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Biomedical subjects

R H Mole

Publications and source records attributed to R H Mole.

At least 19 recordsLinked to original sources
PubMed1990

Childhood cancer after prenatal exposure to diagnostic X-ray examinations in Britain.

Detailed data were provided by the Oxford Survey of Childhood Cancer OSCC on deaths from childhood cancer in Britain after irradiation of the fetus during diagnostic radiology of the mother. In each age group at death, 0-5, 6-9 and 10-15 years, excess cancer deaths decreased suddenly for births in and after 1958. A major factor was concerted action initiated in 1956 to reduce radiation exposure of fetal gonads for fear of genetic hazards. Dose reduction was achieved during 1957 and early 1958 by reducing the rising rate of obstetric radiography and by virtually abandoning pelvimetry as that had been understood. In the 1970s the rate of X-raying increased again and so did cancer risk but not significantly. Direct evidence that diagnostic X-rays can cause childhood cancer is the similar excess rate per X-ray in twins and singleton births when X-raying rate is 5-6 times higher in twins. In the past a dose-response for cancer in OSCC data based on number of films per X-ray examination was taken to be evidence for causation but dose per film varies with kind of X-ray examination. Fixed values for dose per film were mistakenly assumed by UNSCEAR (1972) and used by it and others when deriving risk co-efficients. In updated OSCC data cancer risk is independent of film number. The odds ratio for childhood cancer deaths after X-raying in birth years 1958-61 (1.23 with 95% confidence intervals CI 1.04-1.48) and the mean fetal whole body dose from obstetric radiography in 1958 (0.6 cGy) can each be derived from nationwide surveys in Britain. The corresponding risk coefficient for irradiation in the third trimester for childhood cancer deaths at ages 0-15 years = 4-5 x 10(-4) per cGy fetal whole body dose (95% CI 0.8-9.5 x 10(-4) per cGy). It is the same for cancer incidence and mortality. A lower risk in bomb survivors exposed in utero is not incompatible since its CI are wide. There is no dependable evidence that radiosensitivity is greater in early pregnancy. A significantly raised cancer rate after diagnostic X-raying supports the hypothesis that carcinogenesis by ionising radiation has no threshold.

Child↗
PubMed1990

The effect of prenatal radiation exposure on the developing human brain.

Recently reported dose responses in prenatally exposed Japanese bomb survivors for severe mental retardation (SMR), reduced intelligence, and reduced levels of school performance, are compared. The characteristics of, and differences between, severe and mild mental retardation in man are critically important for such comparisons. The meaning of linearity of dose response is not identical for these different forms of damage. When findings on tissue changes in the brain and in functional tests of irradiated experimental animals are taken into account, the dose response for SMR would be expected to have a threshold as is found using DS86 dosimetry. The dose responses for IQ and for school performance seem doubtfully valid: their underlying assumptions need re-examination.

Animals↗
PubMed1990

Severe mental retardation after large prenatal exposures to bomb radiation. Reduction in oxygen transport to fetal brain: a possible abscopal mechanism.

Reasonable expectations, based on the normal physiology of the human fetus, cast new light on the possibilities of extrapolation from the finding of severe mental retardation (SMR) in Japanese bomb survivors after maternal exposure to 1.8-5.5 Gy T65DR Gy. After such large exposures the fetal haematopoietic tissues (DS86 dose 0.9-2.2 Gy) cannot escape severe damage and a consequent reduction in erythropoiesis. Diminished fetal erythropoiesis will diminish oxygen transport from placenta to fetus. Impaired oxygen transport to the developing forebrain will augment the localized forebrain damage caused directly by large radiation doses. Linear extrapolation of an observed linear dose response for SMR after large radiation exposures is unlikely to be a valid method for predicting the frequency of SMR after much smaller exposures causing minimal damage to the fetal haematopoietic tissues.

Female↗
PubMed1987

The so-called 10-day rule.

The 10-day option aimed at restricting all radiography of potentially fertile women to the first third of the menstrual cycle was introduced in 1959 without any valid supporting evidence. No earlier or later experimental evidence has indicated that diagnostic radiography involving the early embryo might carry a measurable risk to the individual developing in utero.

Female↗