When Home and Office Hurt Your Health

While long-chain per- and polyfluorinated alkyl substances (PFAS) are distributed globally through water as a result of their solubility, short-chain PFAS find their way into the wider world via atmospheric transport. This should not shift the focus of the potential health hazard posed, but rather draw attention to where volatile PFAS are emitted, namely indoors.

Low-angle view of a skyscraper with neon accents disappearing into fog © Bianca - stock.adobe.com

Germans are homebodies and mostly work indoors: According to studies by the Federal Environment Agency, an average of between 80 and 90% of daily life is spent indoors. According to the UBA, we spend 20 out of 24 hours a day indoors, 14 of which are within our own four walls (1), and the air we breathe indoors is often only replaced in short bursts of ventilation. In between those, the air is again loaded up with whatever humans, animals, and materials emit into the air. Whether those substances can be characterized as pleasant smelling is less important. What is more critical is knowing whether they affect our health.

Indoor Air Quality

So, what is the state of our indoor air quality? The question is deemed so important in Germany that an indoor air hygiene commission (IRK) based at the Federal Environment Agency is focused on this topic. In addition to the prevailing temperature and humidity indoors, other essential factors, such as fumes and the concentrations of known toxic compounds—both directly in air and adsorbed to dust particles—must be taken into account when assessing the indoor air quality. These factors play a central role in assessing air quality and potential health risks for people who spend a significant amount of their time indoors. Taken to the extreme, exposure can lead to the non‑specific medical diagnosis “Sick Building Syndrome” when merely being present in the building leads to discomfort and health problems for an occupant.

Sick building syndrome encompasses a range of symptoms such as headaches, mucous membrane irritation, fatigue, allergic reactions, frequent infectious diseases, respiratory problems, depression, or simply a general feeling of malaise, which appear while staying indoors and subside when one leaves the building. The main cause is volatile organic compounds/semi-volatile organic compounds (VOC/SVOC), which can be traced back to emissions from building materials, floor coverings, furniture, paints, or cleaning products, as well as microbial activity.

Focusing on PFAS

A special class of compounds that is anything but naturally occurring, per- and polyfluorinated alkyl substances (PFAS) have recently received a lot of public attention. PFAS belong to a group of artificially produced organic chemicals that are widely used in industry and in our homes because of their special physicochemical properties. PFAS repel water, oil, grease, and dirt. They are also extremely heat-resistant and chemically stable, which explains why they are used as coatings for cookware and outdoor clothing, as components of packaging materials, fire extinguishing foams, carpets, and for cleaning and waterproofing agents (1).

The Chemistry of PFAS: PFAS are purely synthetic organic compounds created by humans in the laboratory. They originate from chemical reactions in which hydrogen atoms, including those of carboxylic and sulfonic acids with a chain length of C4 to C18, are replaced by fluorine atoms. The PFAS relevant for environmental and food analysis can be roughly divided into two groups of substances: perfluorinated alkyl sulfonates (PFAS), with perfluorooctane sulfonate (PFOS) as the best-known representative, and perfluorinated carboxylic acids (PFCA), the best-known of which is perfluorooctanoic acid (PFOA).

There are both good and bad things to say about PFAS. They are resistant to natural external factors by design; Mother Nature has no known mechanism to get rid of them. Once released, they cross national borders and continents, accumulating in the environment and in the food chain. PFAS are ubiquitous and have been detected even in the most remote regions of the Antarctic. To make matters worse, PFAS—at least some of them—are proven to be dangerous to humans and animals. The EU Drinking Water Directive 2020/2184, for example, has paid particular attention to 20 of the approximately 4700 chemical substances that are classified as PFAS. Persistent PFAS are strongly suspected of causing liver damage, thyroid diseases, obesity, fertility problems, and cancer (2).

Children are Most at Risk

According to the UBA, young persons are particularly at risk. Children and adolescents between the ages of three and 17 in Germany carry a too heavy load of PFAS in their blood, the UBA reports, citing an evaluation of the “German Environmental Study on the Health of Children and Adolescents” (3). In it, medical experts provide detailed information on exposure to persistent PFAS chemicals and the health of our children. According to the UBA, the study it cites showed that 100% of children in the study were contaminated with PFOS, while 86% of the 1109 blood plasma samples tested positive for PFOA. PFOS and PFOA were the most frequently found PFAS in the GerES study (3).

