Physics & Health Effects of Radon & RDPs Topic 1 - Audio 1 Course Description – Designed with Your Convenience in Mind • Course Based Upon: • EPA, Indoor Radon & Radon Decay Product Measurement Protocols, July 1992 • EPA, Protocols for Radon & Radon Decay Product Measurements in Homes, June 1993 • EPA, Radon Mitigation Standards, April 1994 • EPA, Home Buyer’s and Seller’s Guide to Radon • EPA, A Citizen’s Guide to Radon •Audio Portion • Audio Sections that follow manual • Tone between each page of manual • Guest speaker interviews • Playable in music CD-players (car, home entertainment system or computer) • Streaming Videos on Web Site • Visual clips of unique elements • Show common measurement devices • Animation sequences • Resource Materials Online • Protocols, model contracts, EPA documents and many other tools to support you • Homework & Quizzes Online • Quizzes online www.certi.us • Access CERTI Education site with username and password provided when course was obtained. • Automatic feedback on questions • Course Completion Certificate downloadable upon completion of Online Quizzes. Note to Canadian Students: Please make sure you complete the Canada Specific Information Section of the Course. 1 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 2 Key Points: • Radon is naturally occurring • Radon is a chemically inert gas • Radon comes from the radioactive decay of uranium 238 • Radon comes from the immediate decay of radium 226 • Much of the radon produced enters the atmosphere • The concern with radon is when it enters a home • Radon can enter all types of buildings, including schools and workplaces • Radon comes from the area directly beneath building and a few meters around it, so it is very localized • Some of the radon that enters a home also leaves through windows and other openings to the outdoors - the concern is when it accumulates in a home. • Tight homes do not cause radon • Although radon can come from man-made situations like landfills or use of radium containing building materials, the vast majority comes from the soil 2 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 3 Key Points: • Vacuums or negative pressures within a building cause radon laden soil gases to enter from the soil beneath a home. • Vacuums are caused by either temperature induced stack effects or mechanical exhaust systems. • Temperature induced stack effects occur when the outdoor air is colder than indoor air. The colder outdoor air is more dense and will move down through the soil and push ahead of it the warmer, less dense air inside the building. As this air moves through the soil, it will pick up soil gases such as moisture and also radon. • Exhaust fans that take air out of a building can also draw radon laden soil gas into the structure. • The combination of temperature induced stack effect and mechanically induced vacuums will draw radon laden soil gas in. • All buildings can exhibit interior negative pressures relative to the soil. • If radon is being produced in the soil beneath the home where the negative pressures are being exerted, radon can enter. • Changes in these negative pressures will change the rate of radon entry, from hour-to-hour, day to day and from season to season as a function of how the interior pressures change. • Pressures in the soil from wind can also push radon in. • Since radon is a single atom, it can come through the smallest of openings in the foundation. • Since all foundations have openings, all types of foundations are susceptible to radon entry. • All types of homes, unless totally suspended (tree-house), can have radon concerns. 3 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 4 Key Points • Radon enters the interior air space of a building. • Radon is an unstable atom and will break down into a family of elements called radon decay products. • Since radon is in the air, the radon decay products formed will also be in the air. • Radon decay products have electrostatic charges. • When you inhale you will breathe in both radon and radon decay products • The radon is exhaled • The radon decay products will stick to the lung tissue • Before your lungs can clear the radon decay products, they can further break down and irradiate the lung tissue. It is the radon decay products that actually present the health risk associated with radon gas. 4 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 5 Key Points • Radon and radon decay products release radiation • Alpha: A particle made up of two protons and two neutrons that flies out of the nucleus of an atom at about 50% the speed of light. • Very damaging due to mass and speed! • Beta: A small particle the size of an electron that is ejected from the nucleus. • Limited damage due to small size. • Gamma: Essentially a light wave. • Minor damage, per single release. • Alpha particles are released when radon and two of its decay products (Polonium 218 and 214) decay. • The alphas from the decay products (rather than from radon) are of the largest concern because they can be released while the decay products are in the lungs. • Alphas can be absorbed by a piece of paper or the dead cells on the outside of our bodies. • That does not mean they cause small damage, but rather their size is so large that the probability of impact is very high. • Lung tissue does not have a thick protective coating, which is why the effect from radon exposure is believed to be lung cancer rather than skin cancer. 5 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 6 Key Points • Radon decay products release alpha particles • Polonium 218 & Polonium 214 • Alpha is very damaging if it hits a live cell • Lung cells are most susceptible because radon decay products are concentrated in lungs and cells do not have a protective covering like skin. • What happens when an alpha particle hits a lung cell? • Cell can die – okay since body can replace • If alpha hits DNA within cell’s nucleus, the DNA can be damaged • Direct hit • Chemical attack by ions formed by alpha particle strike. • Cancer suppressant gene impact • Cell loses defense mechanism against cancer • Defect can be passed on • Increases potential of lung cancer • Probability • Function of number of hits and amount of time 6 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 7 Key Points • Potential for radon induced lung cancer is a function of: • Amount of exposure • Time exposed Analogy - Like a blindfolded person throwing darts at a dartboard • Probability of hitting bulls eye is a function of: • How many darts thrown at a time (from one to a handful) • How long the person continues to throw darts • Linearity: • Probability equally weighted between number of darts thrown (radon activity in building) and how many throws the person makes (time of exposure) • No threshold: • Although unlikely, the person could hit bulls eye with the first dart • The only safe level of radon exposure is when there is no radon (take the darts away from the person) Graph shows excess lung cancer risk over norm (vertical axis) with increasing exposure in terms of radon decay product exposure x time (the working level month is explained in more detail later). Data based on occupational studies of miners with indication of where some home exposures fall on graph. 7 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 8-10 8 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 11 Key Points Radioactive decay is the natural process that an unstable element goes through to reach a stable configuration. • Alpha Release (α): • Atom loses two neutrons and two protons. • Since number of protons define the way an atom reacts with other elements to form molecules, a reduction in number of protons causes the atom to act like another element. • Atomic mass changes since number of particles in atom are reduced by 4. • Very massive and very damaging. • Beta Release (β): • Beta is an electron shot out from nucleus when a neutron changes into a proton. • An increase in number of protons causes atom to behave like another element. • Small mass and causes smaller damage than alpha particle. • Atomic mass does not change because the total number of neutrons and protons within nucleus stays the same. • Gamma Release (γ): • Whenever an alpha or a beta is released, the atom goes to a lower energy level. • The energy released is in the form of gamma which is a light wave. • Some detectors measure gamma as a means of measuring radon activity. • Little damage per individual release. +1P +1P Rn-222 Pb Bi Po At Rn As atoms decay, energy is 82 8384 85 86 released in the form of gamma, like balls making Po-218 sound as they drop through a pin-ball machine. -2 P -2 P Pb-214 -2N Since radon decays more -2N slowly than radon decay Bi-214 The diagram shows how atoms move down the products, the rate of radon periodic chart as they lose protons from alpha decay is controlling Po-214 (aka: Secular equilibrium). decay and back up the periodic chart as they Pb-210 gain protons with beta decay. Gamma is released with each type of decay. 9 Physics & Health Effects of Radon & RDPs Topic 1 - Audio 12 Key Points • When either alpha, beta or gamma is released they collide into other atoms. • Impact of radiation knocks electrons off of other atoms. • When an atom loses electrons it is referred to as an ION. • An ion has a different number of negatively charged electrons than charged protons. • Because of imbalance, an ion has a charge. • Ions are very reactive and can cause damage.