International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item Novel solid phase micro extraction (SPME) Method for GC-MS analysis of Tributyltin.(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Bandara, K. R. V.; Chinthaka, S. D. M.; Manage, P.M.Tributyltin (TBT) is an organotin compound belongs to the group of Persistent Organic Pollutants (POPs) and one of the active ingredients in biocides used to control a broad spectrum of organisms. Antifouling paints which are used for boat hulls, docks, fishnets contain tributyltin to prevent the growth of aquatic fouling organisms. Increasing concentration of TBT in the environment, due to anthropogenic activities cause toxicological impact on target and non-target organisms having sexual disorders like sex changes at ultra-trace level called imposex. According to WHO, the No Observed Effective Level (NOEL) of TBT is below 1 ng L-1, thus a highly specific and sensitive analytical methods are needed to detect TBT in parts per trillion (ppt) level. In the present study, a new ultra-trace quantification method to detect TBT using Solid Phase Micro Extraction (SPME) followed by Gas Chromatography-Mass Spectrometry (GCMS) was optimized. TBT derivatization to tributyltinhydride was carried out using potassium borohydride (KBH4). Medium polar PDMS/DVB, fused silica (65 μm, 24 Ga) SPME fiber were found to be the most appropriate conditions for extraction and pre-concentration of derivatized TBT hydride compound. The best conditions for the extraction were optimized and analyses were done by using GC-MS under 270 ºC desorption temperature and 1 mL min-1 of helium gas flow rate. Field samples were collected from highly polluted and heavy boat traffic area along the coastal belt from Dikkovita to Mirissa, Sri Lanka. The optimal extraction conditions were found to be 10 minutes extraction time, pH 4.9 and the ambient temperature 30 ºC. The highest TBT concentration was detected in Colombo port (303±4.7 ng L-1) following the TBT was recorded in the fishery harbors at Beruwala (124±4.1 ng L-1), Galle (110±4.1 ng L-1), Dikkovita (97±4.3 ng L-1), Hikkaduwa (77±5.3 ng L-1) and Ambalangoda (57±5.2 ng L-1). TBT concentrations in Dehiwala, Wellawatta, Madu, Benthota and Gin ganga river mouths were recorded as 268±4.1 ng L-1, 240±3.4 ng L-1, 214±3.3 ng L-1, 145±2.7 ng L-1 and 50± 2.1 ng L-1 respectively. The recovery of the TBT extraction was 87±2.1 % for the artificial sea water while the Minimum Quantification Level (MQL) was 1 ng L-1. The Minimum Detection Level (MDL) of the method was calculated as0.3 ng L-1. The optimized method is a solvent free and the use of SPME is highly sensitive method to detect TBT in parts per trillion (ppt) levels.Item Bacterial degradation of tetracycline (TET) by TET resistant bacteria; A green solution for antibiotic pollution.(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Liyanage, G. Y.; Manage, P.M.Tetracyclines (TET) have been extensively used in aquaculture for chemotherapy against various fish diseases such as fin rot, skin ulcers. Overuse and misuse of antibiotics are widely regarded as two of the major factors promoting antibiotic resistance. Resistance to TET occurs via two primary mechanisms; ribosomal protection and enzyme inactivation. To minimize the development of resistance, excess amount of TET should be removed from the aquatic environment. Therefore, studies on the biodegradability of TET can be taken as a very first step of an environmental risk assessment. The present study reports the biodegradation of TET by Enterobacter sp., Micrococcus luteus, Enterobacter ludwigii, Bacillus sp. and Streptomyces sp., which were isolated as TET resistance, non-pathogenic bacteria. In a previous study, TET resistant bacterial isolates were identified using the 16s rRNA sequencing. Overnight bacterial cultures grown in a medium without TET, were introduced into a medium containing TET at final concentration of 5 μg/ml. Triplicate samples were incubated at 28 °C with shaking at 100 rpm under dark conditions. Subsamples (0.5 ml) were removed at 2 days interval for a period of 14 days. Remaining TET in the subsamples was analyzed using High Performance Liquid