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Total oxidizable precursor (TOP) assay is an oxidation method to convert precursor compound of polyfluoroalkyl/perfluoroalkyl substances (PFASs) into measurable perfluorinated carboxylic acids (PFCAs). A previous mass balance study has shown that a loss of fluorine was observed after employing the method to convert the precursors in firefighting foams. Further, it has been seen that a large part of the total extractable organofluorine is still made up of compounds with unknown identity; ultra-short chain PFASs might have formed during the TOP assay, but they were not measured in the previous study. The aims of this investigation are to i) assess if the loss of fluorine in mass balance analysis is due to adsorption of the analyte to the reaction container used in the TOP assay and ii) investigate how much the ultra-short chain PFASs which were not measured in previous study contributes to the total amount of unidentifiable PFASs. TOP assay was performed on two commercially available fire-fighting foams, the same fire-fighting foams as the previous study. The analyses of PFASs were performed using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) and ultra performance convergence chromatography mass spectrometry/mass spectrometry (UPC2-MS/MS) as well as combustion ion chromatography (CIC) to determine total organofluorine level. The results showed that for Sthamex AFFF, ultrasonicating the sample (during the oxidative reaction as well as after the reaction), gave an increase in total concentrations of PFAS between 16% and 46%. For the Arc Miljö fire-fighting foam sample, in contrast, no observable increase of total concentration of PFASs was observed. Ultra-short chain PFAS analysis of the two foams showed that ultra-short chain PFASs contributes less than 1% of the total concentration of identifiable PFASs.

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An environment is defined as polluted when contaminants are introduced within it and causeadverse effects to its ecosystem. Chemical pollutants can migrate and often affect severalenvironmental compartments: for instance, chemicals can leach from polluted soil intogroundwater, or they can evaporate and disperse into the atmosphere.The recent advent of industrialisation and urbanisation has brought on the daily discharge ofharmful chemicals, such as heavy metals, organic pollutants and radioactive materials, into theenvironment via a high number of contamination sources, both commercial and industrial.More and more chemicals are identified as harmful to humans and the environment every year;in regard to the seemingly unsurmountable number of new ones being constantly introduced tothe market, it is important that authorities keep improving the efficiency of regulatoryprocedures and safety testing. This includes supporting scientific research which isfundamental for improving our understanding of the mechanisms of action of these chemicalsin order to handle them properly.In the present study, FET (Fish Embryo acute Toxicity) tests and behavioural challenges wereperformed on zebrafish (Danio rerio) embryos and larvae to investigate coumarin 47 andpermethrin in terms of toxicity and effect on larval photomotor response. A change inlocomotor activity in response to a light-to-dark transition stimulus is often the ultimate causeof exposure to specific neurotoxic agents, making it a useful endpoint in assessing centralnervous system toxicity, while FET tests are a guideline tool employed in the determination ofdevelopmental toxicity and teratogenicity.4Overall, the results obtained provided a significant understanding on the toxicity endpoints ofthe selected test compounds to be employed as references for future investigations.

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