Radiation Environment and Medicine 2023 Vol.12, No.2 91–98

Regular Article

The Estimation of Annual Exposure to the Irish Populationfrom Cosmic Radiation due to Air Travel
Fergal Dolan1* and Kevin Kelleher2, 3
1
University College Dublin, Belfield, Dublin 4, Ireland
Associate Research Professor , Institute of Radiation Emergency Medicine, Hirosaki University, Japan
3
Environmental Protection Agency, Richview, Dublin 14, Ireland.

2

Received 20 August, 2022; revised 15 January, 2023; accepted 23 January, 2023

Anytime that someone travels by air they will receive a dose of ionising radiation in the formof cosmic radiation. The aim of this study was to estimate the average dose of cosmic radiation
received by a member of the Irish public over the period of a typical year due to air travel. The
frequency of air travel by Irish residents to several regions was determined using data fromvarious sources. The total dose that one would receive for a typical flight to and from the region
was then calculated using software available for flight crews to estimate the radiation dose thatthey have received through flying. The annual effective dose for an Irish person as a result ofcosmic radiation from air travel was estimated to be 68 µSv.
Key words: cosmic radiation, EPCARD, dose assessment, air travel, public exposure

1. Introduction
Cosmic radiation is the term used to describe both thehigh-energy, charged particles of extraterrestrial originthat strike the earthʼs atmosphere (primary particles), as
well as the secondary reaction products that result fromthe interaction of those high-energy, extraterrestrial
particles with the nuclei of atmospheric constituents(secondary particles)1).The intensity of exposure fromcosmic rays is strongly dependent on altitude and there isalso a dependence on latitude but that is less significant1).
Cosmic radiation is a source of ionising radiation at all
altitudes, but because the intensity of cosmic radiation
increases with increasing altitude, aircraft passengers
and crew are subject to higher rates of cosmic radiation
exposure compared to cosmic radiation exposure at*Fergal Dolan: University College Dublin, Belfield, Dublin 4, IrelandE-mail: fergaldolan2468@gmail.com
https://doi.org/10.51083/radiatenvironmed.12.2_91
Copyright © 2023 by Hirosaki University. All rights reserved.

ground level1). The goal of this study was to estimate theaverage radiation dose received by a member of the Irish
public due to air travel over the course of a typical year.
T his study was conducted as part of a larger
assessment, which is currently ongoing as of early 2023,
with the goal of estimating the annual effective doseof the typical Irish person from all sources of ionisingradiation. Despite the fact that estimations of annual
effective dose from cosmic radiation due to air travel havebeen made before, it was deemed necessary to conduct a
new study due to changes in the flying habits of the Irish
population and changes in flight patterns in the period
since the previous studies were conducted.
2. Methods
2.1. Travel Statistics 2019
The Central Statistics Office (CSO) is Irelandʼs national
statistical office whose purpose is to publish detailed andaccurate statistics about Irelandʼs people, society and92

