Radon - A Homeowners Perspectivebestcountertop.net/wp-content/uploads/2017/04/Article-from-Cornell... · Radon is a concern because it is a radioactive gas. Being a gas, it can move

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Radon Radon --

A HomeownersA Homeowners

PerspectivePerspectiveJeffrey Leavey

Cornell University Environmental Health & SafetyMarch 2007

Map from http://www.epa.gov/radon/zonemap.html

What is Radon?What is Radon?

Radon is a naturally occurring noble gas that is also radioactive. It comes from the decay of Uranium (U) and Thorium (Th) that can be found in all soils and rocks to a varying degree. The radioactive decay of U and Th

leads to a long chain of other radioactive elements and isotopes between U and Th

and stopping at Lead (Pb). About the middle of this decay chain is the well known element Radium (Ra) that was discovered by Madame Curie in 1898. The decay of Ra, which is a solid, leads to Radon

(Rn) which is a gas.

There are three isotopes of interest: Rn-222 (Radon) from the decay of U-238, Rn-220 (Thoron) fom

the decay of Th-232, and Rn-219 (Actinon) from the decay of U-235. Of the three, Rn-222 is of most concern because of it’s much longer half-life.

Why is Radon a Concern?Why is Radon a Concern?

Radon is a concern because it is a radioactive gas. Being a gas,

it can move through the soil and enter your home. Once in the home you breathe it into your lungs where the radiation can deliver a dose to lung tissue. The Environmental Protection Agency (EPA) estimates that Radon is the second leading cause of lung cancer in the United States, with more than 20,000 Americans dying each year from radon-related lung cancer.

Radon BasicsRadon Basics

Where Does Radon Come From?Where Does Radon Come From?

As mentioned, soils and rocks are the primary source of Radon. Generally, average soil contains

about 1 picocurie

per gram (pCi/gm) of Uranium (1 pCi = 2.22 radioactive decays per min). Some rocks are naturally higher in U concentration and therefore Radon too. Granites range from about 2 to 10 pCi/gm while dark and black

shales

can range from 6 to 80 pCi/gm. Rocks usually lower in U are carbonates and sandstones.

Some natural formations in the

United States have higher

concentrations of U. The Reading

Prong is such a formation that runs from Reading, PA through

northern NJ and up to Putnam County in NY. See the map (from The News-Times, Danbury, CT

, March 13, 1986).

How Does Radon Get Into My Home?How Does Radon Get Into My Home?Because soils are a grainy mixture of minerals, organic material

and water, Radium near the surface of these grains emits Radon that can escape the

grain. Once in the interstitial space between grains, Radon can move into ground water or into the soil gas space. In stagnant soil gas space Radon can diffuse 1 to 2 meters before decaying but most indoor Rn originates 10’s of meters away from a home.

It is subsoil pressure differences between inside and outside the home that drive Rn movement. This is also called the chimney effect. During the winter when your home is closed up, large pressure differences (from a Rn movement perspective) can be

generated when your furnace turns on. The furnace draws inside air for combustion and this causes the house to have negative pressure compared to outside. The pressure difference draws Rn through foundation pours, cracks, penetrations, etc. and into your home. Homes with a full basement are more susceptible due to the

large surface area in contact with the ground.

Another less important entry path into the home is Rn in water, especially with well water supplies. With typical household usage, roughly 10,000 pCi per liter in water contributes 1 pCi per liter in air. Overall, the amount of Rn

entering via soil is much greater than Rn released to the air from water. In

addition, the risk breathing Rn in air is much greater than the risk of stomach cancer from ingesting water with Rn in it. There are tests available for both air and water and this is discussed later. The picture shows the typical routes of entry.

Lastly, some building materials using natural components contribute a little to overall Rn concentrations. Some examples are gypsum wallboard, bricks, granite counter tops, stone fireplaces,

and so on. By far, Rn entry from soil is the greatest source of Rn in the home.

Adapted from www.EPA.gov

Why Is Radon A Concern?Why Is Radon A Concern?How Does Radon Expose Me and What Are The Risks?How Does Radon Expose Me and What Are The Risks?

Radon is a class of radioactive materials called alpha emitters.

Alpha particles are very energetic and can deliver a large radiation dose to a small

volume of tissue. Fortunately we all have a dead layer of skin cells over the entire outside of our bodies that can completely stop all alpha radiation. Because these cells are already dead, we get zero dose from alpha sources outside the body.

