Radon: Reducing the Risk

This slide show is an overview of radon and radon mitigation and was prepared by the DEP’s Radon Section.

Radon

Radon is a naturally occurring, tasteless, odorless, colorless radioactive gas. It’s part of the natural decay of uranium in the soil.

Radon Decay Chain

Uranium is found everywhere on earth, most commonly in granite and black shale. On average every square mile down to a depth of 6 inches contains 1 gram of radium. Uranium decays to radium and then to radon. Uranium and radium as solids are trapped in the soil but radon gas can move through the soil. 

Radiation Exposure Sources

Radon contributes 55 percent of the average person’s exposure to radiation. It’s the single largest source of exposure to radiation. Man-made sources of radiation include medical x-rays, nuclear medicine, nuclear energy and consumer products. Naturally occurring sources include cosmic and terrestrial radiation. As far as we know, all radiation is capable of causing damage in cells and genetic material within the cells.

National Academy of Sciences

Although radon is an inert gas and does not attach to anything, the decay products are solids, and will attach to the linings of the lungs.  As the decay products continue to break down, alpha particles are released. Alpha particles have low momentum compared to other radioactive particles; they can be blocked by a single sheet of paper, or by the outside layer of dead cells in our skin.  However, they can cause significant damage to the genetic material in the unprotected lung cells. 

This is why lung cancer is the only health concern from radon, not skin cancer or other types of cancer. The latest review of health risk, by the National Academy of Sciences, estimated that between 15,000 and 22,000 lung cancer deaths per year result from radon in the U.S. Radon is the second leading cause of lung cancer after cigarette smoking.

Lung cancer is the only known health effect that may result from radon inhalation.  It is not linked with any other health problems such as asthma or headaches.

The Link Between Radon and Lung Cancer?

The initial radon law mandated a study to be done by the Department of Health on radon and lung cancer. This study showed a correlation between radon exposure and lung cancer.

However, to get a completely accurate picture of radon’s effect at lower levels from residential exposure would require thousands of subjects with a full history of each individual’s exposure to radon over several decades. Most people have no idea what their radon exposure was 10-40 years earlier when a cancer may have started.

In 1998 a committee of the National Academy of Sciences undertook a major reassessment of all the data including all the studies on miners in different countries (11 studies, 68,000 miners) and epidemiological studies and concluded that the risk is even higher than the EPA’s original risk estimate of 14,000 deaths per year. As stated, the estimate is between 15,000 to 22,000 lung cancer deaths from radon annually.

In 2000 an extremely detailed study by the University of Iowa was published that showed that women exposed to about 4 pCi/L had a 50 percent higher risk of lung cancer than women exposed to about 1 pCi/L. This study provides evidence that radon is a risk even at the lower concentrations found in homes. 

In 2003, EPA conducted an assessment of risks from radon in homes. Estimates indicated that about one-third of the radon-related lung cancers could be averted by reducing radon concentrations in homes that exceed EPA’s recommended 4 pCi/L action level. 

It was known for decades that radon caused lung cancer among uranium mine workers.  However, it was an incident that happened 20 years ago that drew attention to the risk of radon in homes.  In 1985 a new employee at a nuclear power plant in Boyertown, Pennsylvania, was causing the radiation detection monitors to go off when he entered the plant.  After checking to make sure there were no problems in the plant, plant managers went to his home to see if there was a problem there.  They were amazed when they found high levels of radiation caused by naturally occurring radon.

EPA map

At first it was thought to be a local problem, but soon testing around the country revealed radon in homes almost everywhere.  The EPA created this map showing color-coded areas of the United States in which indoor radon levels may be high, medium and low.

NJ Radon Potential Map

New Jersey developed a similar map based on statewide test results.  Municipalities were divided into three tiers based on the potential to have elevated indoor radon concentrations. Red is Tier 1 or high radon potential (25 percent or more of homes have radon levels at 4 pCi/L or above), green is Tier 2 or moderate radon potential (5-24 percent of homes have radon levels 4 pCi/L or above), blue is Tier 3 or low radon potential (less than 5 percent of homes have levels at 4 pCi/L or above).