Fergal Dolan et al. / Radiation Environment and Medicine 2023 Vol.12, No.2 91–98

economy2). The CSO publishes data on the frequency
of international trips undertaken by Irish residents.
This data is collected by the CSO via a household travel
survey3). The data is categorised by the frequency oftravel to several discrete regions and is provided in tablesof data available to be downloaded or viewed on the CSO
website4-6). The CSO data provides information on the total
number of Irish residents who have visited each of theregions each year, but they do not distinguish between
different modes of transport.
Due to its status as an island, international travel from
Ireland must take place either via sea or via air (excluding
Northern Ireland but there are no regularly scheduled
flights to Northern Ireland from Ireland). The CSO also
publishes data on maritime travel from Ireland7). The
only regions that regularly receive maritime passengers
from Ireland are Great Britain, France and Spain7). Dataon the number of visitors who arrived in the UK by
sea in 2019 is provided by VisitBritain8). Since there are
no regular maritime passenger services from Ireland
to Northern Ireland it was assumed that all of thesemaritime passengers travelled to Great Britain. Data on
the number of Irish residents who visited France by sea
in 2019 was acquired using CSO data on total outboundmaritime passengers7). It was assumed in this study
that 50% of total maritime passengers who travelled toFrance from Ireland were visitors to France who wereresident in Ireland. Maritime travel to Spain from Ireland
was negligible compared to the overall number of Irish
residents who visited Spain in 2019. Using the data on
maritime passengers available and the assumptions
outlined above, data on the number of visitors who
travelled to Great Britain and France by air could be
calculated by subtracting the assumed number ofmaritime passengers from the total visitor figures givenin the CSO data on Irish visitors to these regions6). For allother regions it was assumed that 100% of Irish visitors to
the region travelled there by air.
The regional breakdown of places visited by Irish
residents provided by the CSO was, for certain regions,
not sufficient for the purposes of this study. This occurred
when the region was large, members of the Irish public
were flying to numerous destinations within these regions
or there was large variability in the radiation dose that
one would receive from flying to the different destinations
within a region. The regions identified as having thisissue were Spain and North America.
The CSO data only provides information on the total
number of visitors to Spain and does not provide any
information on the distribution of visitors between the
different regions within Spain, there is no indication ofwhether a visitor to Spain travelled to mainland Spain(including the Balearic Islands) or the Canary Islands6).
This is an issue because the Canary Islands receivea relatively large number of Irish visitors9) and there
is a significant difference between the dose received
from a flight from Ireland to one of the Canary Islands,
off the coast of west Africa, compared with a flightto a destination within mainland Spain including theBalearic Islands. Assumptions were made by looking
at data published by the CSO and comparing the total
number of passengers that travelled from Dublin airport
to each of the airports in Spain for which direct flights
were available9). Only flights from Dublin airport were
investigated because it handled the vast majority (86%) of
Irish aviation passengers in 20199). It was thus assumed
in this study that 76% of visits by Irish residents to Spain
were to the mainland or the Balearic Islands, while 24%
were to the Canary Islands. Assumptions about the
distribution of trips to North America were also madeusing the same method utilising this data from the CSO9).
The North American region consists of the US andCanada and for this region it was assumed that 63% of
trips by Irish residents were made to the Northeast, 9% to
the Southeast, 15% to the Midwest and 13% to the Westernregion of North America. This assumption is based on
CSO data on the number of passengers who flew directfrom Dublin Airport to the international airports withinthese regions9).
For all European and North American regions, tochoose a representative destination for each region, theaforementioned CSO data on total passenger numbers
was used 9). The aim in choosing a representative
destination for each region was to have a destination
for which a dose estimation could be made for a return
flight between Dublin and that destination. This dosewould then be assumed to represent a typical dose for avisitor flying to and returning from the region in which
the representative destination was located. In mostcases the destination within a region which received thehighest volume of passengers from Dublin airport on
direct flights in 2019 was chosen as the representative
destination for that region. If the destination which
had received the highest volume of passengers wasconsidered unrepresentative due to its geographicallocation, then a different destination which had still
received a high volume of passengers but was located ina more representative location within the region would bechosen. For example, within mainland Spain including theBalearic Islands, the three locations which received thehighest volume of passengers from Dublin Airport in 2019
were: Malaga with 329,649 passengers, Barcelona with
320,048 passengers and Madrid with 273,035 passengers9).
Both Malaga and Barcelona are located at or near theedge of mainland Spain, with Malaga being located near
the Southern tip of Spain and Barcelona being locatedin the Northeast. That is why, despite receiving lesspassengers from Dublin Airport than both Barcelona andFergal Dolan et al. / Radiation Environment and Medicine 2023 Vol.12, No.2 91–98