Chromatography (HPLC). Complete degradation of TET by M. luteus and E. ludwigii was detected at the end of 14 days of incubation. Descending degradation percentages were followed by Enterobacter sp. (74%), Streptomyces sp. (72%) and Bacillus sp. (70%) at 14 days, respectively. Lowest half-life time of TET was shown by M. luteus and E. ludwigii (6 days), whereas half-life time of 8 days, 11 days and 12 days were recorded for Enterobacter sp, Streptomyces sp. and Bacillus sp., respectively. According to the degradation results obtained, it can be concluded that the selected bacterial strains can be used as potential candidates to be introduced into wastewater effluents to remove TET in effluent water, before reaching natural environmentsItem Cyanobacteria and 2-Methylisoborneol: the influence of Nitrogen and Phosphorous(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Ganegoda, S. S.; Chinthaka, S. D. M.; Manage, P.M.2-Methylisoborneol (2-MIB) is a key compound, which causes taste and odour (T&O) issues in water. Despite of no recorded health hazards reported associated with 2-MIB, water consumers reject the water with 2-MIB due to its unpleasant musty (moldy) T&O. The aim of this study was to study the correlation between cyanobacteria abundance, 2-MIB levels coupled with Nitrogen and Phosphorous levels. 2-MIB contamination level in sixteen raw water bodies, which are being used for drinking in six districts (Anuradhapura, Pollonnaruwa, Ampara, Batticaloa, Trincomalee and Hambanthota) were analyzed using Gas Chromatography–Mass Spectrometry coupled with Solid-phase micro extraction. Enumeration and identification of cyanobacteria was carried out using standard microscopic methods. Anabaena, Microcystis, Oscillatoria, and Cylindrospermopsis species were identified as the most abundant cyanobacteria. 2-MIB levels ranged from 5.3 ± 0.94 to 139.4 ± 0.21 ppt throughout the dry season of the sampling period, where the highest level was recorded in Kondawatuwana tank (139.4 ± 0.21 ppt) and the lowest was detected in Ridiyagama tank (5.3 ± 0.94). At wet season, 2-MIB levels ranged from 4.4 ± 0.78 to 73.8 ± 0.65 ppt, where the highest level was recorded in Jayanthi tank (73.8 ± 0.65 ppt), while the lowest was detected in Ridiyagama tank (5.3 ± 0.39 ppt). Recorded 2- MIB level was greater in dry season compared to the wet season. Seventy five percent (75%) of the sampling locations exceeded the human threshold levels of 2-MIB (5 ppt). Questionnaire survey showed that more than 95% end water consumers rejected drinking water contaminated with 2-MIB. Further it was found that the total cyanobacterial cell density (T.C.D) was positively correlated with 2-MIB and total phosphorous levels (p<0.05). Moreover, cell densities of Oscillatoria, Anabaena and Cylindrospermopsis species showed significant positive correlations (p<0.05) with 2-MIB contamination levels along with Pearson Correlation Coefficients (P.C.C) of 0.788, 0.682 and 0.731. However, no significant correlation was observed between Microcystis sp. and 2-MIB. Further, 2-MIB showed significant positive correlation (p<0.05) with total phosphorous (P.C.C 0.876), electrical conductivity (EC) (P.C.C, 0.771), and pH (P.C.C, 0.825). Increment of pH value leading to alkalinity is a known optimum condition for cyanobacteria growth while the current study shows alkalinity is favorable for 2-MIB. No significant correlation was obtained between total nitrogen (Nitrate –N, Nitrite –N, Ammonia –N) and 2-MIB nor T.C.D and total nitrogen. Thus, the results of the study indicate there is a direct positive correlation between 2-MIB, cyanobacteria and total phosphorous.Item Microcystin -LR contamination status of Nile tilapia (Oreochromis niloticus) and biomarker response(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Abeysiri, H. A. S. N.; Wanigasuriya, K.; Manage, P.M.Microcystin-LR (MC-LR) is a cyanotoxin derived from some cyanobacteria. Nile tilapia (Oreochromis niloticus) is the most popular freshwater fish among people in Sri Lanka. MC-LR accumulation in tilapia from thirteen reservoirs; Nallachchiya Wewa, Galkulama Wewa, Anakattiya Wewa, Padaviya Wewa, Nachchaduwa Wewa and Kalawewa in Anuradhapura