Minimizing PFAS Emissions

PFAS compounds need to be particularly closely monitored to protect human health and the environment. This goes beyond monitoring drinking water and food. Their global distribution and the fact that contamination with PFAS can hardly be prevented, no matter what area of life or activity you look at, means that PFAS intake should be closely observed and their use minimized wherever possible. This requires manufacturers and producers to reduce or eliminate PFAS content, ideally substituting them with less dangerous additives. Currently, as part of consumer protection activities, PFAS emissions from materials are being monitored because these determine the quality of the air we breathe.

Consumer Goods and Building Materials

Researchers at the US Environmental Protection Agency (EPA) have taken a closer look at the relevant sources of volatile PFAS (4). Even as the analytical knowledge and scientific basis for determining PFAS in water, soil, sediments, biosolids, biota, and outdoor air has expanded rapidly, according to the EPA researchers, only limited efforts have been made to develop analytical methods for monitoring volatile PFAS in indoor air. Robbins et al. set themselves the goal of developing a method using thermal desorption coupled to gas chromatography and tandem mass spectrometry (TD‑GC–MS/MS) and sorbent packed tubes to quantify fluorotelomer alcohols (FTOH) emitted indoors by consumer products (4). FTOHs with the molecular structure [CF₃(CF₂)nCH₂CH₂OH] are used to produce synthetic fibre coatings that provide textiles, carpets, and building materials with water- and grease‑repellant properties. Incidentally, 8:2 FTOH decomposes to form PFOA.

Prior to the work of Robbins et al., the team of Morales-McDevitt et al. had determined volatile PFAS in air to estimate the level of risk of exposure indoors (5). The research teams came to similar conclusions: Volatile PFAS, particularly FTOHs, are ubiquitous in our indoor environments. In California kindergarten classrooms, which Morales-McDevitt et al. present as an example, 6:2 FTOH dominated with concentrations of 9 to 600 ng/m³, followed by 8:2 FTOH. The concentrations of volatile PFAS in air, carpet material, and dust correlate well, “indicating that carpets and dust are the main sources of FTOHs in the air” (5). Air poses the greatest risk of exposure to FTOHs and biogenically transformed perfluorinated alkyl acids (PFAA) in young children (5). It is clear, the researchers further report, that indoor air is an important source of exposure to PFAS and that the amounts of per- and polyfluorinated alkyl substances in indoor air need to be reduced.

Air Monitoring is Key

Appropriate measures are needed to minimize PFAS emissions indoors; this can be achieved by monitoring the pollutants using chemical analysis methods capable of accurately and sensitively identifying potential emission sources. Monitoring needs to be expanded using efficient, sensitive, and sustainable methods.

To that end, a method (6) has been developed and evaluated by Jackie A. Whitecavage, Kurt Thaxton, and Robert Collins. The approach is comparable to that of Robbins et al. (4), using solvent‑free TD‑GC–MS/MS, and enables the determination of PFAS in indoor air and the identification of potential emission sources in accordance with the strict requirements of the US EPA.

An FTOH Monitoring Method

Experimental: The sampling technique used is of great importance for the quantification of airborne pollutants. Most experts agree that active air sampling is preferable because it allows the precise determination of the volume of air that was sampled, whereas passive sampling collectors rely on diffusion. Relying on knowledge gained from previous projects (7,8), Whitecavage et al. ventured to determine FTOHs in air (4:2 FTOH, 6:2 FTOH, 8:2 FTOH, and 10:2 FTOH) (9), which are increasingly in the cross hairs of the US EPA. In a further step, Gerstel, the EPA, and other stakeholders then used this method to develop an international standard test at the American Society of Testing and Materials (ASTM); this method was published at the end of 2024 as ASTM D8591-24 (10).Validation of this method is currently in process, with Gerstel laboratories in the US and Germany both participating.

