Risk assessment of toxic heavy metals in Oryza sativa (rice) from CKDu prevalent areas: Dambagolla and Minipe, Sri Lanka

Abstract

Chronic Kidney Disease of unknown etiology (CKDu) has been a significant health issue in North Central region in Sri Lanka. One of the suspected contributing factors to CKDu is the contamination of food crops, particularly rice, with toxic heavy metals. This study assessed the risk associated with toxic heavy metals in rice (Oryza sativa; BG- 300) grown in two CKDu prevalent areas, Dambagolla and Minipe. Despite being only approximately 4 kilometers apart and separated by the Mahaweli River, there is a significant difference in CKDu prevalence. In 2023, Dambagolla reported over 50 CKDu patients, whereas Minipe reported fewer than 10. The objective of this study is to evaluate the concentration of toxic heavy metals in rice samples from these areas and to determine if these concentrations correlate with the incidence of CKDu. Twenty rice samples were collected from each paddy field in Dambagolla and Minipe using a random stratified sampling method. Heavy metal analysis, (lead (Pb), arsenic (As), chromium (Cr), cadmium (Cd), and nickel (Ni)), was conducted using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). All sample analyses were duplicated. The data were analyzed to compare the levels of these metals with the maximum permissible levels (MPL) set by the Codex Alimentarius Commission. Additionally, the Target Hazard Quotient (THQ) levels were evaluated, and statistical evaluation was performed using the two-way ANOVA method. In Minipe, the detected levels of heavy metals were Pb (0.315 ± 0.091 mg/kg), As (0.0504 ± 0.01 mg/kg), Cr (0.735 ± 0.086 mg/kg), Cd (1.071 ± 0.087 mg/kg), and Ni (0.247 ± 0.005 mg/kg). In Dambagolla, the detected levels were Pb (0.291 ± 0.06 mg/kg), As (0.093 ± 0.03 mg/kg), Cr (0.388 ± 0.086 mg/kg), Cd (1.124 ± 0.078 mg/kg), and Ni (2.100 ± 0.017 mg/kg). Among the analyzed metals, the mean concentrations of Cd and Pb exceeded the maximum permissible levels (MPL) set by the Codex Alimentarius Commission in both areas. The Target Hazard Quotient (THQ) indexes indicated significant health risks in both areas. In Minipe, the THQ values for Cr (12.26) and Cd (5.355) exceeded threshold values, suggesting a potential health hazard. In Dambagolla, the THQ values for Cr (4.8653), Cd (1.9442), As (18.73), and Pb (3.000) also exceeded threshold values, indicating a significant health concern. Statistical analysis using two-way ANOVA revealed that the concentrations of As and Ni varied significantly between the two areas (p < 0.05). These findings suggest that the elevated levels of Cd and Pb in rice could be contributing to the higher incidence of CKDu in Dambagolla compared to Minipe. The regular consumption of rice could pose significant health risks, potentially contributing to the prevalence of CKDu in these regions. Further investigation is necessary to identify the sources of these heavy metals and to develop strategies to mitigate their impact on public health.