District and from four reservoirs; Parakrama Samudraya, Halmilla Wewa, Kaudulla Wewa and Ambagas Wewa in Polonnaruwa District Muwapatigewela Wewa in Ampara District and Ulhitiya Wewa and Rathkinda Wewa in Badulla District was determined to evaluate the risk posed by the MC-LR contamination in fish on human health. Sample collection, transportation and analysis were followed according to the standard protocols and MC-LR was quantified by High Performance Liquid Chromatography. Fish skin, flesh and head were analyzed for MC-LR and Tolerable Daily Intake (TDI) values were calculated according to the WHO guidelines. MC-LR levels of fish in different reservoirs were compared with WHO standard of TDI (0.04 μg/kg/day). MC-LR level of fish skin (717.14 ± 0.82 μg/kg), flesh (105.11±0.08 μg/kg) and head (553.24±0.12 μg/kg) collected from Padaviya Wewa were recorded the highest mean concentrations of MC-LR. The mean concentrations of MC-LR in the skin and head of fish were significantly higher than that of flesh (p<0.05). The Average Daily Intake of MC-LR in the skin and head of all fish exceeded the provisional TDI set by WHO. Thus, the results of the present study revealed that consumption of head and skin of fish has a potential risk on accumulation of MC-LR in human body. Cyanobacterial toxins have been shown to affect aquatic organisms such as fish, resulting in oxidative stress. Among the antioxidant enzymes, glutathione peroxidase (GPx) plays an important role in the detoxification of MCs. Fish tissues such as head, flesh and skin were obtained for “GPx” gene expression analysis and results showed availability of detoxifying enzymes in fish skin and head collected from Parakrama Samudraya, Padaviya Wewa, Nallachchiya Wewa and Galkulama Wewa. MC-LR contamination in Galkulama Wewa showed a negative result. Therefore, previous exposure of fish for MC-LR shows indicator of the expression of gene of any detoxifying enzyme. Therefore, the results support the use of GPx in fish as a biomarker to assess the contamination by MC-LRItem Isolation of laccase producing fungi: Aspergillus niger from Sri Lankan textile wastewater effluents and its potential applicability on decolorization of an azo dye: CI Direct Blue 201(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Ekanayake, E. M. M. S.; Wijesekara, I.; Manage, P.M.The complex aromatic structural nature of synthetic dyes show resistance to natural oxidation processes and persist in the surface water and sediments for a long time. The existing physical and chemical treatment methods are costly and create secondary pollution. Therefore, the present study was focused on the degradation of an azo dye: CI Direct Blue 201 (DB 201), by myco-remediation. Aspergillus niger, a filamentous fungus, was isolated from textile wastewater effluent site in Sri Lanka and pure cultures were maintained on Potato Dextrose Agar (PDA) plates. Four cylinders (10 mm diameter in each) of actively growing A. niger cultures were cut and inoculated into mineral salt medium consisted of 50 mgL-1 DB 201 dye. All the experiments were carried out in triplicates, while controls were maintained without addition of the fungus. Flasks were incubated at 28 °C for seven days with shaking at 100 rpm. Three milliliters of sample aliquots were removed at 6 hrs intervals, centrifuged and the changes of the absorbance in the supernatant was analyzed through UV-Vis spectrophotometer at 570 nm. The laccase activity was determined by measuring the increase in the optical density at 420 nm. The reaction mixture for laccase assay contained 5 mM of 2,20-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in 50 mM sodium acetate buffer (pH 4.5) and 50 μL of decolorized dye solution (ε420 = 36000 M−1 cm−1). Decolorized dye sample was analyzed through Fourier Transform Infrared (FTIR) Spectroscopy. A Bio-sorption test was carried out by providing the same incubation conditions using 3-day-old live and autoclaved fungi. The control without adding fungus, remained the same without showing any decolorization. The enzyme activity of laccase has increased during the decolorization processes from 18 Uml-1 to 254 Uml-1. The changes of the FTIR spectra