The serious health effects connected with the presence of uranium, a naturally occurring radioactive element in drinking water sources from different parts of the world and more recently in some parts of India (Kansal et al., 2011; Nagaiah et al., 2013 etc.) have been widely reported. The centre had asked states to check the water quality index for the presence of uranium following these reports.
Drinking water sources can be contaminated with uranium to an extent by certain anthropogenic activities like uranium mining and processing, disposal of spent nuclear fuel, etc. However, the major reason for uranium contamination is the local geological depositions. Leaching of uranium containing minerals like Uraninite, Pitchblende, Coffinite etc. can result in uranium introduction into aquifers.
According to Cothern and Lappenbusch (1983), the major route of exposure of uranium in humans is oral and about 85% of it is through drinking water. When ingested, uranium can induce both radiological and chemical toxicity in humans (Sharma et al., 2012). Moreover, uranium will get deposited in bones and kidney, when it is not excreted through urine (ATSDR, 1999; Kurttio et al., 2002; WHO, 1998; Wrenn et al., 1985).
A recent study by Bhabha Atomic Research Centre for mapping of uranium content in drinking water sources across India indicates uranium was detected in 83.6% of all the collected water samples.
Uranium content in 98% of groundwater samples was within the national limit fixed by the Atomic Energy Regulatory Board for radiological safety, as per the study published in Current Science. Also, no surface water samples exceeded the prescribed regulatory limit.
A recent study by C S Shalumon et al in the journal HydroResearch is an attempt to develop a data base on uranium in drinking water sources of five different districts (Palakkad, Thrissur, Ernakulam, Idukki and Kottayam) of Kerala, India during the pre and post-monsoon seasons.
Also, the area covered under this study has high degree of geographical variability (three zones - south, central and north Kerala) which can significantly induce diversity in water quality of the area. The current study also attempted to estimate the degree of suitability of currently available water for drinking purpose by analyzing the various water quality parameters as well.
According to the analysis done by researchers at the School of Environmental Sciences (SES), MG University, the presence of uranium was positively detected in 91 samples (21.92%) collected in pre-monsoon and 89 samples (21.44%) in post-monsoon period. The concentration of uranium was found to be varying from less than 0.5-12.54 μg/L in pre-monsoon and less than 0.5-5.93 μg/L in post-monsoon, which is well within the standard limit, i.e. 30 μg.
A total of 830 samples in pre-monsoon and post-monsoon season were collected from the study area and were analyzed for uranium concentration and 11 other water quality parameters. They were from different sources like wells (290), bore wells (44), public pipelines (50) and surface water from sources like streams and dams (31).
The spatial and temporal variability in uranium concentration and water quality index were represented as thematic maps using ArcGIS 9.3.1.
The concentration of uranium in the study area showed a maximum of 12.54 μg/L which is well within the allowed limit. The WQI values indicating that more than 90% of the sampling water sources are suitable for drinking water usage and a very low number is in the unsuitable category (<10%).
It shows that the majority of the water sources in the study area are suitable for drinking purpose and those sources are devoid of any considerable toxic effects of uranium since the concentration of uranium is very low and well within the international and national standards.
While conducting the study, 11 other parameters were checked of the drinking water quality index in pre and post-monsoon. The monsoon has been a blessing in that there is a lot of cleansing of surface water, and hence the contamination levels post-monsoon was much less. Most of the water samples analyzed during the study were found to be in the ‘Excellent’ and ‘Good’ categories.
Among all five districts, Idukki has the most samples in the “Excellent” and “Good” categories. None of the samples from Idukki had an “unsuitable” quality of water in both seasons. Kottayam district has the highest number of water sources which are under the “Unsuitable” category in the post-monsoon season (19.75%) followed by Thrissur in the pre-monsoon season (9.2%).
It is found that the uranium concentrations in all the five districts were heterogeneous in distribution. Among the five districts, Palakkad district showed maximum variation in uranium concentration and Ernakulam and Kottayam district had comparatively less variability in pre-monsoon season. Whereas, there is not much difference in uranium concentration distribution among the sampling groups in post-monsoon except for Idukki.
Most of the samples are having lower concentration of uranium especially in the post-monsoon season. But 37 samples (8.95%) in pre-monsoon and 26 samples (6.26%) in post-monsoon exceed the limit of 1.9 μg/L suggested by International Commission on Radiological Protection (ICRP, 1995).
The result of the present study was compared with the concentration of uranium reported from other areas in India from previous studies. It is clear that the concentration of uranium in the study area is much lower compared with the previous reports from some other parts of the country. Also uranium concentration well coincides with similar studies which were reported from the nearby regions.
For example, Ben Byju et al. (2012) studied the presence of uranium in drinking water in Southwest coast of Kerala and it was found that the concentration was in the range 0.31–4.92 μg/L. Also Reeba et al. (2011) and Prabhu et al. (2008) reported comparable concentrations of uranium from certain other areas which is close to the present study area.
A correlation analysis to find the relationship between the presence of uranium and other water quality parameters indicates no correlation.