John "Johnny Doc" Dougherty, head of Local 98 of the International Brotherhood of Electrical Workers, has his own grim metric for measuring the overdose toll in Philadelphia: Eight of his union's members have died of overdoses in the last 18 months.

"One person dying would have been too much," he said. "But eight just put me out."

These days, his shop stewards are being trained to administer naloxone; his health fund limits prescriptions of opioids; and he's hired a full-time substance-abuse counselor to help members struggling with addiction.

Officials in the building trades say their members, who take physically demanding jobs and risk serious injuries that often require pain medication, are uniquely predisposed to addiction.

study released Thursday by the U.S. Centers for Disease Control and Prevention, one of the few analyses of its kind in the country, backs up what Dougherty and others say they have long known: construction workers are more likely than workers in any other occupation in the country to die of a drug overdose. The study found that they were also at higher risk of heroin overdose.

There has been little research on how occupation dovetails with overdose and addiction risk, as it's hard to track. Death certificates, for example, aren't often clear about a person's profession at the time of their death.

The study looked at fatal overdose data from 21 states, including New Jersey, between 2007 and 2012. Another recent study, which focused solely on Massachusetts and used data collected between 2011 and 2015, found construction and mine workers there died of overdoses at a rate six times higher than the general working population.

The CDC study found that miners, food industry workers, health-care practitioners and support staff, and personal care workers also had elevated overdose death rates — showing the crisis is cutting across large swaths of the country's working population.

"We know that people's jobs affect their health and well-being," said the study's lead author, Laurel Harduar Morano of the National Institute for Occupational Safety and Health. "We need to consider occupation as one of the contributing factors to the opioid epidemic, and possibly [as a place] for intervention."

Morano said more research is necessary to determine why certain occupations have a higher risk of overdose.

But the construction industry can be "a perfect storm" for opioid addiction, said Ken Serviss, executive director of the Allied Trades Assistance Program, which for three decades has helped members of Philadelphia's building trades unions and their families seek treatment for substance-abuse disorders. For the last 10 years, he said, he's watched as more and more members have called his office asking for help with an opioid addiction.

It makes a kind of horrible sense, he said. Construction workers risk injuries on the job each day, whether it's "a fall from scaffolding, or bad knees from years of cement work." Those injuries can lead to prescriptions for opioid pain medication, which in turn can lead workers into addiction to pills, then to heroin, which usually is laced with the even more powerful synthetic opioid fentanyl.

"And you also have the environmental problems — a lot of socialization [in the industry] is alcohol and drug use," plus the enduring stigma against drug addiction that cuts across occupations, he said.

When the Allied Trades Assistance Program was set up in the late 1980s, Serviss said, members were mostly reporting an alcohol addiction. During the crack epidemic, which decimated black communities, the majority-black Laborers District Council sent members to ATAP for help, said Ryan Boyer, the union's current leader.

"We had a crack epidemic in the 1980s, and the people affected by it looked different," Boyer said. "But we've never seen people with addiction as criminals, as the rest of the American population did. We haven't done anything radically different [amid the opioid crisis] than we've been doing for the past 30 years."

Today, Serviss said, most of his clients are reporting addictions to heroin and fentanyl; about half are spouses and children of union members, who are also covered under the building trades' benefits plans. For the last year, Serviss has trained building trades workers who have dealt with addiction themselves to act as peer advocates for colleagues returning to the job site after drug or alcohol treatment.

"You're often left alone in early recovery on the job site" when co-workers are headed to the bar after work, he said. "Your advocate is a person that can just pull up a spackle bucket and have a conversation. You can have an Alcoholics Anonymous meeting anywhere, with just two people."

After eight deaths in a year and a half, Dougherty said, his union was shaken. Some of the members who died had hidden their addiction almost entirely from their colleagues.

"People are being asked to do more in a shorter period of time," he said, "and what happens is, we get a lot of people trying to medicate their way through a job." None of his members have died of an overdose on the job, he said, but his shop stewards are now being equipped with naloxone just in case. And the union's new substance-abuse counselor has been fielding calls from members, Local 98 officials added, especially since the union has begun placing signs on job sites advising members that substance-abuse help is available.

The union also recently convinced its health insurers to limit opioid prescriptions to five pills to prevent abuse.

(Serviss echoed concerns of advocates who say such measures, while necessary to curb future cases of addiction, should be taken with caution: "We have to be careful when we have legit doctors who are prescribing legit pain meds for issues. You'll start to see people say, 'If I can't get my prescription drugs, I'm going to find other sources to take care of my pain.'" Dougherty said the union was keeping an eye on that, too: "So far, so good," he said.)

Pat Eiding, the head of Philadelphia's AFL-CIO chapter, which represents thousands of workers, said unions are uniquely placed to help members in addiction — and can work to dispel stigma and make it easier to access treatment.

"We want the average worker to feel comfortable to go to someone with their problem," he said. "If we make that available to our union members, it will help us not have to bury them."