Browsing by Author "Rajapaksha, A. U."

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Assessment of human health risk of cylindrospermopsin by consuming Oryza sativa (rice) from selected CKDu endemic areas in Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Bandara, W. M. S. N.; Wanigatunge, R. P.; Rajapaksha, A. U.; Vithanage, M. S.; MaganaArachchi, D.N.
The proliferation of toxic cyanobacterial blooms in freshwater bodies can seriously threaten human health. Many studies have been carried out on cyanotoxins in water sources, but studies on cyanotoxins in terrestrial plants are limited. Cyanotoxins in water sources can enter terrestrial plants when irrigated with cyanotoxin-contaminated water and cultivated in cyanotoxin-contaminated soil. As the main staple food in Sri Lanka, Oryza sativa (rice) is widely grown island-wide, mainly in the country's dry zone. The rice fields are irrigated with raw water from the reservoirs throughout their cultivation. Previous literature reported the presence of cyanotoxins, and potential cyanotoxin-producing cyanobacterial species in reservoirs in the dry zone in Sri Lanka. Moreover, cyanotoxins are hypothesized as one of the risk factors for chronic kidney disease of unknown aetiology (CKDu) in Sri Lanka. Cylindrospermopsin (CYN) is a cyanotoxin and negatively affects on several organs in the human body, including the kidneys. Therefore, the current study investigated CYN in O. sativa samples (n=102), including the most cultivated variants, samba (n=20), nadu (n=61), rathu kekulu (n=12) and keeri samba (n=9) collected from CKDu endemic Girandurukotte and Dehiattakandiya areas. As a control, rathu kekulu samples (n=22) were collected from CKDu non endemic Sewanagala area. CYN was extracted and analysed by high-performance liquid chromatography (HPLC) with reference to the CYN standard (SIGMA ALDRICH 32087). Estimated Daily Intake (EDI) of CYN was then calculated to determine the potential human health risk, for an adult by consumption of CYN-contaminated rice. Results of the HPLC analysis revealed that the mean ± SE values of CYN concentrations in samba, nadu, rathu kekulu, keeri samba rice from CKDu endemic areas and rathu kekulu from the control area were 6235.74 ± 1289.15, 6821.44 ± 694.80, 6538.66 ± 1797.81, 3702.51 ± 1321.02, and 3460.99 ± 359.91 μg/kg, respectively. Mean ± SE of estimated daily intake when exposure to CYN via consumption of samba, nadu, rathu kekulu, keeri samba rice in CKDu endemic areas and rathu kekulu from the control area were 30.45±6.29, 33.31±3.39, 31.93±8.77, 18.08±6.44 and 16.90±1.75 μg/kg of body weight per day, respectively. All these values exceeded the provisional Tolerable Daily Intake (TDI) of CYN value established by the World Health Organization (0.03 μg/kg of body weight per day), which can pose a health risk to consumers. The present study revealed that the consumption of O. sativa in the studied areas has a potential risk of accumulation of CYN in the human body. However, it emphasized the importance of investigating the uptake of CYN into rice, in large sample sizes in the study areas.
Detection of microcystins (cyanotoxin) in selected drinking water wells in the Gampaha district, Sri Lanka
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Sinhapitiya, S. P. A.; Herath, H. M.; Bandara, W. M. S. N.; Rajapaksha, A. U.; Vithanage, M. S.; Magana-Arachchi, D. N.; Wanigatunge, R. P.
The prevalence of toxic cyanobacteria and various cyanotoxins, such as microcystins (MCs) in drinking water sources have gained considerable attention worldwide due to their potential health risk. Approximately 80% of the Sri Lankan rural population and 34% of the urban population rely on well water for their daily needs. Therefore, people could be exposed to cyanotoxins by consuming well water. This study investigated the presence of potentially toxic cyanobacteria and microcystin variants in the household well water samples collected from the 13 divisional secretariats in the Gampaha district, the second-most populated district in Sri Lanka. Twenty-six well water samples were collected, and physicochemical parameters such as temperature, salinity, pH, conductivity, and Total Dissolved Solids (TDS) were measured in triplicates, in situ using a multi-parameter. All samples met the Sri Lankan Standards (SLS) for drinking water in terms of pH, salinity, temperature and TDS. One well water sample collected from Wattala did not meet the SLS standards in terms of conductivity (829.00±2.05 μS/cm), indicating the well’s unsuitability for water consumption. Morphological identification of cultures originating from well water samples in cyano-specific BG11 medium indicated the presence of nine cyanobacterial genera, including Gloeobacter, Myxosarcina, Dermocarpa, Xenococcus, Synechococcus, Pseudanabaena, Chroococcus, Lyngbya and Geitlerinema. Among them, Synechococcus and Pseudanabaena are reported to be microcystin producers. The presence of extracellular MCs in water samples was detected by High-Performance Liquid Chromatography (HPLC). Extracellular MCs were extracted from water samples using 70% methanol. MC variants and their concentrations in each well water sample were determined using MC-RR-YR-LR standard mixture (Cat no. 33578; SIGMA ALDRICH) by comparing peak retention times and the area of the peaks. HPLC analysis revealed the presence of the microcystin variant MC-LR only in two water samples collected from wells located in the Divulapitiya and Katana areas with MC-LR concentrations of 195.1 μg/L and 278.3 μg/L, respectively. These values exceeded the standard guideline value of 1 μg/L for MC-LR set by the World Health Organization for drinking water. This indicates the potential health risk for consumers of those wells because there is a potential for hepatotoxic MCs to cause acute and chronic illnesses in humans.
Risk factors for endemic chronic kidney disease of unknown etiology in Sri Lanka: Retrospect of water security in the dry zone
(Science of the Total Environment, 2021) Hettithanthri, O.; Sandanayake, S.; Magana-Arachchi, D.; Wanigatunge, R.; Rajapaksha, A. U.; Zeng, X.; Shi, Q.; Guo, H.; Vithanage, M.
The prevalence of chronic kidney disease of unknown etiology (CKDu) is receiving considerable attention due to the serious threat to human health throughout the world. However, the roles of geo-socio-environmental factors in the prevalence of the CKDu endemic areas are still unknown. Sri Lanka is one of the countries most seriously affected by CKDu, where 10 out of 25 districts have been identified as the areas with the high prevalence of CKDu (10–20%). This review summarizes the geographical distribution of CKDu and its probable geochemical, behavioral, sociological, and environmental risk factors based on research related to hydrogeochemical influences on CKDu in Sri Lanka. More than 98% of CKDu patients have consumed groundwater as their primary water source in daily life, indicating the interactions of geogenic contaminants (such as F−, total dissolved solids, Hofmeister ions) in groundwater is responsible for the disease. Apart from the hydrogeochemical factors, mycotoxins, cyanotoxins, use of some herbal medicines, dehydration, and exposure to agrochemicals were alleged as risk factors. Sociological factors, including poverty, living habits and anthropogenic activities, may also provoke the emergence of CKDu. Therefore, the interaction of geo-socio environmental risk factors should be sociologically and scientifically considered to prevent the prevalence of CKDu. Future in-depth studies are required to reveal the individual role of each of the postulated etiological factors, possibly using machine learning and advanced statistics.