ABSTRACT
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.
CHAPTER ONE
INTRODUCTION
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.