Solving a mystery: Why Tri-City ozone levels rival Seattle area

It’s not unusual to find high levels of ground-level ozone downwind of big cities, where there’s lots of traffic and big industries.

But the Tri-Cities?

Air quality specialists were surprised to find ozone readings here are nearly as high as those downwind of Seattle.

“It’s a bit baffling,” said Ranil Dhammapala, atmospheric scientist for the Washington State Department of Ecology. