Police say they will be actively citing pot smokers this weekend at Boston Calling in what could be the first major test of public consumption laws since recreational marijuana sales began last November.

The annual three-day music festival, attended by thousands and often shrouded in clouds of pot smoke, returns Friday to the Harvard Athletic Complex. Medical experts and advocates say secondhand pot smoke can be a health hazard — and just as annoying as tobacco smoke.

Boston police Sgt. Detective John Boyle said, “Anybody that does smoke weed in public is subject to a citation, and we will hold Boston Calling or any major group like this responsible. They’re subject to a license premise violation if the laws of the commonwealth are violated. It’s going to be handled like any other major permitted event in the city.”

Cambridge police spokesman Jeremy Warnick reminded festivalgoers that those under the age of 21 who are caught with weed could face penalties — as could those over age 21 who are found to have more than an ounce of weed on them.

“We strongly encourage attendees to focus on their safety and the safety of others and enjoy what should be another great festival,” Warnick said.

Boston Calling organizers insist they won’t tolerate smoking — of either marijuana or tobacco products — on festival grounds. They say they intend to observe the state’s pot consumption laws: no smoking, vaping or consuming edibles in public. That means no cigarettes and cigars, no joints or Juuls, and no vape pens.

Strict enforcement could prove a buzzkill for some attendees. But anti-smoking advocates say it’s the right call, telling the Herald that secondhand pot smoke contains cancer-causing toxins and chemicals that pose serious health hazards.

“It’s about ensuring everyone has the right to breathe clean air in public places,” said Bronson Frick, associate director of the American Nonsmokers’ Rights Foundation. “The bottom line is smoke is smoke, and secondhand marijuana smoke still creates a health hazard for other people.”

Thomas Carr, policy director with the American Lung Association, said anywhere tobacco smoke is prohibited, marijuana smoke should be, too.

“Secondhand marijuana smoke is emitting the same carcinogens and toxins as directly inhaling marijuana smoke,” Carr said.

Marijuana smoke can contain ammonia arsenic, formaldehyde, lead, mercury and nickel, according to the National Center for Biotechnology Information. Secondhand exposure to marijuana smoke can cause lung irritation, asthma attacks and even respiratory infections, according to the American Nonsmokers’ Rights Foundation.

Non-smokers in a confined area with a high concentration of marijuana smoke have even reported a mild “contact high,” displaying signs of impairment, according to research from the National Institute on Drug Abuse.

“There’s a great body of research affirming that secondhand marijuana smoke is a potent health hazard to non-users,” Frick said. “The bottom line is to not smoke in ways that harm other people.”

But the haze of marijuana smoke has often been unavoidable at Boston Calling before, and it’s unclear whether enforcement efforts will change that this year.

“It’s not easy to get away from secondhand smoke of any kind” at concerts, Frick said.