[ RadSafe ] HPA News - Mortality and Cancer Risks for Radiation Workers
fred-dawson at blueyonder.co.uk
Sat Jan 17 13:08:21 CST 2009
HPS New release
Mortality and Cancer Risks for Radiation Workers
7 January 2009
The risk of developing cancer among radiation workers increases with the
dose of ionising radiation they are exposed to, according to a study by the
Health Protection Agency published today in the British Journal of Cancer *.
The observed cancer risks are consistent with the international scientific
consensus on radiation protection.
The study also shows that overall mortality in the UK's 175,000 radiation
workers is lower than that in the general population. This "healthy worker
effect" has been observed in studies of many other occupational groups.
Dr Colin Muirhead from the Health Protection Agency said: "This is a
continuation of a study started in 1976 and it provides reliable information
on the health of people working with ionising radiation. The results confirm
the cancer risk estimates observed in other studies even though, overall,
radiation workers have lower cancer risks than the general population."
This study provides the most precise estimates to date of mortality and
cancer risks following occupational radiation exposure and strengthens the
scientific evidence for raised risks from these exposures. The cancer risk
estimates are consistent with international radiation protection standards,
both for leukaemia and for all other cancers combined.
Continued follow-up of these workers will be valuable in determining whether
radiation-associated risks vary over time or by age, and enables the study
of specific cancers and causes of death in more detail. The research will
also make a useful contribution to wider national and international studies
on the effects of occupational exposures to ionising radiation.
In a separate paper** published at the same time, researchers at the
Childhood Cancer Research Group at the University of Oxford and the Health
Protection Agency have studied cancer in the children of female radiation
workers. This study does not support an earlier finding of a raised risk of
cancer. In a subgroup of women who worked with radiation during pregnancy,
a weak statistical association was found between maternal radiation work and
childhood cancer, but the evidence is limited by the small numbers involved
and the result may be due to chance.
The two papers are published in the British Journal of Cancer and radiation
workers and their representatives were informed of the results before
Press enquiries: contact the HPA Press Office at the Centre for Radiation,
Chemical and Environmental Hazards on 01235 822744/5 or 822876; e-mails to
chilton.pressoffice at hpa.org.uk
References * Muirhead CR, O'Hagan JA, Haylock RGE, Phillipson MA, Willcock
T, Berridge GLC, Zhang W (2009) Mortality and cancer incidence following
occupational radiation exposure: 3rd analysis of the National Registry for
Radiation Workers. British Journal of Cancer (2009), Volume 100, Issue 1,
** Bunch KJ, Muirhead CR, Draper GJ, Hunter N, Kendall GM, O'Hagan JA,
Phillipson MA, Vincent TJ, Zhang W. Cancer in the offspring of female
radiation workers: a record linkage study. British Journal of Cancer
(2009), Volume 100, Issue 1, pages 213-218.
Notes for Editors
1. The National Registry for Radiation Workers (NRRW) analysis* was funded
by the Health and Safety Executive. Further details of the analysis will be
published in due course in an HPA report available on the Agency's website.
The authors and HPA particularly wish to thank all of the organisations and
individuals participating in the NRRW for their cooperation.
2. Estimates of the long-term health risks from ionising radiation are based
largely on epidemiological studies of the survivors of the atomic bombings
in Japan and of groups exposed for medical reasons. The desirability of
obtaining data on the risks from protracted or low dose radiation exposures
has long been apparent. Consequently, the National Registry for Radiation
Workers (NRRW) was set up in 1976 by the National Radiological Protection
Board, which is now the Radiation Protection Division of the Health
Protection Agency (HPA).
3. The organisations that participate in the NRRW are in the nuclear,
research and industrial sectors. Two earlier analyses of mortality in the
NRRW found some evidence of an association between workers' radiation dose
and leukaemia, after excluding chronic lymphatic leukaemia (CLL) which does
not appear to be radiation-inducible. However, the estimates of radiation
risks derived from these analyses and from a study of nuclear workers in 15
countries, for which NRRW formed the UK component, were imprecise. To
obtain more precise information on the risks of occupational radiation
exposure, the NRRW cohort has now been expanded to include about another
50,000 workers compared to the previous analysis and the period of follow-up
has been extended by nine years, to the end of 2001. Data on cancer
registrations have also been included in the NRRW for the first time,
together with mortality data.
4. As in previous NRRW analyses, there was a strong healthy worker effect
(HWE); overall mortality was 81% of that expected for the general population
of England and Wales, having allowed for the effects of age and gender.
Total cancer mortality was also reduced, being 84% of that in the general
population. The HWE has been seen in many studies of workers, not only
radiation workers, and is likely to reflect factors associated with the
recruitment and retention of persons in work.
5. To study the possible impact of radiation exposure on health whilst
minimising the impact of the HWE, rates of mortality and cancer incidence
within the NRRW were analysed according to workers' radiation dose, which
was assessed through personal monitoring. Mortality and incidence from both
leukaemia excluding CLL and the grouping of all cancers excluding leukaemia
increased to a statistically significant extent with increasing radiation
dose. Estimates of the trend in risk with dose were similar to those for
the Japanese atomic bomb survivors, with confidence ranges that excluded
risks more than 2-3 times greater than the A-bomb values and also excluded
the possibility of no raised risk. There was some evidence of an increasing
trend with dose in mortality from all circulatory diseases combined; for
these diseases, other studies of radiation workers have yielded mixed
results and the NRRW finding may, at least partly, be due to confounding by
smoking. In contrast, both for mortality and incidence, the trend with
radiation dose in cancers other than leukaemia was maintained after
excluding lung cancer, so indicating that this trend is not an artefact due
6. This analysis provides the most precise estimates to date of mortality
and cancer risks following occupational radiation exposure and strengthens
the evidence for raised risks from these exposures. The cancer risk
estimates are consistent with values used to set radiation protection
standards and - both for leukaemia and for all other cancers combined -
exclude the possibility of radiation risks being more than a few times
higher than existing estimates.
7. The separate study** of cancer in the offspring of female radiation
workers was conducted by the Cancer Research UK - funded Childhood Cancer
Research Group (CCRG) at the University of Oxford and HPA. The study was
funded by the Department of Health and follows on from an earlier study
(Draper et al, British Medical Journal, 315, 1181-88, 1997) that examined
whether the offspring of radiation workers were at raised risk of childhood
cancer. This earlier study did not find an association between childhood
cancer and paternal preconception radiation exposure. However, there was
some suggestion of a raised risk of cancer in the offspring of female
radiation workers, although based on small numbers of cases. Consequently,
CCRG and HPA have examined the latter topic further, using more recent data.
Analysis of the new data did not show an association between childhood
cancer and maternal preconception radiation work and does not support the
earlier finding of a raised risk in the offspring of female radiation
workers. However, when the original and new data were combined, a weak
association was found between maternal radiation work during pregnancy and
childhood cancer in offspring, although the evidence was limited by the
small numbers of cases and controls that were linked to the NRRW.
8. The British Journal of Cancer (BJC)
The BJC is owned by Cancer Research UK. Its mission is to encourage
communication of the very best cancer research from laboratories and clinics
in all countries. Broad coverage, its editorial independence and consistent
high standards have made the BJC one of the world's premier general cancer
journals. www.bjcancer.com <http://www.bjcancer.com/>
Fwp-dawson at hotmail.com
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