relevant to the N=N Vibration (1723.3 cm-1), S=O Stretching (1227.3 cm-1) and N-O Stretching (742.88 cm-1) indicated the changes of the initial DB 201 dye structure after the treatment by A. niger. Furthermore, the bio-sorption assay by live (100%) and autoclaved fungi (12 ± 2%) confirmed the decolorization and the degradation of DB 201 dye would be based on the metabolic activity of the fungus rather than surface adsorption. Therefore, the present study emphasizes the potency of A. niger as an eco-friendly candidate for degradation of azo dyes. Further studies regarding the application of enzymes for real textile dye treatments are currently in progress.Item Detection of cylindrospermopsin and microcystin-LR in well water of CKDu prevalent Medirigiriya, Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Abeysiri, H.A.S.N.; Wanigasuriya, K.; Manage, P.M.Cyanobacterial blooms in aquatic systems have increased over recent decades. Many of the blooms are highly toxic, causing a serious hazard to human and animal health. The commonest cyanotoxins are hepatotoxins such as microcystin-LR (MC-LR) and cylindrospermopsin (CYN). Cyanotoxin has been proposed as one of the causative agents for CKDu in Sri Lanka and recent studies have revealed the contamination of drinking dug wells by toxin-producing cyanobacteria in the North Central, Uva and Eastern provinces. Thus, the present study was carried out to determine the contamination of CYN and MC-LR in randomly selected CKDu patients’ household well water. The study was carried out for both dry and wet seasons and water samples were collected from 42 wells in Medirigiriya and 21 wells from Hambanthota as a control area. Water temperature, pH, conductivity, Dissolved Oxygen (DO) were measured at the site itself using standard methods. N-NO3-, N-NO2-, N-NH3, total phosphorous and total hardness were measured by standard spectrophotometric and titrimetric methods. CYN and MC-LR quantification were done using ELISA detection kits (Beacon) (minimum detection limit 0.1 ppb). Identification and enumeration of cyanobacteria were carried out under a light microscope (×400). The results of the study revealed that all the tested general water quality parameters were within the Sri Lanka standards given for potable water. Mean cell densities of Microcystis sp. were varying during dry season from 60 ± 0.03 cells/mL to 307 ± 0.08 cells/mL and from 48 ± 0.07 cells/mL to 127 ± 0.73 cells/mL during wet season where MC-LR ranged from 0.02 to 6.73 µg/L and from 0.01 to 5.34 µg/L during dry and wet seasons respectively. Mean cell densities of Cylindrospermopsis sp. during dry and wet season ranged between 20 ± 0.02 cells/mL to 82 ± 0.29 cells/mL and 14 ± 0.19 cells/mL to 76 ± 0.78 cells/mL respectively, whereas the mean concentrations of CYN during dry and wet season was between 0.38 ± 0.01 µg/L to 1.45 ± 0.08 µg/L and 0.27 ± 0.04 µg/L to 1.25 ± 0.08 µg/L. Cyanotoxins and cyanobacteria were not recorded from well water collected from Hambanthota. Principal Component Analysis was done for cyanotoxin concentration, water quality parameters and a number of CKDu patients in the study area and shows a positive relationship between cyanotoxin in wells and CKDu patients who consume water from the wells (p<0.05).Item Isolation of Salmonella spp. and Shigella spp. from ground and surface water in the lower part of the Kelani river basin: evaluation of resistance against selected antibiotics(2018) Abinaiyan, I.; Mahagamage, M.G.Y.L.; Manage, P.M.In recent years, greater attention has been paid by national and international agencies on microbial contamination of ground and surface water sources. Antibiotics are commonly used to treat emerging infectious diseases due to anthropological activities. Improper application of antibiotics both in human and animal therapy has become the main cause of antibiotic resistance. The Kelani River Basin (KRB) is the home to more than 25% of the Sri Lankan population and it provides about 80% of the drinking water to Greater Colombo. Thus, evaluation of the microbiological status along with antibiotic resistance is important to safeguard consumers within the KRB. Therefore, twenty ground and twenty