Prince George’s County lawmakers passed a bill Tuesday that would ban the use of electronic cigarettes in all places­ where smoking is prohibited, with one notable exemption: the forthcoming MGM casino resort.

In neighboring Montgomery County, lawmakers voted in March to ban the nicotine vaporizing devices­ in all places where tobacco smoking is prohibited.

The Prince George’s amendment that would allow “vaping” at any “facility awarded a video lottery operation license” drew criticism from anti-smoking activists.

“How could anyone in good conscious allow their use in casinos?” said John O’Hara, president of the Maryland Group Against Smokers’ Pollution. He said the county could be vulnerable to lawsuits filing by workers exposed to “second-hand vapor.”

[E-cigarette use triples among middle, high school students]

James Repace, whose research on indoor air pollution nearly four decades ago helped lead to early bans on tobacco use inside county workplaces, said e-cigarettes could release “volatile compounds” that are detrimental to human health. He cited a Johns Hopkins University study involving mice that found that the nicotine-laced liquid and chemicals in some electronic smoking devices­ could be toxic and have adverse effects on the immune system.

The MGM National Harbor casino, which is expected to open in the summer, will be the second casino in the state to allow use of electronic cigarettes. Council member Derrick Leon Davis (D-Mitchellville) first proposed the amendment during committee hearings, citing a similar provision passed by the Baltimore City Council to permit vaping at that city’s Horseshoe Casino.

Three of Maryland’s other five casinos — including Maryland Live, the biggest revenue-generator — prohibit the practice outright.

MGM government relations director Brian Banks, who was called on to testify, said the company did not request the exemption but supported it on behalf of some of its customers and clients. He also said he would like some modifications. “We would like to limit e-cigarettes only to the casino portion of the resort, not in the retail area or rooms,” Banks said.

Council member Todd M. Turner (D-Bowie), who sponsored the legislation, said he would be in favor of changing it to allow vaping in designated areas and not generally on the casino floor: “There is always an opportunity to come back and refine things,” he said.

County Executive Rushern L. Baker III (D) has indicated that he supports the bill, legislative liaison Nathaniel Tutt said.

[Study: Teens who use e-cigs more likely to start smoking cigarettes]

The council’s agenda was full on the last day of the fall legislative session. Bills to clarify zoning laws, amend building codes and tighten oversight on rental and cooperative housing and illegal street signs passed without much discussion.

But legislation proposing a tax credit for urban agriculture in some residential areas elicited debate. Lawmakers approved the credit, saying they would revisit concerns about who can qualify for the credit during the next legislative session, which begins in January.

The council passed a bill backed by Karen R. Toles (D-Suitland) to define and regulate tobacco and e-cigarette shops. The legislation gives the county’s permitting office the ability to keep the shops out of certain retail centers.

In response to concerns about the high number of police retirements, the council voted to ask Baker to release funds designated for emergencies, so they can be used to pay for training a new class of officers. The council could consider such a request from Baker as early as January.

[Chief: I need more officers]

About three dozen residents rallied outside council chambers in Upper Marlboro to support the release of the funds, saying population growth and new development in the county are increasing public safety demands.

“We don’t want to send the message to criminals that they can come in and do anything they want to,” said longtime resident Betty Williams.

Lynh Bui contributed to this report.