The Science of Hog Farm Odors
Hog-farm odors are a bit like good art: You know it when you smell it. But in the North Carolina hog-farming lawsuit, an expert witness attempts to quantify smell with more scientific methods.
EDITOR’S NOTE: This article is republished with permission from North Carolina Health News.
When expert witness Shane Rogers steps into a witness box in federal court these days, he takes pains to explain why he thinks some hog farms in eastern North Carolina create nuisance-level odors.
First, the Clarkson University environmental scientist lays out his approach to feces forensics. He hunts for a very specific bacterium called Pig2Bac, a microbe native to the gut of swine that gets excreted with hog feces.
“If you have found Pig2Bac you have found pig feces,” Rogers this month told 12 jurors hearing the second of 26 hog farm nuisance lawsuits filed against Smithfield Foods, the largest pork producer in the world.
Allies to Smithfield, meanwhile, are working hard to counter Rogers’ narrative.
In court filings and elsewhere, those allies reject the argument that a bacterium from hog guts is a good proxy for unreasonable farm odors.
“Never in the history of the world has anyone used this as a proxy for odor,” said attorney Mark Anderson of McGuireWoods, the law firm representing Smithfield.
On top of that, Smithfield lawyers and their allies want jurors to hear results of company-funded studies that did not detect unreasonable odor on the farms, something the presiding judge in the case has so far rejected.
Where and how smelly?
The reliability of different methods to assess the intensity of hog farm odors is not on trial in these nuisance cases. But sometimes it feels like they are.
Neighbors won their first case, thought to be their strongest, against Smithfield this spring. In the current trial being argued in U.S. District Court in downtown Raleigh, believed to be a weaker case, Duplin County residents Elvis and Vanna Williams accuse Smithfield of producing nuisances at a farm owned by their neighbor Joey Carter.
Their home is a quarter mile from one of Carter’s two clusters of hog barns and about a third of a mile from one of his lagoons, according to their lawyers.
As in all the suits, the plaintiffs fault waste management practices on farms that a highly profitable company pays to raise millions of hogs a year here using company feed and strict company guidelines.
The farms pipe manure and urine from the long barns where swine are confined into open lagoons. From there they spray it onto nearby fields, which neighbors say generates excessive odors, which limits use of their property, creates mental discomfort, and prompts “reasonable” fears of adverse health effects.
During his testimony in trial number two, Rogers, a paid expert, told jurors he visited the Carter farm outside Beulaville in December 2016 to collect samples of air and swine waste inside Carter’s barns. After climbing into a small boat, he took samples of lagoon liquid too. Helpers swabbed the outside walls of homes near Joey Carter’s barns.
Laboratories detect Pig2Bac by finding sequences of its DNA, making it a biomarker fingerprint, said Rogers, an expert in the ways particulates and gases move from livestock farms. He detected Pig2Bac everywhere on the farm they sampled and on all the sampled homes nearby, including the siding of one home about 930 feet from the Williams residence. Not all plaintiff homes were tested due to budget constraints, their lawyers say.
Because bacteria native to a hog gut degrade quickly when exposed to air and sun, the tests likely detect only a fraction of the particles on the move, Rogers stressed.
“It’s a physical measurement of feces moving from one place to another,” Rogers said.
Research has shown that odors from hog operations are released as gases and particulates originating from barns, lagoons and effluent are sprayed on fields, Rogers said.
Because published research has detected Pig2Bac in the noses of hog farm workers, Rogers has told jurors that odorous waste particles may produce the smells some residents complain about.
That’s not the point of view of Anderson, the Smithfield attorney. While the Pig2Bac DNA biomarker has been used to detect swine feces in surface waters and elsewhere, Anderson finds no peer-reviewed studies linking it to odor detection.
To brief jurors on smell, Anderson wants Senior U.S. District Court Judge Earl Britt to admit results from Smithfield-funded odor studies conducted at the Carter farm from mid-September to mid-October of 2016 by a South Carolina engineering firm. That study was adapted from protocols developed by odor perception researcher Pamela Dalton of Monell Chemical Senses Center.
Dalton, an expert witness for Smithfield at the trial, interpreted the study’s results for the company. That study had people with average odor sensitivity monitor odors at the farm.
These monitors were trained to use a portable olfactometer, a device that allows people to smell the same odors mixed with varying ratios of filtered air. Over 30 days, hog smells were detected 323 times at the Carter farm, Dalton reported. It was perceived at the highest recorded dilution, seven parts filtered air to one part unfiltered air, just once.
In a brief Anderson submitted to Britt, Dalton reported that 7:1 odor intensity compares to the intensity of coffee scent in a coffee shop. In contrast, monitors have detected ugly odors in portable toilets at dilutions of 60:1, she noted.
“Testing from Dr. Dalton relates to a method that’s used not just in agriculture but across industry in an effort to evaluate odor levels,” Anderson said.
Britt has ruled against admitting the Dalton results because North Carolina regulations do not have a dilution threshold for objectionable odors on these farms and he concluded the test results could be misleading.
Anderson hopes to persuade the judge otherwise on this matter during the trials, in part because any new large swine farms could be subjected to an odor threshold assessments.
Such farms could not use lagoon and spray systems, however. Due to environmental concerns, lawmakers in 2007 imposed a moratorium on new hog farms with more than 250 animals using the technology to manage waste.
The Smithfield defense team has a cheerleader on this topic outside the New Bern Avenue courtroom. In the latest strong-worded criticism of the trials by industry and some powerful politicians, NC Pork Council CEO Andy Curliss on Wednesday posted a blog entry titled “At hog farm trial, crucial witness is… missing”.
Curliss argues that jurors should have the opportunity to hear Dalton’s test results and criticizes Rogers for, among other things, suggesting that detecting Pig2Bac near homes is evidence that hog farms emit odors.
One attorney for the plaintiffs said the Pig2Bac evidence is vital. It indicates that hog waste is moving off farms to homes, and that is important, said John Hughes of Wallace & Graham in Salisbury.
“We think the very fact that the Pig-2-Bac is on the homes violates the law. The hog producers act under a permit from the state. The permit says do not spray waste that drifts onto other people’s property. And Pig2Bac is waste that got on their property,” said Hughes, whose North Carolina firm is collaborating with the Michael Kaeske law firm of Texas.
Correction: This story was modified to make clear that Smithfield-funded hog farm odor study was conducted by a South Carolina engineering firm. The study was based on protocols published previously by Pamela Dalton of Monell Chemical Senses Center. Dalton interpreted the results for Smithfield and was an expert witness for the company at the nuisance trial.
Catherine Clabby (senior environmental reporter for North Carolina Health News) is a former senior editor at American Scientist magazine. She won multiple awards reporting on science, medicine and higher education for the The Raleigh News & Observer. She is an alumna of the year-long Knight Science Journalism Program at MIT. Contact: firstname.lastname@example.org
Video credit: Elsie Herring of Duplin County, North Carolina, describes her experience living next to a hog farm. The video is produced by the animal protection nonprofit Farm Sanctuary.