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Vegetables are essential for a healthy diet in humans. However, vegetables can carry harmful metal(loid) contaminants such as As, Cd and Pb which are deleterious to health in the long term. It has been postulated that long-term heavy metal(loid) exposure by vegetable consumption is associated with chronic kidney disease of unknown aetiology (CKDu) that prevails in North Central Province of Sri Lanka. We performed a human health risk assessment to identify if there is any link between heavy metal(loid) exposure from vegetable consumption and the prevalence of CKDu. The study includes a survey of food consumption in CKDu-impacted areas and determination of the heavy metal(loid) contents of market vegetables. We found that Solanum tuberosum (potato) and Momordica charantia (bitter gourd) accumulated Pb to a greater extent than other vegetables and exceeded the permissible concentration for foodstuffs. The Cd content of Solanum melongena (Brinjal) also exceeded permissible levels. However, the As content was below permissible levels for all the vegetables tested. The weekly total heavy metal(loid) intake of Cd, As and Pb in vegetables in CKDu-impacted areas was lower than permissible limits. The consumption of an average amount of vegetables does not pose a chronic health risk to the consumers. There was no evidence of a link between the consumption of heavy metal(loid)s in vegetables and CKDu. Since, few vegetables showed marked heavy metal(loid) accumulation, periodical monitoring of heavy metal(loid) concentrations in vegetables will be beneficial for avoidance of future possible health risks.
M. R. D. L. Kulathunga; M. A. Ayanka Wijayawardena; Ravi Naidu. Heavy metal(loid)s and health risk assessment of Dambulla vegetable market in Sri Lanka. Environmental Monitoring and Assessment 2021, 193, 1 -10.
AMA StyleM. R. D. L. Kulathunga, M. A. Ayanka Wijayawardena, Ravi Naidu. Heavy metal(loid)s and health risk assessment of Dambulla vegetable market in Sri Lanka. Environmental Monitoring and Assessment. 2021; 193 (4):1-10.
Chicago/Turabian StyleM. R. D. L. Kulathunga; M. A. Ayanka Wijayawardena; Ravi Naidu. 2021. "Heavy metal(loid)s and health risk assessment of Dambulla vegetable market in Sri Lanka." Environmental Monitoring and Assessment 193, no. 4: 1-10.
Chronic kidney disease of unknown aetiology (CKDu), which is widespread in the North Central Province (NCP) of Sri Lanka, is not associated with commonly known factors such as diabetes, hypertension, and glomerulonephritis. The pathogenicity of CKDu is not well understood, but people with a low body mass index (BMI) and mineral and nutrient deficiencies are more vulnerable to develop CKDu. To understand this situation, the relationship between BMI and the estimated glomerular filtration rate (eGFR) was investigated in people with CKDu in comparison with unaffected age-matched control groups in disease-endemic areas of the NCP. This community-based cross-sectional study was performed in Medirigiriya in the Polonnaruwa district of Sri Lanka, which has one of the highest densities of patients with CKDu. The data for identifying demographic factors and the relationship between CKDu and BMI were investigated by using a validated survey questionnaire. Findings indicated that the group with the highest number of people affected with CKDu (i.e. eGFR of less than 60 mL/min/1.73 m2) had the lowest BMI compared to those with normal eGFR. The majority affected were male farmers. The severity of the disease was inversely associated with BMI values and had a higher prevalence of smoking and alcohol consumption. In addition, those who consume water from household dug wells had significantly lower eGFR (p < 0.0001). A linear regression analysis revealed a significant positive association between lower eGFR and lower BMI (p < 0.001). We hypothesised that the low BMI in those with CKDu may have increased susceptibility to develop CKDu, in the presence of exposure to multiple nephrotoxins and adverse conditions.
M. R. D. L. Kulathunga; M. A. A. Wijayawardena; Ravi Naidu; S. J. Wimalawansa; Aw Wijeratne. Association between body mass index and estimated glomerular filtration rate in patients with chronic kidney disease of unknown aetiology in Sri Lanka. Environmental Geochemistry and Health 2020, 42, 2645 -2653.
AMA StyleM. R. D. L. Kulathunga, M. A. A. Wijayawardena, Ravi Naidu, S. J. Wimalawansa, Aw Wijeratne. Association between body mass index and estimated glomerular filtration rate in patients with chronic kidney disease of unknown aetiology in Sri Lanka. Environmental Geochemistry and Health. 2020; 42 (9):2645-2653.
Chicago/Turabian StyleM. R. D. L. Kulathunga; M. A. A. Wijayawardena; Ravi Naidu; S. J. Wimalawansa; Aw Wijeratne. 2020. "Association between body mass index and estimated glomerular filtration rate in patients with chronic kidney disease of unknown aetiology in Sri Lanka." Environmental Geochemistry and Health 42, no. 9: 2645-2653.
