Dietary exposure and risk assessment of polybrominated diphenyl ethers in the Republic of Korea: A nationwide study.

In this study, the dietary exposure to seven polybrominated diphenyl ethers (PBDEs) congener groups, including 22 types of PBDEs compounds, through consumption of 80 food items in Korean diets along with their risk assessment has been investigated. To process this, the concentrations of the target PBDEs in samples of food items were measured. The consumption amounts of the target food items were derived from the results of the 24 h food recall interview of subjects who participated in the Korean National Health and Nutrition Examination Survey (KNHANES) from 2015 to 2019. Thereafter, the estimated daily intake and risk of exposure for each PBDEs congener group were assessed. Results indicate that although exposure to the target PBDEs was not significant enough to cause a potential health risk, deca-BDE (BDE-209) was the dominant congener in terms of both exposure and risk for consumers in all age groups. Furthermore, while eating seafood was the dominant path for dietary exposure to PBDEs, exposure to octa-BDEs was mostly through livestock products. Accordingly, to protect all consumers, especially those aged below 2 years and over 65 years, more accurate food quality management is required for controlling the dietary intake of PBDEs.

Self-Healing EPDM Rubbers with Highly Stable and Mechanically-Enhanced Urea-Formaldehyde (UF) Microcapsules Prepared by Multi-Step In Situ Polymerization.

The mechanically-enhanced urea-formaldehyde (UF) microcapsules are developed through a multi-step in situ polymerization method. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) prove that the microcapsules, 147.4 µm in diameter with a shell thickness of 600 nm, are well-formed. From 1H-nuclear magnetic resonance (1H-NMR) analysis, we found that dicyclopentadiene (DCPD), a self-healing agent encapsulated by the microcapsules, occupies ca. 40.3 %(v/v) of the internal volume of a single capsule. These microcapsules are mixed with EPDM (ethylene-propylene-diene-monomer) and Grubbs' catalyst via a solution mixing method, and universal testing machine (UTM) tests show that the composites with mechanically-enhanced microcapsules has ca. 47% higher toughness than the composites with conventionally prepared UF microcapsules, which is attributed to the improved mechanical stability of the microcapsule. When the EPDM/microcapsule rubber composites are notched, Fourier-transform infrared (FT-IR) spectroscopy shows that DCPD leaks from the broken microcapsule to the damaged site and flows to fill the notched valley, and self-heals as it is cured by Grubbs' catalyst. The self-healing efficiency depends on the capsule concentration in the EPDM matrix. However, the self-healed EPDM/microcapsule rubber composite with over 15 wt% microcapsule shows an almost full recovery of the mechanical strength and 100% healing efficiency.

The occurrence and distribution of polychlorinated naphthalenes (PCNs), focusing on tissue-specific bioaccumulation in crucian carp in South Korea.

The occurrence and distribution of 41 congeners of polychlorinated naphthalenes (PCNs) were investigated in major tissues of crucian carp (muscle, gonad, liver, and blood) and in river sediment to assess the bioaccumulation potential of PCNs. The total PCN concentrations in sediment ranged from 4.37 to 19.5 pg/g dry weight (dw), mainly comprising CN-13, CN-33/34/37, and CN-38/40. Among fish tissues, higher PCN concentrations were observed in the gonads (29.6 ±â€¯10.3 pg/g wet weight, ww) and liver (25.7 ±â€¯4.35 pg/g ww) of crucian carp than in the muscle (2.17 ±â€¯0.68 pg/g ww). CN-28/43, CN-33/34/37, CN-42, CN-52/60, CN-53/55, and CN-66/67 congeners were detected most frequently and had the highest concentration among all crucian carp tissues. We investigated the association between the PCN concentration in each tissue (muscle, liver, and gonad) and the size of the fish (total length and weight) and found positive correlations between the PCN concentration in the gonads and the total length and weight (p < 0.05, Spearman correlation).