CHICAGO (Reuters) - Workers in U.S. chicken and pork plants face higher risks than other manufacturing workers for musculoskeletal disorders such as carpal tunnel syndrome, according to two studies the U.S. Department of Agriculture issued on Friday.

The findings highlight health concerns for employees who often perform repetitive tasks and use dangerous equipment, including sharp knives, to process meat for consumers. Those roles are disproportionately filled by immigrants and undocumented workers.

More than half of all U.S. meatpacking workers are immigrants, compared with about 17% of the entire workforce, according to the Center for Economic and Policy Research, a think tank.

A USDA-funded study of 1,047 poultry workers at 11 plants operating at faster processing speeds found that 81% of employees were at increased risk of musculoskeletal disorders. Researchers compared their risk for carpal tunnel syndrome to another study of 4,321 manufacturing workers.

Poultry workers who handled more chicken per minute faced higher risks than those who worked at a slower rate, though there was not an association with faster processing line speeds, the study found.

Meat companies are improving processes and equipment to reduce injuries, said the Meat Institute, an industry group that represents producers such as Tyson Foods and JBS USA.

"It is possible to maintain worker safety standards while operating at increased line speeds," the institute said.

In pork plants, 46% of 574 evaluated workers were at high risk for musculoskeletal disorders, and the effect of increased line speeds varied between establishments, according to another USDA-funded study.

Several workers expressed concerns about reporting pain to their supervisor due to the risk of retaliation or out of frustration that their problems would not be helped, the study said.

"Everyone works in pain and is afraid to speak out," one pork worker said, according to the study.

Dangers go beyond the musculoskeletal injuries detailed in USDA's reports, said Stuart Appelbaum, president of the Retail, Wholesale and Department Store Union, which represents more than 15,000 poultry workers.

"Poultry workers toil in cramped, cold conditions, slicing up birds thousands of times per hour as chickens rush down the line," he said.