Vancouver Public Schools alerted families with students at two campuses that testing had detected elevated levels of radon gas.Parts of McLoughlin Middle School and the Lieser Campus tested positive for levels of radon above four picocuries per liter, which, according to the Environmental Protection Agency, can be dangerous for long periods of exposure.Mitigation efforts, such as improving ventilation, have been taken, and radon levels are back within safe and normal limits, according to the letters.Exposure to radon, a colorless, odorless gas, is the second leading cause of lung cancer in the United States. It is a byproduct of the decay of granite. In areas that have a high level of granite in the soil, such as parts of Clark County, radon levels may be high. At McLoughlin, there was elevated radon in four areas of the campus. At Lieser, elevated levels were identified in two areas. The letters don’t offer further details on how high radon levels were, or in what parts of the school elevated levels were identified.