GAMMA RADIATION LEVELS IN THE NIGERIAN ENVIRONMENT By

There are few available data on radiation levels in the Nigerian environment. Pilot measurements of absorbed dose levels of radiation in several towns in Nigeria were made. Although higher elevated and mine areas showed higher absorbed doses, the levels encountered were within normal limits when compared with data in literature but well below those reported in higher radiation areas of the world. This preliminary study has assumed added relevance because, the Chenobyl, recent nuclear accidents and the dumping of 'radioactive' wastes on Nigeria coastlines have shown that radiation does not observe national or regional boundaries. The need for researchers in this field to obtain national background effective dose for Nigeria is emphasized. INTRODUCTION In many countries of the world, there have been concerted efforts made to estimate the levels of natural radiation in the environment. Thus data are available for total natural radiation in Sweden, Austria, Hungary. Poland and Great 1 Britain. The background measurements in these industrialized countries became imperative in order to assess the 2,3,4 increased risk factors arising from the introduction of nuclear devices, such as nuclear weapons, reactors, radiochemicals and other artificial sources of radiation. The recent nuclear station accident in Chenobyl, USSR from which rad ioac t i ve dust escaped in to neighboring countries by wind, food items and even by mail, underlies the importance for proper surveillance of radiation levels in an environment. To date, data from the less industrialized countries especially of the southern hemisphere are fragmentary. Thus the 5,6 contributions of various mines, 4,7 8 building materials and altitude on background radiation in a country like Nigeria, is not yet fully well documented. In this communication, we report on problems encountered in a concerted surveillance of outdoor background radiation in some Nigerian towns. With the increased industrialization of even the rural communit ies, recent telecommunication equipment like masks, many surface and underground exploration mines, the natural radiation load and exposure risks, need to be delineated. MATERIALS AND METHODS Natural background radiation was measured with a Mini-instrument environmental detector Type 6 80 with MC 70 Geiger Muller Tube. The instrument was pre-calibrated by the Central Electricity Generating Board of Great Britain. The equipment is such that the distance of the probe from the material being measured can be adjusted to a distance approximately 0.5 meter off the surface of the ground. Five consecutive meter readings for 100 seconds in a central location of a town or borough were averaged: all readings were therefore converted into dose equivalent in micro Sievert/year. Water and soil samples were counted for radioactivity in two different gamma counters, LKB mini gamma and a Beckman Instrument model and the results were averaged and expressed in Bacquerels (the units of number of disintegrations per second). RESULTS Table 1 shows the location in the country where background radiation levels were BACKGROUND GAMMA RADIATION LEVELS IN THE NIGERIAN ENVIRONMENT By Fidelis I Obioha, Ph.D and Paul O. Okonkwo, Ph.D. From the Departments of Radiation Medicine and Pharmacology and Therapeutics, University of Nigeria Teaching Hospital (UNTH), Enugu, Nigeria. Address for reprints: Prof. P.O Okonkwo, Department of Pharmacology and Therapeutics, U.N.T.H, P.M.B 01129, Enugu, Nigeria.