PFAS Exposure and Health Effects todayheadline

PFAS constitute a large group of synthetic chemicals resistant to oxidation and thermal degradation and exhibit water-repellent properties. These chemicals have been used widely in varied consumer products and industries, entering the environment and persisting as contaminants in water, air, and soil for a prolonged period. In this article, explore the world of PFAS, including their different types, applications, detection methods, human exposure risks, adverse health effects, and strategies to prevent contact to these chemicals.

What Are PFAS?

Per- and polyfluoroalkyl substances (PFAS), sometimes called forever chemicals, constitute a large group of synthetic chemicals that contain at least one fully fluorinated methyl or methylene carbon.¹ These compounds have been widely used across industrial and consumer applications for decades, including in textiles, hard metal plating, paints, cosmetics, and electronics. PFAS can be emitted during manufacturing processes and while using or disposing PFAS-containing products.

Because the carbon-fluorine bond is very strong, PFAS exhibit high thermal and chemical stability, making them highly resistant to oxidation and degradation.² These substances also have unique water and oil-repellent properties enhancing their industrial applications.³ Their long-term presence in the environment poses health and ecological concerns.

     

What are PFAS used for?

Typically, manufacturers use PFAS for products that require waterproofing and anti-reflective coatings. They use PFAS in multiple products including electronics, medicine, fire suppressants (e.g., aqueous film fire-fighting foams—AFFFs), hydraulic fluids in aviation, and others.⁴

Table 1: PFAS types and applications⁴

PFAS as environmental contaminants

In general, PFAS are highly stable and resistant to degradation, so they may remain in the environment for decades or even longer. Because of this environmental persistence, researchers call them forever chemicals.⁵ 

PFAS properties are determined by the length of their fluorinated carbon chain.⁶ For instance, long-chain PFAS that contain 8–20 perfluorinated carbon atoms are more bioaccumulative and toxic because of their poor water solubility and higher affinity for serum proteins, which leads to slow excretion rates from the body. Short-chain PFAS have high mobility in soil and water, reach groundwater quickly when emitted into the environment, and are less bioaccumulative than long-chain PFAS.⁷ 

PFAS contain both perfluoroalkyl and polyfluorinated alkyl substances, and based on their differential chemical structure, one is more persistent as an environmental contaminant than the other. For instance, because polyfluoroalkyl substances have a carbon that lacks fluorine substitution, it may partially degrade or transform in the environment to form perfluoroalkylated acids (PFAA) such as perfluoroalkylated carboxylic acids (PFCA) and perfluoroalkylated sulfonic acids (PFSA), which are highly resistant to further degradation.⁸ 

The Stockholm Convention has classified certain PFAS types, including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), as persistent organic pollutants (POP). Even though PFOS and PFOA use is currently illegal in many countries, they are still found in the environment possibly due to their highly persistent nature. 

Human PFAS Exposure Pathway 

Humans are primarily exposed to PFAS through the consumption of contaminated food and water.⁹ PFAS enter the food cycle via PFAS-containing cookware or packaging materials. Scientists have detected PFAS such as PFOA, PFOS, perfluorodecanoic acid (PFDA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS) in food through migration from microwavable containers or packaging papers.¹⁰ Furthermore, PFOS may reach sewage and sewage treatment plants via industrial effluents.

Additionally, individuals working in fluorochemical manufacturing facilities are at a high risk of PFAS exposure, as are firefighters due to the use of AFFF for training purposes.^9,10 

Other PFAS exposure routes are dermal contact with cleaning or personal care products containing PFAS and aerosolized or volatile PFAS inhalation. Scientists also observed that PFAS readily transfer from the mother to the developing fetus through the placenta, or to newborns via breastfeeding.

