Quest to identify geochemical risk factors associated with chronic kidney disease of unknown etiology (CKDu) in an endemic region of Sri Lanka-a multimedia laboratory analysis of biological, food, and environmental samples

Rising of a global silent killer: critical analysis of chronic kidney disease of uncertain aetiology (CKDu) worldwide and mitigation steps

Chronic kidney disease of uncertain aetiology (CKDu) is an advanced version of chronic kidney disease (CKD) which bears a high burden on the world health economy. More than 200 articles were analysed to understand the disease responsible for more than 30,000 deaths per year. CKDu is a non-communicable occupational disease that has a progressive deterioration of the kidney in the absence of CKD risk factors such as hypertension, diabetes and glomerulonephritis, while the diagnosis is only possible at the later stages when kidney function is no longer effective. Published evidence for the existence of CKDu was found for around 35 countries. This is a growing health issue in Asia, Central America, Africa and Middle East with identified hot spots. Despite many research studies over decades, the exact root causes are still uncertain. Six main suspected causative factors are identified. Those are heat stress, strenuous labour, dehydration, use of agrochemicals, exposure to heavy metals and the use of polluted water and agricultural lands. This review summarizes four key areas which are CKDu and its general medical background, worldwide prevalence, suspected causative factors and potential circumventing steps to mitigate against CKDu. The importance of further studies addressing early detection and surveillance methods, contribution of nephrotoxins in environmental health, soil chemistry on transporting nephrotoxins, geological parameters which influence the prevalence of the disease and other related sectors to overcome the mysterious nature is highlighted. Mitigation steps to lessen the burden of CKDu are also identified.

Could Consumption of Trace Element-Contaminated Rice Be a Risk Factor for Acute Interstitial Nephritis with Uncertain Etiology in the Dry Zone of Sri Lanka?

Ingestion of toxic trace elements in the human body has been considered one of the major reasons for renal dysfunction. Chronic kidney disease with uncertain etiological factors (CKDu) is a recently described clinical entity in which the disease is found in geographically isolated pockets in the dry zone of Sri Lanka. In CKDu regions, an increasing number of cases are reported with acute interstitial nephritis without any known reason (AINu). However, recent exposure to certain risk behaviors or nephrotoxins, or both, is suspected for the AINu. Consumption of foods that are contaminated with trace elements is one of the main pathways of human exposure to environmental toxins. The current study was carried out to assess the possibility of trace element-contaminated rice consumption on the etiopathogenesis of AINu. Samples of rice consumed by 32 clinically diagnosed AINu cases were collected and analyzed for possible nephrotoxic trace elements. Out of 32 patients, 26 were histologically confirmed with tubulointerstitial disease. The results revealed that the mean values of Cd, As, and Pb were 0.18, 0.055, and 0.135 mg/kg, with ranges of 0.020-1.06, 0.012-0.222, and 0.003-0.744 mg/kg (on dry weight basis), respectively. This study indicated that the investigated toxic trace element levels of rice consumed by AINu were reasonably below the recommended levels of the Codex Alimentarius Commission of FAO and WHO. Hence, it is less likely that rice consumption is to be a risk factor for the etiology of AINu.

Cultivating vegetables in tailings from the Fundão dam collapse: metal accumulation and risks to food safety

A great amount of iron ore tailings from the collapse of the Fundão dam in Southeast Brazil was deposited in an extensive agricultural area. The presence of this material creates insecurity for the resumption of agricultural activities, especially the cultivation of vegetables, which can accumulate metals at potentially toxic levels. In this study, two vegetables consumed in the affected area, arugula and radish, were cultivated in tailings and in soil. Productivity, photosynthetic pigment content, photosynthetic performance, metal accumulation, and the possible risk to food safety were analyzed. The productivity of both vegetables, arugula and radish, did not differ between cultivation in tailings and in soil. There were no differences in pigment content nor substantial differences in the photosynthetic parameters of plants grown in the two substrates. Plants grown in tailings had higher Fe, Mn, and Na contents than those grown in soil, reflecting the higher levels of these elements in the former. There were no visual signs of metal toxicity for plants grown in the tailings. The levels of metals potentially ingested through estimated consumption of arugula and radish grown in the tailings were below the maximum allowable limits for human consumption. In addition, calculated risk indices suggest a low potential for harm to the health of consumers of cultivated vegetables in the tailings. The results presented here suggest that agricultural cultivation in the tailings is viable and contribute to the resumption of vegetable cultivation in the region affected by the tailings released with the collapse of the Fundão dam.

