CHAPTER ONE

INTRODUCTION

1.1 Background of the study Drinking water sourced from deep wells and boreholes are usually expected to have high concentration of radioactive nuclides. This is because they pass through fractures in bedrocks or within the soil which contains minerals deposits that might have radioactive constituents and thus leaking into the waterways. Radioactivity in drinking water is one of the major ways in which radionuclides from the environment gets into the human body, which might consequently lead to radiation-induced disorderness (USEPA, 2010). There is evidence from both human and animal studies that radiation exposure at low to moderate doses may increase the long term incidence of cancer and that the rate of genetic malformations may be increased by radiation overexposure (Otton, 1994). It is therefore important to determine the amount of radioactivity in drinking water for every area where people live in, so as to guard against its health hazards (WHO, 2006). Groundwater could be contaminated by radioactive materials because terrestrial radioactivity increases with depth in the earth crust (WHO, 1998). These radioactive materials occur naturally and of most concern are the uranium and thorium series and the progenies (radon and thoron). They contribute to the radioactivity of the rain and groundwater which in turn affects drinking water. Due to these, drinking water from deep wells and boreholes are expected to contain high concentrations of radioactive elements. Radioactive materials could also be washed into wells, boreholes and even enter through burst pipes. Important radioactive elements in drinking water are tritium, potassium-40, radium and radon which are alpha or beta emitters (Surbeck, 1995). People who ingest polluted water can develop illness and with prolonged exposure to radioactive polluted water could cause cancers, toxicity of the kidneys or bear children with birth defects (WHO, 2006). Knowledge of the naturally occurring radionuclide present in drinking water enables one to assess any possible radiological hazards to humans by the use of such water. Manmade pollution of water is divided into two kinds: point source which is caused by the discharge of pollutants from specific location for example discharge from factories sewage treatment plants and oil tankers into rivers, and non-point source which occurs from rainfall or melting of snow and the run-off washes away pollutants into lakes, rivers and coastal waters. Industrial waste is the most common source of water pollution in the present day (Ogedengbe and Akinbile, 2004) and it increases yearly due to the fact that industries are increasing because most countries are getting industrialized. Industries vary in size, nature of products, characteristics of waste discharged and the receiving environment. The major industrial categories in Nigeria are metals and mining, food, beverages and tobacco; breweries, distilleries, textile, leather products, wood processing and manufacture, furniture, pulp and paper industries and chemical and allied industries. Industrial effluents contain toxic and hazardous materials from the wastes that settle in river water as bottom sediments and constitute health hazards to the urban population that depend on the water as a source of supply for domestic uses (Akaniworet al, 2007). Groundwater quality is defined based on a set of health and safety regulations for domestic use. The World Health Organization (WHO) guidelines for drinking water suggest performing an indirect evaluation of committed dose by measuring gross alpha and beta radioactivity and checking compliance to derived limit; the proposed limits are 0.1Bq/l for gross alpha and 1.0Bq/l for gross beta radioactivity(WHO, 2003).

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