For this they used a TD Core thermal desorption system (Gerstel) on an 8890 GC system (Agilent) and a 7000E triple quadrupole MS/MS system (Agilent). The following TD parameters were used: splitless tube desorption at 50 mL/min to the focusing trap with a tube desorption temperature program of 40 °C initial temp (1 min) then ramp to 300 °‘C at a rate of 400 °C/min. The CIS4 focusing trap (Gerstel) was filled with Tenax TA. When the trap was desorbed, a 10:1 split ratio was used. The trap was initially at 10 °C and held there for 0.2 min; from there it was heated to 280 °C at a rate of 12 °C/s. It was held at 280 °C for 3 min before being cooled back to the starting temperature with cryogen-free Peltier cooling.

The GC system (Agilent) was equipped with a 60 m × 0.25 mm, 1.4‑µm CP‑Select 624 CB column (Agilent). The column was run in constant flow of helium at 1 mL/min and a split flow of 10 mL/min during injection. The column temperature was initially 50 °C, held there for 1 min, and then ramped up to 280 °C at a rate of 15 °C/min. It was held there for 2 min before being cooled back down to 50 °C.

Samples were collected onto 3.5” PFCA tubes (Gerstel) custom built for this application with a custom mixture of sorbents. To collect the samples, air was pulled through each tube using an air flow pump (SKC). Flows were 40 mL/min for 24 h, for a total volume of 57.6 L of air sampled onto each tube. The result was a 24 h time weighted average (TWA) sample.

TD-GC–MS/MS Analysis: The concentrations of volatile PFAS in air are in the low ppb to ppt range (v/v). To determine and quantify at such low levels, large volumes of air must be sampled, ideally over a long period of time, which also provides good averaging. Concentrating the target analytes on PFCA tubes (Gerstel) followed by thermal desorption GC–MS/MS has proven ideal for taking and analyzing large sample volumes. As Whitecavage et al. write, however: “large amounts of undesirable accompanying substances are simultaneously collected and concentrated, potentially leading to issues with high background levels and analyte interference” (6). The high selectivity of the GC–MS/MS technique means that the interference can mainly be filtered out, but there may still be a negative impact on the PFAS limits of detection. Whitecavage and colleagues therefore proceeded with the analysis in the following way. First, 3 µL of the calibration standard (cf. [6]) and the internal standard (10:2 FTOH [M+4]) were spiked onto conditioned TD tubes using a 10 µL syringe, followed by a 3 min nitrogen purge (40 mL/min). The prepared and PFAS-spiked TD (3.5+) tubes were connected to a three‑way adjustable low‑flow tube holder and a sampling pump (SKC Pocket Pump Touch). For analysis, the loaded tubes were desorbed in the TD Core System (Gerstel) in splitless mode with a helium flow of 50 mL/min at 300 °C for 3 min (cf. technical details above) and the analytes were dynamically focused in the trap at 10 °C on a liner packed with Tenax TA. Desorption and transfer of the analytes to the separation column were performed in split mode (10:1) at 280 °C (3 min).

Results and Discussion

The team collected air samples from several locations in an office building and a private residence and subsequently analyzed them for FTOH contamination (sampling time 24 h [40 mL/min] in each case). TD-GC–MS/MS analysis of the samples produced a total ion chromatogram (TIC) with extensive background signals, demonstrating the complex composition of indoor air. Multiple reaction monitoring (MRM) was used to look through the complex thicket of signal and FTOH 6:2 was detected at all sampled locations at concentrations ranging from 3.5 to 16.5 ng/m³ air. FTOH 10:2 was detected at four of six locations at concentrations between 3.58 and 16.7 ng/m³. Although the determined concentrations could be described as low, the presence of at least one FTOH in each sample indicates that action is probably needed, in view of the fact that PFAS—in this case FTOH—accumulate in human tissue. This will lead to a stepwise increase in concentration inevitably reaching worrying levels. With the TD-GC–MS/MS method developed by Jackie Whitecavage and her colleagues, even very low PFAS levels in indoor air can be determined in an efficient, economical, and sustainable way, providing a valuable contribution to the race towards healthier indoor air.

