Radon & Radon Inspections

We have compiled this information on Radon so you can be informed of this subject, clearly Radon can be found in the whole of the United States and is considered a health hazard by the EPA. Radon is produced by the decay of Uranium and Radium, which can be found in rocks and soil as well as water. Like other States New Hampshire has it's high and low level areas,it is recommended that every home be tested for Radon. If you need a radon inspection or have any questions on Radon please feel free to contact me.


General Questions

What is radon ?

Radon is a radioactive gas. It is colorless, odorless, tasteless, and chemically inert. Unless you test for it, there is no way of telling how much is present.

Radon is formed by the natural radioactive decay of uranium in rock, soil, and water. Naturally existing, low levels of uranium occur widely in Earth's crust. It can be found in all 50 states. Once produced, radon moves through the ground to the air above. Some remains below the surface and dissolves in water that collects and flows under the ground's surface.

Radon has a half-life of about four days—half of a given quantity of it breaks down every four days. When radon undergoes radioactive decay, it emits ionizing radiation in the form of alpha particles. It also produces short-lived decay products, often called progeny or daughters, some of which are also radioactive.

Unlike radon, the progeny are not gases and can easily attach to dust and other particles. Those particles can be transported by air and can also be breathed.

The decay of progeny continues until stable, non-radioactive progeny are formed. At each step in the decay process, radiation is released.

Sometimes, the term radon is used in a broad sense, referring to radon and its radioactive progeny all at once. When testing measures radiation from the progeny, rather than radon itself, the measurements are usually expressed in working level (WL) units. When radiation from radon is measured directly, the amount is usually expressed in picocuries per liter of air (pCi/L).

What health effects are associated with radon exposure?

The Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. There are currently no conclusive data on whether children are at greater risk than adults from radon. No specific subtype of lung cancer is associated with radon exposure.

Only smoking causes more cases of lung cancer. If you smoke and you are exposed to elevated radon levels, your risk of lung cancer is especially high. The U.S. Environmental Protection Agency (the EPA) provides radon risk comparison charts for people who smoke and those who have never smoked. Stop smoking and lower your radon level to reduce your lung cancer risk.

Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe. As they break down further, these particles release small bursts of energy. This can damage lung tissue and lead to lung cancer over the course of your lifetime. Not everyone exposed to elevated levels of radon will develop lung cancer, and the amount of time between exposure and the onset of the disease may be many years.

Breathing radon does not cause any short-term health effects such as shortness of breath, coughing, headaches, or fever.

In 1998, the National Academy of Sciences (NAS) released the Biological Effects of Ionizing Radiation (BEIR VI) Report, "The Health Effects of Exposure to Indoor Radon." The study reviewed and evaluated data from many prior studies and drew conclusions. It fully supports estimates by the EPA that radon causes about 21,000 lung cancer deaths per year. Though some people debate the number of deaths, it is widely agreed that radon exposure is the second leading cause of lung cancer.

Research suggests that swallowing water with high radon levels may pose risks, too, although risks from drinking water containing radon are much lower than those from breathing air containing radon.



What is the "acceptable" level of radon in air?

The EPA states that any radon exposure carries some risk; no level of radon exposure is always safe. However, the EPA recommends homes be fixed if an occupant's long-term exposure will average 4 picocuries per liter (pCi/L) or higher.


What is a "picocurie" (pCi)?

A pCi is a measure of the rate of radioactive decay of radon. One pCi is one trillionth of a Curie, 0.037 disintegrations per second, or 2.22 disintegrations per minute. Therefore, at 4 pCi/L (picocuries per liter, the EPA's recommended action level), there will be approximately 12,672 radioactive disintegrations in one liter of air during a 24-hour period.


What is a "working level" (WL)?

Some devices measure radiation from radon decay products, rather than radiation coming directly from radon. Measurements from these devices are often expressed as WL. As noted above, conversions from WL to pCi/L are usually approximate. A level of 0.02 WL is usually equal to about 4 pCi/L in a typical home.

If a working level (WL) value is converted to a radon level (pCi/L), the conversion is usually approximate and is based on a 50 percent equilibrium ratio. If the actual equilibrium ratio is determined (which is rare), it should be stated. The 50 percent ratio is typical of the home environment, but any indoor environment may have a different and varying relationship between radon and its decay products.

Technically speaking, 1 WL represents any combination of short-lived radon decay products in one liter of air that will result in the ultimate emission of 1.3 x 105 MeV of potential alpha energy.


How often is indoor radon a problem?

Nearly one out of every 15 homes has a radon level the EPA considers to be elevated—4 pCi/L or greater. The U.S. average radon-in-air level in single family homes is 1.3 pCi/L. Because most people spend as much as 90 percent of their time indoors, indoor exposure to radon is an important concern.


How does radon get into a building?

Most indoor radon comes into the building from the soil or rock beneath it. Radon and other gases rise through the soil and get trapped under the building. The trapped gases build up pressure. Air pressure inside homes is usually lower than the pressure in the soil. Therefore, the higher pressure under the building forces gases though floors and walls and into the building. Most of the gas moves through cracks and other openings. Once inside, the radon can become trapped and concentrated.

Openings which commonly allow easy flow of the gases in include the following:

Radon may also be dissolved in water, particularly well water. After coming from a faucet, about one ten thousandth of the radon in water is typically released into the air. The more radon there is in the water, the more it can contribute to the indoor radon level.

Trace amounts of uranium are sometimes incorporated into materials used in construction. These include, but are not limited to concrete, brick, granite, and drywall. Though these materials have the potential to produce radon, they are rarely the main cause of an elevated radon level in a building.

Outdoor air that is drawn into a building can also contribute to the indoor radon level. The average outdoor air level is about 0.4 pCi/L, but it can be higher in some areas.

While radon problems may be more common in some geographic areas, any home may have an elevated radon level. New and old homes, well-sealed and drafty homes, and homes with or without basements can have a problem. Homes below the third floor of a multi-family building are particularly at risk.


Can the radon level in a building's air be predicted?

No, it is not possible to make a reliable prediction.

The only way to determine the level is to test. the EPA and the Surgeon General recommend testing all homes below the third floor for radon.

A map of radon zones has been created to help national, state, and local organizations to target their resources and to implement radon-resistant building codes. However, the map is not intended to be used for determining if a home in a given zone should be tested for radon. Homes with elevated levels of radon have been found in all three zones.

In addition, indoor radon levels vary from building to building. Do not rely on radon test results taken in other buildings in the neighborhood—even ones next door—to estimate the radon level in your building.

 Use this link for Radon Information in NH,http://des.nh.gov/organization/divisions/air/pehb/ehs/ehp/index.htm The Internet is also a source of information about radon levels in some states.


Where can I get more information about radon issues?

The National Safety Council's Radon Hotline provides a toll-free number, (800) 767-7236. Through this automated number, callers can order a brochure on radon. It contains information on ordering a low-cost short-term test kit. In addition, users are instructed to call another one of our numbers, (800) 557-2366, if they wish to speak with our information specialists. They are available to assist callers between 9:00 AM to 5:00 PM (Eastern) on business days.

The EPA also supports operation of other related Hotlines. See the the EPA Web site for information about the following:

the EPA's Indoor Environments Division provides information regarding indoor air quality issues, including radon, asthma, and environmental tobacco smoke/secondhand smoke. Their radon page addresses issues including the EPA's position on radon, health risks, radon resistant new construction, and their former National Radon Proficiency Program (RPP). Many radon documents are also available there.

