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 Table of Contents 
ORIGINAL ARTICLE
Year : 2022  |  Volume : 45  |  Issue : 1  |  Page : 33-40  

Radiological assessment of petroleum products in Aniocha South Local Government Area of Delta State, South-South Nigeria


1 Department of Science Laboratory Technology, Delta State Polytechnic, Ogwashi-Uku, Nigeria
2 Department of Radiology, Medical Physics Unit, Federal Medical Centre Asaba, Asaba, Delta State, Nigeria
3 Department of Cancer Biology and Therapy, University of Central Lancashire, Preston, United Kingdom

Date of Submission26-Feb-2022
Date of Decision22-Mar-2022
Date of Acceptance23-Mar-2022
Date of Web Publication28-Jun-2022

Correspondence Address:
Akintayo Daniel Omojola
Department of Radiology, Medical Physics Unit, Federal Medical Centre Asaba, Asaba, Delta State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/rpe.rpe_5_22

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  Abstract 


Monitoring the background levels from petroleum products is essential because of the everyday use and the increasing number of fuel, diesel, kerosene, and gas stations in Delta State, Nigeria. The study aims to determine the background ionizing radiation (BIR) in milli-Roentgen per hour (mR/h), absorbed dose rate (ADR) (nGy/h), and annual effective dose rate (AED) (mSv/year) in selected fuel, diesel, kerosene, and cooking gas-dispensing stations in Aniocha South Local Government Area of Delta State. The study was carried out using a calibrated Geiger Muller detector (Radiation Alert Inspector) in count per minute mode for point measurements and a geographical positioning system for determining the longitude and latitude of each point where measurements were taken from. The mean outdoor BIR, ADR, and AED were 0.011 ± 0.002 mR/h, 91.6 ± 19.5 nGy/h, and 0.11 ± 0.02 mSv/year, respectively, with 84% of the BIR below the world average. The mean BIR was below the world average while the ADR and AED were above it. Kerosene stations had the highest BIR. The outdoor measurements from this study were comparable to similar articles with slight variation. The study shows that the attendant and customers were safe in the areas where this study was conducted.

Keywords: Background ionizing radiation, count per minute, global positioning system, permissive dose rate, radionuclide


How to cite this article:
Ijabor BO, Omojola AD, Omojola FR, Chukwueke FC, Azuka PK, Agama P, Okafor FM. Radiological assessment of petroleum products in Aniocha South Local Government Area of Delta State, South-South Nigeria. Radiat Prot Environ 2022;45:33-40

How to cite this URL:
Ijabor BO, Omojola AD, Omojola FR, Chukwueke FC, Azuka PK, Agama P, Okafor FM. Radiological assessment of petroleum products in Aniocha South Local Government Area of Delta State, South-South Nigeria. Radiat Prot Environ [serial online] 2022 [cited 2022 Nov 27];45:33-40. Available from: https://www.rpe.org.in/text.asp?2022/45/1/33/348731




  Introduction Top


The earth is known to contain several radioactive elements that occur naturally as deposits within the earth's crust.[1] They are either from the cosmic ray which comes from outer space or rock and soil. The latter primarily have a deposit of artificial elements which is both beneficial and harmful to human.[2] Rock, soil, and groundwater are primary sources of potassium 40, uranium 238, and thorium 232. They undergo spontaneous disintegration to produce daughter particles such as radium (228Ra, 226Ra, and 224Ra) and radon with the emission of either alpha, beta, or gamma particles.[3],[4],[5],[6],[7]

The geological formations that contain oil and gas deposits also contain naturally-occurring radionuclides, which are common during exploration as waste products. A study by Al-Saleh and Al-Harshan in Riyadh City, Saudi Arabia, has shown that the concentrations of the naturally-occurring artificial elements in petroleum wastes were higher than that of the petroleum products.[8] Further, studies have shown that there might be residual radionuclides such as radium and other radioactive elements that may dissolve in brine and settle to form sludge that accumulates in tanks and pits or forms mineral scales inside pipes and drilling equipment.[9],[10] The International Atomic Energy Agency Safety Report No. 34 has discussed in detail radiation protection programs during exploration involving external exposure.[11] There may be a need to similarly carry out radiation monitoring programs during the loading of trucks with refined petroleum products and during delivery of the product at various petrol stations.

