ASSESSING ANNUAL EXPOSURES DOSE AND OTHER RADIOLOGICAL PARAMETERS FROM COSMIC RADIATION AMONG FLIGHT CREWS IN NIGERIA LOCAL AIRLINE

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INTRODUCTION
The aviation industry plays a vital role in global transportation, enabling millions of people to travel across long distances swiftly and efficiently (Wensveen, 2023).While the benefits of air travel are undeniable, there exists a potential occupational hazard that concerns the health and safety of the flight crews, especially those operating in regions with significant exposure to cosmic radiation (Ramsden, 2011).Cosmic radiation, originating from sources beyond Earth's atmosphere, presents a unique challenge to flight crews working at high altitudes (Sóbester, 2011).The presence of cosmic radiation in the aviation environment raises concerns about its potential health effects on flight personnel (Wilson, 2000).In the quest to ensure the wellbeing of airline employees, the issue of cosmic radiation exposure has gained increasing attention in recent years.Cosmic radiation is composed of high-energy particles, primarily protons and heavy ions, which can penetrate the Earth's atmosphere and reach the cruising altitudes of commercial flights (Paschoa and Steinhäusler, 2010).The impact of cosmic radiation on the human body and the potential health risks associated with prolonged exposure have led to growing interest in the field of radiation protection among flight crews.Cosmic radiation exposure in commercial aviation has been a subject of global concern.Studies worldwide have shown that flight crews are exposed to higher levels of ionizing radiation due to their frequent and prolonged exposure at cruising altitudes (Paschoa and Steinhäusler, 2010).The potential health risks associated with this exposure have led to a growing body of research aimed at understanding and mitigating the effects of cosmic radiation (Nelson, 2016).These studies often involve estimating annual radiation protection quantities to assess the risk.Several international organizations have provided guidelines and recommendations for managing cosmic radiation exposure among flight crews.The International Commission on Radiological Protection (ICRP) and the International Air Transport Association (IATA) have issued publications that set dose limits and provide guidance on monitoring and reducing radiation exposure.These guidelines serve as a foundation for assessing the radiation protection needs of flight crews in Nigerian local airlines.The health effects of cosmic radiation exposure are of paramount concern.Research has shown that ionizing radiation can increase the risk of developing cancer and other health issues.A study by (Grajewski et al., 2015) found that flight crews faced an increased risk of melanoma and other cancers.This underscores the importance of estimating radiation protection quantities to assess and manage these risks.Cosmic radiation exposure varies with geographical location and altitude.Flight crews operating in different regions may face varying levels of exposure due to factors like latitude and solar activity.Studies by (Beck et al., 2017;Zhang et al., 2020)  guidelines for radiation protection in the aviation industry (Osunwusi, 2020).These regulations may need to be aligned with international standards, considering the unique challenges and geographical context of Nigeria (Gomes et al., 2012).The literature discusses the importance of regulatory compliance and the development of specific measures to protect flight crews in Nigerian local airlines.
Effective communication is vital in ensuring that flight crews and the public are aware of cosmic radiation exposure and its associated risks (Ali et al., 2020).The literature highlights the importance of transparency, education, and communication within the Nigerian aviation industry to build awareness and confidence in radiation protection measures.This research focuses on estimating the annual radiation exposures for flight crews operating in local Nigerian airlines.The aviation industry in Nigeria has experienced substantial growth over the years, and it is imperative to assess and manage the radiation risks faced by flight personnel operating within the country.This study aims to contribute to the understanding of cosmic radiation exposure among Nigerian flight crews, as well as to assess the adequacy of current radiation protection measures in place.
The research involves comprehensive data collection and calculations of key radiation parameters, such as absorbed dose rates, annual gonadal dose equivalents, and excess lifetime cancer risks.These estimates provide valuable insights into the level of cosmic radiation exposure and potential health risks faced by flight crews in Nigeria's local airlines.Additionally, the findings will assist in the development of effective radiation protection strategies and guidelines to ensure the safety and well-being of airline personnel.Ultimately, this research endeavors to bridge the knowledge gap regarding cosmic radiation exposure among flight crews in Nigerian local airlines safety standards in the aviation industry, while safeguarding the health of those who make air travel accessible and efficient.

