A review of sample collection and analytical methods for detecting per- and polyfluoroalkyl substances in indoor and outdoor air

Abstract

Per- and polyfluoroalkyl substances (PFAS) are a unique class of chemicals synthesized to aid in industrial processes, fire-fighting products, and to benefit consumer products such as clothing, cosmetics, textiles, carpets, and coatings. The widespread use of PFAS and their strong carbon-fluorine bonds has led to their ubiquitous presence throughout the world. Airborne transport of PFAS throughout the atmosphere has also contributed to environmental pollution. Due to the potential environmental and human exposure concerns of some PFAS, research has extensively focused on water, soil, and organismal detection, but the presence of PFAS in the air has become an area of growing concern. Methods to measure polar PFAS in various matrices have been established, while the investigation of polar and nonpolar PFAS in air is still in its early development. This literature review aims to present the last two decades of research characterizing PFAS in outdoor and indoor air, focusing on active and passive air sampling and analytical methods. The PFAS classes targeted and detected in air samples include fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamides (FASAs), perfluoroalkane sulfonamido ethanols (FASEs), perfluorinated carboxylic acids (PFCAs), and perfluorinated sulfonic acids (PFSAs). Although the manufacturing of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) has been largely phased out, these two PFAS are still often detected in air samples. Additionally, recent estimates indicate that there are thousands of PFAS that are likely present in the air that are not currently monitored in air methods. Advances in air sampling methods are needed to fully characterize the atmospheric transport of PFAS.

Keywords: Air sampling methods; Indoor air; Outdoor air; Targeted analysis; per- and polyfluoroalkyl substances (PFAS).

Fig. 1.

Distribution of PFAS classes detected in passive (A) and active (B) air sampling methods out of the 84 papers investigated. Note that some papers may have more than one citation if multiple sampling techniques were used. PFAS classes include fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamide ethanols (FASEs), perfluoroalkane sulfonamides (FASAs), perfluorinated carboxylic acids (PFCAs), perfluorinated sulfonic acids and fluorotelomer sulfonates (PFSAs + FTSs), monomers, and fluorotelomer unsaturated carboxylic acids (FTUCAs). Passive air sampling (PAS) techniques include sorbent-impregnated polyurethane (SIP)-PAS, polyurethane foam (PUF)-PAS polyethylene sheet (PE)-PAS, XAD-2-PAS, activated carbon fiber (ACF)-PAS, and active air sampling (AAS) techniques include high volume (HV)-AAS, low volume (LV)-AAS, solid phase extraction (SPE), high volume-cascade impactor (HV–CI, without downstream sorbent), HV-CI, with downstream sorbent (HV–CI + Sorbent), and thermal desorption tubes (TD Tubes).

Fig. 2.

Frequency histogram of extraction solvents used for PFAS sample preparation. Monitored PFAS classes [(fluorotelomer alcohols (FTOHs), perfluoroalkane sulfonamide ethanols (FASEs), perfluoroalkane sulfonamides (FASAs), perfluorinated carboxylic acids (PFCAs), perfluorinated sulfonic acids and fluorotelomer sulfonates (PFSA + FTS), monomers, and fluorotelomer unsaturated carboxylic acids (FTUCAs)] are shown along the x-axis. Solvents and solvent mixtures are visualized with increasing polarity moving up the y-axis. Some publications may be represented several times if more than one extraction solvent or class was assessed. Data are included in Table S1. MTBE: methyl tert-butyl ether.