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    Comparison of sensitivity of Lemna perpusilla (minute duckweed) to chromium, nickel, and zinc ions
    (Faculty of Science, University of Kelaniya Sri Lanka, 2022) Ariyawansha, J. M. M. S.; Pathiratne, A.
    In recent times, the pollution of tropical aquatic ecosystems due to heavy metals has become a great issue. The major sources of heavy metal pollution in aquatic ecosystems are effluents from metal-based industries and municipal wastewater. Duck weeds (Lemna species) are widely used in the treatment of wastewater and sewage effluents as they have the ability to absorb nutrients in the wastewater effectively. The species, Lemna minor and L. gibba generally represent temperate areas while L. perpusilla is native to Southeast Asia. Objective of the present study was to compare the sensitivity of L. perpusilla to chromium (Cr), nickel (Ni), and zinc (Zn) ions under tropical temperature exposure based on standard laboratory ecotoxicity tests. Growth reduction of L. perpusilla under Cr, Ni, and Zn exposure was assessed using a standard ecotoxicity procedure with a range of metal ion concentrations (Cr6+: 0, 12, 30, 60, 90 and 120 mg/L; Ni2+: 0, 0.03, 0.06, 0.15, 0.30 and 0.60 mg/L; Zn2+: 0, 0.1, 0.25, 0.5, 1.0 and 2.0 mg/L). Toxicity thresholds of Cr6+, Ni2+ and Zn2+ for the duckweed L. perpusilla under tropical temperature exposure (27°C - 29°C) were estimated based on multiple endpoints (total number of fronds, percentage of green fronds and green frond area). Triplicate test vessels were used for each concentration and the controls. The average specific growth rate and percent inhibition growth rate for each treatment and control replicate were determined. Metal contents in the exposure media were analytically verified using atomic absorption spectrophotometry. One way ANOVA followed by Dunnett’s test was used to estimate the lowest observed effect concentration (LOEC) for each endpoint. Effective concentrations of metals at different percentile effect levels (EC50, EC20, EC10 and EC5) were estimated through nonlinear regression modelling using USEPA Toxicity Relationship Analysis Program software. Based on different endpoints used for the toxicity assessments, lowest observed adverse effect concentrations (7 day LOAEC) for growth reduction of L. perpusilla for Cr6+, Ni2+, and Zn2+ were estimated as 21 mg/L, 0.06 mg/L, and 0.26 mg/L, respectively. For growth reduction of L. perpusilla, the most sensitive 7-day effective concentration for 10% effect (EC10) for Cr6+, Ni2+, and Zn2+ were 21 mg/L, 0.021 mg/L, and 0.2 mg/L, respectively. In conclusion, the sensitivity of L. perpusilla to the three metal ions followed the decreasing order: Ni2+ > Zn2+ > Cr6+. This study revealed that L. perpusilla is more sensitive to Ni2+ than Cr6+ and Zn2+. Of the three metals tested, Cr6+ exposure could be most tolerated by L. perpusilla.
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    Sensitivity of freshwater organisms to cadmium and copper at tropical temperature exposures: Derivation of tropical freshwater ecotoxicity thresholds using species sensitivity distribution analysis
    (Ecotoxicology and Environmental Safety, 2021, 2021) Arambawatta Lekamge, S. H.; Pathiratne, A.; Rathnayake, I.V.N.
    Tropical freshwater ecosystems are increasingly influenced by chemical stressors including heavy metals posing threats to biodiversity. Adequate ecotoxicity data are not available for native tropical freshwater species for ...
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    Use of liver histological alterations and erythrocytic nuclear abnormalities of two native fish in Kelani River, Sri Lanka as biomarkers for pollution impact assessments
    (Journal of the National Science Foundation of Sri Lanka, 2020) Ruvinda, K.; Pathiratne, A.
