- Title
- Cadmium in rice with reference to water management and cultivar variation
- Creator
- Shahriar, Syfullah
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Cadmium (Cd) is ranked 7th in the list of the top 20 toxic metals and classified as a group 1 carcinogen. Rice plants accumulate more Cd than any other cereals. Globally, many populations rely on the consumption of significant amounts of rice as a staple food and it is the major source of toxic element Cd for human exposure. Bioaccumulation of Cd by rice plants has been linked to several soil and environmental factors along with the genotypes of rice, soil concentration of Cd and water management practices. The proposed research focuses on reducing Cd loading in different rice cultivars in relation to human health risk assessment with different farm management practices. In this research a market basket survey, pot experiments in the glasshouse on rice genotypes, rice washing and cooking practices were conducted to ascertain whether: firstly, soil Cd concentration, soil pH, water management practices affected rice Cd concentration; secondly, genetic variation accounts for its uptake which can be employed in human health risk assessment and risk management decisions. The market basket survey included 144 polished rice samples collected from the markets of 16 districts of Bangladesh. The mean and median concentrations of Cd in rice were 43 μg/kg and 34 μg/kg, respectively, ranging between 1 and 180 μg/kg, dry weight. Results indicated that there were significant variations of Cd among (33%) and within (67%) the districts. Daily Cd ingestion ranged from between 0.09 and 0.58 μg/kg body weight (bw) with the incremental lifetime cancer risk (ILCR) for individuals varying between 1.35 × 10-3 and 8.7 × 10-3 in different districts. The 2-5 years and 6-10 years age groups experienced higher risks than others and both males and females were found to be susceptible to Cd exposure from rice. A glasshouse experiment was conducted to examine the influence of alternate wetting and drying (AWD) and continuous flooding (CF) irrigation regimes on the bioaccumulation of Cd by nine Bangladeshi boro (dry) season rice genotypes cultivated in two soils having different levels of spiked Cd. Results indicated that bioaccumulation of Cd in rice grain was 12 times greater in soils with higher levels of Cd (5 mg/kg) coupled with AWD irrigation practices compared to control soils with CF irrigation practices. Using the same rice cultivars another glasshouse experiment was conducted to evaluate the effect of two irrigation practices on Cd bioaccumulation grown in industrially contaminated soil (Cd 3.95 mg/kg). Results indicated that the bioaccumulation of Cd in rice grain was 34% lower with the CF irrigation practice than that with the AWD irrigation practice. The Cd level in grain was the lowest in Local boro among the nine tested rice cultivars. Rice washing and cooking experiment was conducted to assess the influence of different cooking procedures on the removal of Cd along with other toxic elements (As and Pb) and nutrient elements like Zinc (Zn), Copper (Cu), Manganese (Mn), Selenium (Se), Molybdenum (Mo) from different commercially available rice brands sold in markets. We observed 35% (range 24-46%) average removal of Cd from rice when cooked with rice to water ratio 1:6 after 5 times washing of raw rice. Daily dietary intake of Cd was found in between 0.06 and 1.15 ug/kg bw when rice grains were cooked in rice cooker method (rice : water 1:2), where as in the traditional method (rice: water 1:6) daily intake rates ranged from 0.04 to 0.88 ug/kg bw for adults. The HQ and ILCR values for Cd reveals no appreciable risk from consumption of rice.
- Subject
- cadmium; rice; water management; human health risk
- Identifier
- http://hdl.handle.net/1959.13/1430395
- Identifier
- uon:38834
- Rights
- This thesis is currently under embargo and will be available from the 10.12.2022, Copyright 2021 Syfullah Shahriar
- Language
- eng
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