Assessment of Radiation Exposure Levels and Associated Health Risks in Calabar Free Trade Zone, Nigeria

Exposure to chronic levels of ionizing radiation could be detrimental to health even at very low doses. Calabar free trade zone (CFTZ) was established to promote export business in Nigeria and it is yet to produce exposure data of the Zone.
The Zone was divided into three categories depending on the type of business. Category A had facilities with manufacturing businesses, Category B was service providers while Category C was oil and gas businesses. Exposure levels within the CFTZ were measured with exposure meter and results obtained were converted to annual effective dose in mSv/yr. The evaluated doses were used to estimate health risks to workers in the Zone in terms of lifetime cancer incidence and mortality for persons aged between 18 – 65 years using the conversion factors in BEIR VII.
Category B facilities had dose values between 0.21 – 0.31 mSv/yr followed by Category A with dose values between 0.23 – 0.35 mSv/yr. Category C facilities had the highest dose values between 0.33 – 0.40 mSv/yr. The evaluated cancer incidence and mortality rates were generally less than 2 persons in 1,000 persons for both male and female workers.
The study shows that the exposure levels in business facilities within the CFTZ were higher than the background radiation level. The effective doses were not uniform for the different categories. The estimated cancer incidence and mortality were low, and simple linear equations were generated to relate cancer incidence to mortality.