Studies have shown that there is poor knowledge of radiation protection in the environment by the public;[12],[13],[14] this was also the case in a short interview with the petrol attendants in the studied areas in Aniocha South Local Government Area (LGA), who barely have radiation protection awareness. Educational background may be another factor that may limit their knowledge, although this fact has not been investigated. Over the years, the number of petrol stations in Nigeria is on the rise due to the increase in the population size, and it has been known as a lucrative business among the people. Usually, a petrol station in Nigeria may sell any of the products (fuel [premium motor spirit], diesel, kerosene, and cooking gas) or a combination. Avwiri et al. have assessed the level of radiation in oil and gas field in Ughelli in Delta State, Nigeria, using a Digilert nuclear radiation monitor, while Agbalagba et al. have also measured background radiation in selected oil and gas fields in host communities in Delta State, Nigeria, using the same survey detector as Avwiri et al. Both studies assessed the level of background ionizing radiation (BIR) level in relation to the permissive dose rate and other dose rate quantities.[15],[16]

The mean background radiation around the world is known to be 2.4 mSv/year (0.032 milli-Roentgen per hour [mR/h]) based on the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) report from large surveys;[17] this value can vary from one geographical location to another, depending on the activities of the naturally-occurring radioactive materials.[17],[18],[19] In some areas around the world, it can be between 1 and 10 mSv/year and can be more than 50 mSv/year in places in Brazil and Sudan.[18] Extremely high values have been recorded in places in Kerala in India with up to 70 mGy/year,[18],[19] while Derin et al. have reported a mean absorbed dose rate (ADR) of 9795 nGy/h in the same region in India;[20] however, there has been no evidence of cancer-related cases in places where these values are high, but chromosome aberrations have been identified from samples collected.[21]

The focus of this study is in Aniocha South LGA, which lies in the Northern region of the Niger Delta Basin (latitude N06° 00.4200 and longitude E06° 36.3270), with an area of 868 km2. The purpose of the study is to measure the BIR levels from the fuel, diesel, kerosene, and cooking gas points among the selected petrol stations in the above LGA. Similarly, this study estimates the ADR (nGy/h) and annual effective dose rate (AED) in mSv/year in selected fuel, diesel, kerosene, and cooking gas-dispensing stations in Aniocha South LGA of Delta State. In addition, a comparison is also made with the mean world values and related articles.


  Materials and Methods Top


This research was a prospective study over 3 months, involving the use of fuel, diesel, kerosene, and gas stations that are occupied by staff and personnel for an average of 8 h per day. The convenience sampling method was used to select filling stations and gas stations, depending on how accessible they are. Fuel, diesel, kerosene, and gas stations that are not in operation were excluded from the study.

Data were collected externally in 17 petrol stations, having either fuel, diesel, kerosene, and cooking gas in Issele-Azagba (2), Azagba-Ogwashi (1), Ogwashi-Uku (9), Ewulu (1), Nsukwa (2), and Ejeme-Aniogor (2), respectively, as well as 3 gas stations located in Azagba-Ogwashi (1) and Ogwashi-Uku (2), respectively. A global positioning system (GPS) instrument and an inspector USB survey meter calibrated in a Secondary Standard Dosimetry Laboratory in the National Institute of Radiation Protection and Research, University of Ibadan. Oyo State, Nigeria, was used [Figure 1] and [Figure 2].
Figure 1: The geographical positioning system used from an Android phone

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Figure 2: Digital radiation meter: An inspector USB survey meter

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The calibrated inspector USB survey meter was used for radiation measurements. The inspector USB survey meter (S.E. International, Inc.), which is a health and safety instrument, can be operated to detect low levels of radiation. The instrument is designed to measure ionizing radiations such as alpha (α) and beta (β) particles, gamma rays (γ), and X-ray radiation. The survey meter is calibrated in mR/h and count per minute (CPM) or SI units' micro-Sievert per hour (μSv/h) and count per second (CPS) with an operating range of 0.001 (1 μR) to 100 mR/h or 0–350,000 CPM. The technical specification of how it functions is shown in [Table 1]. Similarly, the GPS applications software was downloaded on an Android Phone and was used to measure the longitudes, latitudes, and elevations of points for all the studied areas. Measurements were made by positioning the survey meter at 1 m above the ground level and at 30 cm away from the fuel, diesel, kerosene, and gas pump area. Likewise, the GPS was kept alongside the survey meter to determine the position on the earth's surface. Measurements were taken from three points per source and an average value was determined to estimate the exposure rate.
Table 1: Survey meter technical specifications

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The survey meter was used on the CPM mode and measurement was timed for 3 min in other to get stable values. Conversion to mR/h was carried out using the meter's calibration factor (3340 CPM/mR/h). The relationship between CPM and mR/h was given as:[22]



Where x = count recorded by the survey meter in CPM.

Measurement with both detectors was done simultaneously on the same point, and the data were entered in a record book for documentation. The BIR measurement was computed in CPM and was converted to mR/h using equation (1).