    Multi-biomarker approach is recognised as a complementary tool for environmental monitoring studies to better appraise how pollutants affect ecosystems. This study examined histological alterations in the liver tissues and nuclear abnormalities in the peripheral erythrocytes of two native fish species inhabiting the Kelani River (Etroplus suratensis and Dawkinsia singhala) as ‘effect biomarkers’ for assessing pollution impacts. Surface water and native fish were sampled from two polluted sites in the lower reach (Kaduwela and Mattakkuliya) and a less polluted site in the upper reach (Ruwanwella) of the river covering rainy and dry periods. Physico-chemical analyses of surface water confirmed an increasing trend of pollution towards the lower reach of the river. Significantly greater liver histopathologic condition indices and erythrocytic nuclear abnormality frequencies (p < 0.05) were found in the fish inhabiting lower reaches of the river compared to those in the upper catchment at Ruwanwella. Biomarker responses revealed that the fish populations inhabiting the polluted sites in the river are under stress especially due to hepatic damage and genotoxicity. The results suggest that endemic and nationally threatened fish species in the riverine ecosystem may be at risk due to the contaminant stress under long term exposure. This study supports utility of erythrocyte nuclear abnormality and liver histopathological biomarker responses of native fish as cost effective tools for the identification of potential biological hazards of river pollution.
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    Toxic hazards of industrial waste receiving canal system in the lower catchment of Kelani River basin, Sri Lanka
    (2020) Kuruppuarachchi, H.; Pathiratne, A.
    Assessing toxic hazards associated with polluted riverine ecosystems is essential for the development of effective strategies for their management. The present study explored the combined utility of bioassay responses of the plant, Allium cepa and surface water physico-chemical characteristics to assess the toxic hazards of an industrial waste receiving canal system located in the lower catchment of the Kelani River basin, Sri Lanka. Surface water samples from seven sites, viz. Maha Ela upstream (Site A), Manikagara Ela (Site B), Manikagara Ela - Maha Ela confluence (Site C), Maha Ela downstream (Site D), Maha Ela - Kelani River confluence (Site E), River downreach (Site F) and upper-reach (Site R) were analysed on three occasions in 2015 covering dry and wet periods. Irrespective of the sampling periods, exposure of A. cepa bulbs to water from the Sites B, C, D and E resulted in root growth retardation and mitosis depression (p < 0.05) in the root meristem signifying toxic/cytotoxic hazards. Occasional micronuclei evolution and nuclear bud induction were also found in the root cells exposed to Site B and C samples indicating genotoxicity. Toxic hazards were somewhat reduced towards down-reach of the river, which may be associated with self-depuration effects. The principal component analysis based on surface water characteristics and bioassay responses revealed clear separations of Sites B and C from the other sites. The results revealed that water quality of Manikagara Ela and Maha Ela needs improvements considering toxic hazards to the riverine ecosystem and human health
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    Comparison of Sensitivity of Tropical Freshwater Microalgae to Environmentally Relevant Concentrations of Cadmium and Hexavalent Chromium in Three Types of Growth Media
    (Bull Environ Contam Toxicol, 2020) Munagamage, T.; Rathnayake, I.V.N.; Pathiratne, A.
    Sensitivity of tropical freshwater microalgae (Mesotaenium sp., Chlorococcum sp. and Scenedesmus sp.) to environmentally relevant concentrations of hexavalent chromium (Cr6+) and cadmium (Cd2+) was compared individually in three growth media viz. Bold’s Basal Medium (BBM), Test Medium 1 (TM1) and Test Medium 2 (TM2) based on fluorescence reduction. Free metal content of growth media was determined by Visual MINTEQ (version 3.1). After 24 h, relative fluorescence of microalgae in the three media decreased with increased metal concentration showing a concentration dependent graded toxicity response. All microalgae were more sensitive to the metals when grown in TM1, when compared, more sensitive to Cr6+ than Cd2+. Metal speciation indicated that TM1 and TM2 media have higher percentage of bioavailable Cd2+ than BBM, and chromium was present mainly as CrO42− and HCrO4−. The results suggest that the TM1 medium is more suitable under short term exposure of microalgae to metals in environmental monitoring.
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    Cadmium and arsenic levels in edible fi shes, Oreochromis niloticus (Nile tilapia) and Ompok bimaculatus (butter catfi sh) from Padaviya Reservoir, Sri Lanka and human health risk assessment associated with their dietary exposure
    (2020) Weerasekara, K. A. W. S.; Pathiratne, A.; Kithsiri, H. M. P.
