The U.S. Department of Agriculture is reviewing research showing that new bacteria-killing chemicals used in chicken slaughterhouses may be masking the presence of salmonella and other pathogens that remain on the birds that consumers buy, according to records and interviews.

Academic researchers agree that the chemicals could be overwhelming an antiquated testing process. Several of the scientists have been enlisted by the USDA’s food safety experts to help resolve the matter.

The issue came to the department’s attention this spring after chemical companies pointed to academic research that shows there could be a problem and told the USDA that further study was needed.

“This is a valid concern,” said Catherine N. Cutter, chairman of Penn State University’s Food Safety Impact Group, whose scientific work was referenced in materials that chemical companies provided to the USDA.

The controversy comes as the number and strength of chemicals used on poultry-processing lines is increasing as plants scramble to meet new USDA demands to slash pathogens.

Chemicals might be masking chicken safety-test results

Some experts say the rising tide of chemicals may be causing unanticipated side effects. Some USDA inspectors said they believe such chemicals can contribute to a host of medical problems, including respiratory ailments and persistent skin rashes, The Washington Post reported in April. The Occupational Safety and Health Administration is conducting a follow-up investigation into a New York poultry plant where one inspector, who was profiled in the Post story, died after his lungs bled out in 2011.

The latest allegations — that the stronger chemicals are undermining testing — are spurring finger-pointing among rival companies competing to sell their products to chicken processors. The companies say their competitors are the ones tripping up the tests.

At issue in the latest allegations is the testing procedure the USDA requires. 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.

Scientists say in order for tests to be accurate, it is critical that the pathogen-killing chemicals are quickly neutralized by the solution — something that routinely occurred with the older, weaker antibacterial chemicals. If the chemicals continue to kill bacteria, the testing indicates that the birds are safer to eat than they actually are.

Several chemical companies, which all have a financial stake in the issue, were present at a June briefing on the matter with USDA officials. The department’s food safety experts asked for the briefing this spring after the chemical companies raised concerns.

Jon Howarth, a scientist and technical director of California-based Enviro Tech Chemical, who took part in the meeting, said some of the newer chemicals are not deactivated in the solution.

The company’s scientists put together a lengthy PowerPoint presentation that cited research from a USDA scientist and several university scientists that they believe backed up their assertions about the new chemicals.

“Is it any wonder that the USDA-FSIS data shows the slaughter plants are doing well?” said one of the PowerPoint slides, referring to the department’s Food Safety and Inspection Service. Over the past few years, poultry plants have cut salmonella rates in half, according to USDA test data.

The dramatic reduction in salmonella rates has raised suspicions about the tests among USDA inspectors, a union representative said. “I don’t really know if the new treatments are working or if it’s giving us all false hope,” said David Hosmer, president of the Southwest Council of Food Inspection Locals.

Howarth, who was a main presenter at the briefing, said, “Food is safer; just not as safe as the tests are showing.”

He added that he believes the problem with the testing explains why the number of people getting sick from salmonella in poultry has not dropped in recent years even though the tests results have improved.

Widely used chemical

The chemical that came in for the greatest scrutiny at the USDA briefing was cetylpyridinium chloride (CPC), which is supplied to poultry plants by Safe Foods, an Arkansas company. Over the past three years, CPC has become the finishing rinse of choice in about 30 percent of poultry plants nationwide.

Officials of Safe Foods, which is a competitor to Howarth’s company, Enviro Tech, were not at the briefing.

Enviro Tech recently posted a YouTube video showing a laboratory experiment that the company says proves CPC is not neutralized if not adequately rinsed when the test sample is taken and therefore produces false test results, sometimes called a “false negative” or “false kill.” It makes no mention of Safe Foods. However, within hours of the video’s posting, a Safe Foods attorney threatened the company with a cease-and-desist order, saying the video includes “inaccurate and misleading information.”

In an interview, Safe Foods President Rush B. Deacon dismissed criticism of his product as “potshots” from competitors. “We did our own tests to make sure we are giving a real kill and they showed we are,” he said.

Deacon said his scientists believe the older acid-based solutions, such as the ones Enviro Tech makes, are more likely to produce false test results if “testing protocols are not followed.” Such protocols would include properly neutralizing the chemicals.

Besides CPC, other chemicals getting a closer look from USDA include formulas containing high levels of peracetic acid (PAA) and acidified sodium chlorite. Their use has become common over the past few years in nearly all the nation’s poultry slaughterhouses, scientists and experts in the poultry chemical industry said.

Scott M. Russell, an expert on poultry processing and a professor at the University of Georgia, was a presenter at the USDA briefing and plans to work with the department and other researchers to identify ways to ensure that all chemicals are neutralized prior to testing.

Failure to neutralize the chemicals “could be happening,” Russell said. “There is variance in the data that doesn’t make sense. Further investigation is needed.”

The National Chicken Council, a trade group that represents poultry processors, said it believes the current testing is reliable. “These processing aids are diluted significantly, break down in water to non-harmful substances, are rinsed off after their application and are used to make chicken products safer,” said Ashley Peterson, the group’s vice president of scientific and regulatory affairs.

In a statement about the June briefing, USDA officials said they frequently have such discussions with a “wide variety of researchers and stakeholders” and that they are currently assessing Russell’s work and “will take appropriate steps to adjust our policies and procedures if warranted to ensure that America’s supply of meat and poultry are safe to eat.”

Russell said the research should take between six months and a year to complete and will likely be funded by the chemical companies and through research grants.

Variety of issues

The scientists will look at a variety of issues, including whether the greater concentration of chemicals and the rising number of chemical treatments are causing false test results.

The presentation to the USDA showed that the number of chemical treatments on chicken processing lines has grown from an average of two to four since the early 2000s. It also showed that the chemicals are not as diluted as they were in the past. For example, in 2000, peracetic acid solutions were approved for use at strengths no greater than 220 parts per million. But in 2009, a PAA-based formula was approved at strengths of up to 2,000 parts per million, records show.

CPC is used at concentrations as high as 8,000 parts per million during a new step that has been introduced at the very end of the processing line, records show.

Through the 1980s, most poultry plants used simple solutions of chlorine and water at 20 to 30 parts per million, records show.

Alice Crites contributed to this story.