In this study, the predominant Pb minerals prior to and after Pb relative bioavailability (Pb-RBA) and Pb bioaccessibility (Pb-BAc) tests were identified using SEM (scanning electron microscopy), XANES (X-ray absorption near edge structure) and XRD (X-ray diffraction). The correlations between in vitro Pb-BAc (using the UBM (Unified BARGE Method) and RBALP (Relative BioAccessibility Leaching Procedure) models) and in vivo Pb-RBA (using endpoints of kidney and liver in an mice model) were determined. The results demonstrated that both RBALP and UBM (gastric phase) reliably indicate Pb-RBA (Pb-RBA). However, raising the solid:liquid ratio of the gastric phase of UBM is necessary to determine Pb-BAc if the soils contain total Pb >10,000 mg/kg. The comparison of Pb minerals prior to and after in vitro extractions demonstrated that the relatively soluble forms of Pb (PbSO4, PbO2 and MgO Pb) start to dissolve than other forms of Pb minerals, suggesting there was no difference in Pb2+ release between chemical-based (RBALP) and physiologically-based (UBM) models. The identification of the Pb minerals of Pb5(PO4)3Cl and organically-complexed Pb in mice excreta demonstrated that a portion of Pb2+ combined with food and humic acid to generate organically-complexed Pb in mice excreta, and that Pb5(PO4)3Cl is not bioavailable.
Kaihong Yan; Zhaomin Dong; Ravi Naidu; Yanju Liu; Yeling Li; Ayanka Wijayawardena; Peter Sanderson; Hongbo Li; Lena Q. Ma. Comparison of in vitro models in a mice model and investigation of the changes in Pb speciation during Pb bioavailability assessments. Journal of Hazardous Materials 2019, 388, 121744 .
AMA StyleKaihong Yan, Zhaomin Dong, Ravi Naidu, Yanju Liu, Yeling Li, Ayanka Wijayawardena, Peter Sanderson, Hongbo Li, Lena Q. Ma. Comparison of in vitro models in a mice model and investigation of the changes in Pb speciation during Pb bioavailability assessments. Journal of Hazardous Materials. 2019; 388 ():121744.
Chicago/Turabian StyleKaihong Yan; Zhaomin Dong; Ravi Naidu; Yanju Liu; Yeling Li; Ayanka Wijayawardena; Peter Sanderson; Hongbo Li; Lena Q. Ma. 2019. "Comparison of in vitro models in a mice model and investigation of the changes in Pb speciation during Pb bioavailability assessments." Journal of Hazardous Materials 388, no. : 121744.
Chronic kidney disease of unknown aetiology (CKDu) has emerged as a serious health issue in Sri Lanka. The disease has been recorded in the North Central Province of the country. While studies have elicited many hypotheses concerning the pathogenicity of CKDu, none adequately explains the cause of CKDu and the measures needed to minimise its occurrence. Nephrotoxic heavy metal (oid)s such as cadmium, arsenic, lead, and chromium are present in biological samples of people from endemic areas. This review appraises evidence on the effects of long-term exposure to low concentration of nephrotoxic heavy metals, which could be the principal cause of CKDu. Although a considerable variation exists in metal concentrations in patients’ blood and urine, higher levels of heavy metals were consistently observed in affected areas. This review finds that the populations in the endemic areas are exposed to heavy metal (oid)s at low concentrations, which are considered as safe levels; nevertheless, it influences the incidence of CKDu. Recent global studies on chronic kidney disease (CKD) revealed a low concentration of heavy metals in diseased patients. Research findings indicated that CKDu patients in Sri Lanka demonstrated similar blood levels of Cd, Pb, and higher concentrations of Cr than that have been reported globally. Further studies on the influence of combinations of nephrotoxic heavy metals at low concentrations on reduced glomerular filtration rate and other renal biomarkers could explain CKDu pathogenicity.
M. R. D. L. Kulathunga; M. A. Ayanka Wijayawardena; Ravi Naidu; Aw Wijeratne. Chronic kidney disease of unknown aetiology in Sri Lanka and the exposure to environmental chemicals: a review of literature. Environmental Geochemistry and Health 2019, 41, 2329 -2338.
AMA StyleM. R. D. L. Kulathunga, M. A. Ayanka Wijayawardena, Ravi Naidu, Aw Wijeratne. Chronic kidney disease of unknown aetiology in Sri Lanka and the exposure to environmental chemicals: a review of literature. Environmental Geochemistry and Health. 2019; 41 (5):2329-2338.
Chicago/Turabian StyleM. R. D. L. Kulathunga; M. A. Ayanka Wijayawardena; Ravi Naidu; Aw Wijeratne. 2019. "Chronic kidney disease of unknown aetiology in Sri Lanka and the exposure to environmental chemicals: a review of literature." Environmental Geochemistry and Health 41, no. 5: 2329-2338.
