The effluent was dark red in color and slightly acidic (pH 5.6 ± 0.11). We recorded high conductivity (1563.34 ± 176 µs cm−1), total dissolved solids (920.34 ± 137 mg L−1), BOD (7253.34 ± 1022 mg L−1), and COD (756.67 ± 1124 mg L−1) in the effluent sample (Table 1). The presence of heavy metals with their respective concentration in the effluent is obtained after the analysis with AAS instrument confirmed the presence of Cu, Co, Cd, Ni, Pb, Mn, Cr, Zn, Fe, As, and Hg. The result confirmed that the parameters such as pH, electrical conductivity (EC), BOD, and COD were above the standard prescribed limits of CPCB for effluent discharged into surface water. Comparative reviews with regard to physicochemical characterization were also carried out by various authors (Ramola and Singh 2013; Rohit and Ponmurugan 2013; Rao et al. 2004; Mayabhate et al. 1988; Vanerkar et al. 2013; Sirtori et al. 2009). The high BOD and COD indicated that the different chemical ingredients were used in the preparation of drugs (Hardman and Limbird 1996; Reynolds 1989).
GC–MS analyses of hexane-extracted effluent samples are presented in Fig. 1. GC–MS analyses of effluent sample on the basis of retention time (in minute) revealed the presence of various types of organic compound including trimethyl(phenylmethoxy) (RT = 10.53), 1,6,8-trimethoxy-2-isopropyl-3-methoxy-anthracene-9-one (RT = 13.52), silane,(iodomethoxy)trimethyl (RT = 15.41), hydroquinone (RT = 16.19), monotrimethylsilyl derivative of nicotinamide (RT = 17.67), 2,5-dihydroxy benzyl alcohol 3 TMS (22.27), pantoyl propylamide, bis(trimethylsilyl) ether (RT = 26.49), hexadecanoic acid, trimethylsilyl ester (RT = 27.81), oleic acid, trimethylsilyl ester (RT = 30.31), promethazine (RT = 31.66), kurchessin (RT = 32.26), tocopherol acetate (RT = 40.78), and galactopyranoside, methyl 2,3-bis-O (RT = 43.13) which were compared with standard of National Institute of Standards and Technology (NIST) library. The result indicates that mainly two drugs identified in the effluent are promethazine (used in treatment of allergies and motion sickness) and hydroquinone. Hydroquinone (used for skin bleaching) is an aromatic organic compound, a type of phenol, leading to serious toxic effects on fauna and flora. Pereira et al. (2014) reported that the hydroquinone drug has genotoxic property. The cytotoxicity of hydroquinone is caused by following the primarily oxidative damage methods to DNA (Enguita and Leitão 2013). The compound tocopherol acetate is also found that is used in the preparation of multivitamins tablets.
FT-IR analyses result (Fig. 2) shows that the peaks at 3316 cm−1 and 2903 cm−1 correspond to antisymmetric and symmetric C–H stretching vibrations in methyl groups, 2268 cm−1, 1673 cm−1, 1583 cm−1, and 1384 cm−1 correspond to stretching and deformation vibrations of (C=C) group, and peak 1233–1075 cm−1 shows the in-plane deformed peak of benzene (Ermakova et al. 2015).
Onions grown in different concentrations of effluent showed toxic effects of effluent on root growth. Significant differences were noticed when roots length was compared with negative control (tap water). Root growth was not observed in onions grown in the effluent concentrations ≥ 50% (Fig. 3).
Inhibition in root growth and length of Allium cepa were observed in the present study following the treatment with pharmaceutical industrial wastewater which was in concurrence with previous studies conducted by other researchers (Akintonwa et al. 2009; Bakare et al. 2009).
The MI of onion root in the negative control (tap water) was 64%, whereas MI obtained for the onion root in the positive control (5 mM EMS) was 3.1% (Table 2). The lowest MI was recorded (MI = 9.6%) in 25% concentration of effluent, showing a significant reduction compared to control (p < 0.01). The interference in MI may result from the cytotoxic effect which is in acquired by inheritance in the toxic effluent. The toxicants in effluent may interfere in the normal mitotic cell cycle by prohibiting cells from entering the prophase and thus blocking the mitosis during interphase (Shrivastava 2015; Glinska et al. 2007; Rencuzogullari et al. 2001). The reduction in MI can be assigned to the impact of toxic chemicals on DNA/protein synthesis of the biological system (Chauhan et al. 1998).
No chromosomal aberrations were observed in the root tip cells treated with the tap water (negative control) (Fig. 4 and Table 2). Onion bulbs grown in the positive control (5 mM EMS) showed c-mitosis, chromosomal break, and micronuclei in the root tip cells. The observed CA was stickiness, anaphase bridge, laggard chromosome, tripolar chromosome, vagrant chromosome, chromosomal loss, chromosomal break, c-metaphase, and micronucleated cell. Different chromosomal aberrations have been also reported by other researchers in their study (James et al. 2015; Akintonwa et al. 2009; Bakare et al. 2009). The highest CA was recorded (19.5%) in 25% concentration of effluent. The indication of CA in A. cepa root tip cells may be incorporated with the collective effect of different pollutants such as heavy metals, phenols, drugs, and other organic pollutants (investigated by GC–MS). All these studies suggest that heavy metals, phenols, drugs, and other organic pollutants are responsible for cytotoxic and genotoxic effects of pharmaceutical effluent.