poly- or perfluorinated alkylated substances (PFAS)

What is PFAS?

PFAS (poly- or perfluorinated alkylated substances) is the collective name of man-made chemicals with carbon-fluorine (C-F) bonds in the ‘tail’ and water-liking functional groups in the ‘head’ (Figure 1).

PFAS are amphiphilic chemicals, because the C-F bond is hydrophobic, while the ‘head’ functional groups are basically acids and hydrophilic.

Due to this amphiphilic characteristic, FPAS are water/oil repellant and suitable for many product manufacturing. Different PFAS have been in use since the 1930s in products such as firefighting foams, paints, fabric and carpet stain protection products, food packaging, cookware, etc. Till now, up to 6000 PFAS have been found, the most common ones are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS).

Figure 1 – Molecular structure of PFAS (PFOS and PFOA) compounds.

Transport of PFAS in environment

PFAS enter into the environment through many pathways, e.g. 1) improper discharge from chemical manufacturing facilities; 2) site contamination by using e.g. aqueous film forming foam,(AFFF) in military areas; 3) sludge/soil dumping during e.g. dredging and earth-moving work; 4) leaching from landfill of solid wastes; 5) runoff of stormwater and city waste; 6) air emission due to thermal processing of PFAS-contained products, etc.

PFAS are widespread in the environment. It is estimated that the total factory sites potentially emitting PFAS is in the order of 100 000 in Europe [1]. On the other hand, PFAS are persistent chemicals because the C-F bond is one of the strongest chemical bonds in nature, they are hardly biodegradable. known as ‘forever chemicals’’.

Figure 1 presents the pathway of PFAS into environment and finally the human body.

Figure 2 - The pathway of PFAS into environment and human body [2].

New generation of PFAS

Nowadays, more and more long-chain PFAS have been phased out and substituted by short-chain alternatives. Unfortunately, the short-chain PFAS are also persistent and even more water soluble and bio-accumulative, which can be distributed in shorter time period.

For example, GenX (hexafluoropropylene oxide-dimer acid), as a substitute of PFOA, was used in the Netherlands since 2012. In less than 7 years, this chemical has been detected in an adjacent river water, the river water-infiltrated groundwater and even the drinking water near a fluoropolymer manufacturing plant. The detected level of GenX is surprisingly higher than the previous PFOA used over a long run since the 1970s [3],

Impact on human health

Intake via drinking water and food, being in contact with PFAS-containing materials and inhale of the PFAS contaminated air are possible pathways for human exposure to PFAS. A national survey in the U.S. revealed that, nearly 100% of the population carries certain level of PFAS in the blood serum, this occurs to the newborn babies as well. Reports have also shown that PFAS can impede children development, interfere with human reproductive, thyroid and immune system, and could also be carcinogenic, etc. 

References:

[1] Nordic Council of Ministers, 2019, The cost of inaction - A socioeconomic analysis of environmental and health impacts linked to exposure to PFAS, TemaNord No 516.

[2] A review of the pathways of human exposure to poly- and perfluoroalkyl substances (PFASs) and present understanding of health effects, Journal of Exposure Science & Environmental Epidemiology, 2018

[3] The PFOA substitute GenX detected in the environment near a fluoropolymer manufacturing plant in the Netherlands, Chemosphere, April 2019, 493-500.