RE: Lucas Hts Reactor

["Sandy Perle" <sandyfl@EARTHLINK.NET>]

I received this from Dr. Don Higson, AUSTRALASIAN RADIATION 

PROTECTION SOCIETYNEWSLETTER NO. 25, MARCH 2002



HEALTHY RADIATION WORKERS



An abbreviated literature review by D J Higson



A recent study of health records of the workforce at ANSTO's Lucas 

Heights Science and Technology Centre (formerly the AAEC Research 

Establishment) has shown that radiation workers have lower mortality 

rates from all causes and from all cancers than the general 

population [1]. The Lucas Heights data cover more than 7000 past and 

present employees, from 1957-1998. This study was part of a research 

programme being carried out in conjunction with the International 

Agency for Research on Cancer (IARC) in France and its results add to 

the much larger pool of data already held by IARC.



The findings of this Australian study are similar to the findings of 

epidemiological studies of the health of workers who have been 

exposed to low levels of ionising radiation in the course of their 

occupations elsewhere in the world, and has often been explained as 

the "healthy worker" effect. According to this argument, it is 

reasonable to expect that a group of workers should be more healthy 

than an average group (with the same age and sex distribution) from 

the general population. After all, they must at least be healthy 

enough to get out of bed regularly and go to work.



Another possible explanation is that aspects of their work or working 

conditions contribute to making them healthier, for example:



· medical screening before and during employment

· congenial and salubrious work environments

· specialised training

· exposure to radiation.



The proposition that beneficial effects from exposure to radiation 

could be a major factor contributing to the health of radiation 

workers may be regarded as controversial by many people. From a 

scientific point of view, it is difficult to understand why this 

controversy still exists. The possibility of beneficial effects from 

low doses was recognised by the ICRP in 1990, although the available 

data were considered to be insufficient to be taken into account in 

radiological protection [2]. The available data were reviewed by 

UNSCEAR in 1994 [3] and the existence of biologically positive 

effects of radiation was confirmed, even though their mechanisms were 

not fully understood. Since 1994, further work has been published 

(e.g. at IRPA-10) which helps to elucidate these effects and the ways 

in which they occur.



UNSCEAR [3] discussed several studies of the health of workers who 

were occupationally exposed to gamma-radiation. Significant evidence 

of beneficial health effects was found in the results of the US 

nuclear shipyard workers study (NSWS) [4]. Other studies were 

considered to be inconclusive. In the NSWS, carried out between 1980 

and 1988, the death rates of -

· 28,542 nuclear workers, having cumulative occupational doses 

greater than 5 mSv (collective occupational dose ~1,450 man-Sv), were 

compared with

· 10,462 nuclear workers, having cumulative occupational doses less 

than 5 mSv (collective occupational dose ~26 man-Sv), and with

· 33,352 non-nuclear workers, having the same age distribution but no 

occupational exposure.



The total database for this study covered almost 700,000 shipyard 

workers, including about 108,000 nuclear workers. The three study 

groups were selected to represent workers doing identical work and 

given the same health care. Although the title of the report [4] 

implies that this was a study of the general health effects of 

exposure to radiation, it was primarily directed toward adverse 

health effects - risks - and it did not find any. In fact, the data 

show that mortality rates from all causes and from all cancers were 

lower for the workers with the higher exposures, although this was 

not identified as a finding of the study [4,5].



It is not clear why the reduction of mortality rates was not recorded 

as a beneficial health effect of radiation in the report of the NSWS 

[4]. Apparently, such an effect was not expected when the study was 

undertaken and perhaps it was not considered relevant to the purpose 

of this study. However, the effects are clearly indicated by the data 

[5]. UNSCEAR [3] recognised and drew attention to the reduction in 

mortality rate from all causes, concluding that it "cannot be due to 

the healthy worker effect alone".



I had always assumed that the NSWS data were pooled (with similar 

data from other sources) into the much larger IARC study (published 

in 1995) of cancer mortality among workers who had protracted 

occupational exposures in the nuclear industries of the US, UK and 

Canada [6]. Why would they not be? Advice from the author of 

reference [5] and a rereading of reference [6] has left me in some 

doubt on this matter. In any case, the purpose of the IARC study was 

to look only for significant dose-related increases in mortality; 

data showing significant dose-related decreases were effectively 

excluded. With this vital limitation, the IARC study found that there 

is "no evidence of an association between radiation dose and 

mortality from all causes or from all cancers", for individual doses 

up to 100 mSv. 



