ICAN around the world
Radiation and human health
See below for estimating the risk from radiation and the health effects of a nuclear attack. Download articles by IPPNW doctors on nuclear weapons and health issues:
- Nuclear Weapons, Nature and Society by Dr Sue Wareham.
- PowerPoint presentation on uranium mining, radiation and health by Clive Rosewarne from the Public Health Association of Australia (NT)
We exist in a naturally radioactive environment: the sun, the rocks and mountains produce a “background” level of radioactivity.
Average exposure to background ionizing radiation worldwide is measured at approximately 2.4 millisievert (mSv) a year, but this varies from place to place. About half of this is from radon gas and its decay products.
However, human activities from 1945 onwards have increased our exposure to ionizing radiation, through atomic weapons development, testing and use, and through nuclear power generation, including uranium mining. It is estimated that the atmospheric fallout alone that was taken up by humanity until the year 2000 from the nuclear weapons testing in the 50's and 60's will cause 430,000 fatal cancers worldwide.
There is no level of radiation exposure below which we are at zero risk: even very low-level medical exposures such as chest X-rays (0.04mSv per test) carry a quantifiable risk of harm, such as cancer promotion.
Ionizing radiation also causes damage to DNA: the genetic material in living cells. A cell can repair certain levels of damage in its chromosomal DNA, especially at low levels of damage. However, faulty repairs can occur and may lead to proliferation of abnormal cells, which then form a cancer. Such cancers will generally take many cell generations to develop, and it may be several decades before the cancer is detected.
At higher levels of radiation exposure, cell death results. In parts of the body where cell turnover is normally high, such as the gastrointestinal tract and bone marrow, cells may not be replaced quickly enough, and tissues fail to function. This can be fatal. Because rapidly proliferating and differentiating tissues are very sensitive to radiation damage, the foetus is particularly vulnerable.
Exposure of the foetus to radiation has been shown to increase the risk of childhood cancer. In addition, rates of microcephaly (inadequate brain development) were increased in individuals who were exposed in the womb to the radiation of the Hiroshima and Nagasaki bombings. Long-term genetic effects are also possible if the damage to the DNA occurs in a reproductive cell (egg or sperm), whereby the error may be passed on to future generations.
Radiation health authorities use scientific modelling to calculate and set “permissible limits” for ionizing radiation exposure. As our understanding has increased, the recommended exposures for both the public and for workers in the nuclear industry the workforce have steadily been reduced. Levels once regarded as “safe” are now known to be associated with health risks.
The most widely use recommended dose limits for radiation exposure are those set by the International Commission on Radiological Protection (ICRP). Current recommended exposure limits are 20 mSv / year for workers in the nuclear industry, and 1 mSv / year for the general public. These recommendations were set in 1991, and are significantly lower than levels previously thought “safe”.
In June 2005, the US National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation (BEIR VII) affirmed the “linear no threshold” model of estimating risk from radiation exposure, that is, the risk of cancer proceeds in a linear pattern at low doses and even the smallest dose has the potential to cause a small increase in risk to humans. The BEIR report estimated that a cumulative dose of 100mSv over a lifetime would cause 1 in 100 people to develop cancer.
It should be noted that these are risks averaged over the whole population, and the risks in vulnerable groups is higher. Women have a higher risk of solid cancer induction than men, and children (especially girls) are particularly vulnerable.
Health effects of a nuclear attack
In Hiroshima approximately 80,000 of its one quarter of a million population died immediately from the atomic bombing on August 6, 1945.
By the end of 1945 the death toll was an estimated 140,000 people.
In Nagasaki, the immediate death toll was approximately 40,000 people, and the toll by the end of the year was 70,000.
Stills from footage of a US nuclear bomb test
The effects of these two bombs are continuing. They have led to significantly increased rates of cancer among the bomb survivors and, because of the delay between radiation damage and onset of its effects, the numbers of cancers have not yet reached their peak. According to Mayor Tadatoshi Akiba, Mayor of Hiroshima, the total death toll from the Hiroshima bomb alone, as at August 6, 2004, was 237,062.
There are about 270,000 Hibakusha, "bomb affected people," still living in Japan.
At the hypocentre of a nuclear bomb explosion, everything is immediately vaporised by the high temperatures. At Hiroshima ground temperatures reached 11,000 degrees F. and ceramic tiles within 600 metres of ground zero melted.
Outward from the hypocentre deaths and injuries include burns, multiple fractures and other injuries from flying debris from collapsed buildings, other blast and shock wave effects, blindness and radiation sickness due to acute exposure to high radiation.
Radiation sickness symptoms include haemorrhaging, nausea, vomiting, diarrhoea, mouth and other gastrointestinal ulceration, bleeding gums and bruising, fatigue, and loss of hair. Loss of white blood cells leads to the onset of fever and life-threatening infections. These effects will develop within hours, days or weeks, depending on the size of the dose.
In the longer-term, radiation in the form of “fallout” occurs downwind of a nuclear explosion. The fallout may then be inhaled by people and animals or ingested through contaminated food and water. In Hiroshima, a mild westerly wind was blowing at the time of the explosion, and a “black rain” (rain with fallout) fell from the north to the east of ground zero. The black rain was sticky, and people at that time thought that oil had been dropped.
The long-term effects of radiation include a large number of malignancies: both solid cancers (such as breast, thyroid and lung cancers) and leukemia.
Leukemia risk is greatest for those exposed at a young age and the peak of leukemia onset is about 7 to 8 years after exposure.
For solid cancers the latent period (time to develop) is generally much longer – often many decades after the exposure. In addition, children exposed as foetuses to the Hiroshima and Nagasaki bombs had a significantly increased rate of microcephaly and intellectual disability.