    Consumption of fi sh contaminated with toxic heavy metals is a threat to human health. Cadmium and arsenic are suspected as potential risk factors for chronic kidney disease of unknown aetiology (CKDu), which is highly prevalent in agricultural settlements in dry zone districts of Sri Lanka causing a severe public health crisis. Objectives of this study were (i) to determine cadmium and arsenic levels in muscle, liver and kidney of two edible fi shes (Nile tilapia and butter catfi sh) from the Padaviya reservoir located in the North Central Province, Sri Lanka where CKDu is highly prevalent and (ii) to assess the potential human health risks associated with the dietary exposure through edible muscle of these fi shes. Cadmium and arsenic levels of the tissues in the two fi sh species were determined using inductively coupled plasma mass spectrometry. In both fi sh species, highest cadmium levels were found in kidney (p < 0.05) whereas no signifi cant tissue specifi c diff erences (p > 0.05) were evident for arsenic. In the edible muscle, the maximum detected cadmium level in Nile tilapia was 0.1 mg/kg in wet weight. However, cadmium levels in the muscle of all Butter catfi sh were < 0.05 mg/kg. Arsenic levels in the muscle of all Nile tilapia and Butter catfi sh were < 0.05 mg/kg. Cadmium contents in muscle of most fi shes and arsenic contents in all fi shes (n = 60) were within the maximum permissible limits set by the international food standards regulatory authorities. Based on the estimated daily intake and target hazard quotients (< 1) for lifetime exposure, it is highly unlikely that cadmium and arsenic contents of the muscle meat of these fi shes would pose human health risks to moderate level consumers.
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    Application of cytogenetic model Allium cepa for screening potential cytogenotoxicity of herbal-based hair dyes
    (Journal of Environmental Science and Health, 2020) Nawalage, K. S.; Pathiratne, A.
    Plant models may be useful as test organisms for initial screening of potential toxicity of personal care products. The objective of the present study was to assess the efficacy of the Allium cepa (common onion) test system as a bioanalytical tool for screening potential cytotoxicity and genotoxicity of herbal-based hair dye formulations. Exposure of black hair dye formulations for 48 hours resulted in root growth retardation and mitosis suppression in the root meristems of A. cepa bulbs indicating concentration dependent cytotoxicity. At the 72 hour post exposure, cytotoxic effects on the roots were reduced but not recovered completely signifying prolong toxic action of the hair dyes. The condensed nuclei was the most frequent nuclear abnormality found in the dye exposed root meristematic cells indicating the cell death process. Induction of micronuclei and chromosomal aberrations in the root meristematic cells even at the post exposure stage indicates persistent genotoxicity of the hair dyes which may be attributed to the interactive effects of chemical mixtures present in the commercial hair dye formulations. The results revealed that A. cepa test system is an effective bioanalytical tool for screening cytogenotoxicity of commercial hair dye formulations.
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    Heavy metal levels in Chanos chanos (Milk fish) from Negombo estuary, Sri Lanka and human health risk assessment associated with their consumption
    (4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Bandara, P. R. C. S.; Pathiratne, A.
    Contamination of fish with toxic heavy metals can counteract the nutritional and health benefits of fish food on human health. Objectives of this study were to determine selected heavy metals levels viz. Aluminum (Al), Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Nickel (Ni) and Zinc (Zn) in edible fish, Chanos chanos (Milk fish) from Negombo estuary and assess potential human health risks associated with their consumption. Muscle and liver of freshly captured C. chanos (n=20) from the estuary in 2018 were used for metal analysis. Metal levels were determined by Atomic absorption spectroscopy (graphite furnace method) following microwave digestion using standard analytical chemistry techniques. Two certified reference materials for trace metals were used to check the recovery of the metals based on the analytical method used in this study and recovery percentages were within a satisfactory range. Potential human health risks associated with the dietary exposure to these heavy metals through fish consumption were assessed using multiple approaches by comparing the thresholds viz. Maximum Permissible limit (MPL), Tolerable Daily Intake (TDI) and Target Hazard Quotient (THQ) stipulated by international food standards regulatory authorities. Of the seven heavy metals measured, mean metal concentrations in C. chanos followed the decreasing order, Zn≈Al>Pb≈Cr>Cd>Ni≈Cu in muscle and Zn≈ Cu > Al≈ Cd>Cr≈ Ni> Pb in liver respectively. Concentrations of Cr and Pb in the edible muscle were significantly greater (P < 0.05) than those in the liver of the fish. Human health risk assessment indicated that the detected concentrations of the heavy metals in the edible muscle of the fish were below the MPLs stipulated by international food regulatory authorities except for Cd in 35% of the fish (range 0.06 - 0.08 mg/kg wet weight). Based on mean metal concentrations in the fish muscle, estimated daily intake values for moderate level fish consumers were below the corresponding TDI levels suggested by the food regulatory authorities. THQs for respective metals in the fish muscle were greater than the threshold value of one for Cd (1.5) and Pb (1.7) indicating potential human health risks associated with these metals in edible muscle for non-carcinogenic effects. However estimated maximum allowable fish consumption rates are high enough to safeguard the risks associated with Cd and Pb for moderate level consumers. The results revealed that it is unlikely that the measured seven heavy metals in C. chanos would pose non-carcinogenic health risks to the moderate level fish consumers.
