Radon Levels Explained

First of all there are really no safe radon levels since it's a radioactive gas that causes lung cancer. With that said, we need to recognize that we all live life with some unavoidable risk.

For instance, the average outdoor level is 0.4pCi/L. Thus it's impossible to completely eliminate our exposure to radon gas. But we do have options if our indoor radon results are elevated. So what's a high radon reading?

Unacceptable Radon Levels

The EPA set 4pCi/L as the action level for the United States back in 1988. This is not a "health based level" as they are quick to add.

Homes with readings between 2pCi/L and 4pCi/L should consider mitigation also. As of 2009, the World Health Organization set their threshold to mitigate at 2.7pCi/L.

So what is the risk of having radon in your home?

At level 4pCi/L, the radon you inhale is the same as:

  • Smoking 8 cigarettes per day
  • Having 200 chest X-rays per year

Your risk at 2pCi/L is the same as:

  • Smoking 4 cigarettes per day
  • Having 100 chest X-rays per year

As your radon number doubles so does your risk!
So at 10pCi/L your risk is like smoking more than a pack a day!

How to interpret your radon results

Radon readings will vary throughout the year. Highest levels are typically recorded in mid-winter (when you house is sealed up) with levels decreasing to there lowest concentrations in summer (when you might have your windows open allowing the radon to escape).

So 4pCi/L in summer could be considerably higher in December. Thus, an average of well above the EPA action level can be assumed.

Whereas the opposite may be true of a level of 4pCi/L in winter. Thus the only way to really know for sure is conduct a long term test to account for the fluctuations through out the seasons.

What can cause your level to vary?

  • Frozen soils force more radon into the house.
  • The stack or chimney effect is greatly increased during the heating season.
  • Less ventilation in winter since the building is closed up tight.
  • Rainy periods can cap the soil increasing indoor levels.
  • Wind and storms can increase or decrease levels.

Also important to consider is the time spent in the lowest level of the building. If your level is 2pCi/L in a basement used only for storage, then it's likely that your exposure will be low. But if you have a forced air furnace and central AC system this could create the same level on all floors of the home when in operation.

To be sure of your exposure a long term test kit will give the best picture of overall exposure to radon in your home.

More Radon Pages

Fast Facts  |  How to Test  |  Understanding Radon Levels  |  Health Dangers  |  United States Risk Map  |  Major Risks for Smokers  |  Test Kit Guide

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