Radiological Risk Exposure to the Residential Area Adjacent to Liquor Company in Ado-Odo Ota, Ogun State, Nigeria

Background radiation levels and radionuclides assessment was conducted around the residential area adjacent to the Intercontinental Distillers (Liquor) Company located in Ado-Odo Ota, Ogun state using Gamma Ray Semi-mobile Spectrometer (Super Spec RS-125 Radiation detector). This study was carried out to determine the background gamma dose rate and the associated radiological risk exposure to the public living around the study area. The activity concentrations vary from 2.47 to 25.935 Bq/Kg, 28.826 to 62.52 Bq/Kg, 4.0 to 250.4 Bq/Kg for 238U, 40K and 232Th respectively. The activity concentration of the radionuclides (238-U, 40-K, 232-Th) field data was used to determine the radiological parameters. All the radionuclide activity concentrations found in the study/research area were below the International Reference Standard (IRS) except for Thorium, which surpassed the IRS. The estimated values ranged from 57.27 to 125.98 Bq/kg, 0.15 to 0.34 Bq/kg and 0.19 to 0.38 Bq/kg for radium equivalent, external hazard and internal hazard respectively. The numerically measured values of gamma dosage rates ranged from 26.4 to 59.0 nGy/h. This highest value was 59 nGy/h, which is higher than the 54 nGy/h safe level suggested by the United Nations Scientific Effect of Atomic Radiation (UNSCEAR). The research area’s hot spots that potentially endanger the health of nearby residents if proper precautions are not taken have been identified using a geospatial assessment of the background gamma radiation rate.

IOP Publishing doi:10.1088/1755-1315/1342/1/012031 2 Natural radiation is a component of the earth system and is found in a variety of geologic formations, including rocks, soil, and plants [1], [2].Man's survival is dependent on these geological formations, as he requires underground resources for the construction of offices, schools and homes, among other things.Natural radiation also contributes significantly to the outer section of the absolute total population; therefore, determining the gamma radiation portion is of particular value from a common source [3].Man is routinely exposed to varying degrees of ionizing radiation, depending on the concentration and duration.Gamma radiations are produced in the earth by naturally occurring radioactivity in the soil, hence altering the level of foundation radiations [4].On the earth, everyone is exposed to these fundamental dimensions of ionizing radiations.Thus, it is critical to determine the radiation level at a specific location, much more so when human activities are important, in order to avoid exposure to radiation that could affect one's health.
The principal elements associated with this Naturally occurring radioactive material (NORM) are uranium (226-Ra) and thorium (232-Th), as well as their decay products and primordial potassium radionuclides (40-K) found in the environment.Additionally, soil contains a previously identified natural radionuclide and its progeny.The composition of radionuclide environmental variation is determined by their geochemical properties and geological origin (Moreno et al., 2014).Internal exposure occurs as a result of 226Ra and 232Th and their various decay products, such as Radon (222Rn) and soil progenies, whilst the presence of ecologically monitored radionuclides results in the entire population receiving internal and external indoor exposure.Direct gamma (g) exposure results in external human exposure.Human radiation exposure is a scientific problem that has drawn public attention due to the fact that radiation found in nature accounts for the majority of human radiation exposure [1] and [4].Every person on the planet is exposed to varying levels of radiation [5].Therefore, humans should be aware of this exposure and its effects.Due to their high solubility and quality, 238-U, 232-Th and 40-K, are exceedingly concerning to people in a variety of locations on Earth There is an urgent need for a terrestrial background gamma dose rate and its potential risk zones adjacent to a largest liquor producing company in Nigeria located in Ado-odo Ota in Ogun State.Also, to identify the hotspots to better illustrate the objective of this paper.

Study Location
Iju is a forefront local area arranged in Ado-Odo Ota nearby government territory, Ogun State in Southwestern Nigeria.Iju is arranged between latitude 6o36' 38.6'' N and longitude 3o 5'8.5''E. The people/group lies at the connective course of Nigeria and the republic of Benin, it has straightforward route connection to Sango-Ota.The total population according to the population Census carried out in 2006 was viewed at approximately 50 000 plus.The local geology of the study area is shown in Figure 1.

