Introduction
Radon is the second leading cause of lung cancer.
Radon decay products attach to particles which are inhaled and become lodged in the lungs. Once lodged, they can radiate and penetrate lung tissue initiating the process of carcinogenesis.
Smoking increases the risk of exposure to radon.
State surveys to date show that about 1 out of 5 homes has elevated screening levels.
The only way to know if a home has elevated levels of radon is to test it. Testing is simple and easy. Homes with high radon levels can be fixed for about $500 to $1,500.
Congress has recognized the health consequences of radon and passed legislation in October 1988 that establishes a national goal that indoor radon levels not exceed ambient outdoor radon levels (0.2-0.7 pCi/L). The law recognizes the need for radon testing in schools and workplaces and provides funds for states to initiate a variety of radon activities.
Origin of Radon
Radon is a naturally occurring radioactive gas. You cannot see it, smell it, or taste it. Radon comes from the natural breakdown (radioactive decay) of uranium. Most soils contain varying amounts of uranium. Since radon is a gas, it can be found just about anywhere. It’s usually found in rock and soil, but in some cases, well water may be a source of radon, exposing you when you are showering, washing clothes, and performing other household activities.
Radon emanates from soil, rock and water into the air we breathe. Outdoors, radon is diluted to low concentrations and poses no problem. However, once inside an enclosed space (such as a home) radon can accumulate to significant levels. The magnitude of radon buildup indoors depends both on type of construction and concentration of radon in underlying soil.
The soil composition under and around a house affects indoor radon levels and the ease with which radon migrates towards a house. Normal pressure differences between the house and the soil can create a slight vacuum in the home which can draw radon gas from the soil into the building. Radon gas can enter a home from the soil through dirt floors, cracks in concrete floors and walls, floor drains, sumps, joints, and tiny cracks or pores in hollow-block walls. Radon levels are generally highest in basements and ground floor rooms in contact with the soil. Factors such as design, construction and ventilation of the home affect the pathways and forces which can draw radon indoors.
Health Effects
Radon decay products (polonium-218 and polonium-214, solid form) can attach to the surface of aerosols, dusts, and smoke particles which may be inhaled, and become deeply lodged or trapped in the lungs. Once lodged, they can radiate and penetrate the cells of mucous membranes, bronchi, and other pulmonary tissues. Energy deposited in these sensitive tissues during irradiation is believed to initiate the process of carcinogenesis.
EPA and other scientific organizations estimate that thousands of lung cancer deaths per year are attributable to elevated levels of radon. Epidemiological studies of thousands of uranium and other underground miners have been carried out over more than 50 years in five nations including the U.S. and Canada. These studies provide convincing evidence that exposures to radon and its decay products are associated with an increase in lung cancer mortality. The risk of lung cancer is directly proportional to the level and duration of exposure. For example in one study, miners with cumulative exposures of about 30 WLM [one WLM is equivalent to an average exposure of 1 WL (200 pCi/L) for 170 hours, about 21 workdays] had an increased mortality from lung cancer. Similar exposures might result from people living in homes with average radon levels of 4 pCi/L for about 40 years, assuming 75% occupancy. In addition to the miner data, radon and its decay products in experimental animals cause lung cancer.
The National Academy of Science’s BEIR IV Report, the World Health Organization, the Surgeon General, and other national and international authorities have also identified radon as a serious national health problem. Lung cancer due to inhalation of radon decay products currently constitutes the only know risk associated with radon. Variables such as age and duration of exposure, time since initiation of exposure, and the use of tobacco influence individual risk.
There is evidence from some of the epidemiological studies of underground miners, primarily the U.S. uranium miners, that radon exposure and smoking may have a synergistic relationship. Exposure to both may exceed the effects of either alone. However, both can act independently to increase the risk of lung cancer. The National Academy of Sciences estimates that the increased risk of lung cancer to smokers from radon exposure is 10 or more times greater than to non-smokers.
Some scientific studies of radiation exposure indicate that children may be more sensitive to radon. This may be due to their higher respiration rate and their rapidly dividing cells which may be more vulnerable to radiation damage. The International Council on Radiation Protection concluded that the relative lung cancer risk to children and youths from radiation may be three times that for adults.
Risk of Lung Cancer
The following risk chart compares exposures to various radon levels over a life time to the risk of developing lung cancer from chest x-rays.
Radon is a national environmental health problem. Elevated radon levels have been discovered in virtually every state. The EPA estimates that as many as eight million homes throughout the country have elevated levels of radon.
Testing for Radon
Radon is completely invisible to sight, smell or taste. That’s why special detection kits are necessary.
Short-term testing (a few days to several months) is the quickest way to determine if a potential problem exists. Charcoal canisters, electret ion detectors and alpha track detectors are currently the most common short-term testing devices. Short-term testing should be conducted with the doors and windows shut, preferably during the cooler months of the year.
Long-term testing (up to one year) is the most accurate way to test radon. Alpha track detectors and electret ion detectors are the most common long-term testing devices.
Both short-term and long-term testing devices are easy to use and relatively inexpensive.
Both long- and short-term kits can be purchased for about $20, through the mail or from hardware stores or other retail outlets. After testing is completed, the kit is simply returned to the manufacturer for analysis. The analysis is usually included in the price of the kit. Or, a company can be hired to test a home.
Because no level of radon is considered absolutely safe, radon levels in a home should be reduced as much as possible. The average radon level in homes is about 1.5 pCi/L. Action should definitely be taken to reduce radon levels in a home if the average annual level is higher than 4 pCi/L. In most cases, radon levels can be reduced to as low as 2 pCi/L to 4 pCi/L, and sometimes even below 2 pCi/L.
Short- and long-term results should be interpreted differently. If long-term results are high, homeowners should definitely take action to fix their home as soon as possible. If a short-term measurement result is high, the best way to determine the annual level is to conduct a long-term test of one year. As radon levels indoors tend to be somewhat higher during the fall and winter, short-term measurements made during the cooler months generally overestimate annual levels somewhat. If shout-term test results are low, another test sometime in the future is suggested to ensure that a measurement was not conducted at a time when radon levels happened to be much lower than usual.
Remediation
In deciding about remedial action, the risk of exposure as well as the benefits and costs of the remedial actions, including those over the long term, should be considered. However, possible risks to the family’s health should always be the primary concern. The presence of children might encourage remediation of radon levels.
The EPA conducts the Radon Measurement Proficiency Program to evaluate companies that make and analyze test kits. Therefore, to ensure the public gets accurate results, people should look for a company that has successfully completed the Proficiency Program. Most companies indicate approval on the test kit box. In addition, many states require licensing of radon testing companies and contractors. State radon offices have a list of all radon measurement companies that are state or EPA approved.
When radon testing indicates elevated radon levels, a trained contractor should be consulted to correct the problem. In most cases, homes can be fixed for $500 to $1,500. EPA conducts a Radon Contractor Proficiency Program to evaluate contractors’ ability to reduce radon levels. The names of these contractors appear in a national listing. Trained radon reduction contractors offer their services in virtually every state. Individuals can call the state radon office to locate a contractor.
Radon levels in homes can be reduced by preventing radon entry, increasing the ventilation within the home, and removing radon and its decay products from the air. Preventing radon entry is the preferred approach. One of the most effective techniques is ventilating the soil surrounding the home so that radon is drawn away before it can enter the home. This method is called soil depressurization. This system can be installed in an existing home, or economically installed during construction of a new home.
