Radon

Radon Radon Largely based on the USGS ‘Geology of Radon’ http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/3.html And from the US EPA http://www2.epa.gov/radon/health-risk-radon Radon Largely based on the USGS ‘Geology of Radon’ http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/3.html And from the US EPA http://www2.epa.gov/radon/health-risk-radon

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">The purpose of this talk is to explore the issue of radon exposure. Most of the material shown comes from the USGS ‘Geology of Radon’ or the USEPA on the health risks of Radon </TextFlow>

Uranium (and thorium)– Precursor to Radium http://pubs.usgs.gov/of/2004/1050/uranium.htm Uranium (and thorium)– Precursor to Radium http://pubs.usgs.gov/of/2004/1050/uranium.htm Uranium (and thorium)– Precursor to Radium

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Two radon isotopes, 222 and 220, are created from the decay of the primordial uranium and thorium series that are illustrated in the next two slides. Radon 222 has a 3.82 day t1/2 and comes from the long lived (1600 years) Radium 226 </TextFlow>

Thorium 232 Decay Chain Thorium 232 Decay Chain http://pubs.usgs.gov/of/2004/1050/thorium.htm Thorium 232 Decay Chain http://pubs.usgs.gov/of/2004/1050/thorium.htm

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Radon 220, with a 55 s t1/2 comes from the short lived Radium 224. The difference in half lives between Ra 226 and Ra 224, as well as that of Rn 222 and Rn 220 have broad implications for the presence of radon gas within homes </TextFlow>

Radon Production and Location within Soils Water Air Mineral Grain Radium atom Radon atom Area within the mineral where radon can escape: Radium is distributed in the soil, or dissolved in pore water. Radon is created from the decay of radium. The radon atom recoils away from the site of the radium as a consequence of the decay. Most radon is trapped in the mineral grain. 10 – 50 percent escapes into pore space. If the pore is water filled, the radon stays If the pore is air-filled the radon moves into the pore, and sometimes into an adjacent mineral grain Radon Production and Location within Soils Water Air Mineral Grain Radium atom Radon atom Area within the mineral where radon can escape: Radium is distributed in the soil, or dissolved in pore water. Radon is created from the decay of radium. The radon atom recoils away from the site of the radium as a consequence of the decay. Most radon is trapped in the mineral grain. 10 – 50 percent escapes into pore space. If the pore is water filled, the radon stays If the pore is air-filled the radon moves into the pore, and sometimes into an adjacent mineral grain Radon Production and Location within Soils

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Radon in home air comes largely from the soil underneath the home. Produced largely from the decay in mineral grains, radon has to migrate from the soil particle to the void between soil grains (called the pore space) and then into the home. Radium’s (Ra) position in mineral grain determines if Rn enters the pore space between mineral grains. If Ra atom is deep a grain, then Rn will not be freed Recoil of Rn atom is strong Rn atoms may enter the pore space, cross it and become embedded in nearby mineral grains. If water present in the pore space, Rn atom slows and may stay in pore – but then it may stay in the water. For most soils, only 10 to 50 % of Rn produced escapes from mineral grains and enters the pores. To move into the home, the pore spaces have to connect. Most soils in the United States contain between 0.33 and 1 pCi of radium / g of mineral matter and between 200 and 2,000 pCi /L of Rn in soil air. </TextFlow>

Radon Diffusion from Soils Radon Diffusion from Soils Rn is a noble gas Easily leaves rocks and soils through fractures /openings into pore spaces between grains of soil. Rn in pore space can travel great distances before decaying Method & speed of Rn's movement controlled by Water in the pore space (the soil moisture content), % of pore space in the soil (the porosity), and “Interconnectedness" of pore spaces that determines the soil's ability to transmit water and air (called soil permeability). Radon Diffusion from Soils Rn is a noble gas Easily leaves rocks and soils through fractures /openings into pore spaces between grains of soil. Rn in pore space can travel great distances before decaying Method & speed of Rn's movement controlled by Water in the pore space (the soil moisture content), % of pore space in the soil (the porosity), and “Interconnectedness" of pore spaces that determines the soil's ability to transmit water and air (called soil permeability).

