YAKIMA, Wash. — The Yakima Valley’s air quality often deteriorates when stagnant winter weather and the burning of wood stoves align, but a new study found that agricultural emissions also contribute to pollution.
Scientists from the state Department of Ecology and Washington State University found the amount of ammonium nitrate detected by air monitors in Yakima and Toppenish is far higher than levels typically found elsewhere in the state.
Particle pollution “is a complex mixture of a lot of different stuff, the majority of which is from wood burning smoke, but in Yakima 20 to 30 percent is this ammonium nitrate,” said Jeff Johnston, the science manager for the Ecology Department’s air quality program.
Less than 5 percent is typical, he added.
Researchers aren’t yet sure what implications the higher rate of ammonium nitrates might hold. They are just starting to look at how the different particles might have different health impacts, Johnston said, so it’s too soon to know if the ammonium nitrate has unique health risks.
The ammonium nitrate is not regulated on its own. Instead, the Environmental Protection Agency requires that communities monitor the total level of small particles in the air, including ammonia nitrate, wood smoke, exhaust and other things.
These particles are a serious health concern because they can be inhaled deep into the lungs and cause damage. Long-term exposure to high levels of the pollution is linked to decreased lung function, chronic bronchitis and premature death, according to the EPA.
Ammonium nitrate is what’s considered a secondary pollutant, Johnston said. It’s not emitted directly, but forms in the atmosphere when ammonia emissions from livestock operations and fertilizers mix with automotive exhaust.
Ammonia can come from nonagricultural sources, but in Yakima County, inventories have shown the vast majority come from agriculture, said Tim VanReken, the WSU scientist who led the study.
The study was conducted in January 2013 to take a detailed look at how weather conditions and pollutants interact in the atmosphere.
VanReken said that the chemical reactions are so complex that it is hard to identify effective strategies to reduce the pollution.
“It’s the combination of the meteorology, the ammonia concentrations and the vehicle emissions that make it hard to address,” VanReken said. For example, on clear, cold nights, more ammonium nitrate is formed than on cloudy ones, he said.
The next step, he said, is developing a computer model to look at all the connected chemical reactions to see what type of emission reduction strategies would work.
There are no plans for new regulations at this time, Johnston said.
Yakima County has been under the annual EPA limit for particle pollution since 2005, but just barely. If pollution increases slightly or the EPA tightens the standards, however, Yakima would need to find ways to cut emissions or face penalties.
The Yakima Regional Clean Air Agency is responsible for regulating air pollution in Yakima County, except on the Yakama Nation Reservation, where the EPA has regulatory authority. Clean Air Agency spokesman Mark Edler said he hadn’t had time to read the full report yet, but his sense was that the report was a step in a good direction.
“This could be another tool once we learn more,” Edler said. Current Clean Air programs to reduce air pollution by calling burn bans and helping homeowners replace old wood-burning stoves are working, he said.
He added that representatives from Ecology and WSU were planning to give a presentation on their findings to Clean Air at its board meeting next month.
The monitoring devices that Clean Air uses measure total particle pollution, Edler said, as required by law. The equipment needed to identify the different chemicals, as WSU used for this study, is more expensive.
The Clean Air Agency has requested additional monitoring equipment from the Ecology Department to install in the Sunnyside area, Edler said. One request was for a chemical identification monitor, but he said he didn’t know how the requests would fare.
Lower Valley residents have expressed concerns to the agency that it is not doing enough to monitor the conditions in the Lower Valley, particularly the emissions from large dairy operations.
Johnston said that a study taking more ammonia measurements in more places would be a good idea, but unfortunately, ammonia in the air is difficult and expensive to measure. No such study is planned at this time.