Arsenic and cadmium in food-chain the case of arsenic determination, to 10 mL of each solution (sample, recovery, blank, standard) 1 mL of 5M HCl and 1 mL of 20% KI (w/v) were added and heated in water bath at 80 0C for 30 minutes to reduce As (V) to As (III) and cooled to room tem- perature for analysis of arsenic. The detection limit of arsenic for food samples was found to be 0.3 µg/ kg in solution. Hydride vapour generation-atomic absorption spectrophotometry (HVG-AAS) showed excellent correlation coefficients between 0.9998 and 0.9996 over the concentration range of 2 µg/L to 15 µg/L of arsenic. However, necessary dilutions were made for samples containing high concentra- tion of arsenic. To validate the precision and accu- racy of the method, recovery and duplicate food samples were analyzed (recovery=97%, CV%=±5). For the determination of cadmium, graphite fur- nace-atomic absorption spectrophotometry (GF- AAS) was used, and the method followed was described earlier (14-16). Standard reference materi- als—SRM 1643e (trace elements in water) and SRM 1568a (rice-flour) from NIST (USA)—were used for checking the precision and accuracy of the analysis, which were found to be excellent with CV%=±5. Methods of cooking To evaluate the effects of arsenic concentration from cooked rice, we performed in the laboratory two conventional cooking processes of rice in Bang- ladesh to understand the extent of arsenic removal. The third process was done at the household level in our study area. Process A: An excessive volume of water was used for cooking rice, and excess water was discarded, which is the tradition of the study households. Be- fore cooking, raw rice is washed with water until water is clear and no longer turbid. The water used for washing and cooking arsenic-contaminated rice was arsenic-free. The rice-washed water, discarded water, and cooked rice were analyzed for arsenic, and in the case of cadmium, raw rice and cooked rice were analyzed. Process B: An optimum volume of water was used for cooking rice so that no water was needed to be discarded. The rice-washed water and cooked rice were analyzed for arsenic. Process C: Water generally is not discarded when cooking vegetables as it is perceived that discarding excess water would lead to loss of micronutrients. Cooked vegetables were collected from households as mentioned above and analyzed for arsenic and cadmium. Before analysis, all the samples were treated as de- scribed earlier (15). 580 Khan SI et al. Statistical analysis Statistical analyses were done using the SigmaStat software (version 3.1) (Systat Software, Inc.). Des- criptive frequencies of the study variables were ana- lyzed to assess validity of data, distributions, and assumptions of normality and equal variance. Con- centrations of arsenic and cadmium were expressed as mean±standard deviation in raw and cooked food items. Between-groups comparison was done by Student’s t-test, and for within-groups compari- son, paired t-test was done. The overall significance level of these tests was set at <0.05. rESULtS Cooking processes Cooking process A and B were compared using arsenic-free water in the laboratory. Washing rice until water became clear reduced the concentration of arsenic in raw rice by 13-15%. The conventional cooking process A removed 54% of arsenic in the discarded water (Table 1 and Fig.). The mean con- Table 1. Percentage distribution of arsenic in rice and water after different cooking processes Process* A B Rice- washed water 13 15 diWscaartedred creoAtoarkisneedendirciicne 54 33 Not 85 discarded *Contaminated rice, cooked with arsenic-free water; Process A: Excess water discarded during cooking. Process B: An optimum volume of water used for cooking. No water needed to be discarded after cooking centration of arsenic in raw rice was 240.8 (range 219-253) µg/kg whereas, in cooked rice samples, it was 56.5 (range 18-78) µg/kg. Arsenic concentration in raw and cooked vegetables The ranges of arsenic concentrations (µg/kg) de- tected in raw leafy vegetables (amaranth, spinach, and arum) and non-leafy vegetables (potato, bitter gourd, banana, and eggplant) are given in Table 2. Among the cooked vegetables, the highest concen- tration of arsenic was found in amaranth (309 µg/ kg). Since arsenic-contaminated water was used for cooking vegetables, the concentration of arsenic in cooked vegetables increased and was significantly higher than that in raw vegetables (p=0.024). The increase in arsenic concentration in the cooked JHPN