You may have seen this topic covered in the news recently. Radon is something that is naturally occurring and is a colourless, odourless, and radioactive gas produced by the breakdown of uranium in soil, rocks, and water. It's present in all homes, but high levels can present significant health risks. Newer homes tend to be larger and taller, which contributes to the problem.
But, there are solutions! You can have your home tested for Radon, and have a qualified professional remdiate the problem.