Montgomery residents who sell their homes will have to test for radon and give buyers the results under a bill passed unanimously by the County Council on Tuesday.

Montgomery is the first locality in the country to establish a radon testing requirement, according to the bill’s sponsor, council member Craig Rice (D-Upcounty). Like many other recent regulatory measures passed by the council, however, there are few provisions for enforcement. The radon bill does not specify penalties for noncompliance.

“We’re just trying to get people to test,” Rice said, likening the new requirement to having carbon monoxide detectors in homes and other common safety measures.

Maryland is one of several states that require sellers to disclose to buyers any knowledge of radon in their homes. Buyers often request the test anyway as a condition of sale.

But the Montgomery County attorney’s office told the council that the state law does not create an explicit obligation on the part of the seller to determine whether radon is an issue.

Radon is an invisible radioactive gas produced by the natural breakdown of uranium in rocks and soil. It enters homes through foundation cracks and other openings. According to the Environmental Protection Agency , it is the leading cause of lung cancer among non-smokers and the second-leading cause of lung cancer, after cigarette smoking, for the general population.

Montgomery, Fairfax and other counties in Maryland and Virginia are a “Zone 1” radon risk, according to the EPA. The rating means that indoor radon levels are likely to exceed four picocuries per liter of air. A picocurie is a trillionth of a curie, a measure of radiation.

At that level, the EPA recommends installation of relatively inexpensive ventilation systems that suction the gas out of the ground and into the air.

The real estate industry opposed the county bill, citing the potential for increased costs for sellers. Prior to the vote, the council rejected a last-minute amendment from an industry trade group, the Greater Capital Area Association of Realtors, that would have exempted new single-family homes being sold for the first time.

Current county building codes require such homes to be built with remediation systems already in place that can be activated by the installation of a fan.

In other business Tuesday, the council approved $750,000 for a program aimed at reducing summer-learning loss among low-income children. The program, called BELL (Building Educated Leaders for Life), will also be financed by a grant from the Norman and Ruth Rales Foundation.

BELL, which has served about 100,000 students in other districts since its inception in 1992, is a six-week summer program targeted to second- and third-graders who are working below grade level in reading and math. It is expected to enroll about 1,000 Montgomery County Public Schools students each of the next four summers.

Joshua Rales, a real estate investor and president and trustee of the Rales Foundation, said he hopes the pilot program will begin to address the persistent gap in academic achievement separating Montgomery’s white and Asian students from black and Hispanic students.

“Together we’re going to drive a stake through the heart of the achievement gap,” Rales said.

Council member Nancy Navarro (D-Mid-County) was the lead sponsor of the county appropriation. The Montgomery Board of Education is expected to approve the plan in the next few weeks.