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Soil type matters to the migration of radon. If the pore spaces are large and connected then radon can travel a great distance. The movement and speed of travel is determined by the type of pores, whether or not water is present and the interconnectedness of them. </TextFlow>

Radon Movement in Soils Radon Movement in Soils Moves more rapidly through: Permeable soils Fractures in soil or rock Movement near soil surface usually escapes into atmosphere. Soil air flows toward house foundations due to: Differences in air pressure between the soil and the house, Openings in the foundation, and Increases in soil permeability near the basement / foundation Radon Movement in Soils Moves more rapidly through: Permeable soils Fractures in soil or rock Movement near soil surface usually escapes into atmosphere. Soil air flows toward house foundations due to: Differences in air pressure between the soil and the house, Openings in the foundation, and Increases in soil permeability near the basement / foundation

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">This slide illustrates the difference between non porous and porous soils, as well as permeable and non permeable spaces. </TextFlow>

Increased Potential for Radon Exposure Increased Potential for Radon Exposure Presence of uranium or radium in soils and rocks Permeable soils Dry or drained soils Deep cracks in soil Site is located on a hill or slope Soils are thin with bedrock close to the surface Underlying rocks are fractured Limestone caverns underlay the rock Known instances of high indoor radon in homes in the area http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/page26.gif http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/page15.gif Increased Potential for Radon Exposure Presence of uranium or radium in soils and rocks Permeable soils Dry or drained soils Deep cracks in soil Site is located on a hill or slope Soils are thin with bedrock close to the surface Underlying rocks are fractured Limestone caverns underlay the rock Known instances of high indoor radon in homes in the area http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/page26.gif http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/page15.gif

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">There are multiple factors that can influence the level of radon concentration within a home. The images on this slide are from the USGS website (the links are included). Key factors influencing radon are 1-9. </TextFlow>

Radon Entry Into Homes http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/page13.gif Most houses draw less than one percent of their indoor air from the soil; The remainder comes from outdoor air, which is generally quite low in radon. However, houses with low indoor air pressures, poorly sealed foundations, and several entry points for soil air, may draw as much as 20 percent of their indoor air from the soil. Even if the soil air has only moderate levels of radon, levels inside the house may be very high. Radon Entry Into Homes http://certmapper.cr.usgs.gov/data/PubArchives/radon/georadon/page13.gif Most houses draw less than one percent of their indoor air from the soil; The remainder comes from outdoor air, which is generally quite low in radon. However, houses with low indoor air pressures, poorly sealed foundations, and several entry points for soil air, may draw as much as 20 percent of their indoor air from the soil. Even if the soil air has only moderate levels of radon, levels inside the house may be very high. Radon Entry Into Homes

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Radon enters the home through multiple points of entry. Unsealed substructures allow the gas to diffuse through pipes, sumps, cracks, floor drains and more. Even though the air in most houses comes from outside, soil gas still enters the home. </TextFlow>

Example Range of Radon Concentrations, Bq/m3 (pCi/L) http://energy.cr.usgs.gov/radon/georadon/page4.gif Example Range of Radon Concentrations, Bq/m3 (pCi/L) Bq/m337373703,70037,000370,0003,700,00037,000,000370,000,000 http://energy.cr.usgs.gov/radon/georadon/page4.gif Example Range of Radon Concentrations, Bq/m3 (pCi/L) Bq/m337373703,70037,000370,0003,700,00037,000,000370,000,000

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">This graphic illustrates the range in radon concentrations (expressed in standard units, ) for ground water, soil air, indoor air and outside air. The y axis is shown reversed – with the outdoor air have the lowest concentrations of radon. The ground water has the highest (and greatest range) in radon concentrations. </TextFlow>

Radon in indoor water Radon in indoor water Enters a home through the water systems. Domestic water source impacts radon concentration Surface water sources typically have very little radon, because it escapes into the air; Municipal water systems Aerate the water allowing radon to escape Transit time from water treatment further decays radon. http://water.epa.gov/learn/kids/drinkingwater/watertreatmentprocess.cfm Radon in indoor water Enters a home through the water systems. Domestic water source impacts radon concentration Surface water sources typically have very little radon, because it escapes into the air; Municipal water systems Aerate the water allowing radon to escape Transit time from water treatment further decays radon. http://water.epa.gov/learn/kids/drinkingwater/watertreatmentprocess.cfm

