Influence of water management strategies on cadmium accumulation in rice

Cadmium (Cd) is a naturally occurring toxic element and class I human carcinogen, which poses significant risk to human health such as skeletal damage, renal failure and cancers (IARC 2012). Usually low concentration of Cd is available in nature and Cd contents in soils depend on various geological factors. Phosphate fertilizers, sewage sludge and manure are largely used in agriculture soils and these are the major sources of Cd contamination in soils. Jinadasa et al. (1999) reported that concentrations of Cd in cultivated soils ranged from 0.11 to 6.37 mg/kg (median: 0.85 mg/kg and mean: 1.3 mg/kg) in the Sydney region, Australia whereas in the background soil, Cd ranged from 0.02 to 1.99 mg/kg (median: 0.04 mg/kg and mean: 0.36 mg/kg). The provisional tolerable weekly intake (PTWI) of Cd is 7 μg/kg body weight, set by the Joint Expert Committee on Food Additives (JECFA), the World Health Organization (WHO) and the Food Safety Commission Secretariat of Japan (FSCSJ) whereas the European Food Safety Authority established a tolerable weekly intake for Cd of 2.5 μg/kg body weight (JECFA, 2004; FSCSJ, 2008; EFSA, 2009). Rice (Oryza sativa L.), a staple food for half of the world's human population, is a major source of cadmium (Cd), particularly in Asian countries. Meharg et al. (2013) reported that mean Cd levels in rice grain were the highest in Bangladesh (99 µg/kg) and Sri Lanka (81 µg/kg) followed by India (78 µg/kg). The highest Cd concentrations in grain were 1310 µg/kg, 800 µg/kg and 1000 µg/kg for Bangladesh, Sri Lanka and India, respectively (Meharg et al., 2013).These suggest the importance of reducing grain Cd accumulation in rice for improving human health. There is clear evidence linking human renal tubular dysfunction with contamination of rice with Cd in subsistence farms in Asia (Chaney et al.2005). This study will investigate the effect of water management strategies on Cd accumulation in different rice varieties to determine the rice variety which accumulate less Cd. (author)