Tetrabromobisphenol A and hexabromocyclododecane flame retardants in infantemother paired serum samples, and their relationships with thyroid hormones and environmental factors Un-Jung Kim, Jeong-Eun Oh * Department of Civil and Environmental Engineering, Pusan National University, San 30, Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea article info Article history: Received 1 May 2013 Received in revised form 5 August 2013 Accepted 9 August 2013 Keywords: Organohalogen Human monitoring Congenital hypothyroidism Infant Environmental factors abstract The concentrations of tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs), and their correlations with thyroid hormones, were investigated in sera from 26 infants with congenital hypo- thyroidism, 12 healthy infants, and their mothers. The analyte concentrations were not significantly different in the two infant groups. Polybrominated diphenyl ethers (measured in a previous study) were the dominant brominated flame retardants, contributing 42e87% of the total, and HBCDs contributed 5 e18%. TBBPA concentrations were 2e5 times higher in the infants than in the mothers. The TBBPA concentrations decreased dramatically with age for 2e3 months after birth, which might be caused by its relatively high maternal transfer rate, short half-life, and fast excretion. Significant correlations were found between mothers and infants in the TBBPA and HBCD concentrations, implying that maternal transfer was important. TBBPA correlated weakly with thyroid hormones, showing a positive relationship with FT4 but a negative relationship with T3. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Polybrominated diphenyl ethers (PBDEs), which were exten- sively used as brominated flame retardants (BFRs), have, more recently, been studied for their potential to cause endocrine disruption and other negative effects in humans and other biota. Because of the Stockholm Convention decision to phase out penta- and octa-BDE-based flame retardants in consumer products, other kinds of brominated flame retardants, such as tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs), have been used to replace PBDEs, and these have been found in various environ- mental matrices, including marine sediments, biota, and human tissues (Shi et al., 2009). Even for the BFRs that are suspected to be endocrine disrupting chemicals (EDCs), specific mechanisms for their interference with thyroid hormone activity has not yet been clarified (Yamada-Okabe et al., 2005; Kuiper et al., 2007), although there is some evidence from in vitro toxicity tests that these compounds are EDCs (Hamers et al., 2006; Li et al., 2010). The BFRs mentioned above also have characteristics of persistent organic pollutants (POPs) and the general population is exposed to them during normal daily life. Prenatal exposure to EDCs, in particular, is thought to cause endocrine and related malfunctions that can cause ill effects throughout life (Colborn et al., 1993; Palanza et al., 1999). It is, therefore, important to monitor the internal exposure of both mother and fetus or infant to EDCs. However, there is not currently enough background data to determine whether alternative BFRs act as endocrine disruptors in humans and whether they can cause metabolic malfunctions, such as congenital hypothyroidism. We recently found a statistically significant correlation between thyroid hormone and PBDE concentrations in human blood, and particular PBDE exposure patterns were found in a congenital hy- pothyroidism study group (U.J. Kim et al., 2011, 2012). Congenital hypothyroidism is a common pediatric endocrine disorder that occurs in approximately 1 in 3000e4000 children, and is suspected to be affected or caused, to some degree, by exposure to EDCs during the prenatal period (Bae and Kim, 2007). This was the first case that we are aware of confirming the actual impact of flame retardants on hormone activity in humans, particularly in younger infants. There are similarities between the molecular structures of TBBPA and HBCDs and the structures of PBDEs and thyroid hor- mones (THs), such as thyroxine (T4). It has, therefore, been spec- ulated that TBBPA and HBCDs might disrupt or mimic TH activity in similar ways to PBDEs (Stoker et al., 2004; Julander et al., 2005), and that exposure to TBBPA and/or HBCDs may be statistically related to maintaining homeostasis in humans (Kim et al., 2012). However, * Corresponding author. E-mail address: jeoh@pusan.ac.kr (J.-E. Oh). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol 0269-7491/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.envpol.2013.08.034 Environmental Pollution 184 (2014) 193e200