Is there relationship between CKDU and salts in NCP well water?



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There are also occasional reports that the bedrock in the NCP has soluble salts. This too may contribute to the well water salinity.


Most studies conducted in the NCP have clearly shown very high spatial variation of the EC values in well water. They can range from 1000 to 400 micros within a distance of a few hundred metres. This may be due to occasional discontinuation of the aquifer and the localised presence of salt bearing materials in the subsurface.


By Dr. Sarath Amarasiri


The writer is a former Director


General of Agriculture


The Chronic Kidney Disease of unknown etiology (CKDU) has killed thousands of people in the North Central Province (NCP), caused misery to a very large number of rural families in the region and brought misery upon the entire nation. The prevalence of the disease is mainly in the NCP with relatively fewer deaths in Badulla and Kurunegala Districts. Its specific cause remains unknown though the disease was reported initially nearly twenty years ago. However, there is a commonly held view that the disease is caused primarily by drinking well water containing one or more harmful agents.


The Sri Lanka Standards Institution (SLSI) in its first revision of standards for potable water made in 2013 has stipulated the maximum levels permitted for a number of substances that includes sodium, calcium, magnesium, fluoride, nitrate, arsenic, cadmium, chromium, lead, mercury and total dissolved solids (TDS).


Accordingly, the maximum permissible limit for TDS for drinking water is 500 mg/L. In its first edition of the standards made in 1983, the corresponding limit was given in terms of Electricl Conductivity (EC) as 3500 microsiemens/cm (abbreviated to micros in this article). Most countries use Electrical Conductivity in their list of drinking water standards in preference to TDS for technical reasons as well as for ease of measurement. EC can be determined in the field itself with a relatively inexpensive instrument the size of a pen torch that can even be carried in the shirt pocket. On the other hand, TDS determination is somewhat laborious as the water sample has to be transported to the laboratory, filtered, preserved, evaporated and weighed. The two measures are often converted by researchers from one to the other using a multiplying factor. On this basis the SLSI standard for drinking water can be considered as 780 micros. Electrical Conductivity of water is a measure of its ionic content and is often used to assess the total content of all the salts in the water.


It is well known that fluoride in drinking water is harmful to human health when its value is both low and high. According to SLSI standards fluoride in water in excess of 1 mg/L is not suitable for human drinking. The corresponding WHO guideline value for Asian countries is 0.6 mg/L.


Special features of NCP with respect to salinity build up of well water.


According to Dr. C.R. Panabokke, former Director of Agriculture, as outlined clearly and comprehensively in his book Ground Water Conditions in Sri Lanka – A Geomorphic Perspective (2007), the aquifer in the NCP has several special features that can bring about accumulation of salts. They include the undulating topography, fluctuation of the water table, presence of Reddish Brown Earth and Low Humic Gley soils, and a shallow hard rock that is non porous with low water permeability. The NCP soils have more clay and much less sand in comparison to the major soils of Puttalam, Jaffna peninsula, the Ampara District and the coastal lands in the Eastern province. These areas have hardly reported significant numbers of CKDU patients as of now.


The undulating landscape helps carry salts from the upper lands to the lower lands through surface and subsurface flow. The fluctuating water table arising from alternate high and low rainfall periods and from irrigation also aid in the movement of salts to the wells in the low lying areas. The properties of the bedrock prevent rapid flushing out of accumulated salts. These features make the NCP aquifer (termed Regolith aquifer) to accumulate more sallts than other aquifers in Sri Lanka.


The accumulation of salts in the well water in the NCP


Published information on the chemical composition of well water in the NCP is limited. This review has used the information contained in publications of the Water Resources Board in 2002, Department of Agrarian Development in 2012 and the Department of Agricultural Engineering of the University of Peradeniya in 2013. Their studies indicate the following:


1. Out of 52 wells studied in the Palugaswewa Grama Sevaka Division 81% had high EC values that rendered the water unsuitable for human drinking as their EC values exceeded the SLSI standard of 780 micros. The extremely high state of salinisation of the well water is evident from the fact that ten wells had EC vlaues of 7940, 7300, 5210, 5100, 4200, 4160, 4000, 3600, 3500 and 3100 micros.


2. Out of 238 samples of well water studied in the Malwathu Oya basin 65% were unsuitable for human drinking due to the high EC values.


3. Out of 94 wells studied in 11 Grama Sevaka Divisions in the Anuradhapura district 40% were unsuitable for human drinking.


The fluoride content of well water at Palugaswewa Grama Sevaka Division


Out of 52 wells studied in the Palugaswewa Grama Sevaka Division, 70% of the wells had higher fluoride content than the stipulated SLSI standard. The ten highest values of fluoride were 7.3, 6.9, 6.8, 6.8, 6.5, 6.2, 6.0, 5.9, 4.0 and 3.9 mg/L.


It is clear from the above discussion that some people living in the NCP may have been drinking substandard well water in the past unaware of its health implications, continue to do so at present, and will be compelled to do so in the future as well if good quality drinking water is not available for them.