In New Hampshire -http://des.nh.gov/organization/divisions/air/pehb/ehs/radon/index.htm

State of New Hampshire
29 Hazen Drive, P. O. Box 95
Concord, NH 03302-0095
(603) 271-3503
FAX (603) 271-2867
TDD Access: Relay NH 1-800-735-2964

Testing Air for Radon

Why should I test my home for radon?

Radon is widely believed to be the second leading cause of lung cancer. Therefore, the EPA and the Surgeon General recommend testing for radon in all homes below the third floor.

Radon has been found in homes all over the United States. Any home can have a radon problem. On average, one out of every fifteen U.S. homes have a problem. The only way to know whether or not your home has a radon problem is to test for it.


Who can test a building for radon?

Anyone can use a "do-it-yourself" test kit to check their building. The one-use kits are simple to use and are relatively inexpensive.

If you are not doing your own testing, a qualified/state-certified professional should be hired. Many people find it preferable to hire a professional when testing is being conducted as part of a real estate sales.Some states require providers of radon measurement services to participate in registration, certification, or licensing programs. In states lacking their own certification or licensing programs, you should hire a professional who participates in the national qualification program for radon professionals.

In New Hampshire Visit http://des.nh.gov/organization/divisions/air/pehb/ehs/radon/index.htm to learn about Radon testing or contact me with any questions.


What testing protocol should be followed?

The purpose of the measurements, as well as budget and time constraints, dictate the protocol used. However, the EPA and the Surgeon General recommend testing all homes below the third floor for radon. the EPA recommends that for homes, initial measurements be short-term tests placed in the lowest lived-in level.

The protocol for measurements made for the purpose of assessing the need for mitigation (reducing the radon level) is found in the EPA publication, A Citizen's Guide to Radon.

Protocols for measurements made for real estate transactions are somewhat different. They are described in the EPA document, Home Buyer's and Seller's Guide to Radon.

In New Hampshire Visit, http://des.nh.gov/ or Contact Me with any questions you may have.


Why are short- and long-term tests used?

Radon levels within a building often change on a day-to-day basis. Highest indoor levels are often found during the heating season. Weather conditions, operation of furnaces and fireplaces, and opening/closing of windows and doors are among the factors that cause these patterns.

Short-term test kits are the quickest way to test. These kits should remain in the building from two to 90 days, depending on the device. Testing must be conducted for at least 48 hours. Some devices must be exposed for a longer time. Because radon levels tend to vary from day to day and season to season, a short-term test is less likely than a long-term test to tell you your year-round average radon level.

The EPA recommends that for homes, initial measurements be short-term tests placed in the lowest lived-in level. Short-term testing under closed-building conditions helps to ensure that residents quickly learn if a home contains very high levels of radon. If you are doing a short-term test, close your windows and outside doors and keep them closed as much as possible during the test. If testing for just 2 or 3 days, be sure to close your windows and outside doors at least 12 hours before beginning the test, too. You should not conduct short-term tests lasting just 2 or 3 days during unusually severe storms or periods of unusually high winds.

Because radon levels may fluctuate by as much as a factor of two or three, additional testing is sometimes recommended to better assess the average radon level. Though short-term tests are sometimes used, long-term tests are often recommended.

Long-term tests remain in your home for more than 90 days. A long-term test gives a reading that is more likely to reflect the building's year-round average radon level than a short-term test. Because of season variations in radon levels, the closer the long-term measurement is to 365 days, the more representative it will be of annual average radon levels.

If time permits (more than 90 days), long-term tests can be used to confirm initial short-term results between 4 pCi/L and 10 pCi/L. When long-term test results are 4 pCi/L or higher, the EPA recommends the problem be corrected.


What kinds of test devices are used?

Two groups of devices are more commonly used for short-term testing.

Passive devices do not need power to function. The group includes alpha track detectors, charcoal canisters, and charcoal liquid scintillation detectors. Some charcoal technologies are prone to interference by high humidity, so may not be appropriate for use in all buildings. They are sometimes available in drug, hardware, and other stores, the Internet, and through some laboratories. Electret ion chamber detectors, another type of short-term test device, are usually only available through laboratories. After being used, passive devices are returned to a laboratory for analysis.

Active devices require power to function. This group consists of different types of continuous monitors and continuous working level monitors. Some of the active monitors can provide data on the range of variation within the test period. Some are designed to detect and deter interference. However, they usually require operation by trained testers. These tests often cost more than passive testing.



Where should home testing be done?

The EPA recommends that testing be done in the lowest level of the home suitable for occupancy. This typically represents an area where greatest radon level may occur. Ideally, the test should be conducted in a regularly used room on that level, such as a living room, playroom, den, or bedroom. Avoid testing in a kitchen, bathroom, laundry room, or hallway. High humidity and drafty conditions can bias results from some test devices. Do not disturb the devices while they are sampling. Doing so may alter their results, so they should be placed out-of-the-way.

If the lowest occupied level is not used much, consider also testing a higher-use area. This may help you to better estimate your long-term exposure.

Because most indoor radon comes from naturally occurring radon in the soil, high indoor levels are more likely to exist below the third floor. This is why the EPA recommends testing all homes below the third floor. In some cases, high radon levels have been found at or above the third floor, due to radon movement through elevators or other air shafts in the building. If you are concerned about this possibility, you may decide to test for radon.


If a test result is less than 4 pCi/L (0.02 WL), what should be done next?

If the result of an initial short-term measurement is below 4 pCi/L, or 0.02 WL, a follow-up test is not necessary. However, since radon levels change over time, you may want to test again sometime in the future, especially if use patterns change and a lower level of the building becomes occupied or used more often. Renovations, changes in ventilation, earthquakes, settling of the ground beneath the building, and other changes may cause indoor radon exposures to change.


If an initial short-term test result is 4 pCi/L (0.02 WL) or higher, what should be done next?

The EPA recommends a follow-up measurement be used to confirm whether radon levels are high enough to warrant mitigation. There are two types of follow-up measurements that may be conducted. The choice depends, in part, on the results of the initial test.

An initial measurement result of 10 pCi/L (or 0.05 WL) or greater should be quickly followed by a second short-term test under closed-building conditions. If the average of the initial and second short-term results is equal to or greater than 4 pCi/L (0.02 WL), radon mitigation is recommended. If the average of the short-term test results is less than 4 pCi/L, consider testing again sometime in the future.

If the result of the initial measurement is between 4 pCi/L (or 0.02 WL) and 10 pCi/L (or 0.05 WL), the follow-up test may be made with either a short-term or a long-term method. If a long-term follow-up test result is 4 pCi/L (0.02 WL) or higher, the EPA recommends remedial action. If the long-term follow-up test result is less than 4 pCi/L, consider testing again sometime in the future.

If a short-term follow-up test is done and the result is 4 pCi/L or higher, radon mitigation is recommended. If the average of the initial and follow-up short-term tests is less than 4 pCi/L, consider testing again sometime in the future.

Radon test flowchart

In certain instances, such as may occur when measurements are performed in different seasons or under different weather conditions, the initial and follow-up tests may vary by a considerable amount. Radon levels can vary significantly between seasons, so different values are to be expected.


Radon Resistant Construction

What are radon-resistant features?


The techniques vary for different foundations and site requirements, but the basic elements are:


When should radon-resistant construction be considered?

