Radon Safety in the School Laboratory

Introduction

For many years the hazard associated with radon has been well known. The Environmental Protection Agency (EPA) estimates that as many as 5,000 to 20,000 people may die each year from their exposure to radon gas. More recently, the EPA has become concerned about radon in the nation’s schools. A published report from the EPA entitled, “Radon Measurements in Schools, An Interim Report,” reveals that high radon concentrations have, indeed, been found in many schools.

You will find the following information useful as you have reason to communicate with your school administration, your school board, your students and your students’ parents.

Concepts

• Radioactivity
• Decay series
• Alpha radiation

Background

What is Radon?
Radon is a colorless, odorless, tasteless radioactive gas formed by the decay of naturally occurring uranium. Radon may be found in soil, rock formations, water or air. As the uranium decays into other materials radon is created.

Radon is the first gaseous product of the decay of uranium. As a gas, it can move freely, traveling in the air or hitching a ride in water. Radon is very water soluble. Radon is continually percolating up through the Earth’s soils and releasing itself into the air. Radon poses little threat if the gas is released into the Earth’s atmosphere out of doors. When released out of doors, air dilution minimizes the hazard. The hazard results from the radon being confined in a small area. Release of radon indoors concentrates the hazard.

Radon’s ability to percolate through the soil is limited to relatively short distances of approximately two or three meters at best. In tightly packed soil it is not able to travel long distances. However, since radon is very water soluble, it will literally “hitch a ride” on ground water. Radon’s ability to travel, then, is relatively unlimited. Radon-contaminated well water is a problem in some areas of the United States. However, water containing radon only poses a hazard immediately after it is pumped from the ground. Once above ground, the radon gas either leaves the water or decays before the water reaches the end user.

It is important to keep in mind that the principal danger of radon is as a respiratory hazard and not as an ingestion hazard.

Radon gas seeps into buildings through sump holes, porous foundations, cracks and openings in floors and walls below ground level, as well as many other sources. Frequently, radon is drawn into a building during the wintertime heating season and can become concentrated in well-insulated homes or buildings.

Where Does Radon Come From?
As we have already discussed, radon is formed by the natural decay of uranium commonly found in the earth. When uranium –238 (U) undergoes radioactive decay, it produces radium –226 (Ra) which in turn decays to produce radon –222 (Rn).

Uranium accounts for 4 ppm of the Earth’s crust. However, in some areas of the country, the levels of uranium found in the Earth’s crust are much higher. Some granite formations in the Northeast have concentrations in the order of 10–50 ppm and in the West concentrations are as high as 500 ppm. These formations are found mostly in New England, the mid-Atlantic states, parts of the Great Lakes region, California, and the Appalachian and Rocky Mountains.

High uranium concentrations have also been attributed to some phosphate rock formations. The levels of uranium found in these formations have been found in north and west central Florida, Idaho, Montana, North Carolina, Tennessee and Wyoming. Many of these phosphate lands have been mined, thus bringing the uranium closer to the surface and increasing the radon hazard.

Uranium concentrations have also been found in some formations of shale. The principal area of uranium concentration in shale formations has been found in Chattanooga shale in Tennessee.

The last large source of uranium in this country is, of course, found in uranium ore itself. Uranium ore is mined in western Colorado, northeastern Arizona, eastern Utah, northwestern New Mexico, Wyoming and Texas. The remnants of mining operations in many areas have high concentrations of radon.

How Is Radon Hazardous?
Radon itself is an inert and harmless gas; however, it decays rapidly producing the real culprits. Radon has a half-life of 3.8 days. In simplistic terms, if you have a certain amount of radon, half of it will decay in 3.8 days. Radon decays into polonium-218, lead-214, polonium-214, lead-210 and polonium–210. These are called radon “daughters.” These radon daughters are the real hazards. The decay series is: Radon daughters are very small solid particles that will attach themselves to small dust particles which in turn will be inhaled and latch onto fibers in the bronchial tubes. Normally, the body will rid itself of any intruder in a certain period of time. However, the half-life of the radon daughters is only a couple of hours and the human body does not react fast enough to rid itself of this hazard. Upon decay, the radon daughters release a small burst of radiation called an alpha particle An alpha particle cannot travel long distances or get through tissue like other forms of radiation, but it packs a significant punch for the local area. The bronchial tubes are one of the body’s most sensitive areas for radiation-induced cancer.