surface water samples were collected from a lower part of KRB for the study during March 2018. Water temperature, Dissolved Oxygen (DO), pH and conductivity were measured at the site itself using standard meters and N-NO3−, N-NO2−, N-NH3, Total Phosphate (TP), COD and Total Hardness (TH) were measured by following standard spectrophotometric and titrimetric methods. Total Coliform (TC) and Fecal Coliform (FC) counts were obtained from membrane filtration methods where Salmonella spp. and Shigella spp. were isolated and identified according to the WHO standard protocol. Antibiotic resistance of the isolated Salmonella spp. and Shigella spp. were obtained using Antibiotic Susceptibility Test (AST) following Agar Disk Diffusion Method (ADDM) for some selected antibiotics by commercially available AST disk. Resistant strains were subjected to Broth Microdilution Assay (BMA) to find Minimum Inhibition Concentration (MIC). All the tested general water quality parameters were within the SLSI drinking water standard except pH and COD. It was found that; out of 40 samples, 39 were contaminated with TC and FC and 39 samples exceeded the bacteriological standards given by SLSI drinking water standards. Salmonella spp. and Shigella spp. were recorded in a groundwater sample located in Pattipola where poor sanitation practices were observed. Another sampling location in Kanampella, Shigella spp. was recorded. AST results of the study revealed that the Salmonella spp. and Shigella spp. were resistant to 10 µg/disk of Amoxicillin (AMX) and Ampicillin (AMP). The BMA indicates that MICs of the isolated strains against AMX and AMP were up to 70 µg/mL. Accordingly, treatment, awareness and strategic management plan is a must to safeguard both ground and surface water consumers in the lower part of the KRB.Item Biodegradation of Geosmin and 2-methylisoborneol by novel, native, Gram negative bacteria in Sri Lanka(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Ganegoda, S.S.; Chinthaka, S.D.M.; Manage, P.M.Trans-1, 10-dimethyl-trans-9-decalol (Geosmin) and 2-methylisoborneol (2-MIB) are key compounds which cause taste and odour (T and O) issues in drinking water. Despite no recorded health hazards, consumers reject the water if these odorants are present, due to their unpleasant earthy and musty T and O. Hence, removing Geosmin and 2-MIB from drinking water is a necessity for worldwide water authorities and consumers. Biodegradation has been widely recognized as effective for the removal of these compounds. Biodegradation of Geosmin and 2-MIB was investigated using native bacteria isolated from water and soil from 12 raw water bodies where the drinking water T and O issues are prevailing. Accordingly, five districts: Anuradhapura, Pollonnaruwa, Ampara, Batticaloa and Trincomalee were selected. Isolation of Geosmin and 2-MIB degrading bacteria in water and in sediment were carried out using standard microbiological procedures following enrichment, isolation and screening of potential degraders using Biolog MT2 plate assay. Potential Geosmin and 2- MIB degraders were subjected to degradation kinetics study and identification was carried out using 16S rRNA sequencing. Morphologically different 150 bacteria colonies from Geosmin treated samples and 75 colonies from 2-MIB treated water samples were isolated. Among them, 23 and 9 bacteria were identified as positive Geosmin and 2-MIB degraders respectively using the Biolog MT2 plate assay. Five bacteria showed complete degradation of Geosmin (initial level 20 ppt) at 7 days of incubation and they were identified as Myroides odoratimimus, Providencia rettgeri, and Proteus mirabilis. P . mirabilis isolated from Tissa wewa water, showed 100% degradation of Geosmin (initial level 20 ppt) at 5 days with a half-life time of 3 days when compared to control and other bacteria species. P . rettgeri isolated from Nuwara wewa soil, showed 100% degradation of 2-MIB (initial level 20 ppt) at 4 days incubation having 2 days of half-life time. P . mirabilis and P . rettgeri were previously reported antibiotic and xenobiotic degraders, and this is the first report of them, regarding degradation of Geosmin and 2-MIB.Item Determination of Multiple Antibiotic Resistant (MAR) and MAR Index in bacteria isolated from aquaculture farms.