In the time that elapses between two heartbeats, the radioactive decay of almost 10,000 atomic nuclei occurs in our body. Every hour, about 30,000 nuclei of radioactive isotopes present in the air we breathe disappear in our lungs. Due to the food we eat, about 15 million nuclei of potassium-40 and about 7,000 of natural uranium disintegrate in our stomach and intestines. Tobacco releases radioactive lead and polonium into the atmosphere and into our lungs; those who smoke a packet a day receive three times more radiation than the radon gas around us. A few days at sea provide us with an additional supply of radioactivity: 10,000 atoms per second disintegrate in a cubic meter of seawater. When changing from beach to mountain, the situation does not improve much: in the Pyrenees or in the Picos de Europa we receive three times more radiation than on our favorite coast. To all this we must add the more than 200 million gamma rays that pass through us every hour from the ground and construction materials.
But then there are also the hundreds of thousands of secondary cosmic rays, a by-product of the interaction of subatomic particles emitted by black holes, active galaxies or supernova explosions with atoms in the upper atmosphere. The astronauts, in the first space trips, verified the impact of these particles in their retinas, because their luminous flashes prevented them from sleeping peacefully.
Theradioactivityit has existed in nature forever, without the intervention of the human hand. Not even the reviledNuclear reactorsthey are novel. Almost 2 billion years ago, a spontaneous nuclear reactor was started up in the Oklo quarry in Gabon. It had nothing to do with aliens or advanced vanished ancient civilizations.
In those lands, the proportion of uranium-235, which is the fuel fornuclear power plants, reached 3%, a level sufficient to automatically start a chain reaction that lasted for a million years.
Despite the fear that some environmental groups have devoted themselves to putting us in for decades, invoking the pernicious effects of nuclear energy, radiation of natural origin is responsible for 87% of the total dose that humans receive. Artificial sources, such as those related to radiomedicine – radiographs, radiotherapies, scans with markers -, nuclear power plants, smoke detectors, televisions and air travel account for only 13%. Most of it is due to medical tests and treatments, especially X-rays, with 12%. Nuclear experiments and accidents, such as Chernobyl, only contribute 0.4% of the total, and the activity of nuclear power plants affects a factor 20 times less than this.
Adding up all these anthropogenic contributions, each Spaniard receives half of the maximum recommended dose for the population. Of this amount, between 10% and 15% is sourced fromfood. The tubers have more radius-226 than the aerial part of the vegetables. A half-kilogram steak provides us with 45 disintegrations per second, and a kilo of fruit, between 40 and 90. Bad news for seafood lovers: it is the food that contributes the most radiation, so fans of mussels, oysters and prawns can receive 50% more than the normal dose due to food. Controlling the environment is essential: in a Pittsburgh office, employees received radiation equivalent to eleven chest X-rays a year. Of course, if you have to point out the real danger, the palm is taken by the gasradon, which alone contributes up to almost 50% of the total dose.
In closed areas, such as buildings, mines, subway galleries, tunnels, etc., the concentration of this noble gas can be high due to poor ventilation. In some caves in Tenerife and Lanzarote, values that exceed 5,000 disintegrations per second and per cubic meter have been measured. For their part, the most common building materials, such as wood, bricks and concrete, emit little radon, although they have sometimes given unpleasant surprises, especially if they come from the ashes of thermal power plants or steel mills. In Sweden in the 1960s, the alum shales used in making concrete for houses for decades were found to be quite radioactive. Continuous radon production reaches our homes through cracks and crevices in buildings. When the concentration of radium in the soil is very high, as occurs in some granite formations, uranium or phosphate-rich soils, the level of emissions can be dozens of times higher than normal and contaminate our environment.
This is what happened to Stanley Watras and his family in 1985: Watras worked at the Limerick Nuclear Power Plant in Pennsylvania (USA) and one day, when he went to work, the alarm of the plant went off. Research showed that the Watras’ home was built on soil rich in uranium and with a radon concentration almost 2,000 times higher than usual in the US As for the possibility of contracting lung cancer, breathing the air from your home was equivalent to smoking 135 packs of cigarettes a day. Someone living in a house with ten times less radon than Watras’s would receive the same annual exposure as evacuees in the vicinity ofChernobylin 1986 after the nuclear accident.
Added to natural emissions are certain human activities that contribute to the production of this radioactive gas, such as the burning of natural gas and coal, the manufacture of phosphate fertilizers, which have high concentrations of uranium, and the generation of slag from starting from the treatment of iron in blast furnaces. A typical 1,000 MW thermal power plant consumes about 10,000 tons of coal – which contains uranium – daily, and its daily radiation emission is similar to that produced by two tons of uranium-238.
Groundwater also carries radon, in concentrations much higher than rivers and oceans. The radioactivity of a liter of water is usually 4 decays per second. But if the water comes from a well in a land with a high uranium content, the activity is 5,000 times greater and in some cases it can multiply millions of times in a sinister way, as in some wells that supply the city of Helsinki; Finland is the European country that receives the highest dose from radon. The mineral water in the town of Bad Gastein, Austria, is a million times more radioactive than that of public consumption, but several decades ago visitors were encouraged to drink it and stay in the caves in the area, where they inhaled radon. The measurements carried out in the spas of our country reveal that the situation is not that dangerous, although in some there have been 824 disintegrations per second and per liter of radio-226.
In our homes the real panic room is the bathroom. A study carried out in Finland showed that the concentrations present were three times higher than those in kitchens and 40 times higher than in the living room. For their part, Canadian scientists revealed that radon in bathroom air increased rapidly after a 10-minute warm shower. Once completed, it took more than an hour and a half before the radiation returned to initial levels.
Radon has been suspected of causing lung tumors since 1920, following studies conducted among miners in Bohemia and Saxony. It was in 1986 when the World Health Organization confirmed its carcinogenicity. Of the 136,000 deaths from lung carcinoma recorded in 1987 in the United States, 80% were associated with smoking, 5,500 with asbestos, and about 20,000 with radon. In the UK, exposure to this gas could be responsible for 6% of the annual incidence of this type of tumor. Living in a house with 150 decays per second per cubic meter due to radon increases the risk of lung cancer by between 1% and 3%. Inside homes in Spain we have between 10 and 15,000 disintegrations per second and cubic meter, with an average of 40. The highest values are found in Galicia, Extremadura and the Sierra de Madrid.
Ours is aradioactive world. Some scientists point out that thanks to this there is biological diversity, since many mutations have their origin in the natural radiation background. Living beings have become accustomed to living in this radioactive bathtub that is the Earth.
For example, of every 10,000 people who die, 5 die of cancer from radiation from their own body. It is inevitable, as with oxygen, that in addition to giving us life, it also takes it away, because it burns us from the inside. When we eat we eat not only potassium-40 or carbon-14, but other dangerous substances that are not radioactive: in green beans there are factors that dissolve the red blood cells; the chlorogenic acid in coffee causes DNA mutations; and the potato contains solanine, which produces malformations.
Eliminating the radioactivity of the world would mean eliminating ourselves, for we are all a walking radioactive source. We should even stop sleeping with our partners: for that alone, in a year we absorb 1% of the maximum recommended dose.
