissions and Atmospheric Fate of HFC-1234yf from Mobile Air Conditioners in Europe, Environ. Sci. Technol., 2012, 46 (3), pp 1650–1658 DOI: 10.1021/es2034608.
[3] UNEP Ozone Secretariat, Ecological Issues on the feasibility of managing HFCs: Focus on TFA Inter-sessional informal meeting, 12-13 June 2015 Informal Brief on Ecological Issues on HFCs June 2015 see EFCTC_Learn_about_TFA_from_HFCs_HFOs.pdf
[4] Updated peer review of the pesticide risk assessment of the active substance flurtamone, European Food Safety Authority (EFSA), EFSA Journal Volume15, Issue 9 September 2017, https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2017.4976
[5] from ECHA REACH registration dossier for common salt sodium chloride, https://echa.europa.eu/registration-dossier/-/registered-dossier/15467/7/3/2
[6] IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System, Chapter 2: Chemical and Radiative Effects of Halocarbons and Their Replacement Compounds, page 154.