Radon is a colorless, odorless radioactive gas that is a product of the decay of uranium. Radon occurs naturally in the soil, and can be found almost anywhere in the United States. Radon is the second leading cause of lung cancer in the United States, causing over 21,000 deaths per year. Smoking tobacco products in combination with exposure to radon have a synergistic effect. Therefore, smokers who are also exposed to radon have a much higher chance of developing lung cancer.
Differences in pressure inside and outside the home create the effect of a vacuum, allowing radon to enter indoor environments. Hot air naturally rises, creating a low-pressure zone near the ground and a high pressure zone towards the top of a home. This process of airflow is what allows radon to enter a home and concentrate in higher levels than the outside. The radioactive gas can enter homes through cracks, pores, loose fitting pipes, floor-wall joints, and other openings. During rainfall events, water seeps into the soil creating hydrostatic pressure that displaces air in the soil, which in turn can cause more air to be driven into a home. Poorly ventilated homes can further exacerbate a radon problem by allowing higher levels of concentration.
In the IAQ assessment conducted in 2005, the Environmental Department tested seven buildings on TBR using 48-hr activated charcoal radon tests. All the buildings tested well below the EPA action level of 4.0 piC/L. As shown by the EPA map below, Humboldt County is considered to be a zone 3, with the lowest risk of radon. Because of this, low levels of radon could be expected and don't come as a surprise. However, EPA warns that regardless of the zone, homes should still be tested for radon, as high levels have been found in all three zones. Furthermore, as homes age and deteriorate, it is possible for radon to enter the home through new cracks or pores, so low levels of radon can change in a home over time.