The Committee agreed that the CERRIE Report should state that the Committee was aware that depleted uranium was an ongoing issue, but that it did not have sufficient time to investigate the matter in any detail to add to other recent expert reviews.


In early December, the Chairman had issued a brief press statement to deal with a sudden flurry of media enquiries in East Anglia concerning the Committee's ongoing study on cancer incidence and mortality near the Bradwell power station. This had proved necessary to deal with the volume of queries and the misleading emphases of the press reports. Local reporters had stated they had been telephoned by a member of the Committee. The Chairman invited the member to comment. The member denied having initiated contact with the media. The Chairman reiterated his advice that where members wished to contact the media on a CERRIE matter, they should first contact him to discuss the matter.


The evidence of the A-bomb survivors and radiotherapy patients showed a correlation between mortality from non-cancer diseases - particularly cardiovascular (CV) diseases - and exposures to radiation. These correlations existed at high doses and it was unclear whether they could be extrapolated to low doses. UNSCEAR was currently investigating these associations. Reports existed of increased mortality and morbidity from post-Chernobyl environmental exposures, but the impact of population relocations was unclear. The risk of non-cancer radiation effects could be quite important compared to the risk of radiation-induced cancer; further work was needed in order to more completely assess that risk.

Russian studies of non-cancer effects in children exposed to post-Chernobyl Cs-137 had reported a correlation between Cs concentration and disease, and an association between internally incorporated radio-caesium and increased congenital malformations and a significant increase in cardiac pathology. Further post-Chernobyl studies had found cognitive and psycho-physiological abnormalities in children irradiated in utero, and chronic fatigue syndrome in Chernobyl liquidators. In addition, effects had been observed in those exposed post-Chernobyl including low birth weight, reduced life span, miscarriage, immuno-depression, endocrine disorders, mental retardation and psychological disorders. However these papers were often written in Russian, although presumably they were being considered by UNSCEAR. However a recent study of the age longevity of Japanese bomb survivors had observed little correlation with exposure to radiation. UNSCEAR and other published reports indicated that the life-shortening observed in animal studies was almost totally due to cancer.

Swedish evidence from X-rays of left sides vs right sides of chests indicated a three-fold increase in cardiovascular effects which appeared to indicate that doses to the heart were important. In this case, effective dose would be inappropriate and heart dose should be considered.

The biological plausibility of non cancer effects at low dose and dose rates was examined. Recent molecular studies cast doubt on the monoclonal origin of atherosclerotic plaque in diseased blood vessels and thereby on possible linearity of the dose-response for plaque induction. However other researchers had carried out studies to repeat these findings without success. The available data were only for doses of >0.5 Gy; resolution below these doses was not possible. In non-cancer studies, it was necessary to use organ doses rather than effective doses which were cancer-weighted doses.

Dose-response curves from the A-bomb survivors did not immediately point to a threshold indicating that small risks of radiation-induced heart disease at low doses needed to be examined. The same mechanisms, ie cytokines, existed for cancer as well as non-cancer effects; remarkable similarities existed between the two kinds of effects. The basic mechanisms underlying radiation-induced instability and bystander effects were mechanistically similar to inflammatory responses. Inflammation was a known risk factor for many diseases including both cancer and cardiovascular disease. Therefore the potential existed for similar underlying mechanisms for both cancer and non-cancer effects. If it were accepted that bystander effects amplified radiation effects, then a hypothesis-generating mechanism existed for both cancer and non-cancer effects at low doses.

The Committee concluded that real non-cancer effects were clearly being observed, but with the usual problem of how to extrapolate these effects down to low doses.


The Committee examined data on infant mortality and radioactive contamination from atmospheric weapons testing fallout and other sources. The substantial variation observed in the national rates emphasised the importance of background (eg socio-economic) factors in determining the risk of infant mortality. Significant deviations in the steadily decreasing rate of first day neonatal mortality and stillbirth during 1950-1980 were observed in England & Wales and the USA. However, the temporal pattern of this deviation did not match the temporal distribution of fallout doses, especially the disappearance of the deviation in 1980 when the fallout doses remained high.

The statistically significant increases in post-neonatal infant mortality in two special towns near the Mayak nuclear facility in Russia were due to respiratory diseases heavily influenced by background socio-economic factors. This was indicated by the higher rate of childhood mortality from respiratory diseases in Russia than in the two special towns near Mayak.

The data for infant mortality and stillbirth in Seascale showed reduced rates relative to the national average. This was not unexpected given the socio-economic class profile of the population, but radioactive contamination of the area seemed to have no perceptible influence on these rates. Obstetric outcomes of Seascale births showed no adverse effect of living in the village. Stillbirth rates in the general vicinity of Sellafield showed no relationship with distance from the site or with distance from the coast. In summary, the epidemiological evidence for a discernible impact of radionuclides from fallout or discharges from nuclear reprocessing plants upon the risk of perinatal mortality was unpersuasive in that there was no consistent pattern across the available datasets.

