Which condition is likely to cause significant changes in indoor radon concentrations?

Large subgrade pathways such as Karst geology can significantly influence indoor radon concentrations because these geological features allow for the movement of radon gas from the ground into structures more easily. Karst topography is characterized by soluble rock formations, such as limestone, that have been eroded to create a landscape with sinkholes and underground drainage systems. This unique structure can create pathways for radon, a naturally occurring radioactive gas produced from the decay of uranium found in soil and rocks, to migrate into homes and buildings.

The presence of such pathways means that radon can be more prevalent in areas with Karst geology, making it essential for homeowners and mitigation specialists to assess the radon risk when homes are located in these regions. Understanding the geological context is critical for effective radon mitigation and prevention strategies, as it helps identify areas where higher radon levels are expected.

While conditions such as high indoor humidity, artificial ventilation, and the use of household chemicals can affect indoor air quality, they do not directly influence the geological factors that lead to the entry of radon gas from the soil into structures. Therefore, the impact of subgrade pathways like those found in Karst geology is particularly significant when considering the overall risk of indoor radon concentrations.