Find out if you are buying a home in a high radon area. the NH map of radon zones indicates areas having the greatest potential for elevated indoor radon readings. Homes in places with high potential, called Zone 1 areas, should be built with radon-resistant features.Visit this site to see a map of New Hampshire Radon zones http://des.nh.gov/organization/divisions/air/pehb/ehs/radon/index.htm

If you are planning to make any major structural renovation to an existing home, such as converting an unfinished basement area into a living space, it is important to test the area for radon before you begin the renovation. If your test results indicate a radon problem, radon-resistant techniques can be inexpensively included as part of the renovation. Because major renovations can change the level of radon in any home, always test again after work is completed.


What are the benefits of radon-resistant construction?

Radon-resistant techniques are simple and inexpensive. Besides reducing radon levels, they also lower concentrations of other soil gases and decrease moisture problems. They make a home more energy efficient, and can save on annual   energy costs.


How much does it cost to reduce radon in an existing home?

If a home with a vent system is found to have an elevated radon level, a fan can be added at a low cost. The total cost is much lower than adding the entire system after the building is completed. The average cost to install radon-resistant features in an existing home is $800 to $2,500. The average cost to install radon-resistant features in a new home during construction is $350 to $500 (a 128% to 400% saving).

In New Hampshire In many cases, the removal of radon that originates from infiltration through a home's foundation is the most effective means of reducing one's risk from exposure to radon. The most common method used for radon removal from indoor air is soil-gas ventilation, which works by drawing away radon gas from under and around the house foundation. Typical cost for simple air mitigation ranges from approximately $800 to $1,500. Contractors offering this service may be found in the Yellow Pages under "Radon Testing & Services." For further information concerning radon air mitigation please call DES radon coordinator at 603-271-4764.


Who should I hire to install radon-resistant features?

Talk to your builder about installing a radon-reduction system during major renovations or new construction. Radon-resistant features can be easily and inexpensively installed with common building practices and materials. There is usually no need to hire a special contractor or architect. Many builders already incorporate some of these steps in the construction of their houses to control moisture or increase energy efficiency.

 Radon Mitigation Standards, provides radon mitigation contractors with uniform standards that will ensure quality and effectiveness in the design, installation, and evaluation of radon mitigation systems in detached and attached residential buildings three stories or less in height.


Should a home built with radon-resistant features be tested?

Yes. Every new home should be tested for radon after occupancy. Test your home even if it has the radon resistant features.


Mitigating Radon Problems

What is a radon mitigation system?

A radon mitigation system is any system or steps designed to reduce radon concentrations in the indoor air of a building.

The State of NH recommends that you take action to reduce your home's indoor radon levels if your radon test result is 4 pCi/L or higher.


What are the benefits of radon mitigation?

Radon reduction systems work. In most new homes, use of radon-resistant features will keep radon levels to below 2 pCi/L. Some radon reduction systems can reduce radon levels in your home by up to 99 percent.

Homeowners should consider correcting a radon problem before making final preparations to sell a home. This often provides more time to address the problem and find the most cost-effective solution. In addition, the current occupants—not just the buyer's occupants—will reap the benefit of reduced risk.


What can be done to reduce radon in a home?

Your house type will affect the kind of radon reduction system that will work best. Houses are generally categorized according to their foundation design. For example: basement, slab-on-grade (concrete poured at ground level), or crawlspace (a shallow unfinished space under the first floor). Some houses have more than one foundation design feature. For instance, it is common to have a basement under part of the house and to have a slab-on-grade or crawlspace under the rest of the house. In these situations a combination of radon reduction techniques may be needed to reduce radon levels to below 4 pCi/L.

There are several methods that a contractor can use to lower radon levels in your home. Some techniques prevent radon from entering your home while others reduce radon levels after it has entered. the EPA generally recommends methods that prevent the entry of radon.

In many cases, simple systems using underground pipes and an exhaust fan may be used to reduce radon. Such systems are called "sub-slab depressurization," and do not require major changes to your home. These systems remove radon gas from below the concrete floor and the foundation before it can enter the home. Similar systems can also be installed in houses with crawl spaces. Radon contractors use other methods that may also work in your home. The right system depends on the design of your home and other factors.

Sealing cracks and other openings in the floors and walls is a basic part of most approaches to radon reduction. Sealing does two things, it limits the flow of radon into your home and it reduces the loss of conditioned air, thereby making other radon reduction techniques more effective and cost-efficient. The EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently. It is difficult to identify and permanently seal the places where radon is entering. Normal settling of your house opens new entry routes and reopens old ones.

Any information that you may have about the construction of your house could help your contractor choose the best system. Your contractor will perform a visual inspection of your house and design a system that is suitable. If this inspection fails to provide enough information, the contractor will need to perform diagnostic tests to help develop the best radon reduction system for your home. Whether diagnostic tests are needed is decided by details specific to your house, such as the foundation design, what kind of material is under your house, and by the contractor's experience with similar houses and similar radon test results.


How much does it cost to reduce radon in an existing home?

In many cases, the removal of radon that originates from infiltration through a home's foundation is the most effective means of reducing one's risk from exposure to radon. The most common method used for radon removal from indoor air is soil-gas ventilation, which works by drawing away radon gas from under and around the house foundation. Typical cost for simple air mitigation ranges from approximately $800 to $1,500. Contractors offering this service may be found in the Yellow Pages under "Radon Testing & Services." For further information concerning radon air mitigation please call DES radon coordinator at 603-271-4764,Your costs may vary depending on the size and design of your home and which radon reduction methods are needed.


Who should I hire to correct a radon problem?

Lowering high radon levels requires technical knowledge and special skills. You should use a contractor who is trained to fix radon problems.In New Hampshire Contact

N.H. Department of
Environmental Services
29 Hazen Drive
P.O. Box 95
Concord, NH 03302-0095
(603) 271-3503
TDD Access:
Relay NH 1-800-735-2964
FAX: (603) 271-2867

If you plan to fix the problem in your home yourself, you should first contact your state radon office for the EPA's technical guide, "Radon Reduction Techniques for Detached Houses."


Will any more testing be needed after a radon mitigation system has been installed?

Most radon reduction systems include a monitor that will alert you if the system needs servicing. However, regardless of who fixes the problem, you should test your home afterward to be sure that radon levels have been reduced. This test should be conducted no sooner than 24 hours nor later than 30 days following completion and activation of the mitigation system(s). Potential conflict of interest can be avoided by using an independent tester.

In addition, it's a good idea to retest your home sometime in the future to be sure radon levels remain low. Testing should be done at least every two years or as required or recommended by state or local authority. Retesting is also recommended if the building undergoes significant alteration.


Are funds available to reduce high radon levels in rental housing?

There are some federal programs that might be used to help fund radon reduction in homes that are affordable to limited income families. These programs generally give money to local agencies or groups, which then fund the work. Some examples are:


How does radon get in water?

When the ground produces radon, it can dissolve and accumulate in water from underground sources (called ground water), such as wells. Radon can be a concern if your drinking water comes from a well that draws from an underground source, though not all water from underground sources contains radon.When water containing Radon is run for showers, washing dishes, or for drinking, Radon can be introduced into the air.


Well Types in New Hampshire


Groundwater Sources
New Hampshire is relatively water rich. Wells that take water from the unconsolidated sand and gravel deposits (above the bedrock) are only feasible where the soils are sufficiently porous to transmit water and where the water table is sufficient deep to resist drought effects. Bedrock (also called drilled or artesian) wells are easily developed through out the state.