Lead (Pb) contaminated soil is of particular concern for infants and children due to their susceptibility to exposure, fast metabolic rates and rapidly developing neuronal systems. Determining the bioaccessibility of Pb in soils is critical in human health risk assessments, which can vary due to different soil properties and sources of Pb contamination. In this study, the potential relationships between soil properties and Pb bioaccessibility from various Pb sources including Pb contamination from mining (specifically, Broken Hill), three shooting ranges, a smelter and two industry sites (pottery and battery), were investigated using the Relative Bioavailability Leaching Procedure (RBALP). We found the following: (1) CEC, TOC, sand and silt content, and total Pb were significantly different (p < 0.05) between the two particle size fractions of < 2 mm and < 250 µm; (2) EC, CEC and total Pb were significantly correlated to Pb bioaccessibility (p < 0.05); and (3) soil analyses based on source of Pb demonstrated a strongly significant relationship between Pb bioaccessibility and soil properties (CEC, EC, clay content and total Pb) for mining soils from Broken Hill (r2 = 0.86, p < 0.05, n = 18). These results demonstrated the influences of Pb contamination sources, soil properties and particle size fractions on Pb bioaccessibility as well as the prediction of Pb bioaccessibility using soil properties. The findings documented here will help in developing a predictive tool for human health risk assessment and the remediation of Pb contaminated soils.
Kaihong Yan; Zhaomin Dong; M.A Ayanka Wijayawardena; Yanju Liu; Yubiao Li; Ravi Naidu. The source of lead determines the relationship between soil properties and lead bioaccessibility. Environmental Pollution 2018, 246, 53 -59.
AMA StyleKaihong Yan, Zhaomin Dong, M.A Ayanka Wijayawardena, Yanju Liu, Yubiao Li, Ravi Naidu. The source of lead determines the relationship between soil properties and lead bioaccessibility. Environmental Pollution. 2018; 246 ():53-59.
Chicago/Turabian StyleKaihong Yan; Zhaomin Dong; M.A Ayanka Wijayawardena; Yanju Liu; Yubiao Li; Ravi Naidu. 2018. "The source of lead determines the relationship between soil properties and lead bioaccessibility." Environmental Pollution 246, no. : 53-59.
Soil lead (Pb) hazard level is contingent on bioavailability, but existing assays that estimate Pb bioavailability for human health risks are too expensive or otherwise inaccessible to many people that are impacted by Pb-contaminated soil. This study investigated the use of routine soil nutrient tests to estimate soil-Pb bioaccessibility as a surrogate measure of Pb bioavailability. A silt loam soil was spiked to a target concentration of 2000 mg Pb kg–1 with Pb(NO3)2 and amended with H3PO4 (varying P-to-Pb molar ratios) and KCl (Cl-to-P molar ratio of 2:5) to generate soils with similar total Pb concentrations but a range of Pb bioavailability (and bioaccessibility). Soils were extracted using Mehlich 3, Mehlich 1, Bray P1, Olsen, and micronutrient (DTPA) methods, and the results were compared to U.S. Environmental Protection Agency method 1340 data as well as to extended X-ray absorption fine structure (EXAFS) spectroscopy. The Mehlich 3 and method 1340 treatment effect ratios were well-correlated (r2 = 0.88, p ≤ 0.05), whereas Bray P1, DTPA, and Olsen results were more reflective of EXAFS data. Preliminary animal-feeding trials suggest that the Mehlich 3 is as effective as method 1340 at predicting the impact of P treatment on Pb relative bioavailability; however, both methods over-estimated the Pb hazard to mice in P-amended soil. Other routine soil tests that have heightened sensitivity to P amendment (e.g., Bray P1) may be promising candidates for Pb bioaccessibility assessment.
Shannon A. Plunkett; M. A. Ayanka Wijayawardena; Ravi Naidu; Geoffrey S. Siemering; Elizabeth J. Tomaszewski; Matthew Ginder-Vogel; Douglas J. Soldat. Use of Routine Soil Tests to Estimate Pb Bioaccessibility. Environmental Science & Technology 2018, 52, 12556 -12562.
AMA StyleShannon A. Plunkett, M. A. Ayanka Wijayawardena, Ravi Naidu, Geoffrey S. Siemering, Elizabeth J. Tomaszewski, Matthew Ginder-Vogel, Douglas J. Soldat. Use of Routine Soil Tests to Estimate Pb Bioaccessibility. Environmental Science & Technology. 2018; 52 (21):12556-12562.
Chicago/Turabian StyleShannon A. Plunkett; M. A. Ayanka Wijayawardena; Ravi Naidu; Geoffrey S. Siemering; Elizabeth J. Tomaszewski; Matthew Ginder-Vogel; Douglas J. Soldat. 2018. "Use of Routine Soil Tests to Estimate Pb Bioaccessibility." Environmental Science & Technology 52, no. 21: 12556-12562.
