The health implications of exposure to radon gas (222Rn ) by humans in the indoor environment is a major public concern worldwide. The aim of this paper is the measure the indoor and outdoor exposure rate at different heights and determines the annual effective dose and lifetime cancer risk of residents of six different settlements in Emelogu Community of Odua /Abua local Government Area of Rivers State. In-situ measurements of indoor and outdoor exposure rate of six different settlements were done using a well calibrated radiation Alert-100. The highest indoor and outdoor exposure rate of 0.0237 ± 0.014mRh-1 and 0.0181±0.002mRh-1 respectively were recorded in mud houses. The indoor annual effective dose ranges from 0.54mSvy-1 for concrete not plastered houses to 0.949mSvy-1 recorded in mud houses. Resulting average of the annual effective dose is 1.06 mSvy-1, which is large as compared to the worldwide average of the annual effective dose 0.48 mSv. Whereas outdoor effective doses calculated ranges from 0.204mSvy-1 in burnt mud house to 0.253mSvy-1 recorded around mud houses which results in total mean outdoor effective dose of 0.48mSvy-1. . Estimated excess lifetime cancer risk (ELCR) from indoor AEDE ranges from 1.90 x 10-3 to 3.32 x 10-3 recorded in CNP and MD respectively and ELCR from outdoor ranges from 0.715x 10-3 to 0.887x 10-3 recorded burnt in mud house. Resulting average of the excess lifetime cancer risk is 4.21 x 10-3, which is large as compared to the resulting worldwide average 0.29 x 10-3. The reduction coefficients were obtained by taking the ratio of the indoor and outdoor dose rates. This paper shows that outdoor dose rates decreased as the measurement height increased, whereas the indoor dose rates increased as the height increased and that indoor dose rates at the centers of each houses were lower than other locations on this same room. Therefore residents should spend more time at the centers of their homes and also use smaller windows to reduce their exposure.
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