Radon is one of the sources of nuclear contamination in water and the largest contributor of the total radiation received by the general public from natural radioactive sources. Human exposure to high doses of radon through inhalation as gas or ingestion in water can lead to cancer. In this present work, the activity concentrations of Radon-222 (222 Rn) were investigated from fifteen (15) water samples collected at different locations within Dutsin-Ma town, Dutsin-Ma Local Government Area, Katsina State using
Liquid Scintillation Counter. The concentrations of Radon were found to range from (11.67-152.81⁄), (0.61-172.25⁄) and (21.98-47.17⁄) with mean values of 64.66⁄, 41.15⁄and 34.57⁄for Borehole, open well and Earth-Dam respectively. The results were
compared with the world average maximum contaminant level (MCL) of 10⁄set by World Health Organization and it was noted that 86.67% of the samples exceeded the value with 20% of the samples above the World recommended reference level of 100/. Also, the Annual Effective Doses due to ingestion of Radon in water for the three (3) categories of people were estimated from the measured radon concentrations and their mean values were found to be (0.472, 0.944, 3.304)/ in borehole water, (0.308, 0.616, 2.156)/ in well water and (0.252, 0.504, 1.764)/in surface water (Earth-Dam) for adults, children and infants respectively. All the mean values of the annual effective doses were above the recommended level of 0.1/set by World Health Organization as such it is recommended that the inhabitant of Dutsin-Ma town should always boil their water irrespective of it source before drinking so as to keep the concentration of Radon as low as reasonably achievable. Beside, further studies on the activity concentration of radon in water sources from Dutsin-Ma environs and other parts of Katsina State be carried out so as to determine the fitness of the water for consumption or otherwise.
1.1 Background of the study
Water is the major constituent of the Earth’s streams, lakes and oceans and the fluid of most living organisms. It covers about 71% of the Earth surface. It is vital for all known forms of life especially man. Man uses water for various reasons such as transportation, power generation, Agriculture and other domestic activities hence its availability and quality as regard radiological, microbiological, chemical and any other form of contamination are delicate and vital issues (Garba et al., 2008). Unfortunately, access to potable drinking water in most developing countries such as Nigeria is a major challenge hence most people rely heavily on untreated surface and ground water sources for consumption.
For instance, Dutsin-Ma local Government Area of Katsina State where its inhabitant rely solely on untreated groundwater sources (well and borehole) as well as surface water source. This is because there are only few available pipe born water sources and in most places where such sources are available they are not operational. The Zobe dam located in Dutsin-Ma which is intended to remediate this problem is yet to be completed by the government (Isah, 2009). It is therefore important to investigate the radiological content of ground and surface water sources in Dutsin-Ma town so as to determine it fitness for consumption.
Radon is a naturally occurring radioactive inert gas with a half-life of 3.82 days which is a member of the Uranium decay series (Somlai, 2007). It contributes the largest proportion of the total radiation from natural sources. Studies have shown that Radon-222 (222Rn) and its progeny contribute about 50% of the total effective dose equivalent from natural sources. Radon-222 is soluble in water. The concentration of radon in water is due to the decay of Radium-226 associated with the rock and soil. The Radon-222 gas penetrates through soil and rocks and dissolves in water (Xinwei, 2006). Normally, drinking water from ground water sources has higher concentration of radon than surface water.
The exposure of a population to high concentration of radon and its daughters for a long period has significant health effects ranging from respiratory functional changes to cancer of the lungs (BEIR, 1999). Also a very high level of radon in drinking water can lead to stomach and gastrointestinal tract cancer (Kendel and Smith, 2002).
In Nigeria, most areas lack established data on the activity concentration of Radon-222. Dutsin-Ma town, Dutsin-Ma Local Government Area, Katsina State is one of such areas from the survey of literature and Author’s knowledge, despite the fact that most of its inhabitant rely heavily on untreated surface and groundwater sources for drinking, agriculture and their domestic activities. Since its geology revealed that it is enriched in granite, it is possible that the concentrations of radon in both surface and groundwater sources in Dutsin-Ma town are higher than normal. This research seeks to address the problem of lack of baseline data/information on the activity concentration of Radon-222 in Dutsin-Ma town, Dutsin-Ma Local Government Area, Katsina State, Nigeria.
Our investigation reveals that access to potable source of water has remained one of the major challenges for most people as well as animals in Dutsin-Ma Local Government Area, Katsina State as such majority rely on untreated surface and ground water sources for consumption. This is quite dangerous since the geology of Dutsin-Ma Local Government Area, Katsina State (figure 7), revealed that it is highly enriched in granites and gneisses as studies have shown that high activity concentration of Radon-222 is associated with areas rich in granite (David et al., 1989; Gilbert, 1988). As such, the level of Radon-222 in drinking water which, in high concentration, can lead to a significant risk of stomach and gastrointestinal tract cancer (Zhuo et al., 2001), among others, need to be investigated. This is more so because our knowledge of its level of availability could be of great help in resource planning.