WASHINGTON — The U.S. Department of Agriculture is poised to finalize major changes to the poultry slaughter-inspection process that critics warn could threaten food safety and harm workers.

The proposed rule would allow companies to speed up production lines from 35 birds per minute to 175 per minute, a five-fold increase. It also would cut hundreds of federal inspector jobs and turn over much of the responsibility for spotting defective or diseased birds to plant employees.

The agency says that the proposal, which has been in the works for more than a decade, reduces the risk of foodborne illness by relying on scientific testing to screen carcasses, rather than the naked eye.

Under the rule, one inspector would be stationed at the end of every production line to eyeball chicken carcasses as they whiz by on hooks. Plant employees, rather than federal inspectors, would cull defective birds farther up the line. USDA officials say that frees up the agency’s remaining workforce to perform more important tasks elsewhere in plants, such as random testing for pathogens and monitoring of sanitation.

Inspectors shouldn’t be doing quality-control tasks that have little to do with protecting public health, said Elisabeth Hagen, the undersecretary for food safety at the USDA.

“There’s a role for visual inspection, but in this day and age it can’t be the only way that we define inspection for food safety,” Hagen said. “We’re not doing the right thing by the consumer if we do that.”

The USDA estimates that the changes will save taxpayers $90 million over three years and $256 million in production costs annually. Industry proponents say the new rule will modernize the poultry inspection system, which hasn’t been updated much since the 1950s.

“Look at the data. This is not something that USDA cooked up overnight,” said Tom Super, a spokesman for the National Chicken Council. “This has been in a pilot program for 13 years.”

Twenty broiler-chicken plants have volunteered as “trial plants” to test the proposal since 1999. The food-safety and worker-safety records in the plants are on par or better than those plants participating in traditional inspection, Super said.

“Chicken companies and their employees on this line have every incentive to not let a product with a quality defect into the marketplace,” he said.

Super points out that plants in other countries already run much faster. In Germany and Belgium, for example, line speeds typically reach 225 birds per minute, Super said. In Canada, the maximum speed is 250, he said.

Federal poultry inspectors protest that they can’t see bruises, blisters, tumors, pus, broken bones and other signs of tainted birds when carcasses fly by them at a rate of a third of a second. They can’t look inside the birds for bile, partially digested feed or fecal matter, or examine entrails for diseases such as avian leukosis — contaminants that inspectors say can be disgusting at best and dangerous at worst.

“The rule continuously talks about how much money per pound the plants are going to save by going into this process,” said Stan Painter, the chairman of the National Joint Council of Food Inspection Locals, a union that represents about 6,500 federal inspectors. “Why the hell is an agency concerned about the money that the plant’s going to save? I realize that’s a stakeholder, but our focus should be food safety.”

For Painter, who works as a USDA poultry inspector at a pilot plant in Crossville, Ala., opposition to the rule is personal as well as professional. He suffers from reactive arthritis after eating what he thinks was food tainted with salmonella or campylobacter bacteria at a sports event this summer in Texas.

After days of fever, headaches and diarrhea, Painter had lost 9 pounds and developed such painful swelling in his joints that he couldn’t even walk the 100 yards from his house to his mailbox. He said a doctor told him the condition likely was caused by foodborne bacteria, although it was too late to isolate which ones.

“People don’t realize — I didn’t realize — that you can get (arthritis) from eating something,” Painter said.

He and other union officials say his health troubles underscore the urgency of their longtime fight against the USDA’s proposed rule, which they believe will make chicken less safe for consumers by semi-privatizing poultry inspection.

Fewer federal inspectors in plants means fewer police on the beat, and more opportunities for plants to cut corners, Painter said. “If I know the cops are not going to be on the road in 50 miles, I’m gonna speed,” he added.

“The agency is looking at taking 817 inspectors off the poultry lines. I can’t imagine anything worse than that,” said Trent Berhow, a poultry inspector in St. Joseph, Mo., who’s the vice chairman of the union.

“A lot of people would say, ‘They’re just union blowhards thinking about jobs.’ No, we’re not,” Berhow said. “We’re thinking about lives. … It’s not about jobs. It is about food safety.”