TAYLORSVILLE, N.C. — Sheri Farley walks with a limp. The only job she could hold would be one where she does not have to stand or sit longer than 20 minutes, otherwise pain screams down her spine and up her legs.

“Damaged goods,” Ms. Farley describes herself, recalling how she recently overheard a child whispering to her mother about whether the “crippled lady” was a meth addict.

For about five years, Ms. Farley, 45, stood alongside about a dozen other workers, spray gun in hand, gluing together foam cushions for chairs and couches sold under brand names like Broyhill, Ralph Lauren and Thomasville. Fumes from the glue formed a yellowish fog inside the plant, and Ms. Farley’s doctors say that breathing them in eventually ate away at her nerve endings, resulting in what she and her co-workers call “dead foot.”

A chemical she handled — known as n-propyl bromide, or nPB — is also used by tens of thousands of workers in auto body shops, dry cleaners and high-tech electronics manufacturing plants across the nation. Medical researchers, government officials and even chemical companies that once manufactured nPB have warned for over a decade that it causes neurological damage and infertility when inhaled at low levels over long periods, but its use has grown 15-fold in the past six years.

Such hazards demonstrate the difficulty, despite decades of effort, of ensuring that Americans can breathe clean air on the job. Even as worker after worker fell ill, records from the Occupational Safety and Health Administration show that managers at Royale Comfort Seating, where Ms. Farley was employed, repeatedly exposed gluers to nPB levels that exceeded levels federal officials considered safe, failed to provide respirators and turned off fans meant to vent fumes.

But the story of the rise of nPB and the decline of Ms. Farley’s health is much more than the tale of one company, or another chapter in the national debate over the need for more, or fewer, government regulations. Instead, it is a parable about the law of unintended consequences.

It shows how an Environmental Protection Agency program meant to prevent the use of harmful chemicals fostered the proliferation of one, and how a hard-fought victory by OSHA in controlling one source of deadly fumes led workers to be exposed to something worse — a phenomenon familiar enough to be lamented in government parlance as “regrettable substitution.”

It demonstrates how businesses at once both suffer from and exploit the fitful and disjointed way that the government tries to protect workers, and why occupational illnesses have proved so hard to prevent.

And it highlights a startling fact: OSHA, the watchdog agency that many Americans love to hate and industry often faults as overzealous, has largely ignored long-term threats. Partly out of pragmatism, the agency created by President Richard M. Nixon to give greater attention to health issues has largely done the opposite.

OSHA devotes most of its budget and attention to responding to here-and-now dangers rather than preventing the silent, slow killers that, in the end, take far more lives. Over the past four decades, the agency has written new standards with exposure limits for 16 of the most deadly workplace hazards, including lead, asbestos and arsenic. But for the tens of thousands of other dangerous substances American workers handle each day, employers are largely left to decide what exposure level is safe.

By contrast, OSHA has two dozen pages of regulations just on ladders and stairs.

“I’m the first to admit this is broken,” said David Michaels, the OSHA director, referring to the agency’s record on dealing with workplace health threats. “Meanwhile, tens of thousands of people end up on the gurney.”

Royale Comfort Seating disputes that Ms. Farley’s health problems and those of some other workers were linked to their jobs. Company officials also say that while they have sought to safeguard their workers, they have also feared losing jobs to foreign competitors, as many of their industry counterparts in North Carolina have.

Royale has not switched away from the nPB glues, managers said, because alternatives did not work well, were sometimes more dangerous and were almost always more expensive.

“We, as a company, are also in a tight spot,” said William Lee Isenhour, Royale’s director of personnel and safety.

Chronic ailments caused by toxic workplace air — black lung, stonecutter’s disease, asbestosis, grinder’s rot, pneumoconiosis — incapacitate more than 200,000 workers in the United States annually. More than 40,000 Americans die prematurely each year from exposure to toxic substances at work — 10 times as many as those who die from the refinery explosions, mine collapses and other accidents that grab most of the news media attention.

Occupational illnesses and injuries like Ms. Farley’s cost the American economy roughly $250 billion per year because of medical expenses and lost productivity, according to government data analyzed by J. Paul Leigh, an economist at the University of California, Davis, more than the cost of diabetes or chronic obstructive pulmonary disease. Roughly 40 percent of medical expenses from workplace hazards, or about $27 billion a year, is paid by public programs like Medicare and Medicaid.