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    Assessing neurotoxic potential of titanium dioxide nanoparticles and bulk form using the fish model, Nile tilapia (Oreochromis niloticus)
    (4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Samanthika, A.L.C.; Pathiratne, A.
    Titanium dioxide nanoparticles (nano TiO2) and bulk TiO2 are widely used worldwide in various sectors. Hence they can be released inevitably into the inland water bodies posing health threats to the aquatic ecosystems. Cholinesterase (ChE) activity can be used as a biomarker for screening neurotoxicity in organisms exposed to the environmental contaminants. The objective of the present study was to evaluate the neurotoxic potential of environmentally relevant concentrations of nano and bulk TiO2 using Nile tilapia as the tropical fish model. Groups of fish which had been acclimated to the laboratory conditions for two weeks were exposed continuously to relatively low concentrations (50 and 100 μg/L) of nano or bulk TiO2 for 7 or 14 days (n= 7). The control fish were exposed only to aged tap water. The experimental design also included 7 day nano or bulk TiO2 exposure groups which had been transferred to aged tap water for another 7 days to evaluate potential recovery of the toxicity. Neurotoxic potential was assessed using ChE activity measurements in the brain, gill and liver tissues by a standard spectrophotometric method. ChE activities (mean±SEM in nmol/min/mg protein) in gills were elevated significantly(P <0.05) in the fish exposed to 50 and 100 μg/L bulk TiO2 for 7 days (102±9 and 105±7 respectively) compared to those of the control fish (71 ± 5) whereas brain ChE activities were not affected. Liver ChE activities were significantly elevated at 100 μg/L continuous exposure to bulk TiO2 for 7 and 14 days (279±15 and 315±15 nmol/min/mg protein respectively) compared to those of the control fish (155±12) and were not restored to normal levels after 7 days post exposure. A consistent ChE activity stimulation pattern was not evident with respect to bulk and nanoTiO2 exposures. In the fish exposed to both concentrations of nano TiO2, ChE activities in brain and gill tissues were not significantly different from those of the control fish. However ChE activity in liver tissues of the fish exposed to 100 μg/L of nano TiO2 was elevated significantly (P < 0.05) at 7 days exposure and post exposure periods. The results revealed that environmentally relevant concentrations of nano and bulk TiO2 may pose neurotoxic risks to the fish populations inhabiting the contaminated water bodies and the bulk form of TiO2 is not ecotoxicologically inert as previously assumed
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    Assessing toxicity of two industrial zone effluents reaching Kelani River,Sri Lanka
    (Journal of national science foundation Sri Lanka, 2018) Hemachandral, C.K.; Pathiratne, A.
    Evaluation of the effcaey of waste treatment technologies of industnal waste is a major challenge for sustainable industrial development world-wide. Hence, new strategies are needed to assess interactive toxic effects of all substances present in the treated waste. This study assessed potential toxic hazards of treated effluents discharged from common wastewater treatment plants of two mclustrlal zones located in the Kelani River basin using Allium cepa (common onion) test system. The results showed that the final effluents of both industrial zones under undiluted and diluted (1 IS v/v) conditions mduced cytotoxrcity on all occasions, with evidence of significant (p < 0.05) mlto-depression In the root meristem and retardation of root growth in A. cepa. Genotoxlc hazard of the effuents was evident by frequent mcrease of nuclear and chromosomal abnormalltles, and occasional development of micronuclei in the root merlstem. Dilution of the effluents to 1 reduced the genotoxic effects generated in A. cepa roots by the final effuents_ The results revealed that waste treatment technologies m these two mdustnal zones need to be upgraded m order to ehmmate cytotoxlc and genotoxrc hazards associated with the treated effuents_ The results highlight the importance of incorporatmg practically feasible bioanalytical tools such as A. cepa root based test system on a regular basis for evaluating the efficacy of waste treatment technologies.