As we head in to National Lung Cancer Awareness Month, we are all aware of the role cigarettes and tobacco play in the cause of lung cancer. We also are aware that not ALL lung cancers are caused by smoking, and that 10% of men and 20% of women who are diagnosed in the U.S. with lung cancer are never-smokers.
So what other factors cause lung cancer in these patients? There are links between lung cancer and cooking oil fumes in homes without adequate ventilation in other parts of the world; links with air pollution both indoors and out; links with heavy metal exposures and concerns about diesel exhaust fumes. In the U.S. the second-most common cause of lung cancer behind tobacco exists as a silent presence inside a person’s own home.
Radon is a colorless, odorless gas. It is a naturally-occurring gas that forms as a breakdown product of the small quantities of uranium that exist in rock. As rocks break down over time, the gas is released upward. Radon gas in turn quickly breaks down into radioactive particles, which, when inhaled, can cause damage to the lung tissues leading to increased risk of lung cancer. In a ventilated outdoor area, radon is dispersed into the air into concentrations that are harmless. Radon can build up though in pockets in the earth, such as mines or contained caves, where there is little relative air movement. It can also build up in homes, where basements are a particular area of concentration.
Older homes as we are aware are drafty and not as well sealed as the newer more energy-efficient homes. In terms of radon, this is actually beneficial, as air does not stay contained inside an older home, but is ventilated through. In the more modern homes, however, things are sealed fairly tightly. As radon moves up from the bedrock, it can then collect in the lower areas in a home to levels that can become dangerous.
Radon from home environments initially came to attention in 1984. Stanley Watras was an engineer who worked at the Limerick nuclear power plant in Pennsylvania, andwho did not work directly with radioactive materials. On his way home from work one day, he set off the monitor at a radiation-detection section. He then continued to set off the monitor for 2 weeks as a search was conducted to find the source of the radioactive contamination. It turned out not to be related to a work-related exposure, but his home was found to have incredibly high radon levels. The basement of that home registered 4,400 picocuries of radon (over 1100 times what is thought to be “safe levels”). The relative risk of his (and his family’s) exposure was calculated to be equivalent to smoking 135 packs of cigarettes DAILY. Mr. Watras found a new career in radon mitigation, finding ways to reduce radon exposure.
According to the National Cancer Institute, radon may be responsible for 15,000 to 22,000 deaths from lung cancer each year in the United States.
So is radon everywhere? Are all homes equally at risk? The Environmental Protection Agency has published a map of the United States, measured by county, mapping different levels of radon, shown below.
Zone 1 represents the “highest-level” areas, with predicted average screening levels of at least 4 picocuries/liter. Zone 2 “moderate-potential” areas have an average predicted screening level of 2-4 picocuries/liter, and Zone 3 includes the “low potential” counties with <2 picocuries/liter predicted levels. Although different areas have different levels of risk, the EPA recommends that all homes be tested for radon.
The EPA recommends that if a home registers a level of 4 picocuries/liter or greater, that radon remediation be undertaken. The World Health Organization recommends radon remediation for levels greater than 2.7 picocuries/liter. The difficulty and lack of agreement lie in the fact that at this point it is not certain what the “safe” threshold is for radon exposure. As a comparison, standard outdoor air contains approximately 0.4 picocuries/liter of radon.
There are a number of different ways to test for radon, with test kits of varying cost and reliability. One thing to keep in mind is that radon levels may fluctuate in a home over time (less on windy days, lower in the summer when the windows are more open, etc). By convention some of the most reliable tests measure average radon levels over a long time, some over many months or even a year. I am not aware of any one ideal testing kit, but there is an entire industry now dedicated to this (despite the fact that most Americans still aren’t really aware of radon).
If elevated levels are found in homes, professional companies can install remediation systems. These generally involve a ventilation system for the low-lying areas in a home that would be collecting most of the radon gas in “still” air. The equipment is not terribly high-tech, although systems will vary in cost, with some incorporating ongoing monitoring of levels. Below are a couple of diagrams (courtesy of Google Images) to demonstrate the basic concept of the system.
In certain areas, radon testing is required at the time of sale of a home. As an example, when we purchased our home eight years ago, the mortgage company required radon testing be performed prior to allowing the sale of the house. This makes sense as in the Portland area, our home is located on what is informally termed “Radon Ridge”, due to the underlying rock formations. Our home tests (originally and then repeated) were negative. Some of our neighbors’ tests showed elevated levels. We had a radon reduction system installed in our home. Who needs any extra risk?