Multi-pronged research on endemic chronic kidney disease of unknown etiology in Sri Lanka: a systematic review

Increasing prevalence of endemic chronic kidney disease of unknown etiology (CKDu) in Sri Lanka is a major health problem since the 1990s. Despite numerous studies on CKDu, research groups have been unable to develop a comprehensive approach to mitigate the disorder, and thereby to identify research gaps. We conducted a systematic literature review of 119 publications on CKDu in Sri Lanka from Pubmed, Google Scholar, and Scopus, published until end September 2020. A higher CKDu prevalence in the working population of the North Central Province was reported with recent studies indicating patients from non-endemic regions as well. A majority were etiological studies that recorded conflicting and inconclusive evidence on CKDu etiology. Studies on clinico-pathological, diagnostic, biochemical, and molecular biological aspects of CKDu, studies analyzing CKDu symptom burden, anthropological, and behavioral impacts of CKDu, were reviewed as well. A dearth of research exists on nutritional, demographical, immunological, and microbial aspects of CKDu. The overview of the reviewed literature indicated the absence of a comprehensive plan of action to mitigate this situation. Hence, we propose the "One Health" approach with a systems dynamics model as a potential way forward to alleviate the CKDu epidemic in Sri Lanka. This enables the representation of multiple causative agents (and interactions thereof) among environmental, animal, and human systems, in concert with the "exposome" that provides the totality of exposure the individual has undergone since birth.

Assessment of Dietary Exposure to Ochratoxin A in Lebanese Students and Its Urinary Biomarker Analysis

The present study investigated the dietary and urinary OTA occurrence among 44 Lebanese children. Relying on HPLC-FLD analysis, OTA was found in all the urine samples and in 46.5% and 25% of the 24 h duplicate diet and dinner samples, respectively. The means of OTA levels in positive samples were 0.32 ± 0.1 ng/g in 24 h diet, 0.32 ± 0.18 ng/g in dinner and 0.022 ± 0.012 ng/mL in urines. These values corresponded to margin of exposure (MOE) means of 7907 ± 5922 (neoplastic) and 2579 ± 1932 (non-neoplastic) calculated from positive 24 h diet, while 961 ± 599 (neoplastic) and 313 ± 195 (non-neoplastic) calculated from the urine. Since the MOE levels for the neoplastic effect were below the limit (10,000), a major health threat was detected and must be addressed as a health institutions' priority. Besides, the wide difference between PDIs and MOEs calculated from food and urine suggests conducting further OTA's toxicokinetics studies before using urine to measure OTA exposure.

β-Endosulfan-mediated induction of pro-fibrotic markers in renal (HK-2) cells in vitro: A new insight in the pathogenesis of chronic kidney disease of unknown etiology

Chronic kidney disease of unknown etiology (CKDu), manifested clinically as tubulo interstitial fibrosis, has emerged as the second major cause of chronic kidney disease (CKD) in the Indian subcontinent and various agrochemicals have been implicated in its occurance. Among the agrochemicals organochlorine pesticides particularly endosulfan is well known for its toxicity and recent residue analysis have shown its presence in the blood samples of general population. In this present study, we have investigated the consequences of endosulfan exposure at a concentration (0.01 μM) equivalent to their highest reported presence in human blood sample of some CKDu patients, to human renal proximal tubular epithelial (HK-2) cell line with regard to ROS generation and expression of profibrotic and epithelial to mesenchymal (EMT) markers in order to find out endosulfan's ability to induce profibrotic changes in renal cell. We demonstrated a significant increase in intracellular ROS generation and increased expression of TGF-β1 when cells were incubated with β-endosulfan (0.01 μM) indicating occurrence of oxidative stress and fibrotic process. Again, decreased expression of epithelial marker E-cadherin and increase in the expression of mesenchymal marker α-smooth muscle actin (α-SMA) suggest possible onset of EMT process. Pre-treatment with 5 mM concentration of anti-oxidant N-acetyl cysteine partially attenuated the above process. In conclusion, these findings suggest possible involvement of β-endosulfan in the development of CKDu through oxidative stress and profibrotic signaling.

Two decades of chronic kidney disease of unknown aetiology (CKDu) research: Existing evidence and persistent gaps from epidemiological studies in Sri Lanka

BACKGROUND

Chronic Kidney Disease of unknown origin (CKDu) excludes known primary renal conditions or systemic disease (such as diabetes mellitus or hypertension). Prominence of CKDu has been noted for some decades in Sri Lanka, especially among men in particular rural areas, prompting many studies directed towards environmental causation. This article critically reviews relevant primary studies.