And yet the full price of this epidemic is measured not just in hospital bills and wages lost, but also in the ways, large and small, that life has changed for Ms. Farley and other sickened workers. Glue fumes robbed her of dignity and the joy of small comforts. Her favorite high heels stay in her closet because her feet no longer cooperate. She barks at her 8-year-old daughter, Allie, for hopping around their double-wide trailer because the floor’s vibrations cause intense stinging.

“I did the work,” Ms. Farley said about her years putting together furniture for America’s households. “This doesn’t seem a fair price to pay.”

Foam Country

Two industries converge in North Carolina along the nine-mile stretch of Interstate 40 between Hickory and Claremont. Foam meets furniture here. Cushions find seats.

For nearly a century, towns in these western foothills have been famous for their fine home furnishings, producing roughly half the chairs and tables sold nationwide at the industry’s peak in the 1980s. Every year, several million pounds of a flexible polyurethane foam known as slabstock arrives. It becomes the spongy filling in most of the mattresses, chairs and couches produced in the United States.

Delivered as huge yellow or pink loaves, often about four feet high and the length of a tractor-trailer, the slabstock is cut into pieces and glued into shapes by rows of workers standing in booths. They sometimes attach upholstery or add a top layer of polyester fiber to give the cushions a softer feel.

North Carolina has been especially affected by globalization and federal regulations. Shifting cultural mores and rising cigarette taxes have cleared hundreds of tobacco farms. Foreign competition has closed most of the textile mills. More than half of the furniture jobs once based here are now gone, according to federal labor data.

Still, about a thousand people spread across several dozen plants in the state work in this locally vital industry. For Ms. Farley, the job at Royale making cushions represented something rare: a chance for someone with little more than a high school diploma and an ability to stand on her feet all day to make more than $9 an hour.

Day 1 at the job brought ominous advice. Don’t dally, co-workers counseled her; managers keep track of your cushions per hour. Bring a hair dryer; it helps in warming brittle hands in winter when the plant gets frigid. Stock up on aspirin and tissues: the first to survive the headaches from the glue’s gasoline-like fumes; the second because the fumes clear the sinuses.

Asked about the conditions, Royale officials said their three plants, two here in Taylorsville and one about 15 miles away in Conover, were no worse than others in the business.

But no one denied it was dirty, bone-tiring work. During 10-hour shifts, the gluers held spray guns attached to hoses that ran to a humming compressor and 55-gallon drums filled with the glue. Once sprayed, the glue coated everything — the lights, fans, floors and electrical outlets — and hung over the workers’ cubicles like a shroud.

“It puts the fog in your head,” Ms. Farley said. By the end of a shift, the glue left some workers so dizzy that they walked as if they were drunk. At times, they did not remember driving home.

A Chemical’s Use Grows

Cushion-making companies had every reason to like nPB glues. First marketed in the late 1990s, they were inexpensive, strong, fast-drying and, best of all, unregulated.

“It’s so safe you can eat it,” glue salesmen in North Carolina told customers, according to federal researchers. Plant operators joked, “At worst, it’s a cheap high,” an official from an industry trade association recalled. Water-based glues, though safer, dried slower. And retooling a plant to use them could cost anywhere from several thousand dollars to more than $1 million, in some cases doubling a company’s gluing costs.

Finding a glue that complied with federal rules was a continuing struggle. In the early 1980s, many companies used glue with a chemical called 1,1,1-trichloroethane, or TCA. But the United States and other countries then banned it because it damages the ozone layer, and businesses switched to methylene chloride.

Nicknamed by cushion makers “methyl ethyl bad stuff,” it killed more than 30 workers a year and sickened thousands more across all industries. OSHA tightened safety limits on the chemical, so companies sought a new option. Before long, roughly a third of the cushion-making industry had switched to nPB-based glues.

For the most part, American employers are left on their own to find substitutes when federal agencies impose new rules on chemicals. But when the government forces the phasing out of one hazardous chemical, it is often replaced by another equally or more dangerous one.

From the start, government officials worried about the safety of nPB, which is also sometimes called 1-bromopropane or 1-BP.

In 1999, Adam Finkel, OSHA’s top health officer who had led the agency’s drive to phase out methylene chloride, wrote a letter warning that nPB was being used as a replacement at levels 10 to 200 times what chemical companies said was safe. Something needed to be done, he said, before the number of people exposed to the new chemical “grows from the hundreds to the tens of thousands or more.”