Radon Action Level

The EPA was instructed by Congress to set guidelines for unacceptable levels of radon in the home.  Studies determined that there is no safe level of radon, but 4 pCi/L was technologically achievable – that is, nearly all homes with high levels could be fixed and the concentration of radon reduced to below 4 pCi/L.  So, in the mid-1980s a guideline of 4 pCi/L was set.  However, it is important to remember that no level of radon is safe, so the goal is to reduce radon to the lowest levels possible.

Steps to Take

The DEP recommends every homeowner test for radon in NJ. Homeowners can test for radon themselves or hire a New Jersey certified radon measurement company to perform the testing. Some certified radon measurement companies sell test kits directly to homeowners, and test kits are often available in hardware stores or from local health departments. The average cost to test your own home is $25 to $50. The average cost to hire a certified business to test your home is $50 to $200.

A single short-term test of 2-7 days in length can be used to indicate the radon level in your home. If a second short-term test is conducted in the same location (either simultaneously or at different points in time), and the results of the tests are averaged, the average will provide a slightly more accurate estimate of radon levels.

Short-term tests include charcoal canisters, electrets and continuous radon monitors. The DEP Radon Section considers all short-term test devices by certified companies equally reliable.

A long-term test of 3-12 months will provide your best estimate of average exposure over time, since radon levels fluctuate daily and by season. Because gases are drawn to areas of lower pressure, radon gas will enter the home at a rate that depends on the air pressure inside the home, which is affected by temperature, wind conditions, exhaust systems in the home, etc. Long-term testing should include the winter months, when radon concentrations are often higher than at other times.

Long-term test devices are usually either alpha track detectors or electrets; both tests are considered equally reliable.

For both long-term and short-term tests, the testing device must be placed in the lowest livable level of the home – that is, the lowest livable level of the home that is used, or could be used, as a living space. This would include a first floor without a basement, and a finished or unfinished basement, but not a crawl space The device also needs to be in a location where it will not be disturbed.

Test kits should not be placed in areas exposed to direct sunlight, drafts, high heat, or high humidity. They also should not be placed in kitchens, bathrooms, laundry rooms or closets.

For short-term tests, it is very important to maintain “closed house conditions,” since ventilation can increase or decrease radon levels in unpredictable ways. This means all windows and doors that let in outside air, on all floors, must be kept closed except for normal entrances and exits. You need to maintain closed house conditions until the short-term test is finished. For tests that last less than four days, closed house conditions must start at least 12 hours before you begin the test.

Entry Factors

Radon can accumulate in a closed area, such as a home. The national average indoor radon concentration is 1.3 pCi/L, but it can reach very high levels, up to several thousand pCi/L. A curie is the amount of radiation emitted by 1 gram of radium and a pico is 1 trillionth.

Several factors affect the radon concentration in a home:

1.      Concentration of uranium in the underlying soil.

2.      Permeability of soil – ease that radon gas can move through. If soil is rocky or sandy and less dense, radon will move through easily. Clay soil can block radon movement because it is more dense.

3.      Number and size of entry points into the house. Entry points include cracks in floors and walls, construction joints, sump and drainage system, gaps around service pipes, hollow block foundation walls and the water supply.

Picture of drain

This drain is an example of an entry point for radon.

Picture of wall

This wall shows other entry points for radon.

Radon and Air Pressure

A fourth factor that can affect radon concentrations in the home is the subtle and often fluctuating differences in air pressure. Radon will tend to flow to areas with lower air pressure. Internal air pressure is affected by:

1.      Different temperatures inside and outside the house and in different sections of the house. We all know the common “stack effect” where warm air rises when a home is heated. The warm air rising creates a low pressure area below that will tend to draw in soil gases.

2.      Wind loadings against the superstructure can affect indoor air pressures depending on where windows and doors are located. If there are strong wind currents past windows or doors, it can create pressure differentials within the house.

