Selenium status in food grains of northern districts of India

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Journal of Environmental Management 88 (2008) 770–774 www.elsevier.com/locate/jenvman

Selenium status in food grains of northern districts of India Sanjiv K Yadava,, Ishwar Singhb, Anita Sharmab, Devender Singhb a

Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, MD-9, 10 Kent Ridge Crescent, Singapore 119260, Singapore b Department of Chemistry, Maharshi Dayanand University, Rohtak, Haryana, India Received 26 September 2005; received in revised form 22 March 2007; accepted 9 April 2007 Available online 14 June 2007

Abstract The selenium status in the food grains of the agricultural lands of northern parts of India was estimated by using the HG-AAS technique. The areas where lesser rains were received or less irrigation water was available in northern Indian states viz. Rajasthan and southern parts of the Haryana had higher selenium levels in food grains. Punjab, Himachal Pradesh and northern parts of the Haryana states had normal levels of selenium in their food grains, except for slightly lower selenium levels in a few areas that were affected by floods along the river Yamuna. r 2007 Elsevier Ltd. All rights reserved. Keywords: Food grain; Selenium contents; Food grain; Hydride-generation-AAS

1. Introduction Selenium is an essential bio-element for many bacteria, birds, fish and mammals for their survival and growth (Burau, 1985; Stadtman, 1979). The deficiency of this micronutrient has been also associated with heart failure (Ge et al., 1983; Fleming et al., 1982), muscle pain (Van Rij et al., 1979, 1981), lower risk of cancer (Ip and Ganther, 1994) and various other diseases (Burk, 1994) in humans and animals. Food is the main source of selenium for humans and animals. According to the appropriate dietary intake limits for livestock, different areas of the world can be characterised as selenium deficient, selenium adequate and selenium toxic. Maksimovic et al. (1995) presented a method for the determination of selenium and this method was adopted in the present study. Since selenium is present at nanogram levels in environmental samples, gravimetric and colorimetric methods are not very useful for detection of selenium in food grains due to their low sensitivity and selectivity. In our present work, we studied the selenium contents in food grains by using Atomic Absorption Spectroscopy with Hydride Generation (HG-AAS) techniques. Flame Corresponding author. Tel.: +65 6874 3229; fax: +65 6778 8161.

E-mail address: [email protected] (S.K. Yadav). 0301-4797/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2007.04.012

atomic absorption spectrometry is a well-established technique; its detection limit for selenium is approximately 0.1 mg/ml with an air–acetylene flame. Hydride generation atomic absorption spectrometry (HG-AAS) is a rapid technique with a detection limit of 0.1–0.3 ng/ml using a quartz tube atomiser (Tamari et al., 1992). This technique does not have matrix interferences for trace selenium analysis. We analysed selenium contents of food grains taken from the agricultural lands from the areas of northern India. In the present study, we planned to cover the districts of the Haryana, Punjab, Himachal Pradesh and Rajasthan states of India shown in Map 1. However, in our previous studies, we have analysed the selenium contents in soils by using Atomic Absorption Spectrophotometer with vapour generation accessory (Hydride Generator) [HG-AAS] and Inductively Coupled PlasmaOptical Emission Spectroscopy (ICP-OES) (Yadav et al., 2005). 2. Materials and methods 2.1. Sample collection Food grains such as wheat, gram, mustard seeds, bajra (pearl millet) in the form of raw materials were collected

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flask at 80oC for 30 min. The flask was cooled to room temperature; the digestion solution was diluted to 25 ml with distilled water and was used for analysis by Atomic Absorption Spectrophotometer attached with a vapour generation accessory (Hydride Generator; HG-AAS). 2.3. Selenium stock solution A standard solution of the selenium with a concentration of 100 mg/l was prepared. Selenium metal (0.1 g) was dissolved in the minimum volume of concentrated nitric acid and evaporated to dryness; this was repeated twice. The residue was dissolved in 6 M hydrochloric acid and diluted to 1 l with 6 M hydrochloric acid. Subsequent dilutions were made whenever required. 2.4. Instrumentation An Atomic Absorption Spectrophotometer model ECIL-4129 (PC-based) attached with a vapour generation accessory (Hydride Generator; HG-AAS) and selenium cathode lamp (wavelength 196 nm) was used for analysis of the selenium content of the food grains. An air–acetylene (oxidising) flame was chosen for the purpose of absorption of incident light. 3. Results and discussion Map 1. Area from where sampling was done.