METHODS

Articles for this literature review (n = 86) were found by searching Medline, Embase, Global Health and ProQuest databases over 2000-2020 utilizing a standard algorithm. Articles were critiqued according to criteria for diagnosis of CKDu, aetiological agents investigated, analytic methods employed and findings.

RESULTS

Criteria for diagnosis of CKDu varied significantly, including pre-selection by proteinuria, eGFR and biopsy proven interstitial nephritis. Prevalence studies have been largely conducted in the North Central Province, with recent studies demonstrating the presence of CKDu in other regions. Aetiological factors investigated in primary studies included water source, use of agrochemicals, agricultural work, heavy metals, snake bites, ayurvedic medication, heat stress, infectious diseases and usage of tobacco and betel leaf. There is no conclusive evidence for any one aetiological agent despite consistent evidence of distal factors such as male sex, rural residence and farming.

CONCLUSIONS

The current body of evidence for any aetiological agent as the cause of CKDu in Sri Lanka is limited. Further research with stronger study designs is necessary to increase knowledge of aetiology of CKDu in Sri Lanka to identify and eliminate exposure to possible causative agent(s) prior to concluding that the disease is multifactorial.

The Groundwater Geochemistry and the Human Health Risk Assessment of Drinking Water in an Area with a High Prevalence of Chronic Kidney Disease of Unknown Etiology (CKDu), Sri Lanka

Chronic kidney disease of unknown etiology (CKDu) has become an alarming health issue in Sri Lanka. The disease is more notable among farming communities and people who consume groundwater as their main source of drinking water. To assess the possible links between drinking water chemistry and expansion of CKDu, the study was compared with hydrogeochemical data of drinking water sources in a CKDu prevalent area (Girandurukotte GND, Badulla District) and a reference area (Dambethalawa GND, Ampara District) in Sri Lanka. Based on the results, nephrotoxic heavy metal (Cd, Cr, Pb, and As) concentrations were significantly higher in the CKDu prevalent site than the reference area, compromised the harmful consequences to the people in the CKDu hotspot. Results of the inverse distance weighted (IDW) interpolation tool indicated the nephrotoxic heavy metals contents including Cd, Pb, As, and Cr in CKDu hotspot were changed in the ranges of 9.78–187.25 μg/L, 0.08–0.66 μg/L, 20.76–103.30 μg/L, and 0.03–0.34 μg/L. The random distribution patterns were shown by the result in Moran’s index values. Noteworthy, the results have emphasized a strong association between fluoride and water hardness. The frequency of occurrence above the threshold limit of fluoride was 28% in non-CKDu water samples, while 81% in CKDu prevalent sites. The hardness values in the CKDu prevalent site indicated “moderately hard water,” while the non-CKDu area indicated the “soft water.” Furthermore, this paper quantified overall water quality and heavy metal contamination and assessed the human health risks associated with drinking water. According to the results of the water quality index, 90% of the samples in the CKDu prevalent area were classified as “poor water” and “very poor water” for drinking purposes, while 73.33% of the samples in the non-CKDu area were “good” and “excellent” for drinking usage. Calculated chronic daily intake (CDIoral) and hazard quotient (HQoral) of nephrotoxicants were higher in CKDu hotspot than the non-CKDu site. Besides, the hazard index (HI) values obtained for the CKDu prevalent area exceeding the acceptable limit (HI = 1) indicated potential health risks to the people in those areas. This study suggests that long-term exposure to nephrotoxic heavy metals, water hardness, and fluoride present in drinking water may threaten human health and affect kidney functions. Therefore, regular monitoring and better management of water supplies in CKDu prevalent areas are essential to determine the contamination load and reduce the health impacts due to excessive and long-term exposure to the nephrotoxicants.

A pilot case-control study using a one health approach to evaluate behavioral, environmental, and occupational risk factors for chronic kidney disease of unknown etiology in Sri Lanka

BACKGROUND

Chronic kidney disease of unknown etiology (CKDu) was first recognized in Sri Lanka in the early 1990s, and since then it has reached epidemic levels in the North Central Province of the country. The prevalence of CKDu is reportedly highest among communities that engage in chena and paddy farming, which is most often practiced in the dry zone including the North Central and East Central Provinces of Sri Lanka. Previous studies have suggested varied hypotheses for the etiology of CKDu; however, there is not yet a consensus on the primary risk factors, possibly due to disparate study designs, sample populations, and methodologies.

