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- Castro, Mafalda
(författare)
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Chlorinated Paraffins: improved understanding of their bioaccumulation and toxicity in Daphnia magna
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chlorinated paraffins (CPs) are industrial chemicals, mainly used as flame retardants, plasticizers and metal cutting fluids. Their production has reached historically high levels in the last decade, with an annual production exceeding one million tonnes. In 2017, short chain chlorinated paraffins (SCCPs) were regulated due to their Persistent, Bioaccumulative and Toxic (PBT) properties, while medium and long chain chlorinated paraffins (MC and LCCPs) were suggested as alternatives. The high hydrophobicity of CPs, which complicates bioaccumulation and aquatic toxicity testing, has hindered proper hazard identification by regulatory authorities. This project was initiated in response to the insufficient understanding of bioaccumulative and toxicological properties of these chemicals, which have even surpassed the environmental levels of legacy Persistent Organic Pollutants (POPs) in certain regions.The research presented in this thesis, contributes to filling these knowledge gaps by adapting methods for reliable bioaccumulation and aquatic toxicity assessment. In Paper I, passive dosing, traditionally used for other highly hydrophobic compounds, was adapted and validated for CPs. SC, MC and LCCPs partitioned from silicone into water and, when the crustacean Daphnia magna was introduced into the test system, the CPs were observed to be effectively taken up by the test organism. This passive-dosing approach was further used in Paper II, to investigate the bioconcentration and bioaccumulation potential in D. magna. All tested CPs were found to bioaccumulate in daphnids, including highly hydrophobic, long chained CP congeners. The two most bioaccumulative CPs in Paper II (CP-52 and Huels70C) were thereafter used in a chronic toxicity study (Paper III) and significantly decreased population growth and disrupted fatty acid metabolism of D. magna. Finally, in Paper IV, liposome-mediated delivery of chemicals to aquatic biota was adapted for the first time for organic contaminants, including CPs. This approach yielded stable body burdens of the tested chemicals in D. magna and allowed for kinetic and toxicity assessments.Overall, two alternative bioaccumulation and aquatic toxicity testing methods were successfully adapted for technically challenging (industrial) chemicals. These methods allowed the determination of endpoints of scientific and regulatory interest, such as the high bioaccumulation and toxicity potential of CPs, but were also used to demonstrate their metabolic disruption potential in small crustaceans.
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| 2. |
- Dahlberg, Anna-Karin, 1985-
(författare)
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Environmentally relevant chemical disruptors of oxidative phosphorylation in Baltic Sea biota : Exposure and toxic potentials
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on toxicity and occurrence of hydroxylated polybrominated diphenyl ethers (OH-PBDEs) in Baltic Sea biota. The aims were to assess OH-PBDEs potency for disruption of oxidative phosphorylation (OXPHOS) and determine their and related compounds exposure in Baltic blue mussel, herring and long-tailed duck. A method for analysis of OH-PBDEs in herring and long-tailed duck plasma was also evaluated.Relevant OH-PBDEs were tested in vitro for OXPHOS disruption, using a classic rat mitochondrial respiration assay and a cell mitochondrial membrane potential assay. All compounds were found to disrupt OXPHOS either by protonophoric uncoupling and/or via inhibition of the electron transport chain. 6-OH-BDE47 and 6-OH-BDE85, were identified as particularly potent OXPHOS disruptors. Strong synergism was observed when OH-PBDEs were tested as a mixture corresponding to what is present in Baltic blue mussels.Baltic blue mussel is main feed for several species of mussel feeding sea ducks which have decreased dramatically in numbers. To assess long-tailed ducks exposure to brominated substances, liver tissue from long-tailed ducks wintering in the Baltic Sea and blue mussels were analysed. The result confirms that long-tailed duck are exposed to OH-PBDEs via their diet. However, low concentrations were found in the duck livers, which suggest low retention of these compounds despite daily intake. How the nutritional value of blue mussels as feed for sea ducks are affected by OH-PBDE exposure still needs further studies. Other species of sea ducks foraging on Baltic blue mussels during summer months can also be more exposed due to seasonal variation in primary production.Herring sampled in the Baltic Proper and Bothnian Sea, were found to contain OH-PBDEs and high levels of their methylated counterpart, MeO-PBDEs. As demethylation of MeO-PBDEs is known to occur in fish, MeO-PBDEs may pose as additional source for more toxic OH-PBDEs in herring and their roe.
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