Long before he became a renowned scientist who fought for environmental justice in Los Angeles and beyond, John Froines was an antiwar activist who became a familiar face as a member of the fabled Chicago 7.

The Vietnam War was at a pitch, the nation was heaving with racial tension and college campuses had become battlegrounds when Froines joined Abbie Hoffman, Tom Hayden and the others at the Democratic National Convention in Chicago in 1968 to protest the long-running and increasingly unpopular war.

The convention was a loud, blurry, chaotic event. Activist Jerry Rubin tried to nominate a pig for president and then speak on the hog’s behalf. Dan Rather was roughed up by police while trying to interview delegates, and author Norman Mailer waded through the crowd trying to get a handle on what it all meant — if anything.

There was so much tear gas in the air that it seeped into neighboring hotels, including the suite where Vice President Hubert Humph- rey had set up camp.

A year later, Froines and six others were charged with conspiracy to incite a riot at the convention and stood trial in a spectacle that became a lasting emblem — and a pair of movies — of an era when the nation was all but at war with itself.

Froines, who was one of two acquitted in the trial, lived comfortably with the memories of his days as a street activist but more comfortably still as a leading environmental scientist who helped shape government standards on lead and clean air, particularly in impoverished neighborhoods.

“We still need student protesters because many of the problems of the ’60s continue and new issues have emerged,” he told The Times shortly after he was named director of UCLA’s Occupational Health Center.

“But nobody’s a student activist at 50. You’d have to have your head examined.”

A content grandfather who ran marathons and was an obsessive skier, Froines died Wednesday in Santa Monica, said his wife, Andrea Hricko, a professor emerita at USC Keck School of Medicine. He was 83 and had been suffering from Parkinson’s disease.

As the ’60s slipped into the rearview mirror, the lives of the Chicago 7 scattered in all directions.

Hayden married Jane Fonda and served 18 years as a California assemblyman and state senator before dying in 2016 in Santa Monica. Rubin became an author and stockbroker who was fatally struck by a car while crossing Wilshire Boulevard in 1994. Hoffman committed suicide, and Bobby Seale — co-founder of the Black Panther Party whose trial was severed from that of the others — became a lecturer and college recruiter and wrote a book on barbecuing.

Froines returned to academia. And the fervor he once aimed at the war in Vietnam he now directed at lead, diesel fumes and other environmental hazards that affected the lives of so many, and often those who lived in near poverty.

As head of the occupational health division of the Vermont Health Department, he helped persuade the state’s nuclear power industry to accept health standards tougher than federal regulations. As director of a division of the Occupational Safety and Health Administration in Washington, he was principal author of federal standards regulating workers’ exposure to lead and cotton dust.

As a UCLA professor, Froines conducted a study to determine which Southern California jobs and industries had the highest exposure to 500 chemicals. And as head of the UCLA’s Occupational Health Center, he oversaw a study to determine how some industrial chemicals cause early aging of the brain and how others help trigger the first stages of cancer.

John Radford Froines was born June 13, 1939, and raised in Oakland, where his parents were shipyard workers. His father was murdered while walking home from the shipyards when John was 3. He became a star running back in high school, graduated from UC Berkeley and earned a doctorate from Yale.

At Yale, he joined Students for a Democratic Society, then a hub of left-leaning activity, and got to know Hayden, Rennie Davis and David Dellinger, all future members of the Chicago 7. The three persuaded Froines, along with Hoffman, Rubin, Seale and Lee Weiner, to join them in protest at the convention.

Thousands of protesters there were met by riot po- lice and scores were in- jured in the violence that followed.

The trial that followed was a circus. Hoffman wore judicial robes and paraded in front of the judge shouting “Heil Hitler!” Dellinger called the judge a liar and Rubin plopped his boots on the defendants’ table and pretended to sleep. Seale was so incensed by the attorney the court appointed for him that the judge ordered him bound and gagged. In all, the judge cited the defendants nearly 200 times for contempt of court.

Froines was acquitted, and an appeals court dismissed most of the charges against the others.

After the trial, Froines set off on an antiwar speaking tour and joined the Black Panther Party Defense Committee, which worked with Seale and Ericka Huggins in their controversial murder trial. Both were freed when the jury deadlocked.

“People are always saying, ‘Is John Froines the same radical he was in 1968?’ ” he told The Times years after the trial. “No one is the same now as then. I think it’s more valuable to look at a person’s history — to see if they have been consistent within the context of their values. And I believe I have.”

Froines is survived by his wife of 42 years; a daughter, Rebecca Froines Stanley; a son, Jonathan Froines; and two granddaughters, Kayla and Jessica Stanley.