Great uncertainty over risk assessment for low-dose radiation
Have we overestimated the health risk posed by low doses of ionising radiation, such as those in houses with radon? And, have we underestimated the risk of exposure to combined types of radiation? Andrzej Wojcik, from Stockholm University, is using specially constructed equipment to investigate the potential effects that low doses of radiation may have on our bodies.
We are all exposed to ionising radiation over our lifetime. Sweden’s bedrock contains relatively high levels of uranium, and its decay products continually emit low doses of gamma and alpha radiation. In many places, there are traces of the Chernobyl accident and a large proportion of the population need to undergo diagnostic procedures for various diseases, which use low levels of radiation and radioactive isotopes.
Currently, no one definitely knows how these low doses of radiation affect us over the course of our long lives. Because people cannot be exposed to radiation for experimental purposes, scientists’ knowledge is limited to the events in which large numbers of people were irradiated due to war or accidents.
“Our risk models are mainly based on research on Hiroshima and Nagasaki atomic bomb survivors, a cohort of about 100,000 people. They have been our most important source of knowledge about radiation risks,” says Andrzej Wojcik, professor at the Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University.
Damage caused by atomic bombs is the foundation of radiation protection
By investigating the effects of the atomic bombs, scientists have drawn conclusions about how industrial workers and healthcare staff should be protected from low doses of radiation. However, there is a difference between a short exposure to a high dose of radiation, such as after a nuclear blast, and exposure to much lower doses of radiation over many years, such as during work. Scientists therefore suspect that the risk predicted from the Hiroshima and Nagasaki study for occupational low dose exposures is exaggerated, leading to unnecessary costs for radiation protection.
“Our research group is trying to gain a better understanding of the health risks associated with low doses of radiation, so that we neither underestimate nor overestimate the risks.”
A combination of different types of radiation may be more damaging
Wojcik has been commissioned by the Swedish Government for various tasks – which include educating biologists about radiation biology – to maintain the level of knowledge in Sweden. A separate room inside his laboratory contains specially built equipment that emits alpha and gamma radiation. There, one thing the research group is studying is how cells are affected by exposure to a combination of two types of radiation. Currently, radiation protection guidelines assume that damage is additive, that one plus one is two.
“But our results show that there is an interaction between alpha radiation and gamma radiation, and that this is effect is greater than simply adding them together – so we have probably underestimated the risks of combined exposures,” says Wojcik.
Because exposure to several forms of radiation is relatively common – for example, when we fly, we are exposed to cosmic radiation and gamma radiation – this knowledge is important.
Smoking and radon – an unhealthy duo
Another known combinatory effect is that smoking amplifies the effect of radon, a radioactive gas. People who are exposed to radon and who smoke have 10–20-fold greater risk of lung cancer. Wojcik takes two packages of cigarettes out of a cupboard in his office; these are going to be smoked by a special smoking machine.
“We don’t understand the underlying mechanisms for the interaction between smoking and radon, so we are exposing cells to both of these. We will also expose them to nicotine and other components in smoke, to see what influences the effect of radon.”
Different people resist radiation differently
Another phenomenon that Wojcik is interested in is how people react differently to radiation, something that is apparent in cancer care. Some patients experience severe side effects from radiotherapy, while others have none at all. No one knows why there is such a big difference. One hypothesis tested by Wojcik’s research group was that people whose molecular systems are efficient at repairing damage to their DNA may deal with it better, but the reality turned out to be more complex.
“Both genetic and environmental factors probably play a role, but it would have been good to be able to predict how someone will react to radiation,” says Wojcik.
A biological dosimeter in case of terror attacks
The damage radiation causes to DNA in blood cells can also be utilised. Working with other European researchers, Wojcik has developed a type of biological dosimeter, as part of contingency planning for radiation incidents.
“If there is a terror attack or someone drops an atomic bomb, hundreds of thousands of people could be exposed to radiation. Most of them will want to know their dose.”
Researchers will be able to measure the amount of damage to the blood cells’ chromosomes and use this to estimate the radiation dose that person was exposed to.
Wojcik is also trying to develop a biological dosimeter for low-dose radiation. Using one would make it easier to generate reliable knowledge about how dangerous low-dose radiation actually is. His aim is to fill in the knowledge gaps, so that we neither overestimate nor underestimate the risks of radiation.
Read more on Andrzej Wojcik´s research.
Text: Ann Fernholm
English translation: Clare Barnes
Last updated: February 16, 2023
Source: Communications Office