Wild boar livers used to identify harmful and emerging ‘forever chemicals’ at contamination hotspots

A pioneering study has measured the levels of harmful PFAS "forever chemicals” in the livers of wild boar and used this to map different types of contamination at hotspots in Germany, with researchers suggesting the method could help identify the biggest sources of such pollution.

Per- and polyfluoroalkyl substances (PFAS) are made up of around 10,000 man-made chemicals and are used in a wide range of consumer products due to their water and oil repellent properties, and tolerance to high temperatures. 

The peer-reviewed research, published in the Science of the Total Environment journal, put forward a strong case that wild boars, which have an omnivorous diet, a wide foraging range, and occupy many regions in Germany, could be used to map PFAS soil contamination in the country. 

The researchers analysed samples taken from 50 animals for 66 PFAS, as well as using a research method that can convert oxidizable PFAS precursors, a measurable indicator, into PFAAs to identify short-chain substances that may not be picked up in other tests. Through this they identified 31 types of PFAS in the samples. 

The samples had been chosen from animals in areas impacted by contaminated paper sludges distributed on arable land, industrial emissions of PFAS, and background contamination. The researchers found that the PFAS identified in the samples could be used to map the contamination. 

Legacy PFAS such as PFOA and PFOS, which are long-chain PFAS, were dominant in the contaminated paper sludges and the background contamination areas at levels of 426 and 82 micrograms per kilogram−1 (μg kg−1), respectively.

The PFAS profile of the samples from the area contaminated with paper sludge was distinct from the area impacted by background contamination, which the researchers attributed to “presumably” the fact the paper sludges are loaded with chemicals such as phosphate esters. The findings were also consistent with other studies of wild boar livers in Germany taken from areas where “PFAS-loaded material” was distributed on arable lands. 

For the industrial emissions measure, common substitutes for PFOA – the compounds 4,8-dioxa-3H-perfluorononanoic acid (DONA) and hexafluoropropylene oxide dimer acid – were determined at 15 and 0.29 μg kg−1. DONA has not been identified in many other studies, and is not regulated, however the researchers flagged concern that it is similar in structure to the substance of very high concern HFPO-DA. 

The researchers suggested “the presence of PFOS, DONA and/or other PFAS in the boar liver may indicate long-term exposure to contaminated soil as well as the dietary uptake of organisms living in the soil and of plants grown on it”.

PFOA is a suspected endocrine (hormone) disruptor and possible carcinogen, and is linked to pancreatic and liver cancer in animal studies. Both have a statutory limit of 0.1 micrograms per litre for drinking water in the UK. HSE recently recommended that statutory guidelines need to be developed for other PFAS in drinking water too, such as PFAAs.

READ MORE: HSE’s recommendations for regulating PFAS ‘forever chemicals’ in the UK, explained

The researchers noted that “Despite increasing efforts on PFAS research worldwide, information about the occurrence and environmental behaviour of substitutes, as well as information on many precursors and short-chain PFAS remains scarce.”

The study concluded that wild boar livers are suitable bioindicators for PFAS contamination in the terrestrial environment. It is also pioneering, in that it finds that animal samples are a promising method for identifying emerging substitutes (such as DONA’s) prevalence in the environment. The researchers expressed hope that methods such as these could go on to support regulatory work, and prompt further study in the area.