Mixture exposure to PFAS: A Relative Potency Factor approach

PFAS is a large group of poly- and perfluoroalkyl compounds. They have a dirt-repellent effect and are therefore used, for example, in finishing clothing. For the best known PFAS, PFOA and PFOS, much information is available about the properties have been researched, as have the quantity people may be exposed to without causing negative effects on health. In 2016, RIVM derived such a quantity for PFOA. However, much less is known about most of the other compounds in this group of substances. PFASs often occur together as contamination in soil, groundwater or drinking water. To be able to better assess the risks of this type of contamination, the RIVM has investigated the extent to which it is possible to express the harmfulness of a number of PFASs in relation to PFOA. It was concluded that this can be done by using so-called Relative Potency Factors (RPFs). Here the exposure to a PFAS mixture is expressed as a comparable amount of PFOA. This method can be used for dealing with pollution with PFASs in the environment, e.g. in cases involving contamination in soil, groundwater or drinking water. Measured PFAS quantities are simply expressed in PFOA units, so that they can be compared with PFOA standards for soil or (drinking) water. The use of the RPF method does, however, have an important condition, namely that a (limited) set of comparable toxicity data for individual PFAS compounds is available. For the relevant health effect (on the liver of test animals), such information was available for 11 PFAS compounds. This effect has been investigated, because the liver reacts most sensitively to PFOA in humans and laboratory animals. The effect is an enlargement of the liver (hypertrophy). This is an unwanted effect.