from the agricultural fields of the districts shown in the map (Map 1) from where the soil samples were also collected and analysed (Yadav et al., 2005). The raw grains were washed thoroughly with deionised water and dried in open air under sunlight for several days, finally drying them in an oven at 50 1C. Each sample was crushed to a fine powder with an agate mortar and pestle and passed through a sieve of 200 mesh size. One gram of sample was taken for analysis. 2.2. Digestion of the food grains The digestion of food grains is described elsewhere (Maksimovic et al., 1995). Briefly, 1 g of food grains was taken in a digestion flask. The digestion was continued at 90 1C for 1 h in a digestion flask after the addition of concentrated HNO3. The flask was held in the heating block until half of the volume disappeared. Perchloric acid (1.5 ml) and concentrated H2SO4 (1 ml) were added and digestion was continued at 90 1C for 1 h. The temperature was increased slowly to 100 1C and held for 30 min. Again temperature was increased up to 120 1C and held for 20 min. The residual digestion solution was treated with 6 M HCl (5 ml) to reduce Se(VI) to Se(IV) by heating the digestion

Selenium is an essential micronutrient for animals. The biological and natural cycle of selenium element, shown in Figs. 1 and 2 (Frost, 1973; NRC, 1976), depict that the animals diet directly or indirectly depends upon the soil–plant system. The soil pH can have a marked influence on the selenium content of the plants. Chemical oxidation in alkaline soils produces selenate which is available for plants. Sufficient analytical data are available for soils and food grains showing the selenium status of the USA, Canada, Europe, Australia, New Zealand, Japan and China (GisselNielson, 1984; Frankenberger and Engberg, 1998). However, hardly any information is available about the selenium status of most of the other countries, especially for the areas where people consume food low in selenium and who may be at higher risk for selenium dependant diseases (Burk, 1994). Plant foods are the major dietary sources of selenium. The amount of selenium in food depends on the amount in the soil, which varies widely from region to region. It is observed that there are fewer cancer deaths in the areas where there is more selenium in food and the people with low blood selenium levels are at higher risk for several cancers (Thomson, 2004; Goldhaber, 2003; Burk, 1994). Hence, it is important to find out how much selenium is present in a food and thus how much we are getting from these basic sources. For example, soils in some parts of China have very low amounts of selenium, and hence selenium deficiency is often reported in those regions

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PLANTS

SOILS

ANIMALS

MAN SEDIMENTS & SEDIMENTARY ROCKS

AQUATIC LIFE OCEANS, SEAS & LACKS

Fig. 1. Possibilities of biological cycling of selenium.

because most of the food in those areas is grown and eaten locally (Ge et al., 1983; Keshan Disease Research Group, 1979). Efforts have been made for determining selenium contents in soils and in plants or feed grown in some parts of India. For example, some graminaceous crops from Punjab had a range between 180 and 850 mg/kg with an average of 480 mg/kg of selenium while the legumes had 200–1200 mg/kg (average 530 mg/kg) of selenium (Malik and Singh, 1986). A study by Singh and Kumar (1976) showed the highest available selenium in surface soil was 410 mg/kg in Karnal district, Haryana. Garg et al. (2004) analysed some animal feed grown in Kutch district, Gujarat and found that selenium content in most of the feed was adequate (4150–800 mg/kg). Some studies have also been made on soils of Punjab state for their selenium contents, correlating with contents in crops grown on them and finally with the public health (Hira et al., 2004; Dhillon et al., 2005). In our studies, the selenium status in the food grains which were collected from the agricultural fields of some districts of northern India has been presented in Table 1 and the results are graphically depicted in Fig. 3. Haryana and Punjab are the two northern states of India where most of the population is agriculturist. The state of the Rajasthan is adjacent to Haryana and its soil is sandy, whereas the state of Himachal Pradesh is situated in Himalayan mountains. Adequate water flows in the rivers

ATMOSPHERE

VALCANISM

RUNNING & ROUND WATERS

IGNEOUS ROCKS

MOLTEN ROCK

EARTH’S CORE

Fig. 2. Cycling of selenium in nature.