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Liyanage, G. Y.; Manage, P.M.Concurrent resistance to antibiotics of different structural classes has arisen in a multitude of bacterial species and cause complicating the therapeutic management for both human and animal. The objective of the study was to determine the Multiple Antibiotic Resistance (MAR) and MAR index of isolated tetracycline resistance bacteria from aquaculture sources. 42 tetracycline resistance bacteria, which were previously isolated from aquaculture farms were tested against Oxytetracyline (OTC), Tetracycline (TET), Amphicillin (AMP), Amoxicillin (AM.X), Sulfamethaxasol (SMX), Trimethoprim (TMP), Erythromycin (ERM), Cloxacillin (CLOX) and Ciprofloxacin (CJP). The MAR was determined by using Triphenyl Tetrazolium Chloride (TTC) assay and agar dilution method following CLSI guidelines. Then the MAR index was calculated. Among the isolates, 64.3% were resistant to three or more antibiotics and considered as multiple antibiotic resistant according to the WHO and CLSI guidelines. Among the MAR isolates, 93 % were resistant to OTC, 90% to TET, 34% to AMX, 14 % to AMP, 13 % to ERM, 11 % to SMX-TMP and 2% were resistant to CLOX were detected. None of the bacteria were resistance for CIP. The calculated MAR index was ranged from 0.03 to 0.42 for the isolated bacteria and the highest MAR index was recorded by Staphylococcus sp. (0.42), while the lowest was shown by Enterobacter sp. (0.03). The results of the study indicate that the overuse and misuse of antibiotics led to emergence of MAR bacteria and it compromises effectiveness of antibacterial therapy, leading infectious microorganisms to become resistant against antibiotics.Item Microcystin -LR Contamination status of Nile tilapia (Oreochromis niloticus) collected from reservoirs in Polonnaruwa District, Sri Lanka.(International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Abeysiri, H.A.S.N.; Manage, P.M.Microcystin-LR (MC-LR) is a cyanotoxin derived from some cyanobacteria. Nile Tilapia (Oreochromis niloticus) is the most popular freshwater fish in Sri Lanka. MC-LR accumulation in Nile tilapia from four reservoirs; Parakrama Samudraya, Halmilla Wewa, Kaudulla Wewa and Ambagas Wewa in Polonnaruwa District was determined to evaluate the risk posed by the MC-LR contamination in fish on human health. Sample collection, transportation and analysis were followed according to the standard protocols and MC-LR was quantified by High Performance Liquid Chromatography (HPLC). Fish skin, flesh and head were analyzed for MC-LR and Tolerable Daily Intake (TDI) values were calculated according to the WHO guidelines (0.04 μg/day/person). The standard lengths of 30 fish ranged between 15.2 cm and 21.5 cm. The mean concentration of MC-LR in skin, flesh and head were 18.41 ± 1.76 μg/g, 0.32 ± 0.01 μg/g and 6.69 ± 0.42 μg/g respectively in fish samples collected from Parakrama Samudraya. In Kaudulla Wewa, level of MC-LR in skin, flesh and head were 13.27 ± 0.56 μg/g, 16.21 ± 0.47 μg/g and 3.08 ± 0.35 μg/g respectively and in Halmilla Wewa, MC-LR in skin and flesh were not detected. However, MC-LR in head was recorded as 0.40 ± 0.03 μg/g. In Ambagas Wewa, MC-LR levels were not detected in the fish samples. TDI of MC-LR in fish skin and head in Parakrama Samudraya was 0.35 ± 0.02 μg/day/person, and 0.16 ± 0.01 μg/day/person respectively. TDI of MC-LR in fish skin, flesh and head in Kaudulla Wewa was 0.48 ± 0.03 μg/day/person, 0.41 ± 0.04 μg/day/person and 0.07 ± 0.01 μg/day/person respectively. These values exceeded the TDI value given by WHO. However, the TDI value in fish flesh in Parakrama Samudraya was 0.007 ± 0.001 μg/day/person and the value was below the given WHO standard. Thus the present study revealed that consumption of head, and skin part of fish has a potent risk on accumulation of MC-LR in human body. Therefore, removel of head part and skin is recommended prior to consumption, in order to avoid MC-LR contamination. Further public awareness is needed to minimize the potent risk on accumulations of MC-LR in human body.