Updated: 6:14 PM EST January 7, 2021 CONNECTICUT, USA — January is National Radon Month. Radon is a naturally occurring radioactive gas that can cause cancer. The Connecticut Department of Health (DPH) is asking residents to test their homes for the gas which they say is the leading environmental cause of cancer mortality. It is estimated by Health Officials that radon is responsible for more than 21,00 lung cancer deaths in the country. CT DPH says radon measurement and mitigation, when needed, is especially important during the COVID-19 as families spend more time in the lower levels of their houses where radon levels can be higher.