3.      Appliances can reduce air pressure in the home (e.g., exhaust fans, clothes dryers, furnaces, fireplaces and attic fans).

A house is not simply a passive accumulator; it actively draws radon into the interior.

ASD

If elevated levels of radon are found (4 pCi/L), radon mitigation is recommended. If your test result is less than 4.0 pCi/L, you may want to discuss with mitigation companies whether the radon level can be brought down still further. In about half the homes that have been mitigated in New Jersey, radon levels have been brought to less than 1 pCi/L. Radon mitigation systems usually use a venting system called an Active Soil Depressurization or ASD system.  There are several types of ASDs.

Installation of the most standard ASD system, in which depressurization, or suction, is applied directly to the subslab, involves drilling a hole in the cement slab at the lowest level of the building, placing a pipe through the hole into the subslab area, running the pipe up through the roof of the building, and installing a fan near the top of the pipe that creates a steady suction drawing soil gases into the pipe and venting them outside the building.

The average price of such a system is approximately $1,200, although prices can range from $500 to $2,500, depending on characteristics of the home and the underlying soil. You can install the system yourself, if you are highly experienced  in making home repairs, or you can hire a New Jersey certified radon mitigation company to do the work for you. New Jersey certified radon mitigation professionals meet specified education and experience standards and must take continuing education classes each year to maintain their certification. It is against the law for uncertified contractors to do mitigation work in New Jersey.

Depressurization fan

The depressurization fan that draws radon away from the house is installed in the attic, garage or outside. It generally requires less than 90 watts of power and lasts approximately 11 years.

Caulking Wall-Floor Joint

To retard soil gas entry, all control joints, isolation joints, construction joints and any other joints or holes in concrete slabs or between slabs and foundation walls should be sealed.  

Sealing Joint

A gap between the slab and foundation wall can be sealed to help prevent radon from entering. 

Post-mitigation

After your home has been mitigated, make sure the mitigator does a post-mitigation test to prove the system is working properly. In addition, you can contact the Radon Program to obtain a free post-mitigation test (you will have to provide a copy of your mitigation contract). Retesting your home every two years will determine if your system is still working effectively in reducing the radon level to below 4 pCi/L. If you believe that your system was not installed correctly, you can contact the Radon Program to arrange for a free inspection and test of the system. 

Polyethylene Sheeting

To reduce the costs of mitigation in municipalities that have a high radon potential, referred to as Tier 1, radon-resistant new construction (RRNC) must be installed before a house is built.

New construction in Tier 1 municipalities, as required by the Radon Hazard Subcode, must incorporate radon resistant construction techniques. In this type of construction, a gas permeable layer (e.g., 4-inch layer of gravel) is used beneath the slab to allow the soil gas to move freely underneath the house. Then plastic sheeting is placed on top of the gas permeable layer to prevent the soil gas from entering the home. A 3- or 4-inch PVC or other gas-tight pipe runs from the gas permeable layer through the house and roof to vent radon above the house. If the home is tested and found to have elevated levels of radon, an electrical venting fan is installed to activate the system for a lower cost than the installation of a radon mitigation system without radon-resistant construction. The installation of the fan, however, has to be done by a certified radon mitigator.

Conclusion

Regardless of what tier you are in, you should test for radon. Only testing will tell if your home has elevated levels of radon. The good news is that radon is an easily fixable problem. Our data shows that half the mitigations in NJ have brought radon levels down to below 1 pCi/L.

Feel free to contact the DEP NJ Radon Program with any questions that you have about radon. The information line is staffed five days a week from 9 a.m. to 5 p.m. Thank you for your interest in this important health concern.

File last updated September 09, 2010 * Copyright © 2010 All rights reserved by: Accurate Inspections, Inc. A New Jersey home inspection firm 56 Woodland Drive, Woodland Park (formely West Paterson) NJ 07424 973-812-5100 providing New Jersey Certified Home Inspections in NJ, by New Jersey Licensed home inspectors. Inspector of record Michael Del Greco, New Jersey Home Inspector License GI 0121.

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