On the other hand, the reduction in birth rates due to the large increase in abortions post-Chernobyl might have hidden an increase in infant mortality. Also the discrepancy in the dates between various reports was due to US bombs earlier than 1958. In areas of high fallout high levels of infant deaths from congenital heart defects were observed, and pre-leukaemic children had higher levels of death from infection and respiratory illnesses than healthy children. A 1970 report by the Department of Health and Social Security had concluded that there was an increased rate of childhood deaths in the mid-1960s but the report did not ascertain any reason for this.


The Chairman welcomed Mr. Elliot Morley MP, Minister for the Environment, to the meeting and introduced him to members of the Committee and Secretariat. Mr. Morley stated that he was glad to meet the Committee and he expressed his appreciation for their work. He assured the Committee that he was very interested in its deliberations. He stated CERRIE was an important Committee and he looked forward to reading their final report which he hoped would provide guidance to the Government for the future. He also hoped the Committee would aim for consensus and that a minority report would be avoided.


The interaction between radiation and other agents was a complex issue. Additive interactions were expected where both agents showed a linear dose response in the dose range of interest. Synergistic (ie multiplicative) interactions were more likely when chemicals acted as a tumour promoter after the initiation stage. Various studies indicated that

(a) At low exposure levels there was no clear evidence for major deviations from additivity of response; in general, genotoxic agents were expected to interact with radiation in a concentration-dependent additive manner.
(b) At high combined exposure levels, synergistic or antagonistic effects may be expected eg. the dose-response for some non-genotoxic carcinogens had a recognisable low dose threshold.
(c) Epidemiological data were supportive of a synergistic but sub-multiplicative interaction for lung cancer risk between radon exposure at intermediate to high doses and intakes of tobacco smoke; data on other possible interactions were not suggestive of strong interactions at low to intermediate levels of exposure.
(d) Tumour promoters or antagonists in diet were expected to influence low dose radiation risk in the same way as applies to spontaneous cancer.
Assessments of human cancer risk from single agents at low doses were generally applicable to concurrent exposures involving multiple agents; strongly-acting tumour promoters were an exception to this generalisation. Overall, the most substantial modification of radiation cancer risk probably derives from a complex interplay between dietary intakes (caloric value, fat content, vitamins etc), lifestyle (tobacco use) and, particularly for breast cancer, reproductive factors.

Work on skin tumorigenesis in rats indicated inflammation acted as a tumour promoter but at high radiation doses to surrounding tissue. Various studies had examined interactions between chemicals, vitamins, hormones, UV light and other agents, and had concluded that there was evidence for synergistic as well as additive effects. German studies had found synergistic effects between various agents and radiation, and a UK study had explored synergistic effects between a priming radiation dose and a subsequent chemical insult. It would have been advantageous for there to have been a follow-up to this study to ask specifically whether radiation rendered the receptor sensitive to subsequent insult. A number of UK papers existed on the interplay between chemicals, plutonium and external gamma radiation which provided a strange pattern of results.


The Committee considered a peer-reviewed paper which stated that at least seven steps were involved in the assessing of doses and risks from internal emitters. Each step involved uncertainties which had to be combined in some way to make an overall uncertainty. A key issue was whether one added or multiplied the uncertainty factors from each step. Another issue was the conceptual errors in the models used in each step. The uncertainties in estimated dose coefficients for some nuclides were large and significant.

The consequences of the non-homogeneous distribution of nuclides within tissue were recognised as important. In 1977, the ICRP had concluded that, where inhomogeneity existed, the single application of a weighting factor may lead to errors in risk definitions.

On microdosimetry, events at cell level did not often correspond with events in the macroscopic (ICRP) model, however an alternative microdosimetric model for general application did not exist. The role of microdosimetry was considered to be to question the validity of assumptions made in ICRP models and inform their development. Although gaps existed in current knowledge of the distribution of nuclides in relation to target cells, the ICRP incorporated information when it was available.

The Committee then considered a second paper which stated that uncertainties in radionuclide dose coefficients arose from biokinetic models, dosimetric models, and wR (for equivalent dose) and wT (for effective dose). The ICRP in its publications had not addressed uncertainties in dose coefficients because these were intended for use in prospective dose assessments at doses well below limits, and because of the difficulties in quantifying uncertainties in an understandable way.

Uncertainties depended on the reliability of available human and animal data and the complexity of the behaviour of the element/radionuclide. Least uncertainty attached to Cs and H (as HTO) biokinetics, with good human data supported for HTO by animal data and our understanding of physiological/ biochemical processes, and the simple assumption of homogenous distribution in soft tissues. Substantially more uncertainty was associated with the biokinetics of elements such as Ru, Zr and Sb for which few data were available and whose behaviour was more complex. Uncertainties in dose coefficients were small for some radionuclides (eg. 3H, 137Cs, 90Sr) but large for other radionuclides (eg. 210Pb, 210Po, 239Pu, 241Am), particularly for intakes by children. Reliable quantitative estimates of uncertainties in dose estimates for a range of radionuclides were not yet available.

The present system of dose and sieverts facilitated the regulation of radioactive discharges to the public and radiation exposures at work, and there was no alternative to this at present. However the system had its limitations and was prone to possible error. The Committee agreed for recommendations on this area to be drafted by a subgroup of the Committee for consideration at the next meeting.


