Chlorinated paraffins (CPs) are environmental pollutants extensively used in industries. While the use of short-chain chlorinated paraffins (SCCPs) has been restricted since 2017, the use of medium-chain chlorinated paraffins (MCCPs) has risen as their replacement. Due to lipophilic character, it can be expected that CPs enter the cells; however, the in vitro accumulation potential of CPs remains poorly understood. In this study, we aimed to explore the ability of SCCPs and MCCPs to accumulate in fat cells. We utilized an in vitro model of mouse 3T3-L1 preadipocytes and adipocytes. Using gas chromatography coupled with high-resolution mass spectrometry operated in negative chemical ionization mode, we determined the intracellular amounts of CPs. These compounds accumulated at rates of 8.5 ± 0.1 μg/gcells/h for SCCPs and 7.8 ± 0.3 μg/gcells/h for MCCPs when an initial concentration of 120 ng/ml was present in the medium. This rate increased approximately tenfold when the concentration of CPs was raised to 1200 ng/ml. CPs content in adipocytes steadily increased over 5 days, whereas preadipocytes accumulated 15-20 times less CPs. This highlights the importance of cellular lipid content, which was about 12 times higher in adipocytes. Furthermore, we found that the level of chlorine content in the CPs molecules significantly influenced their accumulation. Our results demonstrate that MCCPs exhibit a similar accumulation potential to SCCPs, with lipid content playing a crucial role. As with SCCPs, restrictions on the use of MCCPs in industry should be considered to mitigate their environmental and health impacts.

Center for Experimental Medicine Institute for Clinical and Experimental Medicine Vídeňská 1958 14021 Prague Czech Republic

Department of Biochemistry and Microbiology University of Chemistry and Technology Technická 3 16000 Prague Czech Republic

Department of Food Analysis and Nutrition University of Chemistry and Technology Technická 3 16000 Prague Czech Republic

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