MATERIALS AND METHODS
This study collected data on flight moment statistics, flight plan data and airport locations data.The data were collected through Nigerian Airspace Management Agency (NAMA) Lagos, Nigeria.Three Nigeria flights (Lagos -Abuja; Lagos -Port Harcourt and Lagos -Kano) from Muritala Muhammed International Airport, Lagos (MMIA) were selected.The three selected flights took place between 2011 and 2022 with a 60, 75, and 44 crew members respectively.This enables the researchers to compare the levels of cosmic radiation exposures received by individual crew members within the period specified.CARI-6M (Civil Aero Medical Research Institute) is an instrument that store and process multiple flight profiles as well as calculate dose rates at user specified locations in the atmosphere was used for this study.It estimates the effective dose (in sv) received by an individual in aircraft flying and were also determined the Annual Effective Dose received by flying crew members (Hwang et al., 2014).The workflow for calculating Annual Effective Dose adopted for the study is shown in Figure 1.individual crew shows that as altitude increases, the concentration of oxygen in the air decreases (Onuh et al.,2023).This can lead to hypoxia, a condition where there is insufficient oxygen reaching body tissues.Symptoms of hypoxia include dizziness, lightheadedness, impaired judgment, and eventually unconsciousness if not addressed.Furthermore, altitude exposure, especially during long flights or in pressurized cabins, can contribute to fatigue due to disrupted sleep patterns, increased physical demands, and environmental factors such as noise and vibration.Also, at higher altitudes, aircrew members may be exposed to increased levels of cosmic radiation, which can pose longterm health risks such as an increased risk of cancer (Ali et al., 2020).However, these risks are typically low for commercial aircrew members due to regulatory limits on exposure.
Solar activity has massive effects on aircrew members from time to time.Aircrew are exposed to higher levels of UV radiation at higher altitudes due to thinner atmosphere, and this exposure can increase the risk of skin cancer, cataracts, and other UV-related health issues if adequate protection is not used.Sun glare can affect visibility for pilots, especially during takeoff and landing (Nelson, 2016).This glare can cause eye strain and reduce the ability to see instruments and other aircraft.Sunlight can cause temperature fluctuations within the aircraft cabin, affecting the comfort and well-being of the crew (Hwang et al., 2014).Adequate climate control systems are necessary to mitigate these effects.Sun exposure can lead to increased dehydration, especially in aircraft cabins where humidity levels are typically lower.Aircrew must stay hydrated to maintain alertness and cognitive function.Geographical positions of aircrew across the three different routes Lagos -Kano, Lagos -Abuja and Lagos -Port Harcourt is given as 45°, 237.03°, 112.5° respectively and their geographical latitude and longitude are as shown in table 3.1 and 3.2.This different geographic location considered in this research work gives flights different time zones and can lead to disruptions in the body's circadian rhythm, resulting in jet lag.Aircrew members may experience symptoms such as fatigue, difficulty sleeping, irritability, and impaired cognitive function as their bodies adjust to the new time zone (Grajewski et al., 2015).

Evaluation of other radiological parameters Annual gonadal dose equivalent (AGDE)
An increase in AGDE has been known to affect the bone marrow and can damage red blood cells which can cause blood cancer.The annual gonadal dose equivalent (AGDE) is calculated using equation ( 1) as used in the work of Okedeyi et al., (2022).
Where   is the radiation-specific factor for the gonads, which represents the fraction of the effective dose that is received by the gonads.The value of   depends on the type and energy of radiation involved.

Excess Lifetime Cancer Risk (ELCR)
This is the probability of developing cancer over a lifetime at a given exposure level, considering 70 years as the average duration of life for human being.ELCR was calculated using equation (2) as used in the research of Ugbede and Echeweozo, (2017).
where: AED is the Annual Effective Dose, DL is the average duration of life (estimated to 70 years), and RF is the Risk Factor = 0.05

RESULTS AND DISCUSSION Effective Annual Dose (AED)
The result in Figure 2 shows that the annual effective dose Annual Gonadal Dose Equivalent (AGDE) Table 3.3 depicts the Annual Gonadal Dose Equivalent (AGDE) across the three routes (Lagos -Kano, Lagos -Abuja and Lagos -Port Harcourt).The results showed that AGDE values range from 7.20 -380 µSv y -1 .The result also revealed that only Lagos -Kano route in year 2017 (380 µSv y -1 ) are above the maximum permissible value of 300 µSv y -1 recommended (UNSCEAR, 2000;Okedeyi et al., 2022) as can be seen in Figure 3.

