Heavy metals, gods, CKDu and govt. policy
Prof. R. O. Thattil
University of Peradeniya
Many articles have been written on possible causes of Chronic Kidney Disease of unknown aetiology (CKDu). Many factors have been suggested as the cause of CKDu. However, the results are based on single factors and univariate analysis. Some research articles are also not based on good scientific principles. Some appear to be guesswork. In one case arsenic has been implicated, and the origin of the suspicion attributed to a God. With respect to the role of Cadmium in the causation of CKDu the articles written carry divergent views. The final report of the World Health Organization (WHO) on “Identification and evaluation of CKDu in Sri Lanka” although informative on some aspects is not conclusive and lacks scientific investigation. The biggest problem is however, when government policy is based on such reports.
The WHO report deals with the establishment of a hospital based CKD registry, establishment of a literature repository for CKD and population prevalence, analytical and environmental studies.
The establishment of a hospital based CKD registry is a very important step in studying diseases of uncertain aetiology. However, the analysis performed on the data is unsatisfactory, since it is based on categorical variables which were dichotomized, analyzed individually and interpreted based on odds ratios (which is a simplistic form of analysis). Obviously this type of analysis is not sufficient to attribute CKDu to any particular cause. This is also stated in the WHO report.
In the population prevalence, analytical and environmental studies conducted by the WHO, no attempt has been made to consider multiple factors and their interactions in the planning of the study as well as in the analysis. The references quoted are divergent on the role of Cadmium in the causation of CKDu in Sri Lanka. The results also imply that fertilizer application could be the source of Cadmium, Lead and Arsenic. A very guarded statement ! However, these elements have not been detected in sufficient quantities in the water sources. Overall the statements made in the discussion are very superficial with no attempt being made at recognizing that CKDu can be caused by a multiplicity of factors. It is also worth noting that factors need not be independently associated while interactions between factors are more likely. Interactions can also mask main effects and therefore Univariate analysis will be non – conclusive.
The conclusions reached in other studies are diverse and questionable. No attempts have been made to treat the cause of CKDu as a multivariate problem. No multivariate analytical procedures have been used. Therefore, no valid conclusions are possible. Whatever model used for the study should include interaction effects, while proper sampling techniques should be used to obtain data. I do not want to talk about the involvement of Gods in pinpointing the problem as it is not my field.
According to the Registrar of pesticides, Arsenic has not been detected in pesticides used in Sri Lanka except for 3 of the 24 pesticides. Even in these cases the levels of Arsenic found were very low. Contrary results have also been published by some authors. A close perusal of these articles show that proper sampling procedures as set out in the pesticides act no. 33 of 1980 have not been followed. Analysis of pesticides for heavy metals have to be performed by properly accredited institutes.
CKDu is a very serious problem in Sri Lanka and we should find ways of means of finding the related causes which will then lead to preventive measures. Piecemeal research is not going to help. What is needed is a multidisciplinary term of scientists to investigate all aspects of the CKDu problem.
Government policy with regard to the problem should not be based on half baked studies and flimsy conclusions. Is reduced use of fertilizer and agrochemicals going to solve the problem ? Fertilizer and agrochemicals are used in all parts of the Island. If then, why is CKDu predominantly present only in the North Central Province ? There may be many other factors involved. The genetic factor and its interactions with other variables have not been studies at all. There are those who swear that rice contains unacceptable levels of heavy metals whose source is the fertilizer and agrochemicals applied to rice. But, they eat the same rice that is eaten by the farmers of the NCP and have no problems! The WHO quite clearly states that Cadmium levels in rice is less than allowable limits.
Policy making bodies of the government must step with caution when basing policies on a very weak WHO report. After all it is the country that is going to suffer by such deeds. The mere presence of heavy metals is not a matter of alarm. After all Arsenic is ranked as 20th in its abundance in the earth’s crust.
Courtesy of The Island August 2, 2013