Malaga in 2019, Madrid was chosen as the representative
destination for mainland Spain including the Balearic
Islands. This was due to it being located relatively
centrally between the two locations which received thehighest volume of passengers from Dublin Airport in 2019
while also having received a relatively large number ofpassengers from Dublin Airport itself.
In the case of the Africa, Asia, Oceania and “Other
America” regions there were little or no direct flights tomost destinations within these regions. As a result of this,
there was not enough data from the CSO publication ofpassenger numbers to choose a representative destination
using the method that had been used for the regions
within Europe and North America. In the case of Africa,
Nairobi was chosen as the representative destination
due to its location in the centre of the continent. There
was no data available on the number of Irish visitors
to different regions within Africa, so it was assumed
that the distribution of Irish visitors was uniform
throughout the continent. The “Other America” region
consists of all of the other countries in the Americas notpreviously mentioned. Buenos Aires was chosen as therepresentative destination of this region due its size andits relatively central location within the region as there
was no data available on the frequency of Irish residentsʼ
trips to Central and South America by region. Sydney waschosen as the representative destination for the Oceanic
region due to it being the largest city in the region10),
and it is located relatively centrally within the region.
Bangkok was chosen as the representative destination
for Asia due to its size and its central location within the
Asian continent.
2.2. Dose Estimation
The average dose received by a visitor to each of theregions was determined by the dose one would receive asa result of flying from Dublin Airport to the representative
destination of the region and back again. The calculations
were made using the European Program Package for
the Calculation of Aviation Route Doses (EPCARD)
software11). The EPCARD software is a tool that calculates
the dose received on a flight once specified parameters
are input. It has been approved for official dose calculation
for flying personnel by the German Federal Aviation
Authority12). It has also been approved by the European
Commission for use in estimating occupational radiation
exposure of aircrew13). EPCARD requires the following
input parameters to make a dose calculation: the date of
the flight, the departure airport, the destination airport,
the ascending and descending times and the cruising
altitude. Estimations for the return trip doses were madeby taking the sum of the outbound and return flightaverage doses. The average doses for the outbound andreturn flights were estimated by making an EPCARD

93

calculation for each flight with the date set as the 15th
day of each month of the year and getting the averagevalue by taking the sum total of all the doses for each of
the 12 months and dividing this by 12. This was done toaccount for variations in the cosmic ray flux throughout
the year14). Dublin airport is by far the busiest airport
in Ireland, it handled 86% of total Irish commercial air
passengers in 2019, so it was used as the departure airport
for all dose calculations9, 15). The destination airport was
taken as the primary international airport within the
representative destination of each region.
The ascending and descending times and the cruising
altitudes were chosen based on the categorization of theflight into one of three categories: short-haul, mediumhaul or long-haul. Flights under 3 hours were consideredshort-haul, flights between 3-6 hours were considered
medium-haul and flights over 6 hours were consideredlong-haul for this study16). For short-haul flights, theascending and descending times were taken as 20 minutes
respectively and the cruising altitude was assumed to be
36,000 feet. For medium-haul flights, the ascending anddescending times were taken as 25 minutes respectively
and the cruising altitude was assumed to be 38,000
feet. For long-haul flights, ascending and descendingtimes were taken to be 30 minutes respectively with anassumption that the plane would be at a cruising altitudeof 37,000 feet 50% of the time and 41,000 feet for the other50%17). Flight times were taken from online flight time
calculators18, 19). The travel statistics from Table 1 werethen used to find the collective dose (manSv) for eachregion. This was achieved by multiplying the return dosethat was estimated using EPCARD by the number ofvisitors to each region.
3. Results
The number of visitors from Ireland by air to each region
considered as part of this study in 2019 are outlined inTable 1.
The return trip dose and collective dose for each region
considered as part of this study is outlined in Table 2.
The total collective dose for all of the flights over a year
was 334 manSv. Dividing this by the population of Irelandin 2019, which was 4,921,500, gives an annual effective
dose of 68 µSv. In 2019 there had been a 26% increase ininternational trips by Irish residents since the most recent
study on cosmic radiation exposure due to air travel in
Ireland that had been conducted previously14).
4. Discussion
Due to the covid-19 pandemic, air travel in Irelanddecreased dramatically during the years 2020 and 202120)
so the average radiation dose received during these94