that traverse the plains of Punjab. Rajasthan and southern part of Haryana states are comparatively drier and less water is available for irrigation. The pH of the soils in these areas is usually alkaline (pH 7.4–8.8). Among the districts of Haryana state, Rohtak and Sonepat had the lowest selenium levels in the food grains. The average selenium level in wheat grown in Rohtak district was found to be 107 mg/kg, for pearl millets 129 mg/kg, and for Brassica indica it was 104 mg/kg. Food grains grown in Sonepat had 124 mg/kg selenium for wheat, 114 mg/kg selenium for pearl millets and a level of 179 mg/kg for B. indica. For these districts, the lower selenium contents were caused by flooding. Soluble selenium (mostly in the selenate form) is likely to have been lost by leaching (Yadav et al., 2005). On the other hand districts such as Mohindergarh, Hisar and Jind had comparatively higher levels of the selenium in food grains as their soil had high selenium levels (Yadav et al., 2005). Similar results were shown for the selenium levels in the districts of Rajasthan state adjacent to the

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Table 1 Selenium status in various food grains in northern districts of India States

Haryana

District

Rohtak

Sonepat

Mohindergarh

Rewari

Gurgoan

Bhiwani

Chandigarh

Hisar

Jind

Narnaul

Rajasthan

Jaipur

Alwar

Punjab

Mansa

Khanauri

Amritsar

Himachal Pradesh

Shimla Dharmsala

By HG-AAS technique Food grains

No. of samples

Selenium concentration (in mg/kg)

s

Wheat P. millet Rice Wheat P. millet Rice Wheat P. millet Rice Wheat P. millet Rice Wheat P. millet Rice Wheat P. millet B. indica Wheat P. millet B. indica Wheat P. millet B. indica Wheat P. millet B. indica Wheat P. millet B. indica

16 15 17 14 15 12 15 16 17 12 15 17 16 12 14 17 16 15 17 15 12 17 15 16 12 14 15 13 15 17

107 129 104 124 114 179 191 186 238 162 123 197 146 134 225 143 131 238 150 114 165 190 128 158 272 144 238 203 177 248

08 29 15 16 17 17 15 11 34 28 33 38 28 26 19 22 21 16 16 10 35 16 16 35 22 22 05 21 32 27

Wheat P. millet B. indica Wheat P. millet B. indica

15 13 14 16 12 14

206 135 248 219 128 264

53 29 10 52 19 10

Wheat Rice B. indica Wheat Rice B. indica Wheat Rice B. indica

16 15 17 15 16 13 12 11 15

121 108 139 142 105 122 140 115 192

17 14 18 19 16 20 19 11 46

Wheat P. millet Wheat P. millet

15 17 16 17

149 123 153 125

23 16 20 18

Hisar and Mohindergarh districts of Haryana state due to close geographical similarities. In another northern Indian state, Himachal Pradesh geographically situated in Himalayan mountains, mean selenium level in wheat grown in Shimla district was 153 mg/kg. Punjab state being on the plains grows wheat as the main crop. This state had mean selenium levels of 140 mg/kg in wheat grown in Amritsar

district while Khanauri had a level of 142 mg/kg similar to that Shimla. The availability of irrigation water is higher for these two northern Indian states in comparison to Haryana and Rajasthan due to plenty of water flowing in the rivers. The agricultural lands in the state of Rajasthan and the southern parts of Haryana are drier and sandier. This indicates the movement of dissolved selenium salts

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Fig. 3. Average selenium concentration (in mg/kg) with sampling sites. Note: All type of food grains were not available with sample sites.