METHODS

The goal of this pilot case-control study was to evaluate the relationships between key demographic, cultural, and occupational variables as risk factors for CKDu, with a primary interest in pesticide exposure both occupationally and through its potential use as an ingredient in brewed kasippu alcohol. An extensive one health focused survey was developed with in cooperation with the Centre for Research, Education, and Training on Kidney Diseases of Sri Lanka.

RESULTS

A total of 56 CKDu cases and 54 control individuals were surveyed using a proctored, self-reported questionnaire. Occupational pesticide exposure and alcohol consumption were not found to be significant risk factors for CKDu. However, a statistically significant association with CKDu was observed with chewing betel (adjusted odds ratio [aOR]: 6.11, 95% confidence interval [CI]: 1.93, 19.35), age (aOR: 1.07, 95% CI: 1.02, 1.13), owning a pet dog (aOR: 3.74, 95% CI: 1.38, 10.11), water treatment (aOR: 3.68, 95% CI: 1.09, 12.43) and pests in the house (aOR: 5.81, 95% CI: 1.56, 21.60).

CONCLUSIONS

The findings of this study suggest future research should focus on practices associated with chewing betel, potential animal interactions including pests in the home and pets, and risk factors associated with water.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s42522-020-00034-3.

A survey of arsenic, mercury, cadmium, and lead residues in seafood (fish, crustaceans, and cephalopods) from the south-eastern Mediterranean Sea

Seafood is capable of bioaccumulating heavy metals (HM), making it a potentially major dietary source of HM for humans. Presently, little data exists on seafood from the eastern-most boundary of the Mediterranean Sea. This study aims to provide exposure insight of the Israeli population to HM through the consumption of locally caught seafood by assessing the levels of arsenic, mercury, cadmium, and lead in raw tissues of seafood. A wide survey of local fisheries was conducted providing 296 samples from 11 different species, including seven fish, two crustacean, and two cephalopod species. Total arsenic, cadmium, and lead were analyzed by graphite-furnace atomic absorption. Total mercury was measured by cold-vapor mercury analyzer. Arsenic speciation was performed by anion chromatography-inductively coupled plasma sector field mass spectrometry. Results suggested that the total arsenic concentrations were significantly higher in crustaceans and cephalopods than fish. Arsenic speciation revealed two samples that exceed 1 mg/kg of inorganic arsenic, whereas methylated arsenic was below the detection limit. Elevated mercury levels were detected in the commercial benthic species Mullus barbatus (red mullet), cadmium was detected in one-third of the samples, and lead detected in eight samples. Comparing the results to health guidelines, 99.4% of seafood tested in this study abide with acceptable levels of heavy metals in seafood, as defined by both Israeli and European Union guidelines.

Impact of water quality on Chronic Kidney Disease of unknown etiology (CKDu) in Thunukkai Division in Mullaitivu District, Sri Lanka

Background

Increase in the number of cases in Chronic Kidney Disease of Unknown etiology (CKDu) in Sri Lanka has become a health issue of national concern. Even though, Northern Province is not identified as a high-risk province, there is an increasing trend of CKDu after the end of civil war in the Northern Province.

Methods

The present study was conducted in Thunukkai Division in Mullaitivu District to investigate the socio demographic and clinical pattern of CKDu patients and to evaluate the quality of their water sources. The samples were selected by using stratified purposive random sampling method which represented 29% of total CKDu patients in Thunukkai Division. Pretested structured questionnaire was administered to collect the data from the CKDu patients. The association between serum creatinine excreted by CKDu patients and the water quality parameters were determined by using linear regression model.

Results

Among the patients, 80% were male with over 68% falling in the age range of 50–70. Majority (90%) were involved in agriculture related occupation. Smoking and alcohol consumption were detected as common habits among 40% of the patients. Secondarily developed, hypertension (60%) and diabetes (34%) were reported as common diseases in the area. Dug wells served as the commonest source of drinking water in the area (90% households) together with few tube wells. Physicochemistry of more than 50% of the water samples revealed higher electric conductivity, salinity, total dissolved solids, total hardness and Na levels compared to drinking water standards in Sri Lanka.

Conclusions

Serum creatinine levels of the CKDu patients were significantly and negatively correlated with phosphate while positively correlated with total dissolved solids (TDS) and arsenic content of the drinking water. Geospatial mapping of TDS and arsenic in drinking water with the occurrence of higher serum creatinine levels confirmed the same trend. Thus, the total dissolved solids and arsenic in drinking water may have positive correlation with the occurrence of CKDu in Thunukkai region in the Mullaitivu District of Sri Lanka.

