Occupational cosmic radiation exposure and cancer in airline cabin crew

134 Pages·2013·2.16 MB·English

by  Katja Kojo

STUK-A257 / MARCH 2013
A
Occupational cosmic radiation
exposure and cancer in
airline cabin crew
Katja Kojo
Säteilyturvakeskus
Strålsäkerhetscentralen
Radiation and Nuclear Safety Authority

KATJA KOJO
Occupational cosmic radiation exposure
and cancer in airline cabin crew
ACADEMIC DISSERTATION
To be presented, with the permission of
the board of School of Health Sciences of the University of Tampere,
for public discussion in the Auditorium of School of Health Sciences,
Medisiinarinkatu 3, Tampere, on March 15th, 2013, at 12 o’clock.
UNIVERSITY OF TAMPERE

STUK-A257 / MARCH 2013
Occupational cosmic radiation
exposure and cancer in
airline cabin crew
Katja Kojo
STUK • SÄTEILYTURVAKESKUS Osoite / Address • Laippatie 4 , 00880 Helsinki
STRÅLSÄKERHETSCENTRALEN Postiosoite / Postal address • PL / P.O. Box 14, FI-00881 Helsinki, FINLAND
RADIATION AND NUCLEAR SAFETY AUTHORITY Puh. / Tel. [phone] • Fax [phone] • www.stuk.fi
The conclusions in the STUK report series are those of the authors
and do not necessarily represent the official position of STUK.
STUK A-257 Acta Electronica Universitatis
ISBN 978-952-478-783-3 (print) Tamperensis 1290
ISBN 978-952-478-787-1 (pdf) ISBN 978-951-44-9070-5 (pdf)
ISSN 0781-1705 ISSN 1456-954X
Electronic version published:
http://www.stuk.fi and http://tampub.uta.fi
Suomen Yliopistopaino Oy – Juvenes Print, Tampere 2013
Sold by:
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P.O.Box 14, FI-00881 Helsinki, Finland
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Fax [phone]
STUK-A257
Academic dissertation
Finnish Radiation and Nuclear Safety Authority (STUK)
Helsinki, Finland
University of Tampere, School of Health Sciences
Tampere, Finland
Occupational cosmic radiation exposure
and cancer in airline cabin crew
Supervised by: Professor Anssi Auvinen
University of Tampere, School of Health Sciences
Tampere, Finland
Reviewed by: Professor Elisabete Weiderpass Vainio
Karolinska Institutet,
Department of Medical Epidemiology and Biostatistics
Stockholm, Sweden
Docent Timo Kauppinen
Finnish Institute of Occupational Health
Helsinki, Finland
Opponed by: Professor Juha Pekkanen
National Institute of Health and Welfare,
Environmental Health, Unit of Environmental Epidemiology
Kuopio, Finland
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STUK-A257
KOJO Katja. Occupational cosmic radiation exposure and cancer in airline cabin
crew. STUK-A257. Helsinki 2013, 83 pp. + Appendices 42 pp.
Keywords: Cabin crew, epidemiology, cosmic radiation, exposure assessment,
occupational exposure, neoplasms
Abstract
Cosmic radiation dose rates are considerably higher at cruising altitudes of
airplanes than at ground level. Previous studies have found increased risk of
certain cancers among aircraft cabin crew, but the results are not consistent
across different studies. Despite individual cosmic radiation exposure assessment
is important for evaluating the relation between cosmic radiation exposure
and cancer risk, only few previous studies have tried to develop an exposure
assessment method. The evidence for adverse health effects in aircrews due to
ionizing radiation is inconclusive because quantitative dose estimates have not
been used. No information on possible confounders has been collected. For an
occupational group with an increased risk of certain cancers it is very important
to assess if the risk is related to occupational exposure.
The goal of this thesis was to develop two separate retrospective
exposure assessment methods for occupational exposure to cosmic radiation.
The methods included the assessment based on survey on flight histories and
based on company flight timetables. Another goal was to describe the cancer
incidence among aircraft cabin crew with a large cohort in four Nordic countries,
i.e., Finland, Iceland, Norway, and Sweden. Also the contribution of occupational
as well as non-occupational factors to breast and skin cancer risk among the
cabin crew was studied with case-control studies.
Using the survey method of cosmic radiation exposure assessment, the
median annual radiation dose of Finnish airline cabin crew was 0.6 milliSievert
(mSv) in the 1960s, 3.3 mSv in the 1970s, and 3.6 mSv in the 1980s. With the
flight timetable method, the annual radiation dose increased with time being 0.7
mSv in the 1960 and 2.1 mSv in the 1995. With the survey method, the median
career dose was 27.9 mSv and with the timetable method 20.8 mSv. These
methods provide improved means for individual cosmic radiation exposure
assessment compared to studies where cruder indicators, such as number of
work years for occupational exposure, were used. When selecting the approach
for further studies, the feasibility issues of the study affect the decision, i.e.,
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can the flight history data of the cabin crew be collected by a survey or are the
historical flight timetables available from the flight company.
In the follow-up of more than 10,000 Nordic cabin crew members, the
standardized incidence ratio (SIR) of all cancers was 1.16 (95% confidence
interval (CI): 1.06 – 1.25) for women and 1.39 (95% CI: 1.17 – 1.62) for men.
These results confirm the evidence for an elevated overall cancer risk among
cabin crew compared to the general population. Of specific cancer types,
the significant risks were observed for breast cancer, cutaneous malignant
melanoma, non-melanoma skin cancer, leukaemia, Kaposi sarcoma, laryngeal
and pharyngeal cancer.
This thesis cannot not provide an explanation for the elevated breast or
skin cancer risk among aircraft cabin crew. Breast cancer is previously known to
be strongly related to reproductive and hormonal factors – including endogenous
hormone levels and exogenous hormone use. Thus, these factors may present the
plausible explanation for the increased risk of breast cancer also among cabin
crew. Exposure to ultraviolet radiation (UVR) is the most likely explanation
for the increased risk of skin cancers, but there was no evidence on cabin crew
excess exposure to UVR compared to general population in this work.
Finding a cause for the increased incidence of cancer among cabin
crew warrants further studies. This work found no relation between estimated
occupational cosmic radiation exposure and cancer risk. The current exposure
limitations of radiation to cabin crew need not be altered.
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