Presentation on theme: "INDOOR AIR POLLUTION: RADON In 1990 EPA placed indoor air pollution at the top of the list of 18 sources of cancer risk Indoor pollution is rated by risk."— Presentation transcript:
INDOOR AIR POLLUTION: RADON In 1990 EPA placed indoor air pollution at the top of the list of 18 sources of cancer risk Indoor pollution is rated by risk analysis scientists as high-risk health problem for humans Radon is one of the three most dangerous indoor air pollutants, along with cigarette smoke and formaldehyde Radon is the second leading cause of lung cancer, after smoking Nearly 1 in 15 homes in the U.S. has high level of indoor radon The U.S. Surgeon General and EPA recommend all homes be tested for radon Homes with high radon level can be fixed
INDOOR AIR POLLUTION: RADON CHARACTERISTICS –Radioactive element –Naturally occurring –Colorless, odorless, and tasteless –Derived from natural decay of uranium –Chemically inert –When it decays, it releases decay products (progeny) which can attach themselves to tiny dust particles in indoor air and can be inhaled into human lungs, exposing them to densely ionizing alpha particles
INDOOR AIR POLLUTION:RADON Radon is estimated to cause about 20,000 deaths per year. The number of deaths from other causes are taken from the 1990 National Safety Council Report.
INDOOR AIR POLLUTION:RADON Most of the cancer risk resulting from radon in the household water supply is due to inhalation of the radioactive by- products that are produced from radon that has been released from the water into the air, rather than from drinking water.
EPA map of radon zones, New York State. Zone 1, red, highest potential (greater than 4 pCi/L) Zone 2, orange, moderate potential (from 2 to 4 pCi/L) Zone 3, yellow, low potential (less than 2 pCi/L)
INDOOR AIR POLLUTION: RADON Radon levels in outdoor air, indoor air, soil air and ground water can be very different.
INDOOR AIR POLLUTION:RADON Radon Formation Each atom of radium decays by ejecting from its nucleus an alpha particle composed of two neutrons and two protons. As alpha particle is ejected, the newly formed radon atom recoils in the opposite direction, just as a high- powered rifle recoils when a bullet is fired. Alpha recoil is the most important factor affecting the release of radon from mineral grains.
INDOOR AIR POLLUTION: RADON Radon can move through crack in rocks and through pore spaces in soils. Radon moves more rapidly through permeable soils, such as coarse sand and gravel.
INDOOR AIR POLLUTION: RADON Some radon atoms remain trapped in the soil and decay to form lead; other atoms escape quickly into the air. Homes in areas with drier, highly permeable soils, may have high levels of indoor radon.
INDOOR AIR POLLUTION: RADON A.Cracks in concrete slabs B.Spaces behind brick walls C.Pores and cracks in concrete blocks D.Floor wall joints E.Exposed soil as in a sump F.Weeping tile, if drained to open sump G.Mortar joints H.Loose fitting pipe penetrations I.Open tops of block walls J.Building materials such as some rocks K.Water, from some wells
INDOOR POLLUTION: RADON In areas where the main water supply is from private wells and small public water works, radon in ground water can add radon to the indoor air.
INDOOR AIR POLLUTION: RADON HEALTH EFFECTS Radon causes about 20,000 lung cancer deaths each year (only effect definitely linked) Even very small exposures to radon can result in lung cancer No threshold below which levels are harmless Many smokers will get lung cancer because of the synergy between radon and cigarette smoking Epidemiological studies (miners) an animal studies are supporting evidence that confirm radon as a cause of lung cancer The BEIR (“Biological Effects of Ionizing Radiation”) VI Report of the National Academy of Sciences, the most comprehensive study to date, supports that conclusion.
INDOOR AIR POLLUTION: RADON Soil Air Radon Data A scientist collects samples of soil air to determine its radon content. The methods for measuring radon can be a passive device buried in the soil, or a sample of soil air collected from a probe driven into the ground.
INDOOR AIR POLLUTION: RADON Methods for measuring alpha particles produced by the decay of the radon in the air.
INDOOR AIR POLLUTION:RADON Active Subslab Suction It is the most common and most reliable radon reduction method. One or more suction pipes are inserted through the floor slab into the soil underneath. A radon vent fan connected to the suction pipes draws the radon gas from below the house and releases it into the outdoor air while creating a negative pressure (vacuum) beneath the slab.
INDOOR AIR POLLUTION: RADON Radon Resistant- Construction Techniques A.Gas Permeable Layer B.Plastic Sheeting C.Sealing and Caulking D.Vent Pipe E.Junction Box Other radon reduction techniques include sealing, home/room pressurization, heat recovery ventilation and natural ventilation.
INDOOR AIR POLLUTION:RADON Conclusions Indoor radon is a public health problem Millions of homes are estimated to have elevated radon levels The solution is straight forward The health risks of radon can be reduced