Home Inspection Confidential: A Blog About HomesInspections By Bob

Note: This article was first posted in October 2010, but bears repeating, and includes some new information!

You’ve probably heard something about radon, where it comes from, and that it is supposed to cause lung cancer, but what about it?

Radon is a colorless, odorless gas that is created by the breakdown of Uranium. It is the only gas in the Uranium-238 decay series. The entire breakdown cycle takes billions of years, going from uranium-238 all the way to Lead 206, which is stable.

Radon has a short half-life of only 3.8 days (half-life is defined as the amount of time it takes for half the nuclei in a sample to undergo radioactive decay). It takes billions of years for Uranium 238 to decay in a five-step process into Radon, but only about 23 years for Radon to decay through eight steps into stable Lead. During each of these decay steps, a radioactive particle is emitted, which can lead to cellular damage that can cause cancer.

On average, about six atoms of Radon emerge from every square inch of soil every second. Outside it is diluted rapidly, but if it enters through a basement floor and is trapped in a tight, energy-efficient house, it can reach dangerous concentrations.

This EPA map shows the radon zones for the U.S.

Maryland's Radon Zone Map shows each county's Radon risk level. The red areas have the highest Radon risk.

The big issue about Radon is that it is a gas when we inhale it, but if it decays into solids while it is in our lungs, those solids stay in our lungs for the rest of the decay cycle, emitting alpha, beta and gamma particles.

The radiation emitted by Radon as it decays would be less harmful if it were outside our bodies. The slow moving, heavy Alpha particle is stopped by the first thing it hits, such as our clothing or even the layer of dead skin on the surface of our bodies. But if Radon is inhaled, it emits the particles very close to sensitive internal tissues, and lung tissue is particularly susceptible to ionizing radiation.

Is There a Safe Level?

There really is no “safe” level of Radon, but since it occurs everywhere, the natural free-air outside level is about 0.4 pCi/L (PicoCuries per Liter). The Level of 4.0 pCi/L was established as a number at which the risk associated with radon is approaching other unacceptable levels. This level of exposure is equivalent to an annual radiation exposure of 4 rem. To put this exposure into perspective, the maximum permissible occupational exposure for persons working in radiation-related occupations is 5 rem per year.

When is Remediation Necessary?

Generally, a Radon level of 4 pCi/l is considered “actionable”. The highest level of Radon Bob has seen during his inspections was 44 pCi/l. The highest level ever recorded in a residence was an astonishing 2700 pCi/l (this was revealed when the home’s owner showed up to work at a nuclear power plant, and set off the radiation alarms when he entered the facility). The average Radon level in homes throughout the western world is about 1 pCi/l. As such, 3.99 pCi/L is not ‘safe’ per se, but it is under the EPA’s “threshold,” and below that at which most contingencies kick in. In 2009, the World Health Organization recommended that the actionable level be reduced to 2.7pCi/l.

It’s Not Just Your Home!

But here’s a bigger issue: even if you get your home’s Radon levels under control with a remediation system, you have no way of knowing the levels of exposure in other structures, such as office buildings, schools, or day care facilities. If you or your children spend a lot of time in basement or ground floor levels of buildings, ask if Radon levels have been tested and what the results were. Only a few states have rules regarding Radon testing in schools, and sending a student to a classroom with a high radon concentration presents a cancer risk similar to requiring the student to smoke a few cigarettes during the school day.

Inspections by Bob strongly suggests that ALL homes be tested for Radon as part of the Real Estate transaction, and that everyone understand the risks associated with whatever values are returned. Obviously, we strongly suggest remediation for values above 4.0 pCi/L, but also suggest that ANY level above ambient be thoroughly understood.