Bioindicator for the occurrence of PFAS

Newswise —

The scientists studied 66 PFAS substances in their research. These can be sorted into three groups:

1) PFAS categories that have long been regulated

2) Novel PFAS that the industry employs as replacements for regulated PFAS

3) Precursors that may break down into other, more stubborn PFAS.

Nonetheless, as these particular analyses can only identify a small fraction of the 10,000+ PFAS utilized by the industry and since many polyfluorinated compounds cannot be gauged due to the absence of analytical standards, the research team also computed a summation parameter for PFAS in wild pigs using a new advanced method, the TOP (Total Oxidizable Precursors) assay. "The summation parameter signifies the total number of precursor substances in a sample that can still respond to generate persistent degradation products," says Jana Rupp, an environmental chemist at the UFZ and the paper's primary author. However, the TOP assay does not disclose the concentration levels of the individual precursor substances.

The UFZ collaborated with the German Water Centre in Karlsruhe to create a biomonitoring technique that was applied in three distinct locations in Germany: One location, situated near the town of Rastatt in the Baden region, is a hot-spot where PFAS-contaminated paper sludge was possibly distributed on fields as recycled compost until the 2000s. The second hot-spot is an industrial region in southern Germany. The third research site, located in the north-east of Germany, is normal with no irregularities. As a result, the baseline levels of PFAS can be determined there.

There are numerous reasons why the scientists selected wild boar liver for their study. "The wild boar is prevalent and hunted across the country. Therefore, this species can provide a comprehensive overview of PFAS hot-spots in Germany," says Rupp. Because wild boar are highly mobile and roam across several square kilometres, they can reflect contamination over a larger area. This is an advantage over soil samples, which make it much more challenging to assess PFAS contamination over larger regions. The liver is a suitable choice because it is well-supplied with blood. "Unlike most environmental pollutants, PFAS do not accumulate in fatty tissue but rather bind to proteins, which is why they circulate in the blood and are easily detectable in the liver," explains Rupp. In contrast to other land-dwelling species like red deer, roe deer, or chamois, which could also be potential indicators for PFAS, the researchers found in another study that PFAS concentrations are highest in wild boar liver. This is due to the fact that the wild boar is omnivorous and at the top of the food chain. It feeds on contaminated prey such as mice, frogs, snails, or worms. Additionally, it frequently burrows in the soil and directly absorbs PFAS through this process.

The study found that wild boar liver is an effective bioindicator for mapping PFAS contamination in wild boar habitats. "PFAS are widespread and can be found in large quantities. We were able to identify significantly elevated levels in regions with known PFAS contamination," says Prof. Dr Thorsten Reemtsma, head of the UFZ Department of Analytical Chemistry and senior author of the study. For instance, the PFAS concentration near the industrial company in southern Germany was almost twice as high as in areas where PFAS-contaminated paper sludge was utilized in agriculture. Additionally, it was nearly eight times higher than the concentrations in areas with background contamination.

The researchers also identified different distribution patterns of the various PFAS groups at the three sites through the analysis of wild boar liver. For instance, the industrial site is still dominated by an older PFAS substance that is already banned but can still be detected due to its extreme persistence. Additionally, newer PFAS substances used by the industry as replacements for banned PFAS groups were found. In contrast, the other two sampling sites predominantly contain older PFAS substances. The researchers observed a similar contamination pattern in soil samples from the two hot-spots, akin to a chemical fingerprint. "The comparison of PFAS contamination in wild boar and soils confirms that wild boar liver is an appropriate bioindicator for PFAS contamination in the terrestrial environment," says Reemtsma. Due to the significant analytical effort required to use soil samples, there is still a considerable amount of undiscovered local contamination in Germany. "Using wild boar liver, contaminated areas can be located and narrowed down in a much simpler manner," says Reemtsma.