Heavy metal(loid)s and organic contaminants are two major groups of pollutants in soils. The fate and exposure of such pollutants in soil depends on their chemical properties, speciation, and soil properties. Soil properties and processes that control the toxicological aspects of pollutants include temperature, moisture, organic matter, mineral fractions, and microbial activities. These processes are vulnerable to climate change associated with global warming, including increased incidences of extreme rainfall, extended dry periods, soil erosion, and a rise in sea level. Here we explain evidence that relates to the effects of climate change-driven soil processes on the mobility, transport, and storage of pollutants in soil. The review found that changes in climate could increase human exposure to soil contaminants mainly due to processes involving soil organic carbon (SOC), surface runoff, redox state, and microbial community. However, uncertainties remain in relation to the extent of contaminant toxicity to human health, which is linked to global change drivers.
Bhabananda Biswas; Fangjie Qi; Jayanta Kumar Biswas; Ayanka Wijayawardena; Muhammad Atikul Islam Khan; Ravi Naidu. The Fate of Chemical Pollutants with Soil Properties and Processes in the Climate Change Paradigm—A Review. Soil Systems 2018, 2, 51 .
AMA StyleBhabananda Biswas, Fangjie Qi, Jayanta Kumar Biswas, Ayanka Wijayawardena, Muhammad Atikul Islam Khan, Ravi Naidu. The Fate of Chemical Pollutants with Soil Properties and Processes in the Climate Change Paradigm—A Review. Soil Systems. 2018; 2 (3):51.
Chicago/Turabian StyleBhabananda Biswas; Fangjie Qi; Jayanta Kumar Biswas; Ayanka Wijayawardena; Muhammad Atikul Islam Khan; Ravi Naidu. 2018. "The Fate of Chemical Pollutants with Soil Properties and Processes in the Climate Change Paradigm—A Review." Soil Systems 2, no. 3: 51.
Chronic exposure to arsenic (As) is a global concern due to worldwide exposure and adverse effects, and the importance of incorporating bioavailability in the exposure assessment and risk assessment of As is increasing acknowledged. The bioavailability of As is impacted by a number of soil properties, such as pH, clay and metal concentrations. By retrieving 485 data from 32 publications, the aim of this study was to determine the relationship between selected metals (Fe and Al) and As bioavailability. In present study, the bioaccessibility (BAC) data measured by in vitro approaches were converted into bioavailability data based on the previously determined relationship between BAC and bioavailability. The As relative bioavailability (RBA) was summarized to be 24.36 ± 18.49%, which is in the range previously reported. A significant association between Fe concentration and the bioavailability of As was observed while this association varied for different types of RBA data. This disparity may suggest a non-reliable association between Fe and As bioavailability. The correlations between logarithmically transformed total content of Fe + Al and As bioavailability is then outlined: RBA = (−8.40 ± 1.02) × Ln(Fe + Al) + (58.25 ± 4.09), R² = 0.25, p < 0.001, n = 212. Jackknife resampling was also applied to validate the relation between total content of (Fe + Al) and As bioavailability, which suggested that the relation is robust. This is the first pooled study to address the relations between selected metal concentrations and As bioavailability, which may provide some implications to establish soil properties-based RBA prediction for As.
Kaihong Yan; Ravi Naidu; Yanju Liu; Ayanka Wijayawardena; Luchun Duan; Zhaomin Dong. A Pooled Data Analysis to Determine the Relationship between Selected Metals and Arsenic Bioavailability in Soil. International Journal of Environmental Research and Public Health 2018, 15, 888 .
AMA StyleKaihong Yan, Ravi Naidu, Yanju Liu, Ayanka Wijayawardena, Luchun Duan, Zhaomin Dong. A Pooled Data Analysis to Determine the Relationship between Selected Metals and Arsenic Bioavailability in Soil. International Journal of Environmental Research and Public Health. 2018; 15 (5):888.
Chicago/Turabian StyleKaihong Yan; Ravi Naidu; Yanju Liu; Ayanka Wijayawardena; Luchun Duan; Zhaomin Dong. 2018. "A Pooled Data Analysis to Determine the Relationship between Selected Metals and Arsenic Bioavailability in Soil." International Journal of Environmental Research and Public Health 15, no. 5: 888.
Pollution of shooting range soils by lead from bullets represents a widespread and potentially significant concern for impact on the environment. High concentrations of lead in particular are reported in bullet impact berms and shot fall zones. The other components of bullets used in shooting including antimony, copper and zinc may also be present at elevated concentrations. Antimony is a concern due to its mobility in the environment. It has been recognised that the status of contamination is important for the risk presented by shooting ranges. Lead bullets are subject to weathering in the soil, forming secondary minerals, which may be solubilised and may release lead and co-contaminants into the soil. The mobility and availability of contaminants in the soil affect their potential for spreading in the environment and for uptake and toxicity in organisms. Soil physicochemical properties affect bullet weathering and availability of contaminants in the soil. A number of strategies have been researched for management of shooting range pollution such as chemical stabilisation, phytoremediation and soil washing. This review considers the current state of knowledge and research of contamination and management of shooting ranges from recent literature (2014–2017) reflecting on new knowledge and novel management strategies for shooting range soil management. Ultimately, management of pollution in shooting range soils should seek to remove bullets from soil, reduce the weathering of bullets and reduce the mobility and bioavailability of contaminants. Adopted management practices should be based an understanding of site-specific condition, to achieve the most optimal outcome.
