Currently, different polymer types are used for producing various consumer products ranging from electric and electronic devices to textiles, building materials, glues, casting resins and engineering thermoplastics. Mostly, these products are polymer and petroleum based and flammable (Alaee et al., 2003; Van der Veen and de Boer, 2012). Therefore, flame retardants have routinely been supplemented.

Flame retardants slow the initiation of fires and/or slow the spread of fire. Flame retardants used as additives in materials can be released easily into the environment by corrosion and vaporization because; they are not chemically bonded (Van der Veen and de Boer, 2012). Flame retardants (FRs) are often used as additives in electronic products, as plasticizers, and antifoaming agents. In various environmental materials found in the waste recycling regions, high FRs concentrations have been detected (Zheng et al., 2015; Zhao et al., 2017).

Triphenyl phosphate (TPhP) is an organophosphate flame retardant (OPFR). It has

been used in many consumer products ranging from electronic apparatuses to building necessaries and plastics. Furthermore, it is used in paints, glues, polyurethane foams and casting resins (Carlsson et al., 2000; Bjorklund et al., 2004; Van der Veen and de Boer, 2012; Matsukami et al., 2015; Hou et al., 2016). Also, it is commonly used as an additive plasticizer in personal care products such as nail polish at levels up to 16.8 mg/g (Mendelsohn et al., 2016). Since it does not chemically bond with polymeric materials, it can be easily released into the environment (Marklund et al., 2003; Wang et al., 2014). While other flame retardants (e.g. PBDEs) were discontinued due to their risks to human health, TPhP use is gradually increased World Health Organization. Environmental Health Criteria 112, 1991; Van der Veen and de Boer, 2012; Wei et al., 2015).

Due to its extensive use in various products, TPhP has been found abundantly in various environmental matrices such as surface water, drinking water, soil, air and dust, and also in human blood and placenta (Meeker and Stapleton, 2010; Van der Veen and de Boer, 2012; Cristale et al., 2013; Salamova et al., 2014; Tan et al., 2016; Ding et al., 2016; Zhao et al., 2016; He et al., 2018). Therefore, the potential risks of TPhP on environment and human health require more caution and investigation. Previous studies reported that TPhP could have toxic effect on vertebrate (Liu et al., 2013; Isales et al., 2015; Du et al., 2016; Yuan et al., 2018). Neurotoxic properties of TCEP and TNBP after chronically exposure were reported in WHO reports (World Health Organization. Environmental Health Criteria 112, 1991; World Health Organization, 1998). However, little information is present about the TPhP toxicity and only a few reports about potential negative effects have been published. Therefore, bio-monitoring of TPhP is important and needed for possible environmental and human health effects.

At least 200 short-term bioassay using microorganisms, plants, or insects have been emerged in the last ten years. They have been used to evaluate the environmental risks (Marcato-Romain et al., 2009). Among these assays, plant bioassays are highly sensitive, easy to use in experiments, relatively inexpensive than animal assays, and good predictors of carcinogens (Ennever et al., 1988). Many researchers widely used the Allium test for investigation of pollution in environment (Bagatini et al., 2009; Leme and Marin-Morales, 2009) and of cyto- and genotoxicity of various agents (Aşkın Çelik and Aslantürk, 2007, Aşkın Çelik and Aslantürk, 2009, Aşkın Çelik and Aslantürk, 2010; Tedesco and Laughinghouse IV, 2012). The Allium test is significant, because it is a perfect model in vivo. In this model, roots of onions grow in direct contact with the solution contained test substance allowing for prediction of possible DNA damage in eukaryotes. Therefore, Allium test results can be extrapolated for all animals and plant biodiversity (Tedesco and Laughinghouse IV, 2012).

In this study, our goal was to investigate potential cytotoxicity and genotoxicity effects by triphenyl phosphate (TPhP) on A. cepa root tips.