Perfluoroalkyl substances (PFASs) in air-conditioner filter dust of indoor microenvironments in Greece: Implications for exposure

Highlights

• A/C filter dust was tested for PFASs levels in Greece.

• Linear correlation between logPFOA vs. logPFOS was found for all sampling sites.

• PFASs profile varied among the microenvironments suggesting different sources.

• Intake of PFASs via dust ingestion were among the lowest reported in literature.

Abstract

The occurrence of perfluoroalkyl substances (PFASs) was for the first time investigated in various working microenvironments (internet cafes, electronics shops, coffee shops, restaurants, etc.) in Thessaloniki, Greece, using the dust trapped by central air conditioner (A/C) filters. Perfluorooctane sulfonic acid (PFOS) was found in the range from 16 to 227 ng g⁻¹, however it was detectable in only 30% of samples. On the contrary, perfluorohexanoic acid (PFHxA) was found in 85% of samples in the range from 3.6 to 72.5 ng g⁻¹, while 90–95% of samples exhibited perfluorooctanoic acid (PFOA), perfluorodecanoic acid (PFDcA) and perfluorododecanoic acid (PFDoDA) in the range from 10–653 ng g⁻¹, 3.2–7.4 ng g⁻¹ and 3.8–13.1 ng g⁻¹, respectively. The PFAS profile varied largely among the different microenvironment categories suggesting different sources. Estimated daily intakes through dust ingestion were calculated.

Introduction

Poly- and perfluoroalkyl substances (PFASs), are used in a variety of commercial products due to desirable properties such as oil and water repellency, thermal stability, and resistance to biotic, chemical or mechanical degradation. Since the 1940s, PFASs have been used in applications such as fire-fighting foams and pesticides, protective sprays and varnishes for fabrics, carpets, and clothing, and more recently in food-contact paper and non-stick cookware (Prevedouros et al., 2006; Shoeib et al., 2016; Zafeiraki et al., 2014).

As a result of their widespread use, PFASs have been detected in water and sediments, air and soil (Barber et al., 2007; Kato et al., 2009; Lau et al., 2007; Meng et al., 2016; Prevedouros et al., 2006; Shoeib et al., 2005; Taniyasu et al., 2003; Wang et al., 2011; Yeung et al., 2013), food products (Domingo et al., 2012; Wu et al., 2012), wildlife (Reiner and Place, 2015), plants (Vestergren et al., 2012), and even in human body (Kärrman et al., 2010; Vassiliadou et al., 2010; Costopoulou et al., 2008).

PFASs include two major chemical classes; Perfluoroalkyl carboxylic acids (PFCAs) and perfluorosulfonic acid homologues (PFSAs), of which the most well-known and investigated are the perfluorooctanoic acid (PFOA) and the perfluorooctane sulfonic acid (PFOS) (Buck et al., 2011). PFOA and PFOS are the most regularly detected PFASs in the environment (Wang et al., 2015). Their potential toxicological effects led to the phase-out of production by the main global manufacturer in 2000–2002 (3M Company) (USEPA, 2014). Furthermore, PFOS, its salts and PFOS-F (perfluorooctane sulfonyl fluoride) have been added to the Stockholm Convention on persistent organic pollutants (POPs) in an amendment of May 2009 while PFOA was listed as recommended chemical for the Stockholm convention (Stockholm Convention on Persistent Organic Pollutants, 2011). The toxicological activities of the long-chain PFASs (>8 carbons), such as perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), and perfluorododecanoic acid (PFDoDA), and their effects on human body are not well investigated (Zhang et al., 2013).

The main routes through which humans are exposed to PFASs are dust ingestion, inhalation, and food consumption (Barber et al., 2007; Haug et al., 2011b; Shoeib et al., 2005, 2011; Björklund et al., 2009b; Goosey and Harrad, 2011; Haug et al., 2011b, 2011b; Kato et al., 2009; Strynar and Lindstrom, 2008; Tian et al., 2016; Ericson et al., 2008; Tittlemier et al., 2007; Midasch et al., 2007; Tao et al., 2008). Only few studies have assessed concurrent measurements of PFASs in indoor dust and serum (Fraser et al., 2013; Haug et al., 2011b). The majority of studies have focused on PFOS and PFOA in dust and diet, suggesting that food sources dominate exposure in adults with exception of some worst-case scenario estimates that use a high dust ingestion factor and maximum PFAS dust concentrations (Björklund et al., 2009b; Egeghy and Lorber, 2010; Zhang et al., 2010). However, the true impact of different exposure pathways to PFASs body burdens remains unclear due to limited data on adult dust ingestion rates, absorption capacities, PFASs levels in indoor dust and air of places where people spend significant amounts of time other than their homes (Fraser et al., 2013). Additionally, and importantly, the released reference doses (RfDs) for PFOS and PFOA have become increasingly conservative over the last decade (Dong et al., 2017). On 25th May 2016, the US EPA released reference doses (RfDs) for PFOS and PFOA equal to 20 ng kgbw⁻¹ day⁻¹, which were much more conservative than the previously drafted values (77 and 189 ng kgbw⁻¹ day⁻¹, respectively, USEPA, 2009a, USEPA, 2009b). PFOS concentrations in humans have been reduced after the ban, although less than expected, given its long estimated half-life (2.3–3.8 years) (Kato et al., 2011).

It is significant for human exposure studies to include exposure to indoor chemicals since humans are spending more than 80% of the day indoors (Katsoyiannis and Bogdal, 2012). Data concerning the occurrence of PFASs in indoor microenvironments in Greece are very scarce. Previously indoor dust of a small number of homes in Athens was investigated for PFCAs and PFSAs, as well as the fluorotelomer-based PFCA precursors polyfluoroalkyl phosphate esters (PAPs) (Eriksson and Kärrman, 2015). The median concentration of ∑PFCAs (40 ng g⁻¹) was at similar levels with those found in Sweden or Spain and was dominated by PFOA (Eriksson and Kärrman, 2015). Concentrations of PFASs in the foodstuff packaging materials used in the Greek market were found to be very low related to other countries (Zafeiraki et al., 2014). PFOA and PFOS were not found in other materials, perfluorohexanoic acid (PFHxA) was found in fast food boxes, and the highest concentrations of PFHxA and perfluorobutanoic acid (PFBA) were detected in microwave popcorn bag. Nevertheless, PFOS and PFOA were found in all blood samples collected in 2009 from individuals living in Athens and other Greek cities, while previous studies reported similar levels for inhabitants of other European cities (Vassiliadou et al., 2010).

The aim of the present study was to investigate the occurrence, concentration level and distribution pattern of 14 PFASs (perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), perfluorodecane sulfonic acid (PFDS), perfluorooctane sulfonamide (FOSA), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA)) (Table S1), in indoor dust from various occupational settings and public gathering spaces in Thessaloniki, northern Greece, by sampling and analyzing the dust accumulated on central air-conditioner (A/C) filters and to estimate the daily intake of these compounds through dust ingestion. To the best of our knowledge, this is the first study on PFASs in A/C filter dust worldwide.