Peter Sanderson; Fangjie Qi; Balaji Seshadri; Ayanka Wijayawardena; Ravi Naidu. Contamination, Fate and Management of Metals in Shooting Range Soils—a Review. Current Pollution Reports 2018, 4, 175 -187.
AMA StylePeter Sanderson, Fangjie Qi, Balaji Seshadri, Ayanka Wijayawardena, Ravi Naidu. Contamination, Fate and Management of Metals in Shooting Range Soils—a Review. Current Pollution Reports. 2018; 4 (2):175-187.
Chicago/Turabian StylePeter Sanderson; Fangjie Qi; Balaji Seshadri; Ayanka Wijayawardena; Ravi Naidu. 2018. "Contamination, Fate and Management of Metals in Shooting Range Soils—a Review." Current Pollution Reports 4, no. 2: 175-187.
The presence of one metal can alter the toxicity of another metal by having an additive, synergistic, or antagonistic impact. Mixed metal pollution has clear ecological consequences. The importance of use of earthworms for ecological health monitoring is recognized widely. This study investigated the effect of binary and tertiary metal mixtures on the toxicity, bioaccumulation, and reproduction of the Eisenia fetida in different South Australian soils. The end points used in this 56-day reproduction study were avoidance behavior, worm mortality, weight loss, reproduction, and metal (Cd, Zn, and Pb) bioaccumulation. The three soils (acidic, neutral, and alkaline) were spiked with selected binary and tertiary concentration mixtures that considered the soil quality guideline values, EC50 and LC50 values for Cd, Zn, and Pb obtained from the previous single metal earthworm experiments done by the authors. In acidic soil, Zn and Cd constituted the most toxic metal combination to earthworms. However, in contrast to this observation, the same metal combination was the least toxic one to earthworms in neutral and alkaline soils. For Zn and Pb spiked soils, relationships between soil and internal metal concentrations were found with R 2 = 0.63, r = 0.8, and R 2 = 0.94, p < 0.01, respectively, for Zn and Pb. This study indicates that earthworms have high tendency to bioaccumulate heavy metals in their tissues and hence serves as ecological indicators of soil heavy metal contamination. The highest bioaccumulation factor (0–9) was evident for Cd in contaminated soils. This study demonstrated the role of soil edaphic factors and metal-metal interactions in the toxicity of metal mixtures to E. fetida. In Zn and Pb binary mixture spiked acidic soil, mortality of 60% was recorded even when the Pb and Zn concentrations were below the Canada and Dutch EIL (ecological investigational levels) values. This indicates the current guideline values are not safe for mixed metal toxicity. Therefore, care must be taken when predicting metal toxicities in mixed metal contaminated soils.
M. A. Ayanka Wijayawardena; Mallavarapu Megharaj; Ravi Naidu; Elizabeth Stojanovski. Chronic and reproductive toxicity of cadmium, zinc, and lead in binary and tertiary mixtures to the earthworm (Eisenia fetida). Journal of Soils and Sediments 2017, 18, 1602 -1609.
AMA StyleM. A. Ayanka Wijayawardena, Mallavarapu Megharaj, Ravi Naidu, Elizabeth Stojanovski. Chronic and reproductive toxicity of cadmium, zinc, and lead in binary and tertiary mixtures to the earthworm (Eisenia fetida). Journal of Soils and Sediments. 2017; 18 (4):1602-1609.
Chicago/Turabian StyleM. A. Ayanka Wijayawardena; Mallavarapu Megharaj; Ravi Naidu; Elizabeth Stojanovski. 2017. "Chronic and reproductive toxicity of cadmium, zinc, and lead in binary and tertiary mixtures to the earthworm (Eisenia fetida)." Journal of Soils and Sediments 18, no. 4: 1602-1609.
Lead (Pb) is a widespread heavy metal which is harmful to human health, especially to young children. To provide a human health risk assessment that is more relevant to real conditions, Pb bioavailability in soils is increasingly employed in the assessment procedure. Both in vivo and in vitro measurements for lead bioavailability are available. In vivo models are time- consuming and expensive, while in vitro models are rapid, economic, reproducible, and reliable while involving more uncertainties. Uncertainties in various measurements create difficulties in accurately predicting Pb bioavailability, resulting in the unnecessary remediation of sites. In this critical review, we utilised available data from in vivo and in vitro studies to identify the key parameters influencing the in vitro measurements, and presented uncertainties existing in Pb bioavailability measurements. Soil type, properties and metal content are reported to influence lead bioavailability; however, the differences in methods for assessing bioavailability and the differences in Pb source limit one’s ability to conduct statistical analyses on influences of soil factors on Pb bioavailability. The information provided in the review is fundamentally useful for the measurement of bioavailability and risk assessment practices
Kaihong Yan; Zhaomin Dong; Ayanka Wijayawardena; Yanju Liu; Ravi Naidu; Kirk Semple. Measurement of soil lead bioavailability and influence of soil types and properties: A review. Chemosphere 2017, 184, 27 -42.
