What is an action to take after earthquakes with respect to radon testing?

After an earthquake, it is essential to re-test radon levels in homes, because seismic activities can disturb the soil and change the pathways through which radon gas enters buildings. Earthquakes can create new cracks in the foundation or increase the permeability of the soil, potentially leading to elevated levels of radon that were not previously detected.

Re-testing allows for the assessment of any changes in radon concentrations that may have occurred as a result of these geological shifts. This is especially important given radon's health risks, as it is a known carcinogen linked to lung cancer.

The other options, while they may sound reasonable in other contexts, do not address the need for immediate assessment of radon levels following an earthquake. For example, testing only if the power goes out does not consider the immediate impact of the earthquake on the radon levels. A comprehensive review of home conditions may be valuable, but it does not directly ensure that radon levels are measured. Waiting for a month before retesting can allow any potential hazards to persist without monitoring, which is contrary to the proactive approach necessary for addressing radon gas exposure.