Sometimes, one can see the danger coming. The storm clouds gather; the ice cracks beneath one’s feet. For my wife and me, the potentially fatal blow was delivered invisibly, soundlessly, without even a trace of an odor. News of the intrusion arrived inauspiciously in the mail, from results of a radon test from the Maine Environmental and Community Health Division, part of the Maine Center for Disease Control and Prevention.

Radon, a naturally occurring type of radiation, can be found everywhere, emanating from the ground. The problem comes when we build houses with concrete foundations and/or slabs. Trapped beneath the concrete, radon concentrates around cracks, seams and any other openings and vents into the house, where it is further concentrated by the structure of the house.

There is no truly safe level of radon, but if the level in one’s home reaches 4 picocuries per liter, then the federal Environmental Protection Agency urges that the problem be mitigated. To be on the safe side, even a level between 2 and 4 pCiL should be addressed. The letter that came in the mail for us reported a level of 100 pCi/L. We had been living in our home for 13 years.

Radon is the second leading cause of lung cancer in the United States. Smoking is the first. We learned that lifetime exposure to 10 pCiL, a tenth of our reading, is the equivalent of smoking a pack of cigarettes per day or receiving 500 chest X-rays per year.

The federal CDC has published a chart that calculates one’s risk of acquiring lung cancer based on the level of exposure. The chart only goes up to 20 pCiL. Extrapolating from this chart, the chances of getting lung cancer for someone exposed to 100 pCiL is about 21%. It is more than double this if you are someone who smokes cigarettes. My wife and I are in the process of trying to get our health insurance company to pay for annual low-dose CT scans, which is the standard for detecting lung cancer in heavy smokers.  We have never smoked.

Here, I think, are some take-aways and the reason that I am writing:

• Approximately one-third of Maine homes will test positive for dangerous levels of radon (4 pCiL or above). However, certain parts of Maine, such as my ZIP code, result in two-thirds of homes testing positive.

• In my opinion, just as important as the prevalence of radon in our state is the variability of the range of concentration. The results are not binary – “Yes, you have it” or “No, you don’t.” While our reading of 100 or more is not likely, measures of twice or three times the standard of 4 pCiL or greater are not at all uncommon. The person we hired to fix our radon problem told me he had worked on a home with a reading of 500 pCiL.

• It is easy and inexpensive to test for radon. There are many good commercial test kits, or for $40 one can order a kit from the Maine Health and Environmental Testing Laboratory, and then return it to them for the analysis.

• It is a straightforward problem to fix. There are many licensed radon mitigation companies in the state. The cost seems to run between $800 to $1,600 to seal seams and cracks and install a ventilation system to pull the radon out. So far, our level is now hovering below 2 pCi/L.

• I have now read lots of information comparing the lung cancer risk of extended radon exposure to the lung cancer risk of smoking. But here is an important difference: While many people who smoke are able to and do quit, it can be difficult and sometimes takes a few attempts. Quitting radon exposure is easy. All I had to do was stop procrastinating and order the test. I wish I had done it a lot sooner.