2.1. Study area and sample collection The studied samples were collected from industrial areas of Jhenaidah and Kushtia districts, Bangladesh. Jhenaidah and Kushtia are densely populated (900 and 1,200/km2 ) districts of the country having an area of 1965 and 1609 km2 , respectively (BBS 2011). There are several types of industrial units including tobacco industries, garments, tannery industries, packaging industry, dyeing, brick kiln, metal workshops, battery manufacturing industries, textile industries, pesticide, and fertilizer industries, different food processing industries, and other industrial areas produce huge volumes of effluents that contain trace metals (Kormoker et al. 2019). The untreated wastes and effluents from these industries are discharged randomly to river and canals. Then that wastes are mixed with soils and the soil is continuously polluted by heavy metals. Crop samples were collected near industrial vicinity and at each sampling station, same species of cereals, pulses, vegetables, and fruits were collected as subsamples and were thoroughly mixed to form a composite sample. Two hundred and seventy samples of twenty five different agricultural crops i.e., rice (Oryza sativa), maize (Zea mays), wheat (Triticum aestivum), mung bean (Phaseolus radiate), lentil (Lens culinaris), black gram (Vigna mungo), bottle gourd (Lagenaria siceraria), chili (Capcicum frutescens), potato (Solanum tuberosum), cucumber (Cucumis sativus), danta shak (Amaranthus lividus), red amaranth (Amaranthus albus), drumstick leaf (Moringa oleifera), okra (Abelmuschus esculentus), Indian spinach (Basella alba), bean (Phaseolus vulgaris), papaya (Carica papaya), brinjal (Solanum melongena), carrot (Daucus carota), banana (Musa paradisiaca), mango (Mangifera indica), guava (Psidium guajava), jackfruit (Artocarpus heterophyllus), tobacco (Nicotiana tabacum), and betel leaf (Piper betle) were collected by hand from the selected agricultural fields during March-April, 2017. The samples were kept in polythene zip-bags with definite marking and tagging and brought to the laboratory on the day of sampling for chemical analysis. Crop samples were washed with distilled water and cut into small pieces by stainless steel knife and was kept in oven at 70–80 C to attain constant weight (Tiwari et al. 2011). The fresh and dry weights were recorded to calculate moisture contents. The processed samples were brought to Yokohama National University, Japan for chemical analysis. 2.2. Toxic metal analysis All chemicals were analytical grade reagents; Milli-Q water (Elix UV5 and MilliQ, Millipore, Boston, MA, USA) was used for the preparation of solutions. The Teflon vessel and polypropylene containers were cleaned, soaked in 5% HNO3 for more than 24 h, then rinsed with Milli-Q water and dried. For metal analysis, 0.3–0.5 g of the crop sample was treated with 6 mL 69% HNO3 (Kanto Chemical Co, Tokyo, Japan) and 2 mL 30% H2O2 (Wako Chemical Co, Tokyo, Japan) in a closed Teflon vessel and was digested in a Microwave Digestion System (Berghof speedwave1, Eningen, Germany). The digested samples were then transferred to a Teflon beaker, and the total volume was increased up to 50 mL with Milli-Q water. The digested solution was then filtered by using syringe filter (DISMIC1–25HP PTFE, pore size ¼ 0.45 mm; Toyo Roshi Kaisha, Ltd., Tokyo, Japan) and stored in 50 mL polypropylene tubes (Nalgene, New York, NY, USA). After that the digestion tubes were then cleaned using blank digestion procedure following same procedure of samples. For toxic metals, samples were analyzed using an inductively coupled plasma mass spectrometer (ICP-MS, Agilent 7700 series, Santa Clara, CA, USA). Instrument operating conditions and parameters for metal analysis are done. The detection limits of ICP-MS for the studied metals were 0.7, 0.6, 0.8, 0.4, 0.06, and 0.09 mg/L for Cr, Ni, Cu, As, Cd, and Pb, respectively. Multi-element Standard XSTC-13 (Spex CertiPrepVR , Metuchen, NJ, USA) solutions were used to prepare the calibration curves. Internal calibration standard solutions containing 1.0 mg/L of indium, yttrium, beryllium, tellurium, cobalt, and thallium were purchased from Spex Certi PrepVR (Metuchen, NJ, USA). During the procedure, 10 mg/L internal standard solution was prepared from the primary standard and added to the digested samples. Multi-element solution (purchased from Agilent Technologies, Japan) was used as the tuning solution covering a wide range of masses of elements. All test batches were evaluated using an internal quality approach and validated to see if they satisfied the defined Internal Quality Controls (IQCs). Before starting the analysis sequence, the relative standard deviation (RSD, <5%) was checked by using tuning solution purchased from Agilent Technologies. The certified reference materials INCTCF-3 (corn flour) bought from the National Research Council (Canada), were analyzed to confirm analytical performance and good precision (relative standard deviation bellow 20%) of the applied method.