Well drillers and pump installers in New Hampshire are licensed by the Water Well Board. The rules of the board are numbered We 100-900. There are no state requirements relative to water quality or quantity for private home wells. Some towns have local requirements for private water wells.

The frequency of occurrence of iron, manganese, taste and odor is approximately the same in all types of wells in New Hampshire.

Bedrock (Artesian) Wells / Drilled Wells
Most wells in New Hampshire are drilled into bedrock. The average bedrock well is 295 feet deep and has a yield of 6.5 gallons per minute (gpm). These wells are often called “artesian,” however the term drilled or bedrock is generally more accurate. For more information on bedrock well design see fact sheet WD-DWGB-1-2- http://des.nh.gov/organization/commissioner/pip/factsheets/dwgb/documents/dwgb-1-2.pdf

Approximately 5,000 bedrock wells are drilled annually in New Hampshire. The yield of bedrock wells can be improved by two processes. Before drilling, the precise placement of the well can be guided by the process called fracture trace analysis. Once drilled and where outputs are low, the well’s yield can often be improved by the process called hydrofracturing. Hydrofracturing is explained in
http://des.nh.gov/organization/commissioner/pip/factsheets/dwgb/documents/dwgb-1-3.pdf Bedrock wells are typically the most expensive to construct. The operations of bedrock wells are also expensive because of the electrical energy needed to lift the water from deep in the ground.

Bedrock wells generally have high reliability relative to bacteria. Bedrock wells can experience the following natural contaminants: fluoride (2 percent over 4 mg/L) and radioactivity including, radium (percent) and uranium (5 percent) compliance gross alpha (2 percent). Radon gas occurs in approximately 90 percent above 300 pCi/L and 70 percent above 2,000 pCi/L. Hardness minerals are typically higher in bedrock wells than sand and gravel type. Arsenic exceeding the new standard of 10 ug/L is likely in 15 percent of bedrock wells.

Wells in Soil

Point Wells. These wells capture water in the loose soil deposits. Fewer than 2 percent of the wells in New Hampshire are point wells. These wells are typically 2-3 inches in diameter and located in fine sandy soil. For more information on point wells see fact sheet WD-DWGB-1-6-http://des.nh.gov/organization/commissioner/pip/factsheets/dwgb/documents/dwgb-1-6.pdf  concerning point wells. These wells have low construction and low operational costs but are subject to drought effects and subject to man made contamination from many “backyard” activities. Point wells are very reliable relative to bacterial quality.

Dug Wells. These wells also capture water in the upper sand and gravel deposits. Fewer than 10 percent of all wells in New Hampshire are dug. Historically dug wells were made from fieldstone. These wells are notorious for poor construction which leads to frequent bacterial problems. More modern dug wells are made from precast concrete components. For more information on a dug well design see fact sheet WD-WSEB-1-4 -“http://des.nh.gov/organization/commissioner/pip/factsheets/dwgb/documents/dwgb-1-4.pdf” The construction cost of dug wells is typically between that of point well and bedrock well. The operational cost of a dug well is low. Dug wells are sensitive to drought effects if not sufficiently deep and they are subject to man made chemicals contamination from many “backyard” activities. Poor configuration and aging of the construction materials can contribute to frequent bacterial problems.

Radon from lakes, rivers, and reservoirs (called surface water) is of much less concern. Most of the radon is released from the water before it enters the distribution system.If you get your water from a public water system that serves 25 or more year-around residents, you will receive an annual water quality report. These water quality reports include information on what is in your water, including radon if it has been tested.


Does radon in drinking water pose a risk?

In most cases, radon entering the home through water will be a small source of risk compared with radon entering from the soil. The EPA estimates that indoor radon levels will increase by about 1 pCi/L for every 10,000 pCi/L of radon in water. Only about one to two percent of indoor radon in air comes from drinking water.

Radon gas can enter the home through well water. It can be released into the air you breathe when water is used for showering and other household uses. Research suggests that swallowing water with high radon levels may pose risks, too, although risks from swallowing water containing radon are believed to be much lower than those from breathing air containing radon.

While radon in water is not a problem in homes served by most public water supplies, problems have been found in well water. If you've tested the air in your home and found a radon problem, and your water comes from a well, contact a lab certified to measure radiation in water to have your water tested.

If you're on a public water supply and are concerned that radon may be entering your home through the water, call your public water supplier.


Should drinking water be tested?

Because radon in indoor air is the larger health concern, the EPA recommends that you first test the air in your home for radon before testing for radon in your drinking water. the EPA and the Surgeon General recommend testing all homes for radon in indoor air (and apartments located below the third floor). The EPA recommends that you take action to reduce your home's indoor radon levels if your radon test result is 4 pCi/L or higher.

If you have tested the air in your home and found a radon problem, you may also want to find out whether your water is a concern. If you get water from a public water system, find out whether the comes from a surface (river, lake, or reservoir) or a ground water (underground) source.

If the water comes from a surface water source, most radon in the water will be released to the air before it reaches your tap. If the water comes from a ground water source, call your water system and ask if they've tested the water for radon. If so, ask for their Consumer Confidence Report.

If you have a private well, the EPA and the NH Dept,of Environmental Services recommends testing your water for radon.



In addition to radon gas, other radioactive minerals such as radium and uranium may be dissolved in drinking water. A test of drinking water for radon gas does not provide meaningful knowledge concerning the presence or absence of any other mineral radionuclide's, nor does an elevated level for these dissolved minerals imply the presence of an excessive amount of radon gas. In other words, a minimum of three different laboratory tests will be required to make an initial assessment of the radioactivity level of a particular well. These tests are:

Radon gas and dissolved analytical gross alpha are the testing priorities.
*The DES laboratory does not process radium 226/228 radioactivity samples. This service, however, is available from some independent laboratories in New Hampshire and through the State of Maine's Public Health Laboratory. The Maine laboratory can be reached at (207) 287-2727. Other specialty radionuclide laboratories are given in


What do the results of a water test mean?

Estimate how much the radon in your water is elevating your indoor radon level by subtracting 1 pCi/L from your indoor air radon level for every 10,000 pCi/L of radon that was found in your water. (For example: if you have 30,000 pCi/L of radon in your water, then 3 pCi/L of your indoor measurement may have come from radon in water.) If most of the radon is not coming from your water, fix your house first and then retest your indoor air to make sure that the source of elevated radon was not your private well. If a large contribution of the radon in your house is from your water, you may want to consider installing a special water treatment system to remove radon. the EPA and the State of NH recommends installing a water treatment system only when there is a proven radon problem in your water supply.


What levels of radon in water should I be concerned about?

There is currently no federally-enforced drinking water standard for radon.

The EPA does not regulate private wells, but is proposing to regulate radon in drinking water from community water suppliers (water systems that serve 25 or more year-round residents). the EPA proposed the rule in October 1999 and plans to finalize it in August 2000.

Development of the Radon in Drinking Water Standard
There are no water quality standards for private home wells in New Hampshire. Consequently, private wells owners often turn to the water quality standards for public water systems (PWSs) to evaluate the safety of their private wells. At present there is no federal or state standard for radon in drinking water. Such a standard is known as a maximum contaminant level (MCL). EPA current schedule is to complete a standard for radon in water by the end of 2005.