Fergal Dolan et al. / Radiation Environment and Medicine 2023 Vol.12, No.2 91–98
Table 1. Number of trips by air by Irish residents to the representative destinations of the regions in 2019
RegionAustria
Belgium
Germany
Spain-Mainland and Balearics
Spain-Canary Islands
Spain Total
France
Italy
Netherlands
PolandPortugal
Great Britain
Denmark/Finland/Sweden
Other EU28*
Other Europe
North America Northeast
North America Southeast
North America Midwest
North America West
North America Total
AfricaAsia
Oceania
Other America

Representative destination
ViennaBrussels
Frankfurt
MadridLanzarote
Paris
Milan
Amsterdam
Krakow
Faro
LondonCopenhagen
Budapest
Istanbul
New York City
OrlandoChicagoSan Francisco
Nairobi
Bangkok
SydneyBuenos Aires

Return trips (1000s)
89
99
261
1430
451
1881
527
590
205
171
522
1727
83
494
208
368
53
88
76
584
57
301
73
63

*EU28 includes the UK as they were still a member of the European Union in 2019

Table 2. Return and collective dose for each region.
RegionAustria
Belgium
Germany
Spain-Mainland and Balearics
Spain-Canaries
Spain Total
France
Italy
Netherlands
PolandPortugal
Great Britain
Denmark/Finland/Sweden
Other EU28*
EU 28 Total*
EU 27 Total
Other Europe
North America Northeast
North America Southeast
North America Midwest
North America West
North America Total
AfricaAsia
Oceania
Other America

Representative destination
ViennaBrussels
Frankfurt
MadridLanzarote
Paris
Milan
Amsterdam
Krakow
Faro
LondonCopenhagen
Budapest

Istanbul
New York City
OrlandoChicagoSan Francisco
Nairobi
Bangkok
SydneyBuenos Aires

Return trips(1000s)
89
99
261
1430
451
1881
527
590
205
171
522
1727
83
494

Return trip dose
(μSv)
35
19
24
27
37

208
368
53
88
76
584
57
301
73
63

54
142
162
168
230

*EU28 includes the UK as they were still a member of the European Union in 2019

20
28
20
41
24
15
29
40

73
140
160
95

Collective dose
(manSv)
3.1
1.9
6.3
38.6
16.7
55.3
10.5
16.5
4.1
7.0
12.5
25.9
2.4
19.8
165.3
139.4
11.2
52.3
8.6
14.8
17.5
93.1
4.2
42.1
11.7
6.0

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95

Fig. 1. Annual effective doses from cosmic radiation due to air travelin 2005, 2012 and 2019, in μSv.

Fig. 2. Annual effective doses for different regions in 2005, 2012 and2019, in μSv.

