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People usually test houses to (a) get an estimate of the lung cancer risk from spending time in that house or (b) to meet some requirement for selling their home. Your lung cancer risk depends on the radon concentration in your living spaces and the length of time that you are exposed. If you want a good estimate of the lung cancer risk in a house, you need to measure the radon concentrations in the living spaces for a period of 6 to 12 months. Indoor radon can change dramatically from floor to floor in a home and from day-to-day, season-to-season (For a sample, see the behavior of this house). If you already occupy your home, waiting a few months to determine your long-term exposure to radon will not significantly add to your risk. Most shorter measurement periods can give very poor estimates of the radon risk in your home. Although some states have specific requirements for real estate transactions, a 6 to 12 month test will satisfy all of them. The wise home seller will conduct the test well before putting the house on the market or as soon as the decision to sell is made. The wise home buyer will insist on a long term test by a qualified device. In my opinion, the EPA has made a serious mistake in allowing real estate transactions to occur based on tests over a short (days) time period. The best detector for general radon testing is an alpha track detector, also called an ATD. Alpha track detectors are easy to use, inexpensive, rugged, and accurate enough to assess your radon risk. ATDs can be used for measurement periods from as short as 14 days for some models to as long as 2 years. For more advice see:
Smoking is the primary cause of lung cancer. Smokers generally have about 10 times higher risk than non smokers. Radon related risk results from exposure over many years. The radon-related increase in risk is believed to increase by roughly 50% over the risk posed by smoking alone as result of 15 years of normal living in a house whose living spaces have an average value of 4 pCi/L. That is, the radon exposure increases your baseline risk by 50%. For example, if you never smoked, your base line risk of lung cancer might be 1% in a low radon home (<1 pCi/L). Your risk in a 4 pi/L home would be 1.5%. For a smoker in a low radon home, the lung cancer risk is approximately 10%, and 15% in a 4 pi/L home. If you have a 20 pCi/L home, the radon risks would be 5% and 50% for never smokers and average smokers respectively. If you spend 30 years in a home, your risk would double compared to a 15 year occupancy. Risks associated with radon exposure in low radon homes have not been adequately quantified at present.
| Radon tests for homeowners: | Radon tests for home buyers |
| Tests for past radon exposure | Radon tests for home sellers |
To get an adequate estimate for the risk, you need to measure your living spaces over a time period where the radon concentration is not likely to change by more than 50%. It is probably wise to test in stages to keep costs low. In most homes, that means that your first test will use an alpha track detector placed on the lowest occupied level of the home for a minimum test period of 6 months. If the lowest occupied level is a basement and you spend most of the time in a higher level, you may be well advised to test the higher level as well. This is particularly true if your heating and cooling system doesn't use forced air since the basement can often have much higher radon concentrations in such homes. A year-long radon test is best. Year-to-year radon changes are usually less than 25%. You should remeasure your home if you make a major structural change or change your heating and cooling system.
If you want additional advice on your personal measurement strategy, e-mail me.
If you plan on living in the home for a few years, you should insist on a measurement that is likely to help you estimate the risk to within 50%. That means a long-term measurement in the lowest level of the home that you plan to spend significant amounts of time. If the seller hasn't measured the radon in that level, you might ask them to start measurements immediately with two alpha track detectors (ATD). Ask that the test take place under closed house conditions. If the negotiations take a few weeks after the start of the measurement, send in one of the ATDs a few days before the final decision time. Ask the lab to rush the report (some labs do provide rush service). The results of that first ATD will help you decide whether or not the house may need work to reduce the level. You will be able to decide in 6 months, based on the second ATD result, if mitigation is needed. If you decide to buy immediately, money could be put in escrow to cover mitigation costs if a 6 month measurement shows high radon concentrations.
If you want additional advice on your personal measurement strategy, e-mail me.
Radon testing strategies for home sellers
Under development
If you plan on selling your home, you should start one or more measurements using alpha track detectors (ATDs) as soon as possible. This would give you time to make a meaningful assessment of your home's radon risk and time to take corrective actions if elevated radon levels are found. Alpha track detectors are easy to use, inexpensive, and rugged. They can be left in place for a variable length of time...the longer the better up to 1 year. If you start with 2 ATDs, then sending one in for analysis after a few months will give you a chance to decide about the possibility of radon mitigation before putting your house on the market. Many buyers in some high radon regions are asking for radon testing and mitigation as a condition for sale. I would recommend measuring a room where people spend significant time on the lowest level of the house. That might be a basement recreation room or a first floor bedroom, depending on your house structure and use.
If you want additional advice on your personal measurement strategy, e-mail me.
Under development
Sometimes people want to find out what radon concentrations have been present in a home in the past. While in the upper Midwest, year-to-year radon changes in most houses are usually less than 25%, much larger changes can occur when a home is modified. Sometimes just a change in residents or their lifestyles (kids leaving the nest) causes dramatic changes. Fortunately, there is a new technique for looking backwards in time to reconstruct past radon in a room where a glass surface has been present for 5 or more years. Some radon progeny are implanted in the glass and can be used to estimate past radon exposure. The technique is new and more costly than ATDs but it can be useful in a number of situations. For example, it can be used in real estate transactions where tampering is a concern. We have developed two kinds of detectors for this technique. One detector, called the Retrospective Radon Detector (RRD) can be used by homeowners, epidemiologists, or real estate agents. This detector requires about 60 days for accurate results. The second detector requires a trained operator. Contact me for details.
Questions/Comments, e-mail: Dr. Steck
Last revised : 30 June, 2004
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