Adverse thyroid hormone and behavioral alterations induced by three frequently used synthetic musk compounds in embryo-larval zebrafish (Danio rerio).

Synthetic musk compounds (SMCs) have been extensively used in numerous consumer products, such as perfumes, cosmetics, soap, and fabric softener. Due to their bioaccumulative nature, these compounds have often been detected in the aquatic ecosystem. However, their effects on endocrine and behavioral effects in freshwater fish have rarely been investigated. In the present study, thyroid disruption and neurobehavioral toxicity of SMCs were investigated using embryo-larval zebrafish (Danio rerio). Three frequently used SMCs, i.e., musk ketone (MK), 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta [g]- benzopyran (HHCB), and 6-acetyl-1,1,2,4,4,7-hexamethyltetralin (AHTN), were chosen. Experimental concentrations for HHCB and AHTN were selected to include the maximum levels reported in the ambient water. The 5-day exposure to either MK or HHCB led to significant decrease of T4 concentration in the larval fish at the levels as low as 0.13 µg/L, even though compensatory transcriptional changes, e.g., up-regulation of hypothalamic crhß gene and/or down-regulation of ugt1ab gene, were taken place. In contrast, AHTN exposure resulted in up-regulation of crhß, nis, ugt1ab, and dio2 genes but did not alter T4 level, suggesting its lesser thyroid disrupting potential. All tested SMCs caused hypoactivity of the larval fish. Several genes related to neurogenesis or development, e.g., mbp and syn2a, were down-regulated, but the patterns of transcriptional changes were different among the tested SMCs. The present observations demonstrate that MK and HHCB can decrease T4 levels and cause hypoactivity of the larval zebrafish. It requires attention that HHCB and AHTN could influence thyroid hormone or behavior of the larval fish even at the levels close to those observed in the ambient environment. Further studies on potential ecological consequences of these SMCs in freshwater environment are warranted.

Urinary paraben concentrations of adult women by fasting status: Comparison between Korea and the United States.

Personal care products (PCPs) are considered as a major source of paraben exposure; however, the dietary contribution is not well known. We compared the urinary levels of methyl-, ethyl-, and propyl-paraben (MeP, EtP, and PrP), and investigated their associations with fasting status and contacts with other potential exposure sources among Korea and the US adult women. A group of fasting, non-pregnant adult women (n = 469) was recruited from Seoul, Ansan/Incheon, and Jeju, Korea in 2015-2016, and their urine was measured for parabens. Non-fasting Korean women of matching age (25-45 years) were chosen from the Korean National Environmental Health Survey (KoNEHS) Cycle 3 (n = 579). For the US women, both fasting (n = 154) and non-fasting (n = 201) females were chosen from the NHANES 2015-2016 participants. In fasting Korean women, the urinary MeP, EtP, and PrP concentrations (median) were measured at 47.30, 17.90, and 2.30 ng/mL, respectively. Urinary EtP and PrP levels in fasting Korean women were significantly lower than those in non-fasting women (EtP and PrP median of 26.40 and 3.57 ng/mL). On average, the difference in urinary EtP levels by fasting status was greater among the highly exposed groups. In the US population, EtP levels were significantly lower (median ranged 1.55-1.80 ng/mL depending on fasting status), but MeP levels were higher (67.90-84.35 ng/mL) than those of the Korean population. When only fasting women were considered, the median EtP levels of Korean women were 11.5-fold greater than those of US women, suggesting that the non-dietary contributions of EtP exposure could not be ignored among Korean women. Regardless of fasting status, MeP and PrP were significantly correlated, and their urinary levels in fasting Korean women were correlated with the use of several personal care products. The major dietary and non-dietary sources that may explain EtP exposure in Korean women warrant further investigation.