two years would not be representative of the average
dose that one would expect to receive in a typical year.
This is the reason why data from 2019 is used in thisstudy, as it is the most recent year, not impacted by thecovid-19 pandemic, that representative data was available
to estimate an annual effective dose for an Irish person
as a result of cosmic radiation from air travel. Domestic
flights were not considered as part of this study. Dueto the fact that Ireland is relatively small in size, there
are very few domestic flights within Ireland. Due to thevery low frequency, low altitude and short durationsof Irish domestic flights it was deemed that domestic
flights would represent a negligible impact to the annual
effective dose calculations from air travel and they were
not included in the overall dose assessment.
The value of 68 µSv for the annual effective dose ofcosmic radiation from air travel received by an Irish
resident estimated in this study is higher than previous
estimated doses, 41 µSv in 2012 and 45 µSv in 2005, as
demonstrated in Figure 114, 17). There are a number ofpotential reasons for this. Firstly, there had been an
increase in air travel between 2012 and 2019 which wassignificantly greater than the increase in population
during that period, there was a 25.6% increase ininternational return trips as opposed to a 7.2% increase inpopulation in that period4, 14, 21). In addition, many of theestimations made in this study for the dose received for a
return flight were higher than they had been in previous
studies for the same destination. This could partly be due
to variations in the intensity of the cosmic ray flux forthe years being assessed but that would be unlikely to
account for the entire increase14). Most of the parametervalues used in this study were consistent with the values
used in previous studies17, 22) apart from the dates ofthe flights and the flight times (there was also a slightdifference arising from the fact that previous studies did
not include a medium-haul flight category)17). In terms of
the flight times, it is possible that reliable data was harder
to source in the past, or perhaps the shortest possible
flight time between destinations was used previously,
which would result in a lower dose estimation. The flighttime calculators used in this study gave an average flighttime based on actual flight times provided by airlines.
This flight time would be more representative of theamount of time that people actually spent in the air, andhence the dose they would have received, comparedto the shortest possible flight time that was used inprevious studies. There were also different representative
destinations used in this study than those that had beenused previously for certain regions, possibly reflecting
the rise and fall in popularity of international destinations
with Irish residents.
In addition, there was variabilit y bet ween the
distribution of passenger visits to the different regions
between this study and the previous studies. For example,
In the 2012 study there were 19,000 visits to the North
America West region14). This had increased to 76,000
in 2019, a 300% increase3). North America West had thehighest estimated dose for a return visit out of all of theregions. This was not the only example of a shift in visits
to regions with a higher return dose, North America asa whole received a larger share of visitors in 2019 than it
did in 2012. See Figure 2.
A potential for inaccuracy in the dose estimation in

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Fergal Dolan et al. / Radiation Environment and Medicine 2023 Vol.12, No.2 91–98

this study could come from the variability in estimateddose that could arise due to the choice of a different
representative destination. Within Europe the variability
between destinations within regions would be relatively
small and the choice of representative destination wasusually an obvious one based on passenger volumedata. Within the North American region, the passenger
volume data also allowed for a relatively well-informed
decision to be made on which destination to choose as
the representative destination. However, with the otherregions, there was limited data available to determine
the choice of representative destination. However, it ispossible to make an estimation of potential variability
between destinations within a region.
Within Asia, for example, Bangkok was chosen due toits size, assumed popularity (no data could be found on theactual number of Irish visitors to Bangkok) and central
location. There was no data available on the frequency
at which Irish residents to travel to different destinations
within Asia, but Dubai and Tokyo are both major Asian
cities, so the assumption could be made that they both
receive a significant number of visitors from Ireland.
Dubai is one of the closest destinations to Ireland within
Asia while Tokyo is one of the furthest Asian destinations
from Ireland. A typical return trip dose for Dubai in 2019was estimated at 81 µSv while a dose for a return visit
to Tokyo in 2019 was estimated at 259 µSv. Comparing
these values with the return dose of 140 µSv estimated for
Bangkok in this study, it can be seen that there is quite alarge amount of variability between different destinationsin Asia. Comparing the estimated dose of 73 µSv for
Nairobi with an estimated dose of 112 µSv for a return
visit to Johannesburg, and an estimated dose of 55 µSv fora return visit to Cairo, it can be seen that the variabilityof dose between destinations within Africa is less thanthe variability of dose between destinations within Asia.
This is, in part, due to the close proximity of the African
destinations to the equator, because the intensity ofcosmic radiation is lowest closer to the equator andhighest closer to the poles23). Considering the relatively
low number of visitors to Africa in 2019 the uncertainty
arising from the choice of the representative destinationin the African region would be relatively small.
The dose for a return visit to Perth was estimatedat 138 µSv compared to the 160 µSv dose estimatedfor a return visit to Sydney, so there is not much of avariation between different destinations within Australia
when comparing the dose for a return trip from Ireland.
It is difficult to estimate the typical dose for a trip to
Auckland as there is a very large amount of variability
in where flights from Dublin will connect through, withmany flights from Dublin to Auckland having at least
two connections. Looking at one of these flights whichconnects through San Francisco as an example, the dose