The ADR was estimated based on the Canadian Health and Safety Code 35 for the installation, use, and control of X-ray equipment, which is given as:[23]



The AED was given as:



AED was calculated using the dose conversion factor of 0.7 Sv/Gy as recommended (UNSCEAR, 1993) for the conversion coefficient from the absorbed dose in air to the effective dose received by adults and an occupancy factor of 0.2 for outdoor exposure.[24]

Statistical analysis

The study used descriptive statistics (mean, median, and standard deviation); we used a one-sample t-test to evaluate the significance of the mean of the products, and an independent sample t-test to assess if there are statistically significant differences between the two means. Similarly, it would use one-way ANOVA to test if the mean for all areas in the filling station is the same or otherwise. In addition, Pearson's correlation would be used to determine the association at the different product (fuel, diesel, kerosene, and cooking gas) points. P < 0.05 shall be considered to be statistically significant and vice versa.


  Results Top


Map indicating the points of measurements in Issele-Azagba, Azagba-Ogwashi, Ogwashi-Uku, Ewulu, Nsukwa, and Ejeme-Aniogor is shown in [Figure 3].
Figure 3: Map showing areas where fuel, diesel, kerosene, and gas stations are located

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BIR measurements were taken at various petrol and gas stations as indicated in the map, respectively [Figure 4].
Figure 4: Map showing background ionizing radiation measurements

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The mean outdoor measurements (BIR, ADR, and AED) from the fuel area in the 17 fuel stations (F1–F17) was 0.011 ± 0.002 mR/h, 87.2 ± 15.7 nGy/h, and 0.11 ± 0.02 mSv/year, respectively. The maximum and minimum BIR values were seen in F9 (0.014 mR/h) and F7 (0.008 mR/h), respectively. One-sample t-test showed that there was a statistically significant difference in the BIR values from the 17 stations (P < 0.001) [Table 2].
Table 2: The geographical location and mean background ionizing radiation, absorbed dose rate, and annual effective dose measurements in the fuel (F) selling point

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Similarly, the mean outdoor measurements (BIR, ADR, and AED) from the diesel area in the 10 diesel stations (D1–D10) was 0.010 ± 0.002 mR/h, 81.7 ± 13.6 nGy/h, and 0.10 ± 0.02 mSv/year, respectively. The maximum and minimum BIR values were seen in D4 (0.014 mR/h) and D14 (0.007 mR/h), respectively. One-sample t-test showed that there was a statistically significant difference in the BIR values from the 10 diesel stations (P < 0.001) [Table 3].
Table 3: The geographical location, mean background ionizing radiation, absorbed dose rate, and annual effective dose measurements in the diesel (D) selling point

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Furthermore, the mean outdoor measurements (BIR, ADR, and AED) from the diesel area in the 5 kerosene stations (K1–K5) was 0.012 ± 0.003 mR/h, 107.5 ± 29.8 nGy/h, and 0.13 ± 0.04 mSv/year, respectively. The maximum and minimum BIR values were seen in K5 (0.018 mR/h) and K6 (0.009 mR/h), respectively. One-sample t-test showed that there was a statistically significant difference in the BIR values from the 10 diesel stations (P = 0.001) [Table 4].
Table 4: The geographical location, mean background ionizing radiation, absorbed dose rate, and annual effective dose measurements in the kerosene selling point

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The mean outdoor measurements (BIR, ADR, and AED) from 3 gas stations (selling point and depot) (G1–G6) were 0.012 ± 0.002 mR/h, 101.6 ± 19.7 nGy/h, and 0.12 ± 0.02 mSv/year, respectively. The maximum and minimum BIR values were seen in G1 (0.016 mR/h) and G5 (0.010 mR/h), respectively. One-sample t-test showed that there was a statistically significant difference in the BIR values from the 10 diesel stations (P < 0.001) [Table 5].
Table 5: The geographical location, mean background ionizing radiation, absorbed dose rate, and annual effective dose measurements in the cooking gas selling and depot point

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Comparison of the mean BIR, ADR, and AED measurements in the fuel, diesel, kerosene, and cooking gas in the stations against the UNSCEAR 2000 report is presented in [Table 6].
Table 6: Comparison of the mean measurements in this study with other articles and world values

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  Discussion Top


The study has determined the mean BIR, ADR, and AED in the studied population. The mean BIR value was noticed to be within acceptable range compared to the public permissive value of 0.013 mR/h (1 mSv/year), with 84% of the total BIR below the world mean value. The ADR and AED in this study were above the world mean values. There was generally no significant difference from an independent sample t-test in the mean measurements for the fuel, diesel, kerosene, and cooking gas selling/depot points, respectively (P > 0.05). One-sample t-test shows that there was difference in mean BIR among the various sources (fuel, diesel, kerosene, and gas) measured (P < 0.001). There were also statistically significant differences in ADR and AED with P < 0.001, respectively. The maximum BIR was from kerosene product. However, these values did not exceed the recommended value. This result indicated that the risk was negligible. It also indicated that the petroleum products pose no risk to the workers and the general public in the studied areas.

