Arsenic and cadmium in food-chain Where shallow groundwater is contaminated, it is likely that arsenic is present in bioavailable forms in soil and in irrigation water (5). During the 1960s- 1980s, shallow tubewells were installed in Bangla- desh to provide ‘safe water’ to prevent morbidi- ty and mortality due to gastrointestinal diseases caused by contaminated surface water. Water from these tubewells was not tested for arsenic or other toxic element contamination. Results of studies in countries where the population has had long-term exposure to arsenic in ground- water indicate that 1 in 10 people who drinks wa- ter containing 500 µg/L of arsenic may ultimately die due to arsenic-induced cancer of lung, bladder, skin and cardiovascular diseases (1,3). A recent sur- vey showed that arsenic-related diseases resulted in 9,136 deaths per year and 174,174 disability-adjust- ed life-years (DALYs) among people who were ex- posed to arsenic concentrations of above 50 μg/L, and this constituted about 0.3% of the total burden of disease in Bangladesh (6). In Bangladesh and elsewhere, exposure to arsenic may involve a number of pathways: (a) by inges- tion of contaminated drinking-water and food and (b) by inhalation of metal-containing dust. After a massive safe campaign by the United Nations Chil- dren’s Fund and other donor organizations, the installation of irrigation tubewells—both deep and shallow—largely began during the decade of 1980 (7). With the increased use of groundwater through irrigation-pumps during the 1990s, arsenic con- tamination of water at different depths of soil sur- face was observed (1,7). Later in the 2000s, the use of water from both shal- low and deep tubewells for irrigation of agricultural lands began, particularly during the dry season (8). In all likelihood, the use of arsenic-contaminated water for irrigation may have contributed substan- tially to the spread of arsenic in the top soil-to crop- to food (9,10). Simultaneously, the use of huge amounts of chemical fertilizers and pesticides also increased dramatically as the crops of high-yield- ing variety are less resistant to pests. We hypothe- sized that the excess use of fertilizers and pesticides might lead to accumulation of toxic elements, such as cadmium in soil, that may eventually reach the food-chain. Thus, in this pilot study, we aimed at assessing the concentrations of arsenic and cad- mium in rice and vegetables collected from rural Matlab—both in raw and cooked form. MAtErIALS AND MEtHODS Sampling site As part of a study published earlier (11), both raw and cooked vegetables and a few traditionally- Volume 28 | Number 6 | December 2010 Khan SI et al. cooked rice samples were collected from two vil- lages. As described elsewhere (12), the tubewells of those villages showed high concentration of ar- senic (81-96% yielded water with more than 50 μg As/L), and the vast majority of farmers used con- taminated groundwater for irrigation. Sample-collection procedure A structured questionnaire was employed for each of the above households in the villages for collect- ing information on the type and quantity of water and foods ingested, and how the foods were being cooked for their consumption. A sample-collection form was used for documenting the address of the household head, type of food, and way of process- ing (11,12). Food items were selected based on usual daily di- etary habit and those available around courtyard. About 250 g of rice (Oryza sativa) and the edible part of each vegetable, such as amaranth (Ama- ranthus viridis), bitter gourd (Momordica charantia), arum (Colocasia esculenta) stem, potato (Solanum tuberosum), spinach (Basella alba), green banana (Musa spp.), and eggplant (Solanum melongena), were collected from various households (n=13) in polyethylene bags. Parts of rice samples were col- lected as raw and parts as cooked in accordance with the cooking customs of the population, which was to discard excess water after cooking. Cooked vegetable was also collected. Both tubewell water and surface water were used during cooking. The samples were transferred to the laboratory and washed with deionized water to remove remains of soil. Both raw and cooked samples were frozen at -20 °C until analysis (13). Elemental analysis Deionized water (18.2 megohm-cm) obtained with a glass distillation and E-pure water system (Barn- stead, USA) was used for the preparation of reagents and standards. HNO3 69%, HClO4 71%, HCl 36%, NaBH 98%, KI 99.5%, NaOH 99%, arsenic pentox- 4 ide, and cadmium standard solution (1,000 mg/L) of analytical grade were purchased from VWR Int. Ltd., UK. The arsenic concentration was measured using an atomic absorption spectrophotometer (AA-6800, Shimadzu, Kyoto, Japan) equipped with an auto- sampler (ASC-6100, Shimadzu), using hydride va- pour generation (HVG-1, Shimadzu). For cadmium, a graphite furnace (GFA-EX7, Shimadzu) was used, along with the atomic absorption spectrophotom- eter. Calibration standards for all the solutions were pre- pared from the working standard 1,000 µg/L. In 579