AMA StyleKaihong Yan, Zhaomin Dong, Ayanka Wijayawardena, Yanju Liu, Ravi Naidu, Kirk Semple. Measurement of soil lead bioavailability and influence of soil types and properties: A review. Chemosphere. 2017; 184 ():27-42.
Chicago/Turabian StyleKaihong Yan; Zhaomin Dong; Ayanka Wijayawardena; Yanju Liu; Ravi Naidu; Kirk Semple. 2017. "Measurement of soil lead bioavailability and influence of soil types and properties: A review." Chemosphere 184, no. : 27-42.
This study investigates the effect of contaminant zinc (Zn) on lead (Pb) bioavailability and bioaccessibility in six contrasting soils spiked with 1500 mg Pb/kg and aged 12 months under laboratory conditions. Zn was added to the soils (7500 mgZn/kg soil) and aged for a further two weeks. In vivo studies were conducted using juvenile swine as a surrogate model for young children. Two compartment pharmacokinetic models were used to analyze the biological response produced by Pb oral solution and spiked soils. Absolute and relative bioavailability of Pb in soils (oral dose of 100 μ g Pb/kg body weight/day) were estimated by comparing them with intravenously administered soluble Pb salt (25 μ g Pb/kg/day) and orally administered the same Pb salt [Pb acetate =(CH3COO)2Pb⋅3H2O] administered to 3 juvenile pigs per treatment. Lead bioaccessibility was calculated using the in vitro RBALP (i.e. relative bioaccessibility leaching procedure) method. The in vitro results of RBALP were compared to in vivo relative Pb bioavailability to ascertain whether the changes in bioaccessibility correlated with the in vivo data. Although the in vivo Pb relative bioavailability (RB) in all soils except in MLA (Mount Lofty Acidic) revealed an increase (18%–159%) in the presence of Zn, the in vitro RBALP bioaccessibility results indicated otherwise (1%–38% decrease). In vivo RB of Pb in MLA declined by 37% in the presence of Zn. However, the RBALP in vitro bioaccessible Pb did not correlate with the relative bioavailabilities of Pb in the juvenile swine dosing experiment. Caution is therefore needed when predicting Pb bioavailability/bioaccessibility in the presence of metal mixtures. The literature contains much information on the correlation of metal and metalloid bioaccessibility with their bioavailability. There is, however, a paucity of studies investigating the effects of other metals on Pb and their IVIVC (in vitro and in vivo correlations). The current study addresses this knowledge gap by assessing in vivoand in vitro bioavailability of Pb in the presence of Zn.
Ayanka Wijayawardena; Ravi Naidu; Mallavarapu Megharaj; Dane Lamb; Palanisami Thavamani; Tim Kuchel. Evaluation of relative bioaccessibility leaching procedure for an assessment of lead bioavailability in mixed metal contaminated soils. Environmental Technology & Innovation 2017, 7, 229 -238.
AMA StyleAyanka Wijayawardena, Ravi Naidu, Mallavarapu Megharaj, Dane Lamb, Palanisami Thavamani, Tim Kuchel. Evaluation of relative bioaccessibility leaching procedure for an assessment of lead bioavailability in mixed metal contaminated soils. Environmental Technology & Innovation. 2017; 7 ():229-238.
Chicago/Turabian StyleAyanka Wijayawardena; Ravi Naidu; Mallavarapu Megharaj; Dane Lamb; Palanisami Thavamani; Tim Kuchel. 2017. "Evaluation of relative bioaccessibility leaching procedure for an assessment of lead bioavailability in mixed metal contaminated soils." Environmental Technology & Innovation 7, no. : 229-238.
Lead (Pb) is a highly studied contaminant with no known biological function that causes harmful adverse effects on ecological and human health. We tried to evaluate how protective the current soil regulatory levels are for Pb towards safeguarding the ecological health. In order to achieve this, our study evaluated the effect of soil texture and pH on the toxicity and availability of lead to earthworms in soils varying in soil properties. The earthworm Eisenia fetida was exposed to Pb in three soils with different physico-chemical characteristics. Pb solutions were homogenously mixed with soil to obtain concentrations ranging from 0 to 10,000 mg/kg Pb dry soil. Avoidance behaviour, weight loss and mortality were measured in this study to calculate the EC50 and LC50 values. Weight loss and mortality in earthworms due to Pb toxicity were in the following order: acidic > neutral > alkaline soil. The EC50 values resulting in 50% decrease in worm weight over control for Pb in acidic, neutral and alkaline soils were 460, 3606 and 5753 mg/kg soil, respectively. Thus, the acidic soil recorded an EC50 well below the soil guideline value for Pb. Whereas, the LC50 values resulting in 50% mortality in worms over control were 1161, 4648 and 7851 mg/kg, respectively, for acidic, neutral and alkaline soils. The Pb concentrations in earthworms ranged from 0.2 to 740 mg/kg wet weight. Soils with low clay content and acidic to neutral pH values demonstrated an increased Pb toxicity in earthworms compared to the soils with alkaline pH. The worm weight loss is a more sensitive parameter than the mortality. This study emphasizes that the soil regulatory levels for Pb are not protective of worms in acidic soils. Therefore, care should be taken when using the current regulatory limits to assess and predict the safety of a contaminated site with acidic soils towards the ecological health.