Since many New Hampshire residents have questions concerning what level of radon in drinking water is safe, and given the lack of a state or federal standard, we summarize below the history of recent radon proposals.

History – In 1991 EPA proposed to limit radon gas in residential PWSs to 300 pCi/L. Over 95 percent of New Hampshire wells would exceed this concentration. During the public comment period, DES and the Department of Health and Human Services (DHHS) commented on the proposal and suggested that in view of both societal cost and health benefit, that EPA set the radon standard for PWSs at 2,000 pCi/L instead of 300 pCi/L.

1996 SDWA Reauthorization – In 1996, Congress reached a compromise on reauthorization of the federal Safe Drinking Water Act (SDWA). Relative to radon gas in water, this legislation specified that EPA would re propose the standard for the radon MCL and complete the entire regulatory task by August 2000. This statute specified that if EPA selected a stringent MCL for radon gas in water, an alternative MCL (AMCL) would also be proposed. The AMCL is explained below. The goal of Congress in establishing the AMCL was to provide regulatory flexibility characterized by both the regulated drinking water arena and the unregulated indoor air quality arena. The alternative MCL would have a risk similar to that from the equivalent concentration of radon normally found in outside air.

On November 2, 1999, EPA began the formal process of establishing a radon gas standard for community PWSs. The proposal consists of two standards that would regulate the concentration of radon gas in community PWSs. A health based standard with two different concentrations is unique in the drinking water field.

b. The second standard would be called the alternative maximum contaminant level (AMCL). If proposing to be evaluated by this AMCL, a water utility will need to apply to DES or EPA for approval to use the higher standard. The approval process will require the establishment of a supplemental program that addresses radon from the foundation of typical homes referred to as multi-media mitigation (MMM), as explained below. The proposed AMCL is 4,000 pCi/L. The AMCL was set at an equivalent to the concentration of radon occurrence in outside air approximately five feet above the ground surface (0.4 pCi/L).

Multi-Media Mitigation (MMM)
The multi-media mitigation (MMM) approach to radon reduction described above is based on an understanding of the two principal radon exposure pathways as explained further below.

In order to use the less restrictive AMCL as identified above, a second health outreach program must be provided. The goal of this program is to reduce radon exposure from the foundation pathway. The MMM program will involve a variety of outreach programs. The basic goal of the MMM program will be to reduce the risk from the radon contribution associated with the foundation pathway by an amount equal or greater than the increased risk associated with using the AMCL of 4,000 pCi/L rather than MCL of 300 pCi/L. Each public water system MMM program will require initial approval by DES/DHHS/EPA and subsequent periodic review of the program's accomplishments. The EPA has not interpreted how the MMM program would apply to a single family home with a private on-site well.

Other State Radon in Water Guidance
In the absence of a final EPA standard, states surrounding New Hampshire (Maine 4,000 pCi/L; Massachusetts 10,000 pCi/L; Vermont 5,000 pCi/L) are offering significantly different recommendations for a safe level for radon gas in drinking water. DES believes it is very unlikely that the future EPA Radon standard would exceed 4,000 pCi/L


How is radon removed from water?

Radon can be removed from water by using one of two methods: aeration treatment or granular activated carbon (GAC) treatment.

Introduction – In some cases, elevated radon gas concentrations exist in both air and water. Normally there is much more health protection to be realized by reducing radon originating from the foundation pathway than reducing radon in water. You are welcomed to contact DES radon health coordinator at 603-271-4764, to discuss radon reduction priorities Treatment to Reduce Radon in Air.Or see link below.http://des.nh.gov/organization/commissioner/pip/factsheets/dwgb/documents/dwgb-3-12.pdf

Aeration Treatment – Radon gas can be easily removed from drinking water by the process known as aeration. Aeration can achieve over 99 percent removal of radon gas from water. The process consists of mixing large volumes of clean air with the well water. The moist radon laden air is discharged outside the home. The treated water is re-pressurized so as to flow through your plumbing. A list of radon aerator distributors is given in this document.

Water Quality – Aeration will intensify the staining affect of untreated iron and manganese. If iron/manganese are meaningfully present, pretreatment for their removal is recommended. If iron and manganese remain untreated, iron bacteria or a film of inorganic precipitates would be expected to form on the inside of the aerator. This condition can loosen in large clumps and may clog pumps or reduce the pump service life. Where high carbon dioxide (CO2) is present in the well water, release of the CO2, may raise the pH of the water. This is beneficial as higher pH water is generally less corrosive.

Aeration Design Considerations – The design concept of a radon aeration devices can be of either of a pressurized or vacuum type. A vacuum type design prevents the possible escape of radon if there were a leak in the outer jacket of the device. Most radon aerators have components made from plastic or stainless steel. This is important since ordinary steel will rust in the high moisture environment of an aerator. Aerators can be relatively noisy. Listen to the aerator while running in the showroom and consider noise when locating the device in the basement. Ease of disassembly of the device is important relative to periodic cleaning. The installation location should be well lit, warm and have good access space on all sides. The device should have redundant solenoid valves or adequate sized floor drain to prevent basement flooding if equipment malfunction occurs. See fact sheet WD-WSEB-2-23 for suggested installation considerations for aeration devices.

Purchase Costs – Aeration treatment devices, installed and warranted by others, typically cost from $3,500 to $4,500. As with all mechanical/electrical devices, aerators will eventually need repair (more likely after approximately five years). Removal of iron or manganese, where necessary, will result in higher cost.

Maintenance Costs – In addition, an aeration device may need cleaning every six to twelve months depending on water quality. Approximate cleaning cost (consisting of flushing, disinfecting and air filter replacement by a water treatment professional) may have a cost of $150-$200 per visit. Cleaning by the homeowner is also possible.

Activated Carbon Treatment – Activated carbon (AC), similar to charcoal, is effective in removing radon gas from drinking water. The water is passed through the AC, which is placed in a water treatment tank, and the entire system works under pressure. There are minimal moving parts in AC type treatment system.

Purchase Cost – The cost of an AC treatment system, installed and guaranteed by water treatment professionals, is approximately $2,000.

Maintenance Cost – AC replacement can be costly. When considering AC treatment determine the expected cost of periodic replacement of the media.

CAUTION: DES does not generally recommend AC for radon removal, since radioactivity will build up on the carbon. In some cases this could make the carbon in the treatment container too radioactive to be near (in the basement or floor above) and would result in very expensive disposal.

Some technical authors have suggested that AC is a reasonable treatment method for radon in water for concentrations below 5,000 pCi/L. DES is considering this recommendation further. In addition to radon, mineral radioactivity may in some cases also be removed by AC. This removal process may be enhanced in the presence of iron (and possibly manganese). Thus the concentration of mineral radionuclide's and iron /manganese should be evaluated and be very low before considering the use AC.

AC Disposal – The AC should be replaced on a periodic basis to prevent excessive radionuclide buildup. DES suggests that the AC canister, when first installed, should be labeled "REPLACE CARBON ANNUALLY" in large letters oriented on the canister so as to be easily seen. (DES is reviewing more specific guidance concerning the frequency of carbon replacement and will provide this information at a future date.)

Manufacturers and suppliers of radon water treatment devices can be found in the Yellow Pages. Look under the listings for "Water Treatment," "Water Conditioning," or "Radon Testing & Services." Well drillers, pump installers, building and code enforcement officials, and Realtors often know of local radon treatment equipment suppliers.

