When Upton Sinclair wrote "The Jungle" in 1906, he hoped that the horrific conditions he described at Chicago slaughterhouses would shock the nation into helping the "workingmen of America," the people to whom his book was dedicated.

Instead, the nation was more appalled by stories of dead rats being shoveled into sausage-grinding machines than worker exploitation. "I aimed at the public's heart," Sinclair famously said, "but by accident I hit in the stomach."

But as Ted Genoways demonstrates in "The Chain," an expansive view into the inner workings of the modern meatpacking industry, workplace conditions and food safety are closely related. Since the 1990s, he writes, a dramatic acceleration of automated-line speeds at U.S. packinghouses has led to an alarming increase in worker injuries and violations for contaminated meat.

Genoways begins his exposé with a little-known experimental inspection program piloted by the U.S. Department of Agriculture (USDA) in 1997. The program reduced the number of federal hog inspectors, and companies could increase line speeds beyond previously imposed limits at five participating pork processing plants.

With fewer hands to prod and squeeze the glands of each carcass, the conveyor-line speed at pork processors rose dramatically. By 2006, the line speed at a Hormel plant in Fremont, Neb., increased from 900 head per hour to as many as 1,350 head per hour.

But the faster production lines came at a heavy cost.

The conveyor belt was moving so fast at Quality Pork Processors in Austin, Minn., Genoways writes, that hog heads started piling up at the Plexiglas shield that guarded workers from the spatter of a device known as "the brain machine." Workers on the other side of the shield would insert an air hose into the back of each pig skull and blast the pig's brains into a pink slurry. The production was so fast that the air never cleared between blasts of the brain machine, coating workers "in a grisly mix of tissue and blood," Genoways writes.

Investigators concluded that inhaling aerosolized pig brains caused permanent neurological damage among some affected workers. One worker, not even 20 years old, was robbed of bowel control and forced to insert a urinary catheter four times a day. The chief culprit was increased line speeds, which made the already grisly job of blasting pig brains even messier.

"The Chain" would be disturbing enough if it ended there. But Genoways describes the atmosphere of fear, including anti-immigration hysteria in the Midwest towns where the pork processors operated, which kept Hispanic workers from demanding safer conditions.

At least six workers affected by the neurological disorder were fired for lacking proper documentation. Others incurred tens of thousands of dollars in medical bills, only to have their disability claims denied by the factory's insurer.

Genoways makes a compelling case that the meatpacking industry's relentless drive for higher output poses a threat to food safety. Three of the pork processing plants that participated in the USDA pilot inspection program had among the worst food safety compliance records in the nation.

Chris Serres is a Star Tribune reporter. On Twitter: @chrisserres