Halogens, including fluorine, bromine, and iodine, are critical components of biogeochemical cycles, naturally occurring in water bodies and accumulating within marine ecosystems. While these elements are vital in trace amounts, they can accumulate to higher levels in aquatic organisms, especially in regions impacted by anthropogenic pollutants.[1] Special attention should be given to the fluorinated organic compounds known as per- and poly-fluoroalkyl substances (PFAS) or “forever chemicals”, which are man-made compounds, highly mobile and persistent in the environment, leading to their accumulation in marine organisms.[2] Since one of the most common exposure routes for humans to halogens and their compounds is through seafood consumption, understanding both their total content and bioavailability — the fraction that, after released from the food matrix, is available for metabolism after transposition of the intestinal wall, respectively [3] — is crucial for assessing dietary exposure risks accurately. This study aimed to develop and assess robust analytical methods to quantify halogens in diverse marine matrices, including shrimp, mussels, and oysters, as well as their bioavailable fraction and residue after digestion. Sample preparation was optimized using microwave-induced combustion (MIC), a technique selected for its high efficiency in decomposing complex matrices. Recovery rates between 92% and 102% demonstrated the reliability of the preparation method across different types of samples. Quantitative analysis was then conducted using ion chromatography (IC, for F) and inductively coupled plasma mass spectrometry (ICP-MS, for Br and I), chosen for their sensitivity in multi-element analysis of total, bioavailable, and residual halogen fractions. Also, high-performance liquid chromatography coupled with tandem mass spectrometry with electrospray ionization (HPLC-ESI-MS/MS) was employed to evaluate the presence of PFAS in the seafood and their bioavailable fraction after ultrasound-assisted extraction (UAE). Results showed that halogen accumulation patterns varied significantly among species and tissue types. In shrimp, for example, halogens were found to accumulate differently between shell and tissue, with the shell generally showing higher concentrations. Culinary treatments such as boiling or frying further modified these concentrations, often decreasing the halogen content in bioavailable fractions due to matrix-dependent losses. Among the halogens analyzed, bromine was observed to be the most bioavailable (from 32 to 63%) across multiple seafood types. Conversely, iodine largely remained in the residual fraction (from 43 to 100%) after in vitro digestion, suggesting limited release of this element during digestion simulation. Besides that, PFAS demonstrated to be bioavailable from seafood in ratios from 8 to 50%, compared to the total PFAS content – but in ratios < 0.03% if compared to total F content. These bioavailability trials underscore the need for tailored analytical approaches that account for variations in the release of halogens and their compounds across different food matrices. The results indicate that matrix composition has a significant role in determining how much of each analyte becomes available for absorption. This study provides a methodological framework that enhances our understanding of dietary halogen exposure from seafood and supports the development of better risk assessments and regulatory guidelines for safe consumption. At the same time, these findings offer valuable insights into how seafood contributes to human halogen intake and the factors influencing its bioavailability.

References

[1] R. Fuge. J Environmental Geochemistry Health, 1988, 10(2), 51-61.

[2] H. Brunn, G. Arnold, W. Körner, G. Rippen, K.G. Steinhäuser, I. Valentin. Environmental. Sciences Europe, 2023, 35(1), 30.

[3] A. El-Kattan, M. Varma. Topics on Drug Metabolism, 2012, 10, 31087.