For more information about radon reduction methods for the air in your home, contact the DES radon health coordinator at 603-271-4764. For more information on radon in water, contact the DES Drinking Water and Groundwater Bureau, at (603) 271-2513. For a detailed discussion of radon from a geological perspective, please see fact sheet http://des.nh.gov/organization/commissioner/pip/factsheets/geo/documents/geo-2.pdfdes.nh.gov/organization/commissioner/pip/factsheets/geo/documents/geo-2.pdf

Drinking water fact sheets are available through the DES web site at,http://des.nh.gov/organization/commissioner/pip/factsheets/dwgb/index.htmdes.nh.gov/organization/commissioner/pip/factsheets/dwgb/index.htm. Please check the INTERNET annually for updates to this document.


Radon Information For New Hampshire

 Radon is the Th element in the chemical periodic table. Odorless, colorless and chemically inert, it is a naturally occurring radioactive noble gas that is found at varying levels everywhere in the environment.

 Radon can only be sensed with instruments, specifically the Geiger counter and, indirectly, with a scintillometer (gamma sensor). Because the gas has a high density, it does not mix well with the Earth's atmosphere. Thus, it tends to be concentrated in low places in the natural environment, including valley floors or topographic depressions and in basements in the built environment.

 Radon is appreciably soluble in water, inversely proportional to the water temperature. This relationship has important repercussions which allow, for example, radon to be easily degassed into the built environment from a combination of heating and aeration of the groundwater in the bathroom shower.

 Radon is especially mobile in groundwater, moving in response to the gravity gradient within saturated fractured bedrock and surficial deposits. The gas is also mobile in air within the fracture network of the bedrock and the pore space of the surficial deposits. Here, it moves by a combination of flow and diffusion, and is sometimes called "soil gas" in levels near the surface of the earth. In some cases, radon in groundwater can be exchanged into the air in soil and fractured rock by evaporation. Radon-bearing air is also capable of migrating directly into an unsealed built environment, especially basements.


 The health risk from radon was not generally accepted until the 1960s when a statistical study of the incidence of lung cancer among uranium miners was done. Actually, an intuitive correlation of lung disease affecting miners was made as early as 1500, but it was not suspected to be radon-related carcinoma until the 1930s. No statistically-based studies of non-miners and radon have been made to date. Thus, the environmental risks of radon exposure to the average citizen cannot presently be established with confidence. Nonetheless, advisory standards for radon in air have been established, and standards for radon in water are under development.

 Radon risk was not of universal concern to the public until 1984 when a worker at a nuclear generating facility in Pennsylvania triggered a personal radiation exposure alarm when he entered, not left, the plant. Investigation showed that his anomalous exposure was caused by excessive radon in his house. The story was featured by the New York Times, and the age of radon awareness began.


 Everyone on earth is subject to some degree of natural radiation (part of which comes from radon), commonly called "background." This background is mostly contributed from the rocks and surficial deposits or objects made from them. Cosmic rays also contribute radiation from outer space, and normal radioactive elements in the food chain add their component to complete this natural exposure. Further, since the nuclear age began, an additional contribution of radiation to the environment has been made from military hardware and reactor accidents.

 Natural radiation is not considered to be a health hazard because the level of exposure is relatively low, and man has seemingly evolved successfully in harmony with it.


 There are more than 100 chemical elements each consisting of several isotopes. The isotopes of any given element have the same number of protons, but different numbers of neutrons. The neutrons have mass, hence the isotopes come with different atomic weights. Some isotopes are unstable, and hence radioactive. This instability is called radioactive decay which lowers the atomic weight, forms a new isotope and a corresponding yield of nuclear energy. The form of this energy determines its radiation type and, in part, the destructive risk.

 There are three unique types of radiation associated with radioactive decay (Table 1): alpha, beta, and gamma. Alpha radiation has mass, a relatively large radius, a positive (+2) charge, and is composed of two protons and two neutrons which move with a velocity of kilometers per second. Beta radiation is simply composed of high energy electrons, normally with a negative (-) charge. Beta is composed of nuclear electrons and has less mass than alpha, but these electrons have greater velocity. Gamma radiation is electromagnetic, has no mass, and travels at the speed of light. Considering the characters of mass and velocity of radiation, gamma has the greatest penetrating power and alpha the least. Alpha can, in fact, be arrested with a sheet of bond paper, but it is the most dangerous form of nuclear radiation for the damage it can do when colliding with living tissue. Gamma radiation is comparable to x-rays and is the least dangerous form of nuclear radiation in relatively low flux.

Table 1


2 protons + 2 Neutrons
(=nuclei of helium atom)
Thousands of
(< 12 Mev)
(+ in rare cases)
Nucleas electrons
(< 4 mevMinimum)
Electromagnetic energy like
X-rays, but of much shorter
wave length (no mass)
(< 2 Mev)

C = velocity of light = 299,776 km/sec = 186,272 mil/sec



 There are three isotopes of radon in nature, but only the isotope with an atomic weight of 222 (222Rn) is abundant enough to be of environmental importance. 222Rn is the product of the radioactive decay of radium (226Ra) which is in the uranium (238U) decay chain. For purposes of simplicity, only the 238U decay chain is considered. In this arrangement uranium is the "parent" element and the lighter isotopes below are called the "daughter" products. Here we see a fundamental relationship: the abundance of radon in any given geologic domain is a function of uranium distribution. Radon ultimately comes from uranium dispersed in the rocks and surficialElement Massnumber Atomicnumber HalfLife Radiation deposits around us. Thus, radon potential is controlled by the geology, specifically the distribution and geochemistry of uranium. Granite and metamorphic rocks are among the rocks of the earth's crust that can be especially endowed with uranium. New Hampshire is underlain by nearly equal amounts of these rocks, thus radon is of critical concern here.

 Radioactive isotopes are unstable and decay at specific measurable variable rates. It is a mathematical convenience, therefore, to express these rates of decay in terms of "half-life," or the time it takes for one-half of a given amount to decay to the next "lower" isotope or a stable isotope (fig. 1 and fig. 2). Note that radon has a half-life of only 3.8 days, in contrast to uranium which has a 4.51 billion year half-life. Radon's relatively short half-life has important epidemiological consequences especially when considering the daughter products that follow from radon decay.

Half - Life
4.5 X 101 years a
24 days B
6.7 hr, 1.2 min (2 isomers) B
2.5 X 105 years a
8 X 104 a
1,620 years a
3.8 days Circled a
Circled Pc
3 min 99.97% Circled a, 0.03% B
Circled Pt
26.8 min. Circled B
or At
2 sec. a
Circled Bi
20 min. 99.6% Circled B, 0.04% a
Circled Pc
1.6 X 10-4 sec. Circled a
or Ti
1.3 min. B
22 years Circled B
5 days B
138 days Circled a
8a + 6B

Figure 1. The Uranium -238 Natural Radioactive Series


The uranium-238 decay series showing the half-lives of elements and their modes of decay.

There are a number of ways to express the measurement of radiation, but the Curie Standard (named for French physicist Marie Curie) has been adapted as a matter of convenience for radon. A curie is the amount of radiation emitted from one gram of 226Ra. This is relatively a lot of radiation, and the use of the pico-Curie per liter (pCi/L) is the most convenient measure. One pCi is one trillionth of a curie (10-12). Thus, the concentration of radon can be expressed in terms of either a liter of air or water.


