RESEARCH ARTICLE Organophosphate esters in human serum in Bohai Bay, North China Dute Gao 1 & Jun Yang 2 & Tadiyose Girma Bekele 3 & Sijia Zhao 1 & Hongxia Zhao 3 & Jun Li 1 & Mijia Wang 1 & Haidong Zhao 1 Received: 2 October 2019 /Accepted: 28 November 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Organophosphate esters (OPEs), as a class of emerging flame retardant and plasticizers, have attracted particular attention due to their ubiquitous existence in the environment and potential effects on human health. Here, we investigated the levels of OPEs in human serum and examined the role of demographic variables on the body burden of such compounds. Of 11 OPEs screened, 8 were detected in human serum samples collected from a population (n = 89) in Bohai Bay, North China. The ∑OPE concentrations ranged from 4.7 to 948 ng/g lipid weight (lw), with a median concentration of 243 ng/g lw. Tris(2-chloroethyl)phosphate (TCEP) was identified as the most abundant OPEs with a median concentration of 214 ng/g lw. The concentrations of the triphenyl phosphate (TPhP) in older adults were higher than those in young adults (p < 0.05), and lower concentrations of tri-iso-butyl phosphate (TIBP) were observed in female samples compared to males. Furthermore, significant differences were observed in tri-n-propyl phosphate (TPrP) concentrations between urban and rural residence groups ( p < 0.05). This study provides important information on the accumulation potential of OPEs in human bodies and suggests the need for further investigation to understand the potential human health risk. Keywords Organophosphate esters . Human serum . Bohai Bay . Demographic characteristics Introduction Flame retardants, which are a group of chemical products to increase the flame resistance of materials, have been extensively used in different products such as electronic equipment, furniture, and plastics (van der Veen and de Boer 2012; Wang et al. 2014). Organophosphate esters (OPEs), as a class of emerging flame retardant and plasticizers, have been widely used in products due to their high flame retardants performance and strong plasticity (Luo et al. 2014). Only in 2013, the global market demands of OPEs were estimated to be 620,000 tons, which accounted for 30% of total worldwide flame retardants consumption, and reached 680,000 tons in 2015 (Sühring et al. 2016; Wang et al. 2015). OPEs are direct- ly added to industrial and consumer products and released easily into the environment due to their weakly chemical bonding to the substrate materials (Marklund et al. 2003; Wensing et al. 2005). As a result, they have been frequently detected in different environmental compartments, such as dust, indoor air, water, and atmosphere (Cequier et al. 2014; Chung and Ding 2009; Gao et al. 2014; Kim et al. 2011; Staaf and Östman 2005). In addition, OPEs have also been detected in foods such as fish, meat, vegetable, and fruit (Bekele et al. 2019; Li et al. 2014; Poma et al. 2017). Several studies have reported that humans are likely to be exposed to OPEs through different exposure pathways due to their ubiquitous existence in the environment. For instance, inhalation, ingestion, and skin contact are reported to be crit- ical pathways (Marklund et al. 2005; Poma et al. 2017; St. Dute Gao and Jun Yang share first authorship of this study. Responsible editor: Philippe Garrigues Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-019-07204-5) contains supplementary material, which is available to authorized users. * Hongxia Zhao hxzhao@dlut.edu.cn * Haidong Zhao z.hddl@hotmail.com 1 General Surgery Department, The Second Affiliated Hospital of Dalian Medical University, No. 467 Zhongshan Road, Dalian 116023, China 2 Department of Neurology, The First Hospital of China Medical University, Shenyang 110001, China 3 Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, No. 2 Linggong Road, Dalian 116023, China Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-07204-5