In a report published in 2018 from OECD, more than 5,000 per- and polyfluoroalkyl substances (PFASs), a group of man-made compounds, are being used on the global market. Due to the intrinsic chemical properties, they are very persistent in the environment and some of them are bioaccumulative. Three of them (e.g., perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonic acid (PFHxS)) have been listed as persistent organic pollutants (POPs) under Stockholm Convention. Several definitions of PFAS exist and their implications have been discussed. Mostly adopted one in Europe is based on a report published by OECD in 2021, which defines PFASs that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it). Based on this definition, approximately 7 million compounds can be regarded as PFAS. No matter which definitions are being referred to, less than 1% of these PFAS are included in human biomonitoring programs, suggesting that we might have overlooked human exposure to many new and unrecognized PFAS.
Studies have shown declining PFOS and PFOA concentrations in human blood; however, a greater proportion of unrecognized PFAS were reported in human blood. In a recent study, 130 whole blood samples from the Swedish general population were analyzed for extractable organofluorine (EOF) and 63 selected PFAS. For the comprehensive PFAS assessment, analysis of EOF has shown to cover other unrecognized fluorinated organic chemicals compared to limited number of PFAS. Organofluorine mass balance analysis revealed that 60% (0–99%) of the EOF in female samples could not be explained by the 63 monitored PFAS; in males, 41% (0–93%) of the EOF was of unidentified origin. The contribution of fluorinated pharmaceuticals to EOF has to be addressed as they might be co-extracted in the analysis and are present in the unrecognized EOF in the samples. A recent study on human sera samples in a Northern Norwegian cohort demonstrated that known PFAS through suspect screening only accounted for 2–4% of the EOF, fluorinated pharmaceuticals accounted for 0–63% of the EOF, and their contribution increased in recent years. Both the diet and the use of personal care products have been identified to contribute to PFAS exposure in humans. However, information on potential exposure pathways for unrecognized EOF exposure in humans is lacking. In another study, the EOF method was evaluated and proved to be an appropriate screening tool for identifying humans experiencing elevated PFAS exposure. The average EOF concentration in the group with historical drinking water contamination from PFAS containing firefighting foam (Ronneby group) was 234 ng/mL F (<107–592 ng F/mL) vs 24.8 ng/mL F (17.6–37.8 ng F/mL) in the reference group. This large difference in the EOF concentrations between the two groups suggest that it is possible to identify samples with high PFAS exposure only using EOF data. Currently several Nordic countries (including Norway, Denmark, and Sweden) are in the lead to propose a general PFAS restriction in the EU. Before implementation of a future general PFAS restriction there is a need to establish a baseline of the concentrations of known PFAS and unrecognized EOF in human blood, facilitating time trend studies in the future.
Objectives of the study
To establish an EOF concentration baseline in human blood prior to the implementation of a future general PFAS restriction.
To conduct a mass balance analysis on EOF to evaluate the amounts and proportion of unrecognized EOF in human blood samples.
To evaluate short-term changes in EOF concentrations in paired samples from the same individuals collected 2 to 3 weeks apart,) to provide insights into pharmacokinetics for biomonitoring purposes.
To assess the impact of dietary habits and personal care product use on the proportion of unrecognized EOF in human samples.
To evaluate the effect of fluorinated pharmaceuticals on EOF and unrecognized EOF concentrations in human blood samples.