Abstract:
All living organisms continuously are exposed to natural radiation, which contributes
most of the effective dose equivalent they receive. Radon, a naturally occurring colorless,
tasteless and odorless radioactive gas is one of these radiations. The gas exists naturally
in various environmental media such as water, geological sediments and air. It has gained
focus since it is the largest contributor to radiation doses received by the human
population via inhalation and ingestion posing great health risks. The main objective is
to determine the radon levels in underground waters in Mutomo Sub County, in Kitui
County using the RAD 7 alpha detector. The study further examined the radium levels in
sediments collected from the proximity of sampled water sources using high purity
germanium (HPGe) gamma-ray spectrometer to establish the correlation with radon in
water. The radon concentration in water ranged from 0 - 120±6 kBqm-3 with an average
value of 30±1.5 kBqm-3 which is above the recommended limit of 11 kBqm-3 suggested
by US-EPA, WHO and EU bodies. The calculated values for the absorbed dose are in the
range 1.26 - 3.24 mSvy−1, which is well below the recommended level. The annual
effective dose (AED) via ingestion averaged 0.006±0.0003 mSvy-1 while the radon in air
from water averaged 0.07±0.003 mSvy-1, which are both below the safety limit of 0.1
mSvy-1 recommended by WHO 2004, and ICRP 2005 for ingestion and inhalation.
Radium in sediments reported an average of 41 ±2.07 Bq/Kg which is above the world’s
average of 35 Bq/ kg reported in UNSCEAR reports. The radiation doses in water from
sampled underground water are insignificant to term the water unsuitable for drinking
and other domestic purposes. Correlational analyses between radium in sediments and
radon in the water reported a weak positive coefficient suggesting a difference in the
geological composition of surface matter and underground aquiver holding water.