The Committee returned to the subject of tritium, and considered a paper which discussed RBEs for HTO and 3HTdR. Based on dose to the nucleus, the RBE for the latter was twice that of the former. Based on averaged dose to the cell, the difference was a factor of about 6, although many uncertainties were involved in the calculation of doses at these levels. Environmental exposures to tritiated DNA precursors were negligible in most areas of the country. OBT in flounders near Cardiff had been shown to be largely in the carbohydrate and lipid fractions. A UK study suggested the intestinal absorption of intact 3HTdR was less than 10%, with subsequent catabolism such that only about 2% was incorporated into DNA. As regards the need to increase tritium's wR, the ICRP did not distinguish between low LET radiations in specifying wR values - a value of 1 was used despite differences in RBE of up to a factor of four. It was suggested that this was consistent with other generalisations used in calculating dose coefficients, including the use of a single wR of 20 for alpha particles.


The Committee considered an ICRP editorial on the changes in radiation weighting factors recently introduced by ICRP Report 92. The changes were for protons and neutrons and were of little significance for CERRIE. The editorial contained a warning not to use effective dose for epidemiological studies or other specific investigations of human exposure. For these other studies, absorbed dose in the organs of interest and specific data relating to the RBE of the radiation type in question were the most relevant quantities to use. In addition, in paragraph 32 of ICRP 60 the ICRP had encouraged the use of specific information where this was appropriate - including RBEs - for example, in interpreting epidemiological data or attributable risk calculations. However it was argued this advice did not apply to tritium, as a study on carcinogenesis had indicated an RBE of 1.3, although a considerable body of other experimental evidence and theoretical information indicating RBEs of 2 to 3.


The Committee considered a paper on the distribution of internal emitters, particularly auger and weak beta emitters. Auger emitters were nuclides some of whose decays occurred via atomic inner shell vacancies following electron capture, internal conversion or isomeric conversion. The process resulted in the emission of between 1 to 30 electrons from KLM shells with low energies, medium LET values and extremely short ranges in tissue. This meant that their effectiveness depended very much on their distributions in cells and tissues. Auger emitters with the following characteristics were important in terms of radiation protection:

• occurrence in significant quantities
• significant % of decay numbers via Auger process
• significant % decay energies via Auger process (nuclides with small Auger energies but high energy gammas which largely escaped the body were also important)
• evidence of concentration in cell nuclei, or in DNA with extremely weak Auger emitters
• a large number of Auger electrons from a single decay, allowing substantial overlap of electrons within a few nanometers from decay point

Because of the great diversity of Auger emitters, it was advisable to refer to radionuclides individually rather than refer to Augers as a group. Augers occurred naturally in the various Uranium series, in nuclear wastes, and particularly in nuclear medicine where annual collective doses from Auger administrations were estimated to be high. These considerations also applied to low energy beta emitters, which decayed via the emission of an electron from the nucleus rather than from electron shells: the most significant low energy beta emitter was tritium.


The Committee decided not to use the "some said this, some said that" approach in the final report. This had used in the Preliminary Report, and had been the subject of adverse comment during the Cerrie Workshop. It would be necessary to be transparent in the reporting the balance of views within the Committee on each issue in the final report.


The Committee examined a paper which examined published childhood leukaemia registration data from the cancer registries in Connecticut, Saskatchewan and New Zealand. This also utilised the incidence datasets based on annual registrations in Denmark, Sweden, Norway, and Finland and Great Britain that had been made available to CERRIE. All eight of these registries possess reliable incidence data covering the period following the sharp peak of weapons testing fallout. When the registration rates for young children under five years of age during 1950-1990 were plotted a striking consistency across the eight rates was found, and there was no evidence of the notable increase in childhood leukaemia in the mid and late 1960s that would be predicted if the risk of exposure to fallout radionuclides had been greatly underestimated. Further, the doses from fallout were materially lower in the Southern than in the Northern Hemisphere, and yet the incidence rate of childhood leukaemia in New Zealand was very similar to the rates pertaining in the Northern Hemisphere after the peak fallout exposures. Consequently, the incidence rates of leukaemia in young children in the period following the sharp peak of fallout doses provided evidence against a major underestimation of the risk of childhood leukaemia from exposure to radionuclides in weapons testing fallout and discharges from nuclear installations.

The Committee then considered a second paper which examined data sets on annual leukaemia incidence in children from 1948 to 1983 for the five Nordic countries to see whether these could be related to radioactive fallout from weapons testing. Except Denmark, the data for the other Nordic countries showed annual variations reasonably in line with a Poisson distribution. For Denmark, a non-random anomaly existed: for children under 5 years of age, born in 1965 and 1966, the leukaemia incidences were far above the normal statistical fluctuation. If radioactive fallout were postulated as a likely cause, the absence of a similar anomaly in the other four Nordic countries, with higher rainfall, would require explanation. Thus, whilst a raised leukaemia incidence in the 1965/66 birth cohorts from Denmark had occurred, no obvious cause was apparent and it was unlikely to be due to fallout.

Next (Meeting 13)