Retrospective monitoring of perfluorocarboxylates and perfluorosulfonates in human plasma archived by the German Environmental Specimen Bank

Abstract

Due to the increased awareness of the ubiquitous contamination of all environmental compartments and of human beings with perfluoroalkyl substances (PFAS), voluntary withdrawals and shifts in products and manufacturing technologies, as well as in regulatory measures, have been made. To investigate whether these activities are reflected in the human exposure to PFASS, we examined human blood archived by the German Environmental Specimen Bank. Plasma samples (n = 258, age range 20–29 years) covering the observation period 1982–2010 were analyzed for eleven perfluoroalkylcarboxylates (C4–C14) and five perfluoroalkylsulfonates (C4–C10) by HPLC–MS-MS. We detected perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorohexanesulfonate (PFHxS) most often of all PFASs. Following a sharp increase from 1982 to 1986, median PFOS concentrations remained in the range of 20–24 ng/mL until the end of the 1990s. Between 2001 and 2010, PFOS concentrations decreased steadily to 4 ng/mL in plasma. Except for a similar strong increase from 1982 to 1986, we observed PFOA concentrations fluctuating between 4.8 and 6.3 ng/mL in the following years. Since 2008, ESB data suggest a decreasing trend of PFOA. PFHxS concentrations increased continuously between 1982 and 2001 from about 1–2 ng/mL. After nearly unchanged concentrations until 2005, a downward trend of PFHxS in plasma became apparent and in 2010 resulted in levels which were about 20% lower than those observed in the early 1980s. In the case of shorter and longer chained PFASs, quantification frequencies were between 0 and 60% and we found no indication of any temporal trends in human plasma concentrations.

Introduction

Per- and polyfluorinated chemicals have been produced since the 1960s for various uses, e.g. certain fluoropolymers, surface protectant for textiles and fire fighting foams. In May 2000, a main producer of perfluoroalkyl substances (PFASs) in the United States announced that the company would phase out the perfluorooctanyl chemistry used to produce certain repellents and surfactant products (Company, 2000, Prevedouros et al., 2006). Main reasons for this phase-out were comparatively high PFAS levels observed in employee's blood samples. In 2006 the European Union amended Regulation 76/769/EEC to restrict marketing and use of PFOS, its salts and derivatives; later on this restriction was transferred into Annex XVII of the REACH-Regulation (EU, 2006). In 2010, PFOS was included as a persistent organic pollutant in Annex B of the Stockholm Convention on Persistent Organic Pollutants (Stockholm Convention, 2008) and with the amendment of the European POP-Regulation (EU, 2010) deleted from REACH Annex XVII (EU, 2011).

However, PFOS was not the only perfluorinated chemical which was increasingly detected in the environment, in biota, and humans. Perfluorooctanoic acid (PFOA), mainly used as processing aid to manufacture polytretrafluooethylene (PTFE), has also been found to be widespread in the environment. For PFOA, US-EPA and eight important producers of fluorochemicals agreed on a stewardship program. The target was to reduce the global emissions of PFOA and longer chain perfluoroalkyl acids including their relevant precursors to 95% of the level of the year 2000. The program's main objective was to reduce these emissions completely by 2015 (US EPA, 2006). A Hazard Assessment prepared in 2006 by the US-EPA and the German Federal Environment Agency and supported by DuPont identified PFOA as a candidate for further work. Regulatory measures for PFOA in the European Union were suggested by several Member States (overview see Vierke et al., 2012).

Against this background, environmental and human exposure to PFASs still concern the scientific community, and subsequently regulatory authorities, and raise attention in the broad public. Therefore, the success of regulatory and other activities to reduce emissions of PFASs need to be verified. Moreover, concentrations of unregulated PFASs in humans and environmental media must be critically monitored and evaluated.

Important instruments for both issues measuring success of risk management, and monitoring temporal trends of chemicals in organisms and environmental media are specimen banks. The German Environmental Specimen Bank (ESB) regularly collects environmental samples from marine, fresh water and terrestrial ecosystems as well as human samples on a yearly basis (BMU, 2008). Blood and other human specimens have been collected since 1981 from a group of about 120 young, non-occupationally exposed adults. Every step in the procedure from sampling to transport, preparation, chemical analysis and long-term storage is carried out consistently according to strict Standard Operating Procedures (Wiesmueller et al., 2007). Although the ESB study group is not representative for the German population, it is however an appropriate collective for monitoring time trends in non-specifically exposed individuals (background exposure). As a consequence, the archived ESB samples allow answering pending questions on the temporal development of regulated and unregulated PFASs in Germany's natural environment and population.

Therefore, human plasma samples archived in the ESB were analyzed for eleven perfluorocarboxylates (C4–C14) and five perfluorosulfonates (C4–C10) covering the observation period from 1982 to 2010. Main objectives of this study were to evaluate whether the measures already in force for PFOS have been effective, to check whether the voluntary PFOA regulations are reflected in human samples, and to monitor blood levels of other PFASs which might be used as alternatives for PFOS and PFOA.