In the lung, however, living tissue is in contact with the air we breathe –

there is no dead cell layer lining the lung. When you inhale Rn in air, some

of the Rn may decay while it’s in the lung and the alpha particles emitted can expose living lung cells. In addition, the decay products of Rn are also radioactive and they

also contribute to the dose to the lung.

At elevated Rn concentrations over a long period of time, the risk of lung cancer can be significant. The EPA estimates that 1 in 15 homes has an average Rn concentration above the EPA action limit of 4 pCi/l. See the risk comparison charts below.

From EPA Citizens Guide to Radon 2005 http://www.epa.gov/radon/pdfs/citizensguide.pdf

Testing for RadonTesting for RadonWhat is the Radon Limit and How Do I Test for Radon?

The EPA recommends that the average Rn concentration should be below 4 pCi/l and preferably as low as practical. The two inexpensive (about $25) methods to measure Rn in air: a short-term test and a long-term test. The short-term test is usually a small canister filled with activated charcoal that is exposed to the air for 2 to 5 days. The long-term test is called a track etch detector and is placed for 1 to

12 months.

A charcoal canister (left picture) test provides a snap shot of the Rn concentration at a moment in time. It’s useful for quick tests such as real estate transactions. A word of caution –

a charcoal test provides no information about what the average Rn

concentration really is unless you run several of these tests over an extended period.

The charcoal test works best in low humidity. Place the canister

at least 30 inches above the floor and test in the lowest occupied level in your home. After the canister is exposed it must be properly sealed for shipment and promptly sent to the processor –

time is a factor with this test. The processor will detect the radiation emitted by the Rn decay products adsorbed on the charcoal and then calculate the Rn concentration the canister was exposed to.

The track etch detector (center pictures) is a small piece of plastic that provides a long term average result because its unaffected by environmental conditions and can be exposed for months. The alpha particles emitted by Rn in the air

next to the detector leave microscopic tracks in the plastic that, when processed, can be counted. The number of tracks provides information on the Rn concentration. Track etch detector placement is the same as for charcoal except that humidity does not affect this type of detector. These detectors can also be used for testing water when used with a special holder –

ask the provider for a water test kit if you are concerned about Rn in your water.

Slightly more expensive, at about $120, are electronic

monitors (right picture). These have an electronic sensor to detect the radiation emitted in air and are calibrated to give the Rn concentration. The advantage is real time read out but they are susceptible to dust and dirt, humidity, and need to be calibrated.

Mitigating RadonMitigating Radon

I Have Radon I Have Radon ––

What Do I Do?What Do I Do?

Before hiring a Radon mitigation company, try a few simple passive fixes first and retest. To greatly reduce Rn

concentration in a home during winter you simply want to prevent the basement air pressure from being less than outside air pressure. Ventilating the basement by running a 4-inch plastic tube from the outside to your furnace room or area to provide outside combustion air may fix the Rn problem. Also seal all cracks,

penetrations, and joints to block Rn entry; seal porous cinder blocks with epoxy or cement paint; and cover and seal sump

pumps and exposed soil. Note that sealing alone is not effective, nor recommended by the EPA.

If passive remedies do not reduce Rn concentrations low enough, more active methods can be done next. The more common remedy is to install sub-slab

ventilation. With this method several holes are drilled into the basement slab and

fitted with piping that leads to a fan unit in the attic or outside. The fan lowers the air pressure under the slab, drawing Rn out and up the piping before it can enter the home. This method costs about $1,200 to $2,500 depending on the number of pipes to be run. If Rn levels are very high, more invasive sub-slab ventilation may be

necessary at a higher cost.

In homes being built, sub-slab ventilation can be built in and can provide the best Rn mitigation. Other construction techniques can be optimized for Rn reduction and the EPA provides several publications on this topic; see the next section.

From EPA Citizens Guide to Radon 2005http://www.epa.gov/radon/pdfs/citizensguide.pdf

For More InformationFor More Information

Where can I get more information?Where can I get more information?

The EPA web site http://www.epa.gov/radon/pubs/index.html

has information about Radon, testing, mitigation, and preventing Radon in new construction.

For New York, the state Radon office can be contacted at http://www.health.state.ny.us/environmental/radiological/radon/index.htm

or the Depatment

of Health Hotline at 1-800-458-1158 ext. 27556 or (518) 402-7556.

Another NY radon site is http://www.nyradon.org/

.

Also: National Safety Council at http://www.nsc.org/issues/radon/

There are many links from these pages and any web search will find even more information.

You may also contact the Radiation Safety staff in the Cornell University

Environmental Health and Safety Department. Call 255-8200 or visit www.ehs.conrell.edu.