According to the CDC, the exposome is “the measure of all the exposures of an individual in a lifetime and how those exposures relate to health.”
Read time: 6 minutes
During a recent webinar, Simon Roberts of SCIEX and Christian Lindh of Lund University shared their insights about chronic human exposure to per- and polyfluorinated alkyl substances (PFAS). They also answered many questions, which are compiled here in this blog with the hope that they will inspire your own exposome research.
What is the typical route of entry into the human body for PFAS compounds, and what are the sources of PFAS?
Simon: The typical route of entry into the body is ingestion from water, food or dust. Because many PFAS are highly bioaccumulative, even very small amounts of PFAS in food or water can increase the body’s levels over time.
PFAS are diverse industrial chemicals used directly in final products and during the synthesis of other substances. The most prevalent PFAS are currently found in firefighting foam, known as aqueous film-forming foam (AFFF). AFFF-derived PFAS have contaminated the groundwater at thousands of sites worldwide where fire-suppression and fire-suppression tests using AFFF have been conducted. In addition, many plastics, especially fluoropolymers and some polyethylene and other non-fluorinated polymers, are synthesized using PFAS, which may then end up in final products such as food packaging, medical equipment and other plastics relevant to human exposure.
What is the toxic concentration of PFAS in humans, and can it be excreted from the body? If not, why do PFAS molecules accumulate in the body?
Simon: While the exact toxic concentration of PFAS is currently unknown , chronic exposure at commonly detected levels of PFAS in the human body, such as 1–5 ppb, could result in chronic toxicity to the human endocrine system.
PFAS molecules accumulate in humans via a protein-binding mechanism and are slowly excreted from the body. Studies indicate that urine is an important pathway for the excretion of PFAS. However, there can be significant interindividual variations in the excretion of PFAS in urine. Animals are different from humans, for example, and the type of PFAS can also be a factor. In humans, gender and likely genetics matter as well.
What solvent did you use to isolate PFAS from the blood sample?
Christian: PFAS is associated with proteins that are not covalently bound. By adding acetonitrile and/or methanol, you “crash” out proteins in the blood samples. You need to do a strong shaking for 30 minutes or put the samples in an ultrasonic bath.
Has any correlation study been performed between PFAS in plasma/blood and PFAS in urine? Does PFAS get excreted in the urine at all?
Christian: Yes, it is excreted in urine, with interindividual variations. We will soon submit an extensive study on this topic. In the meantime, if you’re interested, you can check out some examples in the following publications:
Xu, Y.; Fletcher, T.; Pineda, D.; Lindh, C.H.; Nilsson, C.; Glynn, A.; Vogs, C.; Norström, K.; Lilja, K.; Jakobsson, K.; Li, Y. Serum Half-Lives for Short- and Long-Chain Perfluoroalkyl Acids after Ceasing Exposure from Drinking Water Contaminated by Firefighting Foam. Environ Health Perspect. 2020 Jul, 128 (7), 77004. DOI: 10.1289/EHP6785
Calafat, A.M.; Kato, K.; Hubbard, K.; Jia, T.; Botelho, J.C.; Wong, L.Y. Legacy and alternative per- and polyfluoroalkyl substances in the U.S. general population: Paired serum-urine data from the 2013-2014 National Health and Nutrition Examination Survey. Environ Int. 2019 Oct, 131, 105048. DOI: 10.1016/j.envint.2019.105048
Many thanks to Simon and Christian for their dedication to this subject matter and for answering these questions. To access the on-demand webinar, click here. Feel free to ask any additional questions in the comments below.
About the Presenters
Simon specializes in developing methods for PFAS analysis at SCIEX for both targeted and non-targeted analysis. Before working at SCIEX, Simon performed PFAS discovery research at Colorado School of Mines during his postdoctoral fellowship. He worked on projects that identified dozens of novel PFAS in groundwater and industrial chemicals. Recently, Simon has focused on educating the public about PFAS via his YouTube channel, Environmental Chemistry Explained.
Christian has extensive experience in the method development of various biological and environmental monitoring techniques using mainly mass spectrometry as an analytical tool. He studies human exposure to toxicants in the general environment and in occupational settings and evaluates their impact on the human body, with a particular focus on epidemiological studies using small volumes of biobank samples. Christian has been involved in many studies about PFAS exposure over the past 10 years.