How much radon is dangerous? Unfortunately, no one knows the precise answer. The EPA measures radon in picocuries per liter of air (pCi/l). The EPA has said that living in a house that contains 10 pCi/l carries about the same lung cancer risk as smoking one pack of cigarettes a day! The EPA has recommended action be taken on any building or room testing above the 4 pCi/l level. A 4 pCi/l level may not be completely safe, but it is a generally acceptable level above which corrective action should be taken.

Radon concentrations have been found to be high in one building and nonexistent in the building right next door. High levels of concentration have been found in one room at a school and in the very next room the levels have been found to be minimal. One simply cannot predict where radon will be found. Tests must be run to determine its presence.

Procedure

The EPA recommends testing for the presence of radon begin with a short-term screening test to determine if concentrations are high enough to pose a health hazard. The test results will dictate what, if any, further testing is warranted.

The short-term sampling kit consists of a canister of activated charcoal. The radon gas will adsorb to the charcoal. The decay products remain in the canister and are analyzed by the laboratory when the canister is sent in.

To begin the test, determine the location to be sampled. The EPA recommends testing frequently-used rooms most susceptible to radon concentration (e.g., lower level rooms, rooms with foundation or slab cracks, room with slab joints, rooms isolated from the main heating and ventilation system). See Teaching Tips.

Once the location is determined:

1. Open the package and remove the canister.
2. Remove the gray vinyl tape and lid from the canister. (Save both the lid and gray vinyl tape.)
3. Place the canister in the selected area, on a hard surface with open side up.
4. Record the date and time on the information card.
5. After 48 to 96 hours, replace the lid and reseal the canister with the gray vinyl tape.
6. Mail canister to laboratory within 24 hours. Include information card.

The laboratory analysis is included in the price of the kit. The laboratory will mail the results back. The EPA recommends an immediate follow-up test if results of screening test indicate radon levels of 4pCi/L or higher. This follow-up test is more accurate and is used to confirm that radon levels are indeed high enough to warrant mitigation.
This confirmatory sampling kit contains an alpha track detector. The detector has a plastic film that becomes etched with small tracks when struck by alpha particles emitted by the radon daughters upon decay. Once sampling is complete, the laboratory will chemically treat the film. This enlarges the tracks, making them visible. The tracks are then counted, with the number of tracks proportional to the amount of radon.

Teacher Tips

• Do not locate sampler near areas with drafts, heat sources, direct light or high humidity.
• Select a position that won’t be disturbed during test period.
• Select location at least three feet from any door or openings, such as windows, one foot from any wall and at least four inches off the floor.
• If possible, do the test over a weekend when there would be no traffic.

Discussion

If these follow-up tests also confirm the existence of high levels of radon, please read the EPA publication mentioned earlier in this article, “Radon Measurements in Schools, An Interim Report,” EPA publication number 520/1-89-010. This publication is easy to read and extremely helpful. It is available from your EPA regional office.

High levels of radon usually can be reduced easily and inexpensively. The generally accepted radon reduction methods are sealing and dilution. First, prevent as much radon as you can from entering the building. Secondly, dilute the radon with air to dramatically lower radon levels in the building. In the case of radon gas, air dilution is the solution.

A Special Note About Radon in Your Home
The EPA views the radon hazard in your home to be potentially much more severe than that in your school. Why? It is simply a matter of the amount of time you spend at each place. You spend twice as much time in your home as you do at school. The EPA strongly recommends you test your home for radon.

Conclusion
The decay products of radon gas are potentially hazardous. It is not possible to accurately generalize where radon may be found geographically. If you’re concerned, acquire the least expensive (but reliable) screening device available and test the air in those rooms or areas most likely to be contaminated. If the screening test results raise suspicions, then move to a more sophisticated testing technique for confirmation. In the interim, try to provide improved levels of mechanical ventilation in suspicious areas. However, do not try to change conditions during the time you are testing for radon.

Beware of charlatans selling useless products or unneeded services. Rely upon local, state or federal agencies for good information and confirm what you learn from several sources before proceeding. Unlike the asbestos problem, the solution to radon gas contamination should be relatively simple and inexpensive.

Contact Flinn Scientific, Inc. if you need more information. We will try to be helpful or, failing that, we will direct you to someone who can be helpful.

Radon Test Kits
Detectors are exposed to room environment for a specified test period. After exposure the kit is sent to a laboratory. An analysis of the kit is completed and you are sent a detailed report. The lab analysis and report are included in your purchase price for the kit. There are no additional charges.