Chernobyl 30 years on: lessons on low-dose radiation exposure
In the early hours of April 26th 1986, a planned test of reactor 4 at Russia’s Chernobyl nuclear plant led to what the United Nations have termed “the greatest environmental catastrophe in the history of humanity”. Now thirty years on, studies following the health of workers who helped clean up after the disaster may help scientists better define the risks to healthcare professionals from low doses of radiation from medical diagnostic imaging.
Chernobyl’s ‘liquidators’ are heralded as heroes. They were an army of around 600,000 people, mainly men, who consisted of plant workers, firefighters, soldiers, miners, construction workers and volunteers who were called in to clean up after the explosion.
It was a job they had never been trained for. At great risk to their own health, and with little to no equipment, they dropped sand, lead and boron into the reactor, cut down and buried acres of pine forests, bulldozed villages and built settlements for evacuees. For months they worked tirelessly on securing the 30km exclusion zone surrounding the site and building the metal and concrete sarcophagus around the reactor to prevent the release of further radioactive particles into the atmosphere. The sarcophagus which sealed in 200 tonnes of uranium within reactor 4 (97% of its original contents), has stood for 30 years and will only be replaced next year with a new structure costing €2.15bn.
Many of the liquidators did not have adequate equipment to protect them from radiation. Some attached lead aprons to their cotton work clothes, others had nothing at all. In the first year following the disaster those working directly on the site were exposed to high levels of radiation. In the following three years approximately 500,000 liquidators are estimated to have received lower doses (10-25 centigrays). How many liquidators have died as a consequence of radiation exposure is a matter of some debate. The International Atomic Energy Agency state that 28 workers lost their lives to acute radiation sickness, whilst a further 106 where treated but survived. However, a special commission by the Ukrainian Health Ministry suggests that 20,000 liquidators die from Chernobyl related illness each year.
A 20 year study following over 110,000 liquidators hopes to shed new light on the leukaemia risk associated with moderate to low doses of radiation. The study unsurprising showed that the Chernobyl workers share a significant risk of developing leukaemia. However, findings also showed that they had a greater than expected risk for chronic lymphocytic leukaemia, a type of leukaemia which many experts had not considered to be associated with radiation exposure. Researchers behind the study, which is led by a team of international scientists, from the University of California, believe their findings shed new light on the issue of estimating cancer risk from low doses of radiation[1]. An important issue for healthcare professionals working in diagnostic imaging. For many years, doctors have known that ionising radiation from x-rays sources can cause leukaemia. However, the exact level of risk associated with moderate or low doses of radiation has been a difficult to answer. Until now, best estimates have come from studies involving the survivors of Hiroshima and Nagasaki. However, the researchers point out that someone who undergoes a CT scan is exposed to a different type of radiation than that emitted by the atomic bomb. The researchers hope the information from the liquidator study will help bridge the knowledge gap between the high radiation levels received by those exposed to the atomic bomb and the lower levels involved in diagnostic imaging.
Lydia Zablotska, the lead researcher on the study believes “low levels of radiation are important” and hopes their work will help to raise awareness of that amongst people who work within low radiation environments.
[1] Radiation and the Risk of Chronic Lymphocytic and other Leukemias among Chernobyl Cleanup Workers, by Lydia B Zablotska et al.
Key facts
- 250,000 – people moved to safety
- 30km exclusion zone still surrounding the reactor
- 200,000 sq km contaminated with radiation
- 4000 – estimated number of deaths (United Nations)
- 93,000 – estimated number of deaths (Greenpeace)
- 2000 the date Chernobyl plant closed down
