It is now widely accepted that radiation can cause harm to human beings. It causes cancer, it can lead to mutations and it can affect generations beyond those exposed. The first radiation-induced cancer of the skin was seen in 1902 only six years after its discovery. New evidence has led to the radiation dose limit being lowered five times since its introduction in 1934 (see Figure 1).
Health impacts
A variety of health impacts can occur depending on whether the harm occurs within the individual affected (somatic) or in a descendant (genetic), and they also vary according to whether they occur quickly or after a long time lag. Both somatic and genetic effects can be acute or chronic. Cells can be damaged in two ways — high doses can cause damage to the bone marrow, skin burns such as those found in the early radiologists, or death; whereas low doses can trigger cancers which do not show up for a long time varying from two to 40 years.
DNA (deoxyribonucleic acid) – the coded information contained within the chromosomes which carries the genetic memory of the cell – can be easily damaged by the radiation induced free radicals if they form close to it, or, DNA can be damaged if it experiences a direct hit.
Defence systems
The body has developed systems by which it can defend itself and thus prevent diseases from developing. Besides making it difficult for substances to gain entry, the immune system operates to protect against infections using some specialised cells. One such, lymphocytes, develop from stem cells in the bone marrow and produce antibodies. This lymphatic element effectively is the immune system. The problem with mutated cells is that they are part of the human body. They are one of its own cells gone wrong and are thus not detected by this system. In children who are affected, this can mean developing an allergy or a cancer.
Non-cancer effects
One of the problems for understanding these effects can be the period of time which elapses between the exposure and the appearance of a disease which is known as the ‘latency period’. Some work has demonstrated such effects at low doses; a Swedish study of people X-rayed young (less than 18 months old) to treat benign tumours of the blood vessels showed adverse effects on intellectual development.
Chernobyl
Following the Chernobyl accident, an increase in childhood thyroid cancer was observed. It was suggested that the latency period was too short and that the pathology had been faulty; that cases were only being found because people were looking for them and that Iodine-131 was safe. However, the increased incidence was verified by Professor Dilwyn Williams when he compared a map of the exposure to I-131 fallout with that of the distribution of cases. While I-131 is used to treat adults, such exposure is not benign for young people. Williams is convinced of the need to study Chernobyl on a scientific basis – just as Hiroshima and Nagasaki continue to be studied - in order that data arising from fallout after the accident can be incorporated into the risk estimates which evolved from the studies of the atomic bomb survivors (ABS) and which did not capture these early years.
Childhood leukaemias
25 years ago Yorkshire TV made a programme about childhood leukaemia in the vicinity of the Sellafield nuclear power plant. Later it was discovered that there were also increased incidences of childhood leukaemias near the Dounreay reprocessing plant and around the Aldermaston Atomic Weapons Establishment in Berkshire and elsewhere in Europe. Recently a case control study of the Childhood Cancer Registry in Germany showed that there was an increased risk of children developing tumours or leukaemia. Those under five years old living within five kilometres of one of the 16 nuclear power stations in Germany had twice the risk.
Summary
Some of the effects of radiation are difficult to detect and they take time to show up so that the full story is not yet available. One of the problems in obtaining full coverage of those experiencing the effects of ionising radiation is that they can contract or die from some other illness before the effect of the ionising radiation becomes apparent. The development of a cancer in itself contributes to a loss of immune system. Thus someone is more likely to die from an infection than from the underlying cause. In the case of children infections are 400 times more likely to kill them than the underlying cancer.
Dr Alice Stewart referred to this as “Competing Causes of Death”. One of the reasons that the emerging rise in childhood leukaemias became apparent in the 1950s was that the introduction of antibiotics had led to a decrease in infectious causes of death.
A good epidemiological study requires that the confounding factors – things which could affect the true picture – are recognised and taken account of. Damage to the bone marrow has complicated the picture emerging from the studies of Atomic Bomb Survivors. Also it can be very expensive and difficult to locate and follow the populations needed for a comprehensive and meaningful study. The accident at Chernobyl has shown that. There are much safer, more effective and more sustainable answers to the energy crisis then a return to nuclear power — and remember, no-one has an answer to what to do with the waste from the first generation yet….
Jill Sutcliffe is a scientist. She has written about the environmental and health effects of the use of uranium.
