1、Indoor Air Pollution,Radioactivity from Radon Gas Group members: 刘佳颖，叶秋雯，裴伟,Outline,IntroductionWhere does radon come from?How does radon get inside buildings? The level and distribution of radonThe Risk of Living With RadonReducing Radon Risks,Introduction,Although pollutant concentrations vary sig
2、nificantly from building to building, the levels of some common air pollutants often are greater indoors than outdoors. Since most people spend more time indoors than outdoors, exposure to indoor air pollutants is an important environmental problem.,Whats indoor air pollution?,Indoor Air Pollution i
3、s the term used to describe the amount of contaminants in the air inside a building from sources such as cigarette smoking, fuel combustion for heating or cooking, certain wallboards, carpets, or insulation as well as the geology of the area (radon in soil or rocks beneath the structure).,Whats rado
4、n(氡)?,Radon is a naturally-occurring radioactive(放射性的) but inert(惰性的) gas part of the decay chain that starts with uranium(铀) and ends with plumbum (铅).,Property of Radon,Single atom gasInert, colorless, odorless at ordinary temperaturesMelting point: 202 degrees K Boiling point: 211 degrees K Atomi
5、c radius: 1.34 angstroms (the heaviest known gas)Half-life: 3.8days,Where does radon come from?,Natural source: Earth and rock beneath home;Well water; Outdoor air;Artificial source:Daily life materials: leather; low density plastic (like plastic bags, etc.); paintsBuilding materials: gypsum board (
6、sheetrock), concrete block, mortar, sheathing paper (tarpaper), wood paneling, and most insulation.,Some uranium is present in all earth materials.On continental surfaces the rocks, sediments and soils typically contain between 1 and 3 parts per million (abbreviated ppm) of uranium. Some earth mater
7、ials may have more.,How does radon get inside buildings?,Cracks in solid floors,Construction joints,Cracks in walls,Gaps in suspended floors,Gaps around service pipes,Cavities inside walls,The water supply,Radon from soil gas is the main cause of radon problems.How much of radon reaches the surface
8、depends on the uranium content of the underlying earth materials together with their depth and permeability (that is, the presence of fractures and interconnected pore spaces that act as conduits for radon).Enter the lowest level of a building using whatever pathways are available.,Soil,For structur
9、es with basements or slab-on-grade foundations, the entry points includeCracks and pores in floor slabs, walls, and floor-wall joints; Openings around sump pumps, floor drains, and pipes penetrating floors and walls.,Structures with a crawl space between the ground and lowest floor level may be less
10、 vulnerable to radon, which tends to escape to the outside air when appropriate vents are installed, but can still admit some of the gas through cracks in the flooring.,Water,Radon can also enter into homes through the water system.This is mainly true for houses in which ground water is used as the
11、main water supply.,Small public water works and private domestic wells often have closed systems and short transit times that do not allow radon to decay to harmless by-products before entering a home. Once inside, radon escapes from the water to the indoor air as people take showers, wash clothes o
12、r dishes, or otherwise use water. The areas most likely to have problems with radon in ground water are those with have high levels of uranium in the underlying rocks.,Water in rivers and reservoirs usually contains very little radon, because it escapes into the air. Thus homes that rely on surface
13、water usually do not have a radon problem from their water. In big cities, water processing in large municipal systems aerates the water, which allows radon to escape, and also delays the use of water until most of the remaining radon has decayed.,The Average Level of Radon Found in a Home,Based on
14、a national residential radon survey completed in 1991, the average indoor radon level is about 1.3 picocuries(皮居里=10-12Ci) per liter (pCi/L) in the United States. The average outdoor level is about 0.4 pCi/L.,The safe level of radon,There is no safe level of radon-any exposure poses some risk of can
15、cer.,Zone 1 counties have a predicted average indoor radon screening level greater than 4 pCi/L (pico curies per liter) (red zones) Zone 2 counties have a predicted average indoor radon screening level between 2 and 4 pCi/L (orange zones) Zone 3 counties have a predicted average indoor radon screeni
16、ng level less than 2 pCi/L (yellow zones),The Risk of Living With Radon,Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe.As they break down further, these particles release small bursts of energy. This can damage lung tissue and lead to lung cancer over
17、 the course of your lifetime.,Smoking combined with radon is an especially serious health risk.Children have been reported to have greater risk than adults of certain types of cancer from radiation, but there are currently no conclusive data on whether children are at greater risk than adults from r
18、adon.,Radon Risk If You Smoke/Never Smoke,EPA (Environmental Protection Agency 美国环保署) estimates that radon causes thousands of cancer deaths in the U.S. each year.,Reducing Radon Risks,There are two ways to protect yourfamily from Radon.,First, the hard way,Holding Your Breath,Lower the Radon Level
19、in Your HomeYour Family Will Breathe A Lot Easier.,How to Lower the Radon Level,The most effective way to lower the radon level is set a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside.,There are also other ways:Test your home for radon.Be careful when
20、you choose building materials.Fill the gaps and cracks in the ground, floor, and walls. Pay more attention to the basement and the first floor where there is a high level of radon.Dont smoke in the room, especially the one for children and elders.,Liu Jiaying: Collect Information& Draft pptYe Qiuwen: Make pptPei Wei: Presentation,Thank you!,
