The increase in the incidence of lung cancer was first seen in uranium miners exposed to high concentrations of radon. In addition, studies in Europe, North America and China have confirmed that even low concentrations of radon, such as radon found in houses, have health risks and are an important cause of lung cancer all over the world.
Every time the average radon concentration increases 100 Bq/m3 for a long time, the risk of lung cancer increases 16%. Their content-response relationship is linear, that is, the increase of lung cancer risk is directly proportional to the increase of radon exposure.
Radon will increase the chance of smokers suffering from lung cancer. In fact, the risk of lung cancer caused by radon in smokers is estimated to be 25 times higher than that in non-smokers. So far, no other cancer risks have been found. For most people, the most exposed place to radon is in the house. Indoor radon concentration depends on the following factors: uranium concentration in underground stones and soil; Possible ways for radon to enter the room from soil; The exchange speed of indoor and outdoor air depends on the building structure, the ventilation habits of residents and the air tightness of buildings. Basements, cellars or other building areas in contact with soil usually have high radon concentration. Radon enters the house through the gap between the ground and the wall, the gap around the water pipe or cable, the small hole in the hollow brick wall or the sewage pool or sewer.
The radon concentration in adjacent houses may be different, and the daily and hourly conditions in the same house may also be different. Radon concentration in a house can be measured in an economical and simple way. Because of the fluctuation, it is best to estimate the annual average value of radon concentration in indoor air according to the measured values for at least 3 months. However, measurement must be based on national plans to ensure consistency and reliability of decision-making. There are fully tested, lasting and economical methods to prevent radon in new buildings and reduce radon in existing buildings. Radon prevention should be considered when building new houses, especially in areas prone to radon. In many European countries and the United States, it has become a routine practice to add radon prevention and protection measures for new buildings. This has become a mandatory procedure in some countries.
The indoor radon concentration can be reduced by the following measures: increasing underground ventilation measures; Install radon storage system in basement or under solid ground; Prevent radon from entering the room from the basement; Do a good job of sealing the ground and wall; Improve the ventilation environment of the house. Passive mitigation system has been proved to reduce indoor radon concentration by as much as 50% or more. If a radon ventilator is installed, the radon concentration can be further reduced. In many countries, drinking water comes from underground water sources, such as spring water, well water and drilling water. The radon concentration of these water sources is usually higher than the surface water of reservoirs, rivers or lakes.
So far, epidemiological studies have not found any correlation between drinking radon-containing drinking water and the increased risk of gastric cancer. Radon dissolved in drinking water will be released into indoor air. Usually, the inhaled radon content is higher than the intake of drinking water.
WHO Guidelines on Drinking Water Quality (20 1 1) suggest that the radon screening level of drinking water should be determined according to the national reference level of radon concentration in the air. It is prudent to measure radon concentration when the radon content in drinking water is expected to be high. Radon concentration in drinking water can be reduced by direct and effective technologies such as ventilation or granular activated carbon filtration.