M. A. Ayanka Wijayawardena; Mallavarapu Megharaj; Ravi Naidu. Bioaccumulation and toxicity of lead, influenced by edaphic factors: using earthworms to study the effect of Pb on ecological health. Journal of Soils and Sediments 2016, 17, 1064 -1072.
AMA StyleM. A. Ayanka Wijayawardena, Mallavarapu Megharaj, Ravi Naidu. Bioaccumulation and toxicity of lead, influenced by edaphic factors: using earthworms to study the effect of Pb on ecological health. Journal of Soils and Sediments. 2016; 17 (4):1064-1072.
Chicago/Turabian StyleM. A. Ayanka Wijayawardena; Mallavarapu Megharaj; Ravi Naidu. 2016. "Bioaccumulation and toxicity of lead, influenced by edaphic factors: using earthworms to study the effect of Pb on ecological health." Journal of Soils and Sediments 17, no. 4: 1064-1072.
Defining the precise clean-up goals for lead (Pb) contaminated sites requires site-specific information on relative bioavailability data (RBA). While in vivo measurement is reliable but resource insensitive, in vitro approaches promise to provide high-throughput RBA predictions. One challenge on using in vitro bioaccessibility (BAc) to predict in vivo RBA is how to minimize the heterogeneities associated with in vivo-in vitro correlations (IVIVCs) stemming from various biomarkers (kidney, blood, liver, urinary and femur), in vitro approaches and studies. In this study, 252 paired RBA-BAc data were retrieved from 9 publications, and then a Bayesian hierarchical model was implemented to address these random effects. A generic linear model (RBA (%)=(0.87±0.16)×BAc+(4.70±2.47)) of the IVIVCs was identified. While the differences of the IVIVCs among the in vitro approaches were significant, the differences among biomarkers were relatively small. The established IVIVCs were then applied to predict Pb RBA of which an overall Pb RBA estimation was 0.49±0.25. In particular the RBA in the residential land was the highest (0.58±0.19), followed by house dust (0.46±0.20) and mining/smelting soils (0.45±0.31). This is a new attempt to: firstly, use a meta-analysis to correlate Pb RBA and BAc; and secondly, estimate Pb RBA in relation to soil types.
Zhaomin Dong; Kaihong Yan; Yanju Liu; Ravi Naidu; Luchun Duan; Ayanka Wijayawardena; Kirk T. Semple; Mohammad Mahmudur Rahman. A meta-analysis to correlate lead bioavailability and bioaccessibility and predict lead bioavailability. Environment International 2016, 92-93, 139 -145.
AMA StyleZhaomin Dong, Kaihong Yan, Yanju Liu, Ravi Naidu, Luchun Duan, Ayanka Wijayawardena, Kirk T. Semple, Mohammad Mahmudur Rahman. A meta-analysis to correlate lead bioavailability and bioaccessibility and predict lead bioavailability. Environment International. 2016; 92-93 ():139-145.
Chicago/Turabian StyleZhaomin Dong; Kaihong Yan; Yanju Liu; Ravi Naidu; Luchun Duan; Ayanka Wijayawardena; Kirk T. Semple; Mohammad Mahmudur Rahman. 2016. "A meta-analysis to correlate lead bioavailability and bioaccessibility and predict lead bioavailability." Environment International 92-93, no. : 139-145.
Exposure to chemical mixtures is a common and important determinant of toxicity in human and environmental health issues. Although there is a wealth of information on single metal interactions, very few studies have been conducted on the effects of mixtures of heavy metals on environmental quality and human health. Current national regulatory guidelines for soils are based solely on individual metal and metalloids concentrations. However, heavy metals and metalloids do not exist in isolation at the majority of sites. Soil properties such as pH, Eh, clay minerals, and cation exchange capacity influence multiple metal interactions. There are numerous adverse health effects on human, animals, and the environment due to mixed metal exposure resulting from additive and synergistic interactions even when concentrations of the individual metals are below their ecotoxicological benchmark levels. Two key strategies currently recognized as suitable for predicting toxicity of a mixture are: first, concentration addition, also known as Loewe additivity and second, effect addition, also referred to as the Bliss model of independent action. In this review we draw attention to research illustrating the interactions of multiple metal contaminants and their potential health impacts.