References

(1) Brantsch, T. Monitoring PFAS in Water. Gerstel Solutions 2024, 20, 15–17. https://www.gerstel.com/sites/default/files/2024-05/GERSTEL_Solutions_20-Water-analysis.pdf. (accessed 2024-09-04).

(2) Directive (EU) 2020/2184 of the European Parliament and of the Council of 16 December 2020 on the Quality of Water Intended for Human Consumption (recast). Directive - 2020/2184 - EN - EUR-Lex. https://eur-lex.europa.eu/eli/dir/2020/2184/oj (accessed 2024-11-22).

(3) Duffek, A.; Conrad, A.; Kolossa-Gehring, M.; et al. Per- and Polyfluoroalkyl Substances in Blood Plasma – Results of the German Environmental Survey for Children and Adolescents 2014–2017 (GerES V). Int. J. Hyg. Environ. Health 2020, 228, 113549. DOI: 10.1016/j.ijheh.2020.113549

(4) Robbins, Z. G.; Liu, A.; Schumacher, B. A.; Smeltz, M. G.; Liberatore, H. K. Method Development for Thermal Desorption-Gas Chromatography-Tandem Mass Spectrometry (TD-GC–MS/MS) Analysis of Trace Level Fluorotelomer Alcohols Emitted from Consumer Products. J. Chrom. A 2023, 1705, 464204. DOI: 10.1016/j.chroma.2023.464204

(5) Morales-McDevitt, M. E.; Becanova, J.; Blum, A.; et al. The Air That We Breathe: Neutral and Volatile PFAS in Indoor Air. Environ. Sci. Technol. Lett. 2021, 8, 10, 897–902.DOI: 10.1021/acs.estlett.1c00481

(6) Whitecavage, J. A.; Thaxton, K.; Collins, R. Determination of Fluorotelomer Alcohols in Indoor Air Using Cryogen-free Thermal Desorption GC-MS/MS. Gerstel AppNote 262. https://www.gerstel.com/de/Determination_of_Fluorotelomer_Alcohols

(7) Thaxton, K.; Stuff, J.; Whitecavage, J. A. Analysis of PFAS Compounds in Air Using Solid Sorbent Tubes with Thermal Desorption Gas Chromatography Mass Spectrometry. In Proceedings of the National Environmental Monitoring Conference, Minneapolis, MN, United States; 3–7 August 2020

(8) Thaxton, K.; Stuff, J.; Whitecavage, J. A. Analysis of PFAS Compounds in Indoor Air Using Thermal Desorption GC-MS Part 3: Using Tandem Mass Spectrometry to Improve Detectability and Improve Reliability. In Proceedings of the National Environmental Monitoring Conference, Bellevue, WA, United States; 2–5 August 2021.

(9) Liu, X.; Guo, Z.; Folk 4th, E. E.; Roache, N. F. Determination of Fluorotelomer Alcohols in Selected Consumer Products and Preliminary Investigation of their Fate in the Indoor Environment. Chemosphere 2015, 129, 81–86. DOI: 10.1016/j.chemosphere.2014.06.012

(10) ASTM, D8591-24, Standard Test Method for Determination of Fluorotelomer Alcohols in Test Chamber Air by Thermal Desorption-Gas Chromatography-Triple Quadrupole Tandem Mass Spectrometry (TD-GC-MS/MS),https://www.astm.org/d8591-24.html

Kurt Thaxton is an international product manager for Gerstel. For 25 years, Kurt has been a user of thermal desorption and pyrolysis as a research scientist at International Paper and later as a product specialist for Varian Inc. Later Kurt became involved in both the commercial and technical aspects of these techniques at Markes Intern

ational and now Gerstel. Kurt also serves actively in different capacities at SAE, ASTM, and ISO. Kurt has an M.S. in analytical chemistry form The Ohio State University where he focused on using mass spectrometry to solve analytical problems; MS remains a central interest and focus of Kurt’s work today.

Direct correspondence to: kurt_thaxton@gerstel.de

Website: www.gerstel.com