for a return trip was estimated at 305 µSv. This is muchlarger than the 160 µSv dose for a return trip to Sydney.
However, it was assumed in this study that visits to New
Zealand did not make up a large portion of Oceanic visits.
In addition, total visits to Oceania were relatively small
compared to the total number of Irish outbound trips
so this variability would not have a huge effect on theuncertainty on the total collective dose estimation for all
regions. For the “Other America” region, a return visit toHavana and a return visit to Sao Paulo were estimated at
143 µSv and 89 µSv respectively compared to the valueof 95 µSv estimated for a return visit to Buenos Aires.
Once again due to the relatively low number of visits to
the region, the uncertainty to the overall estimation thatwould arise due to this variability is small.
Given that the collective dose for Asia was much larger
than it was for other regions where there were similardifficulties in picking a suitable representative destination,
the Asian region is likely to be the biggest contributor topotential uncertainty within this study. This is because
the variability between doses flying to and from different
destinations within the region is large. Despite the factthat the European and North American regions madeup a much greater distribution of the overall estimatedcollective dose, the potential uncertainty that could arise
from these regions is lower. This is due to the fact that
there is less variability between potential representative
destinations within these regions and there is sufficient
flight data available for the European and North
American regions when compared to Asia.
It is also worth noting that since the previous dose
surveys on the annual effective dose for an Irish person
as a result of cosmic radiation from air travel 17, 22)
the EPCARD software has been updated to ensurecompliance with the latest European Basic Safety
Standards Directive13), where a new methodology forcalculating doses was introduced, based on the latest
scientific evidence on radiation risks and radiationand tissue weighting factors from the International
Commission on Radiological Protection (ICRP 103)24).
A study by Mares et al.25) found that the updated
radiation weighting factors recommended by ICRP 103
for neutrons, and protons results in a dose differenceof less than 8% when compared to older recommended
radiation weighing factors used in previous versions of
the EPCARD software. This change in dose per flight isinsignificant when compared to the overall dose estimatedas part of this survey.
5. Conclusion
In summary, the estimated figure for the annual effective
dose of cosmic radiation due to air travel in this study
was higher than previous estimates. In this study, theFergal Dolan et al. / Radiation Environment and Medicine 2023 Vol.12, No.2 91–98

estimated annual effective dose of cosmic radiation due
to air travel for a typical Irish was 68 µSv, comparedwith an estimate of 41 µSv in 2012 and 45 µSv in 200514, 17).
In 2014, the overall annual effective dose of ionisingradiation received by a typical member of the Irish publicfrom all sources of ionising radiation was estimated to be
4,037 µSv14). It can be seen from this value that cosmic
radiation exposure is not a major source of ionisingradiation when compared to other sources of ionisingradiation received by a typical person in a year. 2014 is
the most recent year that data was available on the total
dose of ionising radiation that the typical Irish person
could expect to receive in a year. The 68 µSv value forcosmic radiation exposure in 2019 estimated in this study
would comprise only approximately 2% of the total annual
effective dose of ionising radiation a typical Irish person
would receive, assuming the total dose was similar to thevalue estimated in 201414).
The potential reasons for the estimated annual effective
dose in this study being higher than in previous studies
include:• An increase in per capita international air travel by
Irish residents up to 2019
• A greater proportion of international air travel
being on higher dose routes in 2019 compared toprevious years• The fact that the flight times used in this study
were the average flight times as opposed to theshortest possible flight times, which may havebeen the flight times used in previous studies.
Longer flight times would give a higher dose as
they would lead to a greater duration of exposure
The greatest potential for uncertainty in this study isfrom the estimation made for the collective dose for air
travel to Asia. This is due to the large variability in return
trip doses for different destinations within Asia, therelatively large number of Irish visitors to this region andbecause of the uncertainty in choosing the representative
destination due to a lack of available data on the numberof Irish visitors to specific locations in Asia.

97

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United Nations Scientific Committee on the Effects of Atomic
Radiation. Sources and Effects of Ionising Radiation. New York:
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