Erie, Pennsylvania (CNN) Inside a factory near this lakeside city, a man holding a blowtorch is putting the finishing touches on a plastic rain barrel that will soon make its way to a home and garden section somewhere in America.

He is Talib Alzamel, a 45-year-old Syrian refugee who arrived here last summer with his wife and five children. He can't speak much English, but neither can most of the 40 refugees who work at Sterling Technologies, a plastic molding company based near the shores of Lake Erie. They earn $8-14 an hour.

The refugees at Sterling come from all over the world, from Syria to Sudan, Chad to Bhutan. And they've all passed the company's standard drug test.

"In our lives, we don't have drugs," said Alzamel, who was hired within three months after arriving in Pennsylvania. "We don't even know what they look like or how to use them."

But for an increasing number of American-born workers, passing drug tests is a big problem.

The percentage of American workers testing positive for illegal drugs has climbed steadily over the last three years to its highest level in a decade, according to Quest Diagnostics , which performed more than 10 million employment drug screenings last year. The increase has been fueled in part by rural America's heroin epidemic and the legalization of recreational marijuana in states like Colorado.

More than 9% of employees tested positive for one or more drugs in oral fluid screenings in 2015, the most recent year for which data was available. And the problem is even worse at places like Sterling Technologies.

"Twenty percent of the people are failing," said Cary Quigley, the company's president. "We're seeing positive tests anywhere from marijuana through amphetamines, right all the way through crystal meth and heroin."

Which is why refugees like Alzamel, despite some language barriers, are quickly snapping up jobs.

"The big factories ... they have a problem with the drugs, so like every time they fire someone, they replace him with the refugee, to be honest," said Bassam Dabbah, who works at a US Committee for Refugees and Immigrants field office in Erie. "The only barrier is the language, but they are picking it up very quick."

'It's like the United Nations'

The status of refugees in the US has been under scrutiny since President Donald Trump's executive orders limiting the number of immigrants to the country. On March 6, Trump signed a new order that bans immigration from six Muslim-majority nations and reinstates a temporary blanket ban on all refugees.

But because of the increase in positive drug tests, the refugees who have reached America in recent years are finding a more welcoming hiring climate, at least for menial manufacturing jobs.

Nearly 6,000 refugees have settled in the last five years in Louisville, Kentucky, helping companies hire workers for jobs that had gone unfilled. Methamphetamine use is so high in Louisville that the number of people testing positive for meth in workplace drug tests is 47% higher than the national average, according to Quest Diagnostics.

Workers at White Castle in Louisville, Kentucky.

Inside the White Castle food processing plant, where they make 50,000 hamburgers per hour, "it's become like the United Nations," says Jamie Richardson, a company vice president.

Antigona Mehani, employment services manager at Kentucky Refugee Ministries, says she can usually find a refugee a job within three days.

Employers tell her, "send us as many as you can," she said. "I hear this every single day."

CNN's reporting discovered a similar dynamic in many parts of the country, from Columbus, Ohio, to Albany, New York, to a company in Indiana that supplies parts for Ford cars.

While many employers insist that drug testing keeps the workplace safe and ensures a productive and stable work environment, there is no conclusive evidence that it's necessary for all jobs or that it lowers risks or reduces drug use

And workers flunking drug tests is not a new problem, said Calvina L. Fay, executive director of the Drug Free America Foundation.

But it's a problem that is getting worse, she said.

Fay said employers are especially concerned about the increasing failure rates in "safety sensitive" workplaces, where a lapse by a employee under the influence of drugs could cost lives.

"They're frustrated for a number of reasons. In some cases they are having trouble hiring drug-free workers," Fay said. "They can't drug-test people every day, so there will be people who slip through the cracks."

In Colorado, where marijuana is legal, some businesses have told Fay, "they see employees smoking pot on their lunch break and then going back to work."

One oil and trucking company in Colorado did random drug screening at one of their locations last year and found 80 percent of their employees failed, Fay said. (Colorado's Supreme Court has ruled that companies may fire employees who smoke pot, even if legally.)

"They had to replace everyone," she said. "The employer was glad he found the problem because his employees do extremely dangerous work. He was shocked and disturbed."

'A really good source of labor'

Sterling Technologies in Erie, Pennsylvania.

In the last five years, nearly 4,000 refugees have resettled in Erie, PA, a city that has struggled economically in recent decades.

Locals say the area also is dealing with a drug epidemic.

"'Right now around here, heroin's big, sad to say," said Sterling Technologies floor manager, Marty Learn, who has seen four or five workers in his department fail drug tests in recent months.

"I've had no refugees fail it," he added.

"In the Sunday newspaper there was a four- or five-page spread for employment advertisements and almost every one of them said, 'Must pass a background check and a drug screen.' So there's a lot of people who are unemployed as a result," said Amanda Milleren, a drug-addiction counselor at Cove Forge Behavioral Health System in Erie.

Erie has lost over half its manufacturing jobs since the 1980s, says Shannon Monnat, a rural sociology professor at Penn State University. Meanwhile the city has faced rising rates of drug overdoses, alcohol-related deaths, and suicides.

"When business owners are telling you that they can't find native residents who will do these jobs, or they can't find enough people in the community to pass a drug test, what are they to do?" said Monnat. "They need to seek out employees somewhere. And for now, immigrants are a really good source of that labor."

Companies and staffing agencies in Erie and other cities have come to see refugee resettlement agencies as good partners to help expand the local labor pool.

And recovering drug addicts in Erie told CNN they can see why employers have had to look elsewhere for workers.

But some still think they deserve a second chance.

"I know that refugees need an opportunity when they come here, and employers give them the opportunity. But people like us that live here also need an opportunity," said Bethany Kaschak, 34. "I'm not saying they don't deserve it. But we deserve it as well."

Sterling Technology's management voted for Trump and hopes he will push for tax cuts that will allow them to reinvest in their business . But at the same time, they don't want to see their refugee-powered workforce go away.

"Do I want to see all of my people deported?" asked Quigley, the Sterling Technologies president. "Absolutely not. They're a part of this company. They've helped build this company," he said.

"Our goal is to continue to grow the company. We can't grow the company without people that want to do the work."