Warning: “Radon is all around us. You are now entering a radioactive area.”. It could be the sign at your front door. Would you stay – or would you turn round into the open air?
It is an invisible, odourless gas that seeps out of the ground and it is called radon.
Radon poses a major threat to human health, and therefore, it is a matter of great concern to all human beings. Being a monoatomic gas, radon can easily penetrate the walls and concrete of a building. As we breathe, radon particles get accumulated inside our body and directly alters our DNA, thereby causing lung cancer. After smoking, radon is the largest known cause of lung cancer around the world.
Alpha particles (α) are positively charged and made up of two protons and two neutrons from the atom’s nucleus. Alpha particles come from the decay of the heaviest radioactive elements, such as uranium, radium and polonium. Even though alpha particles are very energetic, they are so heavy that they use up their energy over short distances and are unable to travel very far from the atom.
The health effect from exposure to alpha particles depends greatly on how a person is exposed. Alpha particles lack the energy to penetrate even the outer layer of skin, so exposure to the outside of the body is not a major concern. Inside the body, however, they are very harmful. If alpha-emitters are inhaled, swallowed, or get into the body through a cut, the alpha particles can damage sensitive living tissue. The way these large, heavy particles cause damage makes them more dangerous than other types of radiation. The ionizations they cause are very close together – they can release all their energy in a few cells. This results in more severe damage to cells and DNA.
The most important pathway for human exposure is permeation of radon gas into buildings, but radon from water, outdoor air and construction materials can also contribute to the total exposure. What makes it dangerous is that, being odourless and colourless, it is easy to ignore.
Professor Sir Richard Peto, a well-known cancer epidemiologist, once remarked: “If only it were blue and people could see it they would take it seriously, but unfortunately it isn’t.”
At home we are at risk from unsafe exposure to indoor radon gas, which may cause lung cancer. Smoking is the leading cause of lung cancer. Radon is the number one cause of lung cancer among non-smokers. The largest and most rigorous study of radon, published in 20014, showed that the gas is responsible for about 20,000 deaths from lung cancer in the European Union each year. The research combined the results from 13 studies and showed that smokers were at greatest risk. Worldwide, radon causes a million deaths every decade. Neil McColl, of the HPA’s Centre for Radiation, Chemicals and Environmental Hazards, says: “The scientific evidence has shown that the lung cancer risk is proportional to the long-term exposure to radon. There is no safe or unsafe level. We want to keep our focus on homes above 100 becquerels (bq) but we also want to make sure that people who are reducing the level should not think that below 100 they are safe. The risk is smaller, but it is not zero – particularly if they are smokers or ex-smokers.”