 Health risk concerns about radon require separate approaches for radon in air, which is inhaled into the lungs, and radon in water, which is mostly ingested into the digestive tract. Though there is a danger of cell damage from the powerful alpha radiation energy produced from the decay of radon, a far greater risk comes from the radiation emitted by radon's daughters which can reside within the body because they are compatible with human biochemistry. Radon-rich water arrives with human biochemistry. Radon-rich water arrives with a considerable population of its daughter products because of the short half-life of the isotope. Radon levels in outdoor air, indoor air, air in fractured rocks and surficial deposits, surface water, and groundwater can be quite different,See link be;ow for more information



 It has been observed that radon production is ultimately linked to the natural distribution of uranium in the earth's crust. All rocks contain measurable amounts of uranium varying according to their geochemical controls and genesis. Background amounts of uranium are less than 3 parts per million (ppm) in most rocks and surficial deposits. Uranium content in rocks can, however, vary greatly up to ore grade (>1,000 ppm). Surficial deposits are derived from the process of mechanical and chemical weathering of rocks, often with transport and redeposition by ice, water, or wind. Most of these deposits also contain less than 3 ppm uranium. Residual soils and closely redeposited weathering products of rocks, thus, tend to mimic the uranium content of the rocks that they came from if chemical weathering has not been profound. This is especially true of some glacial tills which are abundant in New Hampshire.

 Some rocks frequently have an above-average uranium content, including specialized granite, light-colored volcanic rocks, carbonaceous shales, and metamorphic rock. We have observed that New Hampshire is underlain almost entirely be granitic and metamorphic rocks. Interestingly, many of the metamorphic rocks were deposited as light colored volcanics, such as rhyolite, and black carbonaceous sediments. Thus, many rocks of the state present a high potential for uranium. Fortunately, most of the granite in the state is of a type that is known to have a low to moderate uranium content (<5 ppm). One variety of red to pink granite in the White Mountains, Conway Granite, is among the most uranium-rich known in the world (averaging about 25 ppm). This particular rock, however contains abundant weathering-resistant accessory minerals, such as zircon, which effectively lock-up the uranium (and most of the radon) making the rocks less dangerous than they could be.

 A unique type of granite, called "two-mica granite," and related pegmatite is abundant in the southeastern, central, and western parts of the state. This rock is characterized by moderate amounts of uranium (about 5 to 10 ppm), but it contains only minor amounts of resistate accessory minerals. Thus, the uranium is quite mobile (labile) in weathering processes in these rocks, and is capable of being dissolved and redeposited into local concentrations, sometimes exceeding ore-grade, creating sources of radon.

 A unique type of uranium deposit that is found in peat has recently been discovered in New Hampshire as well as in other states. Some of these deposits can contain as much as 1 percent uranium. This uranium is young," however, fractionated away from its daughters. As such, it is not notably radioactive because of the long half-life of uranium, and it is not associated with significant radon. It can, however, present a risk as a toxic metal.

 Faults, fractures, fissures, and especially the shatter zones which cut the rocks, can be important conduits for radon migration. Some of these features have been identified in New Hampshire where the structures are venting radon either from groundwater found along them or uranium deposits that have formed there. Glacial till that is comprised of material from uranium-rich rocks and transported by ice movement can also present a radon source over rocks not other wise enriched in uranium. Thus, in areas with faults, shatter zones, and glacial tills, there is not always a direct correlation between rocks and radon.


 As noted, the distribution of uranium in the bedrock is dependent on a combination of the genesis, geochemistry, and mineral content of a rock unit. Fractionation of uranium into surficial deposits is dependent on variables such as weathering processes, transport, and redesposition sedimentation of bedrock products. In order to assess radon potential, knowledge of the character and distribution of rock types and surficial deposits must be known. Such information is furnished by geologic maps of different types (fig. 4). These geologic maps can also be augmented by radioactivity maps that portray directly measured values made either on the ground or from the air (fig. 5). From these types of maps, derivative maps can then be created that show radon potential for estimating human risk. The ultimate map is obviously one complied from direct ground emanation of radon measured with special instruments that, quite literally, "sniff" radon. These maps compiled at scales fo 1:24,000 (1" equals about 0.4 mil) and larger have engineering importance and can be useful in deciding upon the suitability of land for development. Such maps, however, would be of limited use in forecasting radon levels in water wells drilled into the bedrock.

 Click on This Link to See Radon Map http://des.nh.gov/organization/divisions/air/pehb/ehs/radon/index.htm


Outdoor Air. Radon in outdoor air poses no risk to human health. The range in concentration varies from 0.1 pCi/L to 30 pCi/L, averaging about 0.2 pCi/L. Higher, but not dangerous, concentrations are possible during passive weather conditions along the floors of sharp topographic depressions that signal faults and shatter zones. No deep mines are operated in New Hampshire, and quarries operated for stone and aggregate production are probably sufficiently ventilated by nature to present no radon risk.

Surficial Deposits. Air (soil air) in water-unsaturated surficial deposits including glacial sediments has much more variable concentrations and higher levels of radon than free air. These levels vary from about 100 pCi/L to more than 100,000 pCi/L, but probably average between 200 and 2,000 pCi/L near the surface. The radon in these surficial deposits is mainly attributable to the decay of radium. Soil gas radon can come from groundwater evaporating or "pumping" within the surficial deposits, especially during periods when the water table is rising and falling. Once mobile in the soil, the radon is free to respond to the controls of the diffusion gradient (migration from a higher to a lower concentration) and flow (pressure) gradient.

Surface Water. Radon in surface water is free to rapidly enter the atmosphere, and thus seldom exceeds levels of about 100 pCi/L. Certainly, public surface water supplies do not pose a radon risk. Moreover, these waters are required to be tested for radioactivity. Some springs in New Hampshire, especially in the western part of the state, are known from ground radiation measurements to carry appreciable amounts of radon. Testing them for radon is recommended, especially where spring waters are emanating from known faults, fissures in two-mica granite, and either rocks or surficial deposits, especially within the White Mountains.

Groundwater. Groundwater is obtained in New Hampshire from surficial deposits (dug wells and screened wells) and from bedrock sources (drilled wells). The water in surficial deposits is contained in pore space, and the water in rock-drilled wells is contained principally in fractures (secondary porosity).

 The crystalline rocks of the state do not have appreciable primary porosity. The radon levels in New Hampshire groundwater vary as much as six orders of magnitude ranging from about 100 pCi/L to as much as 4 million pCi/L! The groundwaters of primary porosity in surficial deposits carry much lower radon levels than those of secondary porosity in bedrock. The radon level range of groundwater of primary porosity is not established with any confidence, but is probably less than 40,000 pCi/L in most wells.

 There is a general consensus among specialists working in radon that 10,000 to 20,000 pCi/L of radon in groundwater is cause for concern and 100,000 pCi/L requires remedial action. Levels of radon approaching 100,000 pCi/L in water supplies are capable of being the principal contributors to excessive radon levels in the built environment simply by degassing during water use.

 Research into the geology of radon has not progressed to the point where the radon potential of a proposed well in bedrock can be predicted. We know that parameters such as (1) well depth, (2) depth of water production, (3) water yield, (4) pumping rate (stress), and (5) proximity of other wells play important roles. Studies in New Hampshire have not, to date, produced any consistent pattern. It appears, in fact, that drilled wells each have individual personalities. The only consistent relationship appears to be related to rock type. Thus, well planning, including a concern for radon, begins with the interpretation of a geologic map. The evolving technology of drilling into bedrock to exploit the groundwater resource opens questions about artificially accelerating the mobility of radon by pumping stress. It is reasonable to believe that stressing an aquifer increases groundwater mobility rates far beyond those predicted by nature. Such accelerated rates could result in "sweeping" a much larger volume of rocks for its groundwater and enhancing both radon concentration and mobility.

