Here’s how the system is supposed to work, Kindy writes:
As the chicken moves down the processing line, the bird is sprayed with, and bathed in, an average of four different chemicals. To check that most bacteria have been killed, occasional test birds are pulled off the line and tossed into plastic bags filled with a solution that collects any remaining pathogens. That solution is sent to a lab for testing, which takes place about 24 hours later. Meanwhile, the bird is placed back on the line and is ultimately packaged, shipped and sold.
But for the pathogen tests to be accurate, the bacteria-killing chemicals must be rapidly neutralized by the solution—"something that routinely occurred with the older, weaker antibacterial chemicals," Kindy writes. If the chemicals aren’t neutralized and instead continue working, the tests will deliver results indicating that the birds are more free of pathogens—and safer to eat—than they actually are.
There’s circumstantial evidence that new, stronger chemicals are indeed compromising the validity of the tests. For one thing, according to the USDA’s testing program, the rate at which salmonella is found on chicken carcasses has plunged by half over the past few years, Kindy reports. Great, right? Except that, according to the Centers for Disease Control, the actual rates of salmonella infection among the general public have barely budged. Salmonella still leads to more hospitalizations and deaths than any other food-borne pathogen. Poultry products are a major source of salmonella poisoning, the CDC reports.