UK COMARE 8th Report: A review of pregnancy outcomes following preconceptionalexposure to radiation

["Fred Dawson" <fd003f0606@blueyonder.co.uk>]

COMARE Press release







http://www.comare.org.uk/press_releases/comare_pr07.htm











26 February 2004







COMARE 8th Report: A review of pregnancy outcomes following preconceptional

exposure to radiation







Report available @







http://www.comare.org.uk/press_releases/documents/COMARE8thReporteBook.pdf











Studies on people show little evidence for increases in adverse pregnancy

outcomes in general when mothers or fathers have been exposed to ionising

radiation. Human populations are generally exposed to only relatively low

doses of radiation. Animal studies do suggest that much higher parental

irradiation could increase the frequency of adverse pregnancy outcomes. It

is less easy to make firm judgements about particular adverse outcomes, such

as specific types of congenital abnormality.







The COMARE 8th Report shows that human studies, taken together, provide

little evidence that adverse pregnancy outcomes in general are related to

parental exposure to radiation at the relatively low doses to which most of

the study populations have been exposed. However, the studies of pregnancy

in human parents exposed to radiation have not all looked at the same

outcomes, and do not draw identical conclusions so there are some

uncertainties in their interpretation. Most of the studies of workers have

looked at the effects of radiation exposure of fathers because fewer mothers

have worked with radiation. Only a few studies have enough statistical power

to address specific outcomes, because either the doses are too low or the

study populations are too small.







The data do not indicate a link between congenital abnormalities as a whole

and parental exposure to radiation. Nevertheless, the data on congenital

abnormalities are more suggestive than for other adverse reproductive

outcomes. If there is an association, it is most likely a link between

paternal (not maternal) radiation exposure and incidence of stillbirths and

neural tube defects (spina bifida and anencephaly). However, not all the

relevant epidemiological studies reported such effects, and the only human

studies that did show these effects were conducted on two groups of workers

who received higher radiation doses than workers experience today.







In contrast, animal experiments do suggest that parental irradiation may

increase the frequency of adverse pregnancy outcomes. However, the radiation

doses used in these animal experiments are generally considerably higher

than doses to which humans are exposed. Also, animal experiments are not

necessarily a good model for how humans react to exposure to radiation.















Press enquiries to Professor Bryn Bridges, Chairman (Tel no: 01273-877510)











Notes for editors



The adverse pregnancy outcomes examined in this report include miscarriage,

stillbirth, death in early infancy, congenital abnormalities and alteration

of the ratio of boy babies to girls. Overall, the incidence of stillbirth

and early infant death has declined greatly in recent decades. It is already

known that socio-environmental factors such as coming from a low income

family, having very young parents, parents who smoke, or being first babies

or being one of a multiple birth are associated with a higher risk of

adverse pregnancy outcome. These possible confounding factors can complicate

the interpretation of epidemiological studies.







Recently radiation has been shown to produce subtle changes in chromosomes

that are unlikely to cause outcomes as serious as those described above.

Whether such changes have any significant consequences for human health is

at present unclear.







COMARE, in its Seventh Report, published in 2002, considered the evidence on

whether irradiation of parents resulted in increased levels of cancer in

their offspring. COMARE concluded that most studies found no evidence of a

causal link between workers exposure to radiation and cancer in their

children. However, there is a well-known cluster of childhood cancer in the

village of Seascale, close to Sellafield, which had been suggested to result

from paternal exposure to radiation. This now seems unlikely and while the

reasons for this cluster are not understood, it has been suggested that

population mixing or some related factor may well play a part.



=====================================



Fred Dawson

New Malden

Surrey. KT3 5BP

England



020 8287 2176





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