Aarhus University Seal

No. 199: Conversion of PFAS content between muscle and liver in fish

Larsen, M.M. & Bossi, R. 2021. Omregning af indhold af PFAS mellem muskel og lever i fisk . Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 44 s. - Teknisk rapport nr. 199


The Water Framework Directive (WFD; EU, 2008) sets an Environmental Quality Standard (EQS) for PFOS based on human healt from food. The EQShh is interpreted as limit level for the edible part of the fish, i.e. the muscle, but measurements have typically been performed in livers, as these have a significant higher content of PFOS than muscle, and hence a conversion factor between liver and muscle is needed to compare the measured levels in liver with the EQShh. There have been some studies into this factor, mainly in Sweden, but focussing primarily on eelpout, herring and perch. These show factors of 10-20 between muscle and liver concentrations. To supplement this, an investigation of danish pooled and individual samples of plaice, European flounder and trout samples have been performed, to investigate if the same factors apply to marine flatfish, mainly used in the marine part of the Danish NOVANA monitoring, and trout mainly used in the Danish watersheeds.


Results summary


The PFAS level was generally highest in the liver compared to muscle, with an linear regression with a slope of 9.8±0.6 for individual flatfish and trout individuals or pooled samples. For pooled flatfish samples, no difference was found between plaice and flounder, but the linear regression indicated a slope of 4,6±0,4, probably due to pooling of 10-25 individual flatfish compared to 5 for trout.


Confounding factors


The length versus PFOS concentration relationship was also tested, but showed no correlation for flatfish or trout. This could be due to the low number of results (10 individuals for each species, and 10 pooled samples of 5 individuals for trout and 10-25 for flatfish), small span of fish lengths and mix of different stations with different contamination levels.




The level measured of a factor of 5 – 10 between muscle and liver PFOS levels are lower than previously established for Swedish herring and Perch with around a factor 19±2, but in agreement (for trout pooled and individual samples and flatfish individuals) with the Eelpout and cod factor of 11±5. For pooled PFOS liver samples with 10-25 fish, the ratio seems to be 5, in accordance with observations from the UK, whereas liver:muscle ratios for individuals are generally higher at a factor of 10. The reason for this was not evident, but concentration in pooled vs. individual samples at 4 stations (figgure 3) of flatfish shoved different results in liver, with a factor of 0.2 to 5 higher level in average of 5 individual fish samples than pooled samples of 10-25 fish.