Comparison with other outdoor studies

The range of the BIR in this study was slightly higher than the lower limit and was lower than the upper limit (0.0072–0.0180 mRh−1) compared to a study carried out in Warri, Delta State, by Agbalagba et al., where the measured mean exposure rates ranged from 0.006 to 0.0290 mR/h. 16% of the BIR from this study exceeded the recommended permissive dose rate compared to Agbalagba et al., where 68% of the total BIRs were exceeded. The difference in BIR may be due to activities in the geographical locations. There is oil exploration and gas flaring activity in Warri, where Agbalagba et al. conducted their research. This may have increased BIR slightly in comparison with this study.[25] The overall mean BIR, ADR, and AED in this study were lower compared to those obtained in Agbalagba's study.

Further, this study was compared with a study by Ugbede and Benson, who investigated radiation level in Emene Industrial Area in Enugu State. The mean BIR from their study (0.015 mR/h) was higher than this study (0.0110 mR/h), with a variation of 22%. Similarly, the average ADR in their study was (126.15 nGy/h) higher compared to this study (91.579 nGy/h), by a variation of 22%. The same trend was noticed for AED where the values obtained were slightly higher than what we obtained. Causes of the differences observed are due to industrial activities, which may have slightly increase background radiation level.[26]

The range in BIR (0.0072–0.0180 mR/h), ADR (62.64–156.60 nGy/h), and AED (0.008–0.192 mSv/year) was lower than a study by Avwiri et al., who investigated occupational hazards from outdoor radiation in oil field facilities in Rivers State in Nigeria, where their BIR was 0.014–0.027 mR/h, ADR was 120.4–234.2 nGy/h, and AED was 0.12–0.26 mSv/year. The dose rate discrepancies observed could be due to other environmental conditions. The oil field is considered to have more air pollution and spills, which may contain little quantities of radioactive elements compared to our study.[31]

The mean in BIR measurements from this study (0.011 mR/h) was slightly lower compared to a study (0.015 mR/h) by Agbalagba et al., who investigated BIR levels around fossil fuel and gas-dispensing stations and assessment of their radiological risk implications. Similarly, the ADR and AED from their study were above our estimated measurements. However, independent sample t-test shows that there was no statistically significant difference in BIR and other parameters that was estimated (P > 0.05). Differences may be due to detector used and other environmental factors.[27]

The outdoor ADR measurement in select region of AL-Qizwini Najaf in Iraq[32] using a Portable Dosimeter Survey (Inspector Alert Model RAP RS1, S.E. International, Inc., USA) was 810.84 nGy/h. The ADR obtained from their study was approximately 9 times higher than this study. The BIR level in the Middle-East has been shown to be higher than normal (Mubarak et al., 2017), but this is largely dependent on the geographical area. Further, the ADR (45 nGy/h) from a study by Joel et al., who assessed the radiological implication of background radionuclide and gamma distribution in residential buildings in Otta, Ogun State, Nigeria, was lower compared to our study and the mean world values. The above results indicated that BIR varies from one geographical location to another.[28] Similarly, the ADR (45 nGy/h) and AED (0.36 mSv/year) in a study by Mahmoud Pashazadeh et al. in Bushehr city in Iran was lower compared to this study.[29] Likewise, the mean BIR (0.005 mR/h) and ADR (10.03 nGy/h) from a study by Olagbaju et al. in Ijebu-Ife in Ogun State were lower compared to this study.[30] The lower values encountered in the above studies compared to our study may be due to soil, water, and the atmospheric activities. The mean ADR in this study (92 nGy/h) was highest compared to the national published data in the UNSCEAR 2000 report: Algeria (70 nGy/h, Canada (63 nGy/h), Paraguay (46 nGy/h), India (56 nGy/h), Thailand (77 nGy/h), Iran (71 nGy/h), Finland (71 nGy/h), Norway (73 nGy/h), France (68 nGy/h), the United Kingdom (34 nGy/h), Portugal (84 nGy/h), and the United States (47 nGy/h).[17] The reason for the difference was because this study sample size covered a small part of Aniocha South LGA in Delta State.


  Conclusions Top


A study to estimate BIR, ADR, and AED has been carried out in petrol stations in Delta State. Estimated values were comparable to studies in Nigeria and other parts of the world. The BIR from this study was below the value recommended in the UNSCEAR report, but ADR and AED appear to be higher. The study showed that the workers (petrol attendants) and customers (motorists) are not exposed to any additional radiation other than background and their exposure is same as other pubic in the region. However, there is a strong need for public sensitization and enlightenment on radiation protection in the environment.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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