## 1 Introduction  
Excessive use of pharmaceuticals and personal care products (PPCPs) by the modern population has loaded the aquatic ecosystems with xenobiotics [1]. PPCPs are a class of emerging contaminants ubiquitously found in water and soil all over the world and cause deleterious effects on humans and non-target organisms. Triclosan (TCS), a common antibacterial and antifungal agent, is incorporated in a majority of household products such as soap, shampoo, detergent, cleansing kits, chopping boards and containers. During the COVID-19 pandemic, excessive use of TCS-containing sanitizers and handwash has further increased its discharge into water bodies. One of the serious issues related to TCS is its incomplete removal by the conventional waste water treatment plants [2]. Dhillon et al. [3] reported concentrations of TCS in the range of 0.0014-40 \(\mathrm{\SIUnitSymbolMicro g}\)/L in the surface water of lakes, rivers and streams with direct input of raw waste water and in the range of 100-53,000 \(\mathrm{\SIUnitSymbolMicro g}\)/kg dry weight in the sediments of fresh water bodies. The concentration of TCS has been reported to be 3.8-5.16 \(\mathrm{\SIUnitSymbolMicro g}\)/L in the Tamiraparani River of India [4]. However, Nag et al. [5] detected TCS levels in the range of 1.1-9.65 \(\mathrm{\SIUnitSymbolMicro g}\)/L in the surface water, 5.11-50.36 \(\mathrm{\SIUnitSymbolMicro g}\)/kg in the sediments and 13-1040 \(\mathrm{\SIUnitSymbolMicro g}\)/kg in the fish of the Gomti River in India. High concentrations of TCS have also been recorded in different fish species (91.1-589 \(\mathrm{\SIUnitSymbolMicro g}\)/kg) of the Torsa River in India [6]. TCS is reported to cause varying degrees of toxicity in aquatic organisms such as developmental abnormalities [7], behavioral alterations [8], hematological and histopathological changes [9], endocrine disruption [10], oxidative stress [7; 11] and transcriptomic alterations [12; 13]. Due to its antiseptic nature, it disturbs normal cell functions, which leads to cytotoxic [14], cladogenic and aneugenic effects in organisms. Earlier studies have reported significant cytotoxic and genotoxic effects from TCS in _Dreissena polymorpha_[15], _Oreochromis niloticus_[16], embryos of _Danio rerio_[17], _Pangasianodon hypophthalmus_[18; 19], adult zebra fish [20] and _Labeo rohita_[9; 13]. Of all the organisms, fishes are sensitive to even low levels of such xenobiotics in a water body, as these may enter the fish body from water as well as food at the same time and affect its normal physiology, biochemistry and metabolism [21; 22; 23; 24]. Biochemical profiling in fishes is consideredas an essential tool against environmental stress, as it provides an early warning signal for the target organs of toxicity and health status of fish and aquatic ecosystem [25]. TCS-induced significant biochemical changes have been reported in zebra fish [26], _Chamma punctatus_[27], _Oreochromis niloticus_[16], _Labeo rohita_[9] and _Catala catala_[28]. Marked variations in biochemical parameters may ultimately cause harmful effects in both exposed fishes and consumers. The goal of the present study was to evaluate the cyto-genotoxicity and biochemical toxicity of 4 environmentally relevant concentrations (6.3, 12.6, 25.2 and 60 \(\mathrm{\SIUnitSymbolMicro g}\)/L) of TCS to the hatchlings of an important food fish, _L. rohita_, after 14 days of exposure and 10-days deprivation period. The selected concentrations were 1/20, 1/10, 1/5 and 1/2 of 96-h LC\({}_{50}\) of TCS for the hatchlings already reported in our previous study [13], and the interaction of fish with these levels of TCS is expected in nature. The selected concentrations were non-lethal, and evaluation of the biochemical and genotoxicity parameters after extended exposure to these concentrations had its own importance because of the absence of immediate visible signs of toxicity.