M.A.A. Wijayawardena; M. Megharaj; R. Naidu. Exposure, Toxicity, Health Impacts, and Bioavailability of Heavy Metal Mixtures. Advances in Agronomy 2016, 175 -234.
AMA StyleM.A.A. Wijayawardena, M. Megharaj, R. Naidu. Exposure, Toxicity, Health Impacts, and Bioavailability of Heavy Metal Mixtures. Advances in Agronomy. 2016; ():175-234.
Chicago/Turabian StyleM.A.A. Wijayawardena; M. Megharaj; R. Naidu. 2016. "Exposure, Toxicity, Health Impacts, and Bioavailability of Heavy Metal Mixtures." Advances in Agronomy , no. : 175-234.
Soil plays a significant role in controlling the potential bioavailability of contaminants in the environment. In this study, eleven soils were used to investigate the relationship between soil properties and relative bioavailability (RB) of lead (Pb). To minimise the effect of source of Pb on in vivo bioavailability, uncontaminated study soils were spiked with 1500 mg Pb/kg soil and aged for 10–12 months prior to investigating the relationships between soil properties and in vivo RB of Pb using swine model. The biological responses to oral administration of Pb in aqueous phase or as spiked soils were compared by applying a two-compartment pharmacokinetic model to blood Pb concentration. The study revealed that RB of Pb from aged soils ranged from 30 ± 9% to 83 ± 7%. The very different RB of Pb in these soils was attributed to variations in the soils’ physico-chemical properties. This was established using sorption studies showing: firstly, Freundlich partition coefficients that ranged from 21 to 234; and secondly, a strongly significant (R2 = 0.94, P < 0.001) exponential relationship between RB and Freundlich partition coefficient (Kd). This simple exponential model can be used to predict relative bioavailability of Pb in contaminated soils. To the best of our knowledge, this is the first such model derived using sorption partition coefficient to predict the relative bioavailability of Pb.
M.A. Ayanka Wijayawardena; Ravi Naidu; Mallavarapu Megharaj; Dane Lamb; Palanisami Thavamani; Tim Kuchel. Using soil properties to predict in vivo bioavailability of lead in soils. Chemosphere 2015, 138, 422 -428.
AMA StyleM.A. Ayanka Wijayawardena, Ravi Naidu, Mallavarapu Megharaj, Dane Lamb, Palanisami Thavamani, Tim Kuchel. Using soil properties to predict in vivo bioavailability of lead in soils. Chemosphere. 2015; 138 ():422-428.
Chicago/Turabian StyleM.A. Ayanka Wijayawardena; Ravi Naidu; Mallavarapu Megharaj; Dane Lamb; Palanisami Thavamani; Tim Kuchel. 2015. "Using soil properties to predict in vivo bioavailability of lead in soils." Chemosphere 138, no. : 422-428.
Aging is a time-dependent process that causes metal bioavailability to decrease with time. The current study investigated the bioavailability change of Pb in four contrasting soils over a time period until the Pb relative bioavailability (RB) levels achieved a steady state to assess the extent of the following: firstly, bioavailability change in each soil and secondly, correlation of these changes with the soil properties. Relative bioavailability of soils spiked with 1500 mg Pb/kg were measured in swine that were fed these soils, throughout an aging period (56 days) to investigate relationships between soil properties and in vivo bioavailability of Pb. Spiked soils were used to minimize the effect of varying sources of Pb on RB. The RB of Pb in GTA, IWA, and MLA decreased from their initial Pb RB values until a steady state RB of 34, 45, and 59 % was reached, respectively, by the 56th day. In contrast, however, to these RB decreases, NTA soil indicated no change in RB over the whole aging period of the experiment. The lack of change in RB in the NTA soil over time was attributed to it achieving a steady state RB within a very short time due to its comparatively high sorptive capacity (K d = 112).
M. A. Ayanka Wijayawardena; Ravi Naidu; Mallavarapu Megharaj; Dane Lamb; Palanisami Thavamani; Tim Kuchel. Influence of ageing on lead bioavailability in soils: a swine study. Environmental Science and Pollution Research 2014, 22, 8979 -8988.
AMA StyleM. A. Ayanka Wijayawardena, Ravi Naidu, Mallavarapu Megharaj, Dane Lamb, Palanisami Thavamani, Tim Kuchel. Influence of ageing on lead bioavailability in soils: a swine study. Environmental Science and Pollution Research. 2014; 22 (12):8979-8988.
Chicago/Turabian StyleM. A. Ayanka Wijayawardena; Ravi Naidu; Mallavarapu Megharaj; Dane Lamb; Palanisami Thavamani; Tim Kuchel. 2014. "Influence of ageing on lead bioavailability in soils: a swine study." Environmental Science and Pollution Research 22, no. 12: 8979-8988.