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Even though most radon enters homes through subsurface pathways into the foundation, there is another way: water supplies. The source of domestic water largely determines the amount of radon from this source. Surface water sources generally have very little radon. </TextFlow>

Indoor water from wells Indoor water from wells Ground water for domestic supply may have elevated radon Small public or private wells may have closed systems and short transit times Radon escapes as people shower, wash clothes or otherwise use water. A rule of thumb is house water with 10,000 pCi/L of radon contributes about 1 pCi/L to the level of radon in the indoor air. Areas with elevated uranium in rocks are most likely to have high radon in water. Diagram of an automated water well system powered by a jet-pump. © 2008 Samuel Bailey Indoor water from wells Ground water for domestic supply may have elevated radon Small public or private wells may have closed systems and short transit times Radon escapes as people shower, wash clothes or otherwise use water. A rule of thumb is house water with 10,000 pCi/L of radon contributes about 1 pCi/L to the level of radon in the indoor air. Areas with elevated uranium in rocks are most likely to have high radon in water. Diagram of an automated water well system powered by a jet-pump. © 2008 Samuel Bailey

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">If ground water is the source of supply to a home, then radon may be elevated. It depends on if the system is aerated, if there is a short transit time, and if the there is elevated uranium or radium in the source of drinking water. </TextFlow>

http://water.usgs.gov/nawqa/trace/radium/maps/fig1.html USGS and USEPA, sampled untreated source water from1270 domestic, public supply and monitoring wells About 3 percent of the sampled wells had combined radium concentrations greater than the EPA standard for drinking water. Almost all wells with concentrations greater than the standard were located in the eastern United States http://water.usgs.gov/nawqa/trace/radium/maps/fig1.html USGS and USEPA, sampled untreated source water from1270 domestic, public supply and monitoring wells About 3 percent of the sampled wells had combined radium concentrations greater than the EPA standard for drinking water. Almost all wells with concentrations greater than the standard were located in the eastern United States

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Elevated radium concentrations occur most commonly in aquifers in the eastern and central United States for the wells sampled in 15 principal aquifers across the United States. About 3 percent of sampled wells had combined radium concentrations greater than the MCL. Ninety-eight percent of the wells that exceeded the combined radium (radium-226 plus radium-228) drinking-water standard of 5 picocuries per liter established by the U.S. Environmental Protection Agency were in aquifers east of the High Plains. The highest concentrations of combined radium were in the Mid Citation-- Szabo, Zoltan, Fischer, J.M., and Hancock, T.C., 2012, Principal aquifers can contribute radium to sources of drinking water under certain geochemical conditions: U.S. Geological Survey Fact Sheet 2010-3113, 6 p.-Continent and Ozark Plateau Cambro-Ordovician aquifer system and the Northern Atlantic Coastal Plain. More than 20 percent of sampled wells in these aquifers had combined radium concentrations that were greater than or equal to the MCL. </TextFlow>

http://www2.epa.gov/radon/epa-map-radon-zones http://www2.epa.gov/radon/epa-map-radon-zones

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">This map shows the level of radon (by county) across the US. Note there is some similarity between the radon in drinking water (from the previous slide) and this map. </TextFlow>

From data at: http://www2.epa.gov/radon/health-risk-radon From data at: http://www2.epa.gov/radon/health-risk-radon

<TextFlow xmlns = "http://ns.adobe.com/textLayout/2008" fontFamily = "Verdana" fontSize = "9">Radon is considered a significant contributor to lung cancer . This data is from the epa, which shows that radon related lung cancers are estimated to be a significant contributor to annual deaths from cancer in the USA. </TextFlow>

Summary - Radon Summary - Radon A naturally occurring decay product arising from the uranium and thorium series A noble gas that can Move through soil pores into homes Move from ground water into homes Abundance is related to uranium / radium in surrounding soils and water Estimated to be a significant cause of lung cancer in the USA Summary - Radon A naturally occurring decay product arising from the uranium and thorium series A noble gas that can Move through soil pores into homes Move from ground water into homes Abundance is related to uranium / radium in surrounding soils and water Estimated to be a significant cause of lung cancer in the USA