Excess lifetime cancer risk (ELCR)
The excess lifetime cancer risk is the possibilities of crew members developing cancerous cell due to exposure to cosmic radiation in their lifetime.The calculated ELCR of the study indicated that values from year 2016 -2022 across the three routes (Lagos -Kano, Lagos -Abuja and Lagos -Port Harcourt) as revealed in table 3.3 were higher than average standard value of 0.29 x 10 -3 by (UNSCEAR, 2008).Figure 4 show the time series plot of the ELCR.The finding is in agreement with earlier report by (Ugbede and Echeweozo, 2017).The implication of this result is that there are possibilities of the crew members between year 2016 and 2022 of developing symptoms of cancer within their lifetime.
have emphasized the significance of considering geographical and altitude variations when estimating annual radiation protection quantities for flight crews in Nigerian local airlines.Various technologies are available for monitoring cosmic radiation exposure.Personal dosimeters, such as thermoluminescent dosimeters (TLDs) and electronic dosimeters, are commonly used by flight crews to measure their individual exposure.Aircraft-based monitoring systems also play a crucial role in assessing radiation doses during flights.The Nigerian Civil Aviation Authority (NCAA) and other relevant authorities have established regulations and FUDMA Journal of Sciences (FJS) ISSN online: 2616-1370 ISSN print: 2645 -2944

Figure 2 :
Figure 2: Graph of annual effective dose for Lagos -Kano, Lagos -Abuja and Lagos -Port Harcourt route between 2011 and 2022 against Year

Figure 3 :-
Figure 3: Annual Gonadal Dose Equivalent for the three routes between 2011 to 2022

Figure 4 :
Figure 4: Time series plot of ELCR for the three routes between 2011 and 2022 CONCLUSION This study assesses the annual exposures dose and other radiological parameters from cosmic radiation among flight crews in Nigeria local airline using aircrew cosmic radiation exposure estimation methods of radiation dose measurements and computer model calculations (computer code -CARI -6M).The finding of the study shows that annual effective dose (AED) received by the air crew members (Lagos -Kano, Lagos -Abuja and Lagos -Port Harcourt) ranges between 0.230 and 1.90 µSv y -1 .This finding is lower than earlier studies byFriedberg et al., (2000)  andFeng et al., (2002) that reported 6.6 -9.7 µSv and 2.19 -2.38 µSv.The result also indicated that there is direct relationship between the time of flight, flight altitude and the effective dose received by the crew members.The Annual Gonadal Dose Equivalent (AGDE) across the three routes ranges from 7.20 -380 µSv y -1 with only Lagos -Kano route in year 2017 (380 µSv y -1 ) above the maximum permissible value of 300 µSv y -1 , while the Excess Lifetime Cancer Risk (ELCR) values from year 2016 -2022 across the three routes were also higher than average standard value of 0.29 x 10 -3 .The AED follows the trends of solar cycle however; it is within the average background radiation levels.The associated significant excess lifetime cancer risk increases with cumulative doses and dependent of the flight routes.The implication of the finding is that there are possibilities of the crew members developing symptoms of cancer within their lifetime.It's therefore recommended that, Nigerian Civil Aviation Authority should introduce regulations to reduce flight crew exposure as well as training programs that can identify potential sources of radiation exposure as well as safety of Nigerian flight crews.

Effects of Altitude, Sun's activities and geographic positions on Air Crew members
For this present research, the altitude of Lagos is 135 ft, Abuja is 1123 ft, Portharcourt is 81 ft and Kano is 1565 ft.The effects of this varying altitude on a total of 179 crew members have been analyzed.The effect of altitude radiations on