PFAS Testing Methods

Although scientists use different chromatographic methods to detect PFAS contamination, liquid chromatography with tandem mass spectrometry (LC-MS/MS) is the standard method to identify targeted PFAS species including PFOS and PFOA.¹⁰ 

To enhance target analyte detection selectivity and sensitivity, scientists prepare samples prior to chromatographic analysis using specific extraction methods such as solid phase microextraction (SPME), solid phase extraction (SPE), liquid-liquid extraction (LLE), and dispersive liquid-liquid microextraction (DLLME).¹¹

For PFAS analysis, researchers typically prefer ultra-performance liquid chromatography (UPLC) and ultra-high-performance liquid chromatography (UHPLC) over high-performance liquid chromatography (HPLC) due to their improved analysis time and capacity to detect more analytes in a single run.¹²

Scientists also use sensor-based technology including optical sensors based on colorimetry and electrochemical sensors based on potentiometric and voltammetric approaches to detect PFAS in different media.¹³ Additionally, researchers have developed fluorescence sensors to quantify PFOS concentration in water samples by creating molecularly imprinted polymers (MIPs) coated with silicon dioxide nanoparticles and fluorescent dye.¹⁴

Alternative methods such as the total oxidizable precursor (TOP) assay, 3D-printed cone spray ionization (3D-PCSI) technique using ambient ionization mass spectrometry, and high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS-GFMAS) have also enabled PFAS detection.¹²

Currently, scientists at the US Environmental Protection Agency (EPA) are developing new analytical methods to measure large groups of PFAS in water and water-related samples. They aim to create non-targeted methods to determine and characterize unknown and new PFAS as well.

PFAS Health Risks

Scientists have conducted toxicological research on PFAS and observed that exposure to certain types of PFAS has detrimental effects on human health. For example, exposure to PFOA and PFOS results in adverse health effects including lipid and insulin dysregulation, kidney disease, altered immune and thyroid function, adverse reproductive and developmental outcomes, liver disease, and cancer.⁶ However, there are thousands of different PFAS types and limited available toxicity data for many types beyond PFOA and PFOS. Although researchers have established links between PFAS exposure and disease, much remains unknown.

Factors that contribute to the severity of health effects include PFAS concentration, and exposure route and duration.⁶ An individual’s age, sex, genetic predisposition, health status, and ethnicity also determine PFAS exposure outcomes. 

• Reproductive and developmental outcomes: PFOS and PFOA exposure leads to a decrease in serum levels of sex hormone-binding globulin (SHBG) in men and follicle-stimulating hormone (FSH) in women. It also negatively affects spermatogenesis and sperm quality, and possibly influences the menstrual cycle. PFAS in the placenta and breast milk may adversely influence fetal or breastfed infants’ development.
• Immune responses: Exposure to PFAS in infancy and childhood triggers immunosuppression as evidenced by the increased incidence of lower respiratory tract infections and atopic dermatitis. Researchers correlated a modest down-regulation of the C-reactive protein response with PFOA blood levels.
• Thyroid function: Researchers found a negative correlation between PFAS exposure and serum total thyroxine levels, which indicates PFAS exposure results in thyroid dysfunction and disease. These chemicals can alter human thyroid hormones and potentially contribute to thyroid autoimmunity.
• Lipid and insulin dysregulation: PFAS exposure leads to an increase in serum cholesterol levels in adults and children. Even a low PFAS dose can increase blood cholesterol levels.
• Liver disease and cancer: The liver is the primary organ for long-chain PFAS storage, which could subsequently trigger hepatocyte fat infiltration, apoptosis, hepatocellular adenomas, and carcinomas. Scientists observed that PFAS exposure increases alanine aminotransferase levels in the liver which could result in nonalcoholic fatty liver disease (NAFLD). 

Strategies to Reduce PFAS Exposure 

Scientists have reported that water filtration can potentially reduce PFAS exposure through drinking PFAS-contaminated water.¹⁵ Among different water filtration methods, researchers observed that reverse osmosis and dual-stage filters are the most efficient strategies for removing PFAS from drinking water. 

Additionally, individuals using PFAS-free furnishings are at lower risk of exposure from indoor dust.¹⁶ However, the lack of consistent product labeling complicates consumer choices to avoid PFAS.

Scientists investigate medications that can elevate bile sequestration as a potential strategy to decrease PFAS bioaccumulation. For example, researchers observed that cholestyramine treatment, traditionally used to reduce low-density lipoprotein (LDL) cholesterol, can effectively decrease serum PFAS levels.¹⁷ 

Phlebotomy, a procedure that involves drawing blood from a vein, can effectively reduce serum PFAS concentration in highly PFAS-exposed individuals.¹⁸ For instance, firefighters who donated blood or plasma for over 12 months exhibited lower blood PFAS levels in comparison to those who did not.¹⁹