Quantitative versus qualitative risk assessment of meat and its products: what is feasible for Sub-Saharan African countries?

Prevalent risks in meat value-chains of sub-Saharan African (SSA) countries are increasingly attributed to microbial rather than chemical hazards. Resource constraints and lack of capacity has limited the utilization of risk assessment tools in the instituting of food controls to mitigate the risks. The review sought to bring to light the focus of risk assessment studies in SSA while generating evidence of feasible options to further the contribution of this component in risk mitigation. The informal street vending sector emerges as a priority in the meat value chain with a vendor population that are unwilling to abandon it. Campylobacter and Staphylococcus aureus are prevalent risks that have bedeviled this sector. However, limited risk assessment studies with capacity to inform proper food controls for the sector have been done. Evidence in place indicate that the incorporation of qualitative aspects in quantitative approaches serve as less-costly and effective ways of generating risk estimates. Limitations of capacity and gaps in epidemiological data are also circumvented. Considering that the street-vending sector is robust and its dynamics of operation are not fully in the picture of policy actors; incorporation of a participatory approach that combines qualitative and quantitative aspects of risk assessment is highly recommended.

Water quality and chronic kidney disease of unknown aetiology (CKDu) in the dry zone region of Sri Lanka: impacts on well-being of village communities and the way forward

There has been a growing concern in the dry zone of Sri Lanka that the contaminated surface and ground waters and ecohydrological changes are possibly linked to a number of health issues and overall well-being of village communities, including the widespread renal failure termed as chronic kidney disease of unknown aetiology (CKDu). Two types of data were collected for this study, namely qualitative data from key informant interviews and abstracts of 33 peer-reviewed research articles during the past decade. A total of 35 key informants were recruited, mainly from communities in the northern dry zone region where a higher number of CKDu patients have been reported. The interview transcripts were examined using a range of techniques including content, thematic and semantic network analyses. The findings of the research articles were explored through a word cloud analysis. The study indicates that CKDu seems to be influenced by multifactorial ecohydrological changes linked to anthropogenic stressors such as inefficient use of fertilisers and weedicides in agriculture. This situation is made further complicated by factors such as high fluoride level and hardness of local groundwater. Inappropriate agricultural and water policies and poor governance are other factors, particularly little or no restriction on the use of agrochemicals and pumping of groundwater and limited access to clean municipal water supplies. The key informants indicated grave concerns on the flow on effects of poor surface and groundwater quality in the region on health, livelihood and well-being of communities. There are also inevitable economic implications such as loss of human capital and families losing assets to pay for ongoing health issues. The study highlighted the need for more in-depth research to better understand how the surface and groundwater quality influence CKDu and other health conditions in the region. Furthermore, there is a need for implementing an active water quality management strategy with emphasis on developing locally relevant guidelines, educational programmes and integrated heath monitoring programmes in the region.

CKD of Uncertain Etiology: A Systematic Review

BACKGROUND AND OBJECTIVES

Epidemics of CKD of uncertain etiology (CKDu) are emerging around the world. Highlighting common risk factors for CKD of uncertain etiology across various regions and populations may be important for health policy and public health responses.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We searched PubMed, Embase, Scopus and Web of Science databases to identify published studies on CKDu. The search was generated in January of 2015; no language or date limits were used. We used a vote-counting method to evaluate exposures across all studies.

RESULTS

We identified 1607 articles, of which 26 met inclusion criteria. Eighteen (69%) were conducted in known CKDu-endemic countries: Sri Lanka (38%), Nicaragua (19%), and El Salvador (12%). The other studies were from India, Japan, Australia, Mexico, Sweden, Tunisia, Tanzania, and the United States. Heavy metals, heat stress, and dietary exposures were reported across all geographic regions. In south Asia, family history, agrochemical use, and heavy metal exposures were reported most frequently, whereas altitude and temperature were reported only in studies from Central America. Across all regions, CKDu was most frequently associated with a family history of CKDu, agricultural occupation, men, middle age, snake bite, and heavy metal exposure.

CONCLUSIONS

Studies examining etiologies of CKDu have reported many exposures that are heterogeneous and vary by region. To identify etiologies of CKDu, designing consistent and comparative multisite studies across high-risk populations may help elucidate the importance of region-specific versus global risk factors.