A more recently published paper [7], examining the causes of death of 

2,698 British radiologists over a period of 100 years, contains some 

of the most interesting and revealing information on the health 

effects of working with radiation. This is despite the fact that the 

subject group is relatively small and, again, the findings of the 

study are somewhat clouded by its main aim of looking primarily for 

evidence of increased cancer risk. The data are clearly summarised in 

the paper, as follows.



Male radiologists who first registered in the period 1897-1920 

incurred individual lifetime doses of the order of 20 Sv (20,000 mSv) 

and experienced substantially higher rates of cancer mortality than 

other male medical practitioners and members of the public. 

Radiological protection measures, introduced from 1920, led to the 

progressive reduction of lifetime occupational doses to around 

100 mSv by 1955-1979, and to the reduction of cancer mortality. For 

radiologists who first registered in the period 1955-1979, the 

total cancer mortality rate was substantially lower than for other 

medical practitioners and for members of the public. Furthermore, 

the radiologists had a lower rate of non-cancer mortality than other 

medical practitioners, over the whole 100-year period covered by 

this study.



The low cancer and non-cancer mortality rates in the group of 

radiologists who first registered in the period 1955-1979, compared 

with other medical practitioners, is explained in the report of the 

study as "likely to be at least partly owing to the healthy worker 

effect". Well! There may be various reasons for medical practitioners 

being healthier than the general public. However, when a group 

of medical practitioners who work with radiation is shown to be 

healthier than the rest of the medical profession, it seems likely 

that 

this is because they work with radiation.



The same may be true for others who work with radiation and 

radioactive materials. Clearly, high levels of occupational exposure 

should be avoided, but low levels of radiation (up to, say, 100 mSv 

in a working life) appear more likely to be beneficial than harmful.





References

[1]	Habib, R. (2001), doctoral thesis submitted to the University of 

New South Wales (see ANSTO Briefing at 

http://www.ansto.gov.au/info/press/2001b/b05.html ).



[2]	International Commission on Radiological Protection, 1990 

Recommendations of the International Commission on 

Radiological Protection. ICRP Publication 60, Pergamon Press, Oxford 

(1990); paragraph 46.



[3]	United Nations Scientific Committee on the Effects of Atomic 

Radiation (1994), Adaptive Responses to Radiation in Cells 

and Organisms. Document A/AC.82/R.542, contained in the 1994 UNSCEAR 

report to the United Nations General Assembly. 



[4]	Matanoski, G. (1991), Health Effects of Low-Level Radiation in 

Shipyard Workers. Final Report (471 pages). Report No. 

DOE DE-AC02-79 EV1005. US Department of Energy, Washington, DC, USA 

(1991).



[5]	Cameron, J. (2001). Is Radiation an Essential Trace Energy? Forum 

on Physics & Society of The American Physical 

Society, October 2001 (see also 

http://www.aps.org/units/fps/oct01/a5oct01.html )



[6]	Cardis, E., Gilbert, E.S. et al (1995), Effects of Low Doses and 

Low Dose Rates of External Ionizing Radiation: Cancer Mortality among 

Nuclear Industry Workers in Three Countries. Radiation Research, 142, 

117-132, 1995. 



[7]	Berrington, A., Darby, S.C., Weiss, H.A. and Doll, R. (2001), 100 

Years of Observation on British Radiologists: Mortality from Cancer 

and other Causes 1897-1997. The British Journal of Radiology, 74, 507-

519, 2001.







-------------------------------------------------

Sandy Perle

Director, Technical

ICN Worldwide Dosimetry Service

ICN Plaza, 3300 Hyland Avenue

Costa Mesa, CA 92626



Tel:(714) 545-0100 / (800) 548-5100  Extension 2306

Fax:(714) 668-3149



E-Mail: sandyfl@earthlink.net

E-Mail: sperle@icnpharm.com



Personal Website: http://sandy-travels.com

ICN Worldwide Dosimetry Website: http://www.dosimetry.com



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