from the top soils toward the deeper soils and larger amount of selenium was found in the agricultural lands of Rajasthan and its adjacent areas, thereby increasing the selenium levels in the food grains grown on these agricultural lands. The results of the selenium levels found in other main crops grown in these states are shown in Table 1. 4. Conclusion In conclusion, we find higher selenium levels in food grains where soils are relatively high in available selenium due mainly to less irrigation, or where the soil is dry and more likely to be sandy in the lower rainfall areas of the Rajasthan state, as compared with areas like Punjab, where irrigation is more common. Floods also appear to be important factors for decreasing soil selenium level, which is the source of selenium for plants and finally to food grains. References Burau, R.G., 1985. Environmental Chemistry of Selenium. California Agriculture 39, 16–18. Burk, R.F. (Ed.), 1994. Selenium in Biology and Human Health. Springer, New York. Dhillon, K.S., Rani, N., Dhillon, S.K., 2005. Evaluation of different extractants for the estimation of bioavailable selenium in seleniferous

soils of Northwest India. Australian Journal of Soil Research 43, 639–645. Fleming, C.R., Lie, J.T., McCall, J.T., O’Brien, J.F., Baillie, E.E., Thistle, J.L., 1982. Selenium deficiency and fatal cardiomyopathy in patient on home parenteral nutrition. Gastroenterology 83, 689–693. Frankenberger Jr., W.T., Engberg, R.A. (Eds.), 1998. Environmental Chemistry of Selenium. Marcel Dekker, New York. Frost, D.V., 1973. The selenium cycle and health. Paper delivered at the 66th Annual Meeting of the Air Pollution Control Association, Chicago. Garg, M.R., Bhanderi, B.M., Sherasia, P.L., 2004. The status of certain trace minerals in feeds and fodders in Kutch district of Gujarat. Indian Journal of Animal Nutrition 21, 8–12. Ge, K., Xue, A., Bai, J., Wang, S., 1983. Keshan disease-an endemic cardiomyopathy in China. Virchows Archiv A-Pathological Anatomy And Histopathology 401 (1), 1–15. Gissel-Nielson, G., 1984. Improvement of selenium status of pasture crops. Biological Trace Element Research 6, 281–288. Goldhaber, S.B., 2003. Trace element risk assessment: essentiality vs toxicity. Regulatory Toxicology and Pharmacology 38, 232–242. Hira, C.K., Partal, K., Dhillon, K.S., 2004. Dietary selenium intake by men and women in high and low selenium areas of Punjab. Public Health Nutrition 7, 39–43. Ip, C., Ganther, H.E., 1994. Novel strategies in selenium cancer chemoprevention research. In: Burk, R.F. (Ed.), Selenium in Biology and Human Health. Springer, New York, pp. 171–180 (Chapter 9). Keshan Disease Research group, 1979. Chinese Medical Journal 92, 471–482. Maksimovic, Z., Nikolic, M., Jorga, J., Rsumovic, M., Radosevic, P., 1995. In: Conference on Selenium, vol. 78, Serbain Academy of Science and Arts, Scientific Meeting, Belgrade, pp. 77–78. Malik, R.V.S., Singh, V., 1986. Selenium status of common fodders in western Uttar Pradesh. Journal of the Indian Society of Soil Science 34, 220–221. National Research Council (NRC), 1976. Selenium: assembly of life science, Committee on Medical and Biological Effects of Environmental Pollutants, DC, National Academy of Sciences, Washington. Singh, M., Kumar, P., 1976. Selenium distribution in soils of bio-climatic zones of Haryana. Journal of the Indian Society of Soil Sciences 24, 62–67. Stadtman, T.C., 1979. Some selenium-dependent biochemical processes. Advances in Enzymology and Related Areas of Molecular Biology 48, 1–28. Tamari, Y., Yoshida, M., Takagi, S., Chayama, K., Tsuji, H., Kusaka, Y., 1992. Determination of selenium in biological samples by hydride generation AAS. Bunseki Kagaku 44, T77–T81. Thomson, C.D., 2004. Assessment of requirements for selenium and adequency of selenium status: a review. European Journal of Clinical Nutrition 58, 391–402. Van Rij, A.M., McKenzie, J.M., Thomson, C.D., Robinson, M.F., 1979. Selenium deficiency in total parenteral nutrition. American Journal of Clinical Nutrition 32 (10), 2076–2085. Van Rij, A.M., McKenzie, J.M., Thomson, C.D., Robinson, M.F., 1981. Selenium supplementation in total parenteral nutrition. Journal of Parenteral and Enteral Nutrition 5 (2), 120–124. Yadav, S.K., Singh, I., Singh, D., Han, S.D., 2005. Selenium status in soils of northern districts of India. Journal of Environmental Management 75 (2), 129–132.