G. W. Kneale

Radiation exposures of Hanford workers dying from cancer and other causes.

AbstractData from the Hanford study have shown that sensitivity to the cancer-induction effects of radiation is at a tow ebb between 25 and 45 yr of age. Nevertheless, at younger and older ages there is probably a cancer hazard associated with low level radiation which affects bone marrow cancers mo

A-bomb radiation and evidence of late effects other than cancer

Cancer risk coefficients for ionizing radiation are currently based on the assumption that, after the bombing of Hiroshima and Nagasaki, there were no late effects of early selection (survival of the fittest) or acute marrow damage. These negative findings were the result of applying a linear model of relative risk to the deaths of 5-y survivors. By applying a linear-quadratic model to these deaths (i.e., a model with more than one degree of freedom), we have obtained evidence of longstanding competition between selection effects of the early deaths and other radiation effects, and also evidence that late effects of radiation include marrow damage as well as cancer. Consequently, the present method of risk estimation--by linear extrapolation of high dose effects--should no longer be used for estimating the cancer effects of occupational exposures or background radiation.

Job related mortality risks of Hanford workers and their relation to cancer effects of measured doses of external radiation.

This paper continues the series by Mancuso, Stewart, and Kneale (MSK) on studies of cancer risks for radiation workers at Hanford. It concentrates on the statistical problems posed by the need to estimate and control for job related mortality risks when there are several changes of occupation and no certainty about how different occupations are related to two socioeconomic factors which have strong health associations--namely, education and income. The final conclusion is that for tissues which are sensitive to cancer induced by radiation there is a risk of cancer for Hanford exposures whose dose response is curvilinear with long latency and increasing effect with increasing exposure age.

Immunizations against infectious diseases and childhood cancers

SummaryA study based upon an unusually large series of childhood cancers and matched controls found a significant deficit of case/control pairs in which the cancer case had fewer immunizations against infectious diseases than the matched control. All types of immunizations and cancers were affected but the case/control differences were more pronounced for older cases with late immunizations than for younger cases with early immunizations, and more pronounced for solid tumours than leukaemia. Therefore there may be immune system responses to immunizations (or simulated infections) which make it difficult for small clones of cancer cells to enlarge and are more successful in preventing localised tumours in adolescents than childhood leukaemias.

The immune system and cancers of foetal origin

SummaryEvidence of early loss of immunological competence in cases of neoplasms occurring in juveniles was found in an analysis of OSCC data (Oxford Survey of Childhood Cancers). The effects observed included heightened sensitivity to infection from birth onwards for all types of childhood cancer, higher levels of sensitivity for leukaemia than for lymphomas, and higher levels for lymphomas than for other solid tumours. The findings as a whole are consistent with in utero loss of immunological competence, which is an essential promoter of cancers of foetal origin and thus allows the outcome of an in utero cancer induction to be influenced both by maternal levels of immunological competence and postnatal infection.

Identification of occupational mortality risks for Hanford workers.

Though most of the production work at Hanford is done by manual workers, 46% of the most dangerous jobs are performed by people who have professional or technical qualifications. For these privileged workers occupational mortality risks are positively correlated with radiation doses but for manual workers, who have relatively high death rates, there is an inverse relation with dose. The high ratio of professional to manual workers is clearly the reason for the industry having fewer observed than expected deaths and the inverse relation with dose for less privileged workers is probably a sign that there has been selective recruitment of the most highly paid manual workers--that is, skilled craftsmen into the more dangerous occupations. Evidence of this selective recruitment was obtained by equating danger levels with levels of monitoring for internal radiation. Therefore, there should be some control for these levels in any analysis of cancer effects of the measured dose of radiation.

A-bomb survivors: reassessment of the radiation hazard.

Newly released data from the Radiation Effects Research Foundation on the survivors of the Hiroshima and Nagasaki A-bombing allow a reassessment of radiation hazards. It appears that deaths from marrow damage (such as aplastic anaemia) continued after 1950. The Life Span Study cohort appears biased in favour of persons with high immunological competence, the result of infants and the elderly being more likely to die before 1950 than young adults. A study of survivors of in utero exposures suggests that embryos are more sensitive to the lethal effects of radiation than more mature foetuses. Current estimates of cancer risks from radiation may only apply to young adults with high immunological competence; young children and the elderly may be at greater risk.