 A corollary to this observation raises another interesting question. How do radon levels of well water immediately after drilling compare to radon levels after sustained use? Some rock wells in New Hampshire have, indeed, shown a steady build-up of radon with service, but others have shown fluctuating radon levels with time and season. Further, the dynamics of bedrock aquifer recharge also has much to do with radon level.

 It becomes obvious that no two aquifers are alike and, therefore, no consistent set of variables govern the potential for radon in the groundwater.

Habitat and Workplace. Ancestral man unwittingly placed himself at risk with radon when he took up residence in certain caves and used water from radon-enriched springs. The course of human history has been, therefore, one of coexistence with the isotope, but obviously with ever-increasing exposure. As technology advanced, man learned to enjoy the comforts of enclosed architecture which eventually brought conveniences such as central heating. In short, the evolution of architecture and equipment brought about the opportunity for radon to concentrate in the built environment, especially in climates marked by a distinct winter season.

 Cold weather results in reducing ventilation and creating a pressure differential between the colder atmosphere and the heated structure. Such a differential results in the structure acting as "vacuum cleaner" for radon-slaked soil gas if basement floors and foundations are not sealed. If there is an important amount of radon in the water supply, aeration by equipment such as showers and washing machines add this radon to that already there. Air conditioning of structures diminishes the ventilation, but the pressure differential is reversed. Structures without air conditioning are ventilated to the atmosphere and reduce the radon risk in the warmer months.

 Meaningful statistics for radon levels in New Hampshire structures exist only for indoor air in homes. A study completed by the N.H. Division of Public Health Services on a random selection of 1,810 homes between 1988 and 1990 found that the average was 4.8 pCi/L and that 27.8 percent of the homes recorded levels in excess of 4 pCi/L. One home was measured at 479 pCi/L.

 Interim hazard levels of 4 pCi/L in air and 40,000 pCi/L in water have been used in advisory context. As a first approximation, 40,000 pCi/L in the water supply of a home results in 4 pCi/L in the household air. Almost 7,000 public and private water supplies in New Hampshire have been tested for radon levels (Table 2). More than 16 percent of these supplies exceed 10,000 pCi/L which is probably a level that can make a measurable, but not dangerous, contribution to the radon within structures. About 18 percent of New Hampshire homes and some commercial buildings are dependent upon private unregulated water supplies obtained from wells drilled into bedrock. Radon testing to date in this class of water supply indicates that 5 to 10 percent of the well waters exceed 40,000 pCi/L. It has been noted that such waters can make a potentially unhealthful contribution of radon to the indoor air. The amount of this contribution, however, depends on variables, especially the volume of air and the volume of water used during a specified period of time.

 Table 2.

Radon Analysis in New Hampshire Water Supplies (data from DES laboratories for a sample group from 1/1/84 through 12/31/92).

Radon - 222 (pCi/L.)
0 - 300




301 - 10,000




10,001 - 40,000




Greater than 40,000









Grand Total 6981
0 - 300
301 - 10,000
10,001 - 40,000
> 40,000


 Once "excessive" levels of radon are delivered "free of charge" by geology, mitigation becomes a problem for engineers and health specialists. In cases where groundwater is not the major contributor of radon into a structure, a combination of ventilation and sealing is indicated to prevent radon build-up and recharge. The elimination of excessive radon in water is also possible through the use of engineered devices that aerate the radon into the atmosphere. The daughter products of radon that the water also carries can be stripped and captured by adsorption or chemical exchange-processing systems such as activated charcoal filters. The use of such systems, however, requires a commitment to the safe disposal of cartridges or liquids that become dangerously radioactive.

 Pioneering work has been done by the Environmental Research Group at the University of New Hampshire in safely reducing the levels of radon and its decay products from water supplies. The U.S. Environmental Protection Agency maintains a register of commercial specialists approved to do radon mitigation in indoor air and water. The use of only approved practitioners is strongly advised.

 It is recommended that all residents of New Hampshire test their dwellings for indoor air radon levels. Also, homes and commercial buildings supplied from wells drilled into bedrock should test their water supplies. Ideally, water in newly drilled wells should be tested both before sustained use and then several months to a year later. If the radon level has increased significantly on the second test, yearly periodic tests should be done until the radon level stabilizes. Water tests can be done by either EPA-certified commercial testing laboratories or by the state analytical chemistry laboratory operated by DES in Concord. New Hampshire residents are showing an increasing commitment not only informing themselves about radon risk, but also assuring themselves that radon levels in their indoor air and water supplies are at "safe" levels.


 Questions on radon mitigation and health risk should be directed to Bureau of Radiological Health Services, Health and Welfare Building, 29 Hazen Drive, Concord, NH 03301, (603) 271-4674 or 1-800-852-3345 x-4674. 



  • Cracks in floors and walls
  • Gaps in suspended floors
  • Openings around sump pumps and drains
  • Cavities in walls
  • Joints in construction materials
  • Gaps around utility penetrations (pipes and wires)
  • Crawl spaces that open directly into the building
  • Radon FIX-IT Program—assists consumers with elevated radon levels of 4 pCi/L or higher by providing information that will allow them to take the necessary steps toward fixing their homes
  • Indoor Air Quality Information Clearinghouse (IAQ INFO)—helps locate information about indoor air pollution
  • The National Hispanic Indoor Air Quality Hotline—provides bilingual (Spanish/English) information about indoor air pollutants that consumers may find inside their homes, offices or schools.
  1. Gas Permeable Layer—This layer is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. In many cases, the material used is a 4-inch layer of clean gravel.
  2. Plastic Sheeting—Plastic sheeting is placed on top of the gas permeable layer and under the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor.
  3. Sealing and Caulking—All openings in the concrete foundation floor are sealed to reduce soil gas entry into the home.
  4. Vent Pipe—A 3- or 4-inch gas-tight or PVC pipe (commonly used for plumbing) runs from the gas permeable layer through the house to the roof to safely vent radon and other soil gases above the house.
  5. Junction Box—An electrical junction box is installed in case an electric venting fan is needed later.
  • Community Development Block Grant (CDBG) program—funds rehabilitation and repair of affordable housing. For more information, call the U.S. Department of Housing and Urban Development (HUD) at (202) 708-3587.
  • "203k" program—funds rehabilitation and repair of single family homes. For more information, call HUD at (202) 708-2121.
  • Environmental Justice Grants—funds community-based organizations and tribal governments addressing environmental concerns of people of color and low income communities. For more information, call the EPA's Office of Environmental Justice at (800) 962-6215.
  • Radon gas. DES processing cost $20.
  • Dissolved analytical gross alpha radioactivity. DES processing cost $50.
  • Radium 228 testing.*
  • Radium 226 testing - the need for radium 226 testing can be partially evaluated by a review of the analytical gross alpha data.
  1. a. One standard would be the conventional MCL. If a PWS meets this MCL, the utility will be in full compliance with the requirement and will have totally satisfied its responsibilities under the Safe Drinking Water Act (SDWA). The proposed MCL is 300 pCi/L.

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