INSTRUMENTATION FOR GAMMA RAY MEASUREMENTS
The instrument used in this study is a compact hand-held radiation locator (Super SPEC RS 125).This equipment is most suited for detecting naturally occurring radionuclides and presenting portions to understudies who live in close proximity to the waste site zone.The hardware is extremely precise, with estimated inaccuracies of less than 5%.It features an integrated structure that includes massive locator, data storage, direct readings and comprehensive climate control.
The front panel displays an overall RS-125 Super SPEC check at a refresh rate of 1/sec in cps.It has an abrasive straight tone that allows for unrestricted eye movement.It features headphone compatibility for reviewing loud areas, and the RS-125 Super SPEC variable rate scan method retains data in memory or transfers it through bluetooth to an external storage device.External GPS is included into the information stream via Bluetooth connectivity with surrounding information.
The RS-125 Super SPEC measurement provides immediate information on test concentrations in K (%), U (ppm) and Th (ppm).It also has user-selectable example energy for perfect testing.The RS-125 Super SPEC provides utility software for downloading memory information.All memory information is transferred by USB or bluetooth to the RS-Analyst on a personal computer.This can gather spectrum over 1024 channels, measure data, or output data in addition to GPS.Additionally, the application provides numerical and graphical information perspectives.It is also possible to resend the data as the content document's enemy.The radiation identifier was positioned one metre off the ground for each estimation purpose, readings were obtained many times at every point, and their normal set to assure precision.19 stations were estimated throughout the inquiry territory.Prior to beginning the estimation phase of the research, the instrument is given a 15 minute stabilize and balance out, as recommended by the manufacturer to ensure reliable results.GPS ranges (coordinates) for each station were recorded.The distance between the two stations was approximately 12 metres.Each section included a 90-second reading interval.The instruments employed were partial (ppm), the average values were obtained, and converted them to Becquerel per kilogram (Bqkg -1 ) according to IAEA, 1999.To avoid restriction, readings were not taken near patches of vegetation.Microsoft excel was used for the transformation of data

Results and Discussion
The combined activity concentrations of 238 U, 232 Th and 40 K measured in the study are shown in Figure 2 with the highest value of the radionuclides reported in station 5.This higher value found in station 5 may be the effect of waste channel of the liquor company.The lowest value of the activity was found in station 18 which is about 500 m away from the company.

COMPARING THE HIGHEST VALUE OF RADIONUCLIDES AGAINST INTERNATIONAL REFERENCE STANDARD IRS
The International Reference Standard (IRS) for radionuclides of U-238, Th-232 and K-40 (32,45,420 Bq/kg) was compared with the highest activity concentration of U-238, Th-232 and K-40 (25.9,62.5,250Bq/kg) in the study area shown in Figure 3.This current study for U-238 and K-40 are lower than the IRS by factors of 0.53, and 0.13 respectively, whereas Th-232 activity level reported higher than the IRS by a factor of 0.88.In the study area, Th-232 seems to be the radionuclide threat to the residence in the study area.The gamma dose rate, longitude, latitude, and elevation of field data are listed in Table 2.The field gamma dose rate data were used for the geospatial analysis map interpolation of background radiation in the study area.This geospatial analysis is to identify the hotspot regions in the study area and the zone that could pose health risks to the residents.Figure 6 shows the traced points on the spatial distribution of gamma dose rates in the study area.These surrounding of stations 5, 9 and 10, respectively are potential risk zones where the public could be avoided due to high radiation level.It also indicates that these zones are about 20, 50 and 80 m away from the possible source which is the liquor company.

Conclusion and Recommendation
The background gamma dose rates and activity concentration level of 40 K, 238 U and 232 Th were determined using a well-calibrated Super Spec RS-125 gamma spectrometer at Ado-Odo Ota, Ogun State, Nigeria.The estimated gamma dose rate is slightly higher than the recommended level, which identified station 5 as the potential risk zone that requires urgent attention.The measured concentrations of activity were utilised to delineate the equivalent effect of radiation metrics to determine the radiological hazard level to the area of study's populace.The measured radionuclides and estimated radiological metrics were correlated and compared with the International Reference Standard (IRS) and were within the recommended standard except Thorium (Th-232) that was slightly higher and the standard suggested by [1].The radiological parameters of AEDR was 5 times higher than the permissible limit.This showed that Thorium has high affinity of association to solid waste presumed to be from company and as well, low geochemical mobility.From the result, this study has identified the regions that may pose health implications to the general public living adjacent to the Intercontinental Distillers Company located in Ado-Odo Ota, Ogun state Nigeria.It has also found the stations with the highest radionuclides and the dominance nuclides that could cause such.Significantly, the areas closer to the company were the most prone zones to this gamma dose rates and higher radioactivity exposure.This study recommends more details of geochemical and traces elemental concentrations in the region to IOP Publishing doi:10.1088/1755-1315/1342/1/0120319 ascertain if the exposure is from radiological or chemical toxicity risks due to the waste channel from the company.Finally, it recommends that the government should make an effort to provide basic monitoring centres and device for radiation.

Figure 2 :
Figure 2: The Activity Values of 238 U, 232 Th and 40 K in the study area

Figure 3 :
Figure 3: Highest activity concentration against IRS

Figure 4 :
Figure 4: Identifies the locations of the hotspots on the base map of the sampling points

Figure 5 :Figure 6 :
Figure 5: The gamma dose rate distributions in the study area

Table 1 :
The acquired field data of the dose rate and the radionuclides ( 238 U, 232 Th and 40 K).

Table 2 :
The acquired field dose rate data used for gis interpolation of the spatial distribution