Your neighbors may have poor air quality inside their homes due to everyday activities, not because they live near a pork operation.

“This is great news for pork producers and for our neighbors,” says Craig Christensen, an Ogden, Iowa, producer who runs a 2,000-sow, farrow-to-finish operation. “This study follows another project by the Iowa Department of Natural Resources, which shows that our way of life does not create odor that should require special considerations for schools, churches or other public gathering places.”

A 16-month, air-quality study measured ammonia and hydrogen sulfide concentrations on pork operations and neighboring residences. IowaStateUniversity researchers found that meteorological factors such as wind speed and solar radiation, affect hydrogen-sulfide and ammonia concentrations more than a hog operation’s size or the type of manure storage.

Steve Hoff, an IowaState agricultural engineer, conducted the study in 2004 and 2005 to examine hydrogen sulfide concentrations at the perimeter of nine pork operations throughout Iowa. He looked at ammonia and hydrogen sulfide concentrations near, as well as inside, residences located close to pork operations. He also took measurements in an area of the state that’s not associated with livestock. The nine study sites ranged from 1,200 to 4,800 finishing pigs.

Results show that at the perimeter of the nine sources, the overall average hydrogen sulfide concentration ranged from 1.9 parts per billion to a high of 26.3 ppb.  “As a frame of reference, Iowa established 30 ppb hydrogen sulfide as a Health-Effects Value measured at residences for the protection of “sensitive populations,” says Hoff.

He also collected hydrogen sulfide and nitrogen measurements at five residences, four of which were located near sites monitored for perimeter hydrogen sulfide levels.

At these sites, overall average ammonia concentration inside the homes ranged from a low of 28.6 ppb to a high of 94.7 ppb. Outside of the residences, the overall ammonia concentrations ranged from a low of 11.7 ppb to a high of 55.1 ppb.

Hydrogen sulfide concentration inside the homes ranged from a low of 0.7 ppb to a high of 2.5 ppb, says Hoff. Outside levels ran from a low of 0.4 ppb to a high of 2.4 ppb.  Obviously, they are well below Iowa’s Health-   Effects Value.

The study revealed that if researchers measured higher concentrations of either gas outside of the hog buildings, it still did not translate to high concentrations at nearby residences. The exception was if a residence was less than 0.4 mile (2,149 feet) from the hog operation and weather conditions were calm. 

Even at that close distance, hydrogen sulfide concentrations inside the residence measured less than half of the 30-ppb level.   

The IowaState study also found that ammonia concentrations inside homes tend to be more concentrated than ammonia levels in the air outside of a home or at a pork operations’ property line. Several sources contribute to a home’s ammonia levels, such as cleaning materials, pets and cigarette smoke. “The highest ammonia levels occurred inside a home where both adults were smokers,” notes Hoff. Some floor cleaners produce ammonia concentrations five to 10 times higher than the long-term concentration recommended by the federal government for sensitive people.

“The bottom line is that pork operations aren’t causing high ammonia and hydrogen sulfide concentrations at neighboring residences that are located at or beyond the required separation distance,” he says. “The concentrations are far below the federal level.”

Hoff hopes to do another project to further explore these gas levels inside homes under varying conditions. He wants to provide solid evidence concerning the hydrogen sulfide and ammonia levels that pork operations actually release.

The take-home message for the pork industry is positive — the air quality around pork operations isn’t as bad as some neighbors contend.

Linking Dust Particle Size to Odor

It’s not a new theory that dust particles in and around livestock confinement buildings carry odor. However, few researchers have dug into the connection between the size of those dust particles and the odor emitted.

But a recent laboratory study at IowaStateUniversity found that small dust particles carry more odor per weight and surface area than coarse dust.

“One of the implications from the study, is that as we work to develop effective odor controls for livestock operations, we must target fine dust,” says Jacek Koziel, assistant professor in IowaState’s agricultural and biosystems engineering department.

Steve Hoff, also a professor in that department, collaborated with Koziel on the research.

While the study was conducted mostly in a laboratory, Koziel says the real-life implication is that controlling swine dust has the potential to control odor.

In addition, the small particles carry a disproportionate fraction of the total odor, and they are able to travel longer distances from the source.

For the study, researchers placed three monitors that provide continuous, real-time measurement of airborne particles in a 1,000-head finishing building. They collected seven sets of swine-barn-particulate-matter samples during the three-month period, then evaluated the samples in the laboratory.

Fifty different compounds were identified in the samples. One surprise was that no previous studies had ever reported 21 of those compounds as being present in swine-barn dust.

Once researchers isolated the compounds, they used an instrument to identify different substances within a test sample. It is equipped with computer software and a “sniff port,” where trained panelists evaluate odors associated with each compound.

“The software records the aromas and odors caused by each chemical in a sample. It then records information about the odor intensity associated with each compound,” says Koziel.

From there, the researchers matched the odor-intensity data with dust-particle size. That’s how they determined the smallest particles absorb the most odor. Hoff’s previous research showed that filters can reduce odors by minimizing dust movement.

“Measurement equipment is becoming available to allow simultaneous assessment of chemical composition and the associated odor,” says Hoff. “This technology will help identify which compounds can help maximize odor reduction at the source.”

Koziel and Hoff hope to expand their past research and conduct new studies to find better ways to reduce odor by controlling dust, with an emphasis on the smallest dust particles.