How could NCP well water accumulate high levels of salts?


Ground water is recharged from rainfall, streams, rivers and tanks big and small. The chemical analysis of water of a number of reservoirs in the dry zone carried out since 1964 has hardly shown an EC value above the SLSI limit for safe drinking. It can therefore be reasoned that water from local catchments or from irrigation cannot be the primary source of salts leading to values of several thousands of micros in the shallow wells of the NCP. Rainfall in Sri Lanka does not contain significant quantities of ions either.


On the other hand, many have observed the presence of salt layers in the soil at 2 to 3 metres depth in some agro wells. It is possible that salts in the NCP shallow wells may have originated from the dissolution of sub surface salt layers deposited perhaps millions of years ago. The raising of groundwater levels from transbasin irrigation could have facilitated the dissolution of subsurface salt layers.


There are also occasional reports that the bedrock in the NCP has soluble salts. This too may contribute to the well water salinity.


Most studies conducted in the NCP have clearly shown very high spatial variation of the EC values in well water. They can range from 1000 to 400 micros within a distance of a few hundred metres. This may be due to occasional discontinuation of the aquifer and the localised presence of salt bearing materials in the subsurface.


Salts in water, Franz Hofmeister and kidney damage


Prof. Franz Hofmeister born in Czechoslovakia, was a famous protein researcher in his day. He published a paper in 1888 having conducted extensive research on the effect of salts on protein stability. In this article he presented a list of ions in the order of their ability to denature (ie. damage) proteins.This is now referred to as the Hofmeister Series. Although his research included a study of a large number of ions only those in the top of the Series are given below.


Positive Ions or Cations: Ammonium>Potassium>Sodium >Magnesium>Calcium


Negative ions or Anions: Fluoride> Phosphate>Sulphate>Bicarbonate > Chloride>Nitrate


The effect of the denaturants will depend on the position of the ion in the series and its concentration in the water and perhaps on many other factors. In NCP well water the concentrations of sodium, calcium, magnesium, chloride and bicarbonate are relatively high. Although fluoride concentrations higher than 10 mg/L would be scarce, its position of being at the top of the anion list should be a matter of much concern to human health.


Hofmeister died in 1930 and his findings lay dormant for over a century. However, their implications are becoming the subject of lively discussions among scientists in many parts of the world today in Europe and the United States. Scholarly papers on the Hofmeister Series have been written by researchers at the National Institute of Diabetics and Kidney diseases in Maryland, USA, the Medical Centre of Stanford University, California and the European Molecular Biology Laboratory in Grenoble, France; and published in prestigious journals including Nature, Biophysics Journal and Journal of Biotechnology. Furthermore, an International Symposium on the Hofmeister Series was held at Queens College, Oxford University in 2012 organised by the Royal Society of Chemistry.


Prof. Chandre Dharmawardena, former Professor of Chemistry of the University of Ceylon and a former Vice Chancellor of the then Vidyodaya University and currently at the National Research Council in Ottawa, in an article published in the Journal of Environmental Geochemistry and Health (2014) suggested the possibility of high salt content in drinking water in the NCP wells as being a cause of CKDU owing to the Hofmeister effect.


The high salt content of the NCP well waters, the presence of major ions in the Hofmeister Series with fluoride leading the list of anions, and the non prevalence of CKDU in low-salt surface water drinking communities, suggest a strong association of salts and fluoride in well water with CKDU prevalence in the NCP.


Surface water vs well water as sources for human drinking


In the Palugaswewa study of well water mentioned above the researchers also studied the water quality of five small tanks in close proximity to the shallow wells. The names of the tanks are Palugas wewa, Alapath wewa, Yakadangath wewa, Udakawala wewa and Horiwila wewa. The EC values of the tank waters were 240, 290, 340, 610 and 680 micros respectively, all below the SLSI ceiling. These low values strongly suggest that much greater attention should be paid to utilising surface water for drinking purposes in the NCP.


Concluding Remarks


1. A large number of samples of well water collected from the NCP have shown high levels of salinity and are therefore not suitable for human drinking according to the SLSI standards.


2. A large number of samples of well water collected from the NCP have shown high levels of fluoride and are therefore not suitable for human drinking according to the SLSI standards.


3. The Electrical Conductivity values of five small tanks in Palugaswewa are low and below the stipulated SLSI limits for human drinking.


4. Much greater attention should be made to the utiisation of surface water sources such as streams, rivers and reservoirs for human drinking in the NCP.


5. The scarcity of CKDU cases in communities using pipe borne surface water for drinking, and from springs in Kebetigollawa, and the abundance of Hofmeister Series ions in shallow well water in the NCP suggest a strong association between soluble salts in water and CKDU.


6. Water quality of all water bodies in the country should be regularly monitored, inventorised and publicised so that tragedies as in the NCP do not occur elsewhere in the future.


Note: Details of the publications mentioned in this review may be obtained from the writer by emailing sa3546@gmail.com.


 
 
 
 
 
 
 
 
 
 
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