Some companies pulled back. Protonique SA, a Swiss circuit-board maker, banned it for its workers, who used a form of the chemical that was less toxic than that inhaled by Royale workers. “There is a weight of evidence that should sound warning bells to any thinking person,” the company said in 1999. By 2003, Atofina and Great Lakes, two large chemical companies, had decided they would no longer sell nPB.

In the six years after Mr. Finkel wrote his warning letter, federal authorities learned that more than 140 cushion workers nationwide, mostly from plants in Utah, Mississippi and North Carolina, including Royale, had been exposed to dangerous levels of the chemical, many of them sickened and unable to walk.

Cushion makers in the 30,000-employee foam industry were among the most vulnerable of all workers using nPB because they breathed it in aerosol doses. Those employed in other businesses mostly used it in other forms, which pose lower risks, according to scientists, who are finding mounting evidence that nPB is also a carcinogen.

Pinpointing the cause of a worker’s ailment is an inexact science because it is so difficult to rule out the role played by personal habits, toxins in the environment or other factors. But for nearly two decades, most chemical safety scientists have concluded that nPB can cause severe nerve damage when inhaled even at low levels.

Ms. Farley sued Royale for workers’ compensation payments. Her case, along with several other lawsuits related to glue fumes brought by other workers, has been settled.

When news of exposure problems at Royale reached officials at Mid South Adhesives, the maker of the glue that Royale used, they sent an inspector who found that Royale’s Conover plant showed levels at least 10 times what Mid South deemed safe. Mid South officials wrote to Royale to say they could “not stress enough” the need to provide better protections or to stop using their glue.

Royale officials, though, responded that even though they had added fans, had trained workers handling toxic chemicals and planned to put in a new ventilation system, problems persisted.

“We tried to use a water-base adhesive, which did not work for us,” a Royale official wrote, adding that the company saw no alternative but to stick with nPB glue.

Other companies were also reluctant to switch from nPB glues. Officials of the Franklin Corporation, a cushion plant in Houston, Miss., explained in court documents that safety was important but that nPB glues were attractive because they dried so fast that the cushions could be produced in a third of the time.

“There are people lined up out there for jobs,” said John Lyles, a vice president at Franklin, according to testimony by a plant manager in a successful lawsuit in Mississippi brought by four cushion workers who suffered severe nerve damage from the glue. “If they start dropping like flies, or something in that order, we can replace them today.”

Businesses found nPB appealing partly because the E.P.A. had given it an endorsement of sorts by adding it to a list of chemicals that do not harm the ozone layer. But an unintended effect of that action was to allow sellers of the chemical to market it as federally approved, “nonhazardous,” green and worker-friendly.

As the chemical’s popularity grew, E.P.A. officials worried about its use in spray glues, especially in cushion-making factories where the agency had determined that even with “state of the art” ventilation, “nPB-based adhesives cannot be reliably used in a manner that protects human health.”

Environmental officials figured that OSHA, pressured by the Bush administration and Republican lawmakers to be more business-friendly, would not be capable of policing the growing threat. “OSHA is tough,” E.P.A. officials said, according to notes from a November 2006 meeting on concerns about nPB. “But their budget is small, and they are not going to crack down on small businesses.”

OSHA has never set a standard establishing safety limits on workers’ exposure to nPB. The E.P.A. recommended such a limit and considered banning the nPB glues, but it has yet to finalize the plan. It determined that most cushion companies using the glue had fewer than 100 employees, which meant they were less able to absorb the cost of another regulation.

“There just wasn’t the political will,” an E.P.A. official who was part of the decision-making said on the condition of anonymity.

Improvised Remedies

A single tattered page from a 2005 workers’ compensation log summed up the emerging situation at Royale. Beneath a column headed “Injury or Illness” stretched a dozen rows, each reading “Alleged Neurological Injury” — one for each worker in the Conover plant sickened in the first three months of the year. Each missed more than 40 days of work because of the glue fumes, which were especially intense after the company moved the work stations closer together.

Thousands of additional pages of court and government documents, as well as interviews with more than two dozen current and former employees — some speaking on the condition of anonymity — present a fuller view of the conditions in the plant and how things got that way.

By 2005, Efrain Robles Avila was using a walker because he could no longer stand on his own, according to medical records. Victor Gonzales, a father of three, needed help putting on his clothes because he had lost control of his hands. Laura Garcia, who had worked for Royale for less than a year, complained of a cold numbness running from her waist to her toes. “It was like your legs didn’t receive the signal when you had to walk,” she said in court documents.