EFSA Project on the use of NAMs to explore the immunotoxicity of PFAS

Perfluorinated substances (PFAS) are a class of synthetic chemicals widely used in industry, to which people and ecosystems are exposed. Epidemiological studies have shown that PFAS can cause immunosuppression, increased risk of infections and decreased response to vaccination, with the underlying mechanism(s) of action still remaining elusive. The aim of this project was to fill some of the data gaps identified in the 2020 EFSA Opinion, using new approach methodologies (NAMs). In particular, we aimed to get information on the mode of action for the immunosuppression effects observed in epidemiological studies (i.e., reduction in the vaccination efficacy and possible increase in the susceptibility to infectious disease), and to address the immunotoxicity of PFAS other than PFOS and PFOA (PFNA and PFHxS), including the assessment of a possible common mode of action and to provide insight into the relative potencies of the tested PFAS. To reach these goals, an integrated testing strategy (ITS) consisting of in vitro and in silico methods was developed. The effects of PFAS were investigated using target immune human cell‐based in vitro models, suitable to assess the relevant immunotoxic parameters observed in epidemiological studies (i.e. decreased antibody production). Results obtained fully support the evidence from human epidemiological studies. Furthermore, mathematical fate and distribution models were used to identify nominal concentration of PFAS in the in vitro cell system and physiologically based kinetic (PBK) models were used to perform quantitative in vitro to in vivo extrapolation. The ‘Universal Immune System Simulator’ was used to complete the ITS and investigate the reduced response to vaccination also on vulnerable populations. The use of these selected NAMs may provide a tool to support, by providing mechanistic information, regulatory risk assessment and to study the immunotoxic potential of other PFAS. The participation of immunotoxicologists, molecular biologists, risk assessors, and computational experts within the Consortium, together with EFSA's engagement, ensured the successful performance of this project and delivery of a NAMs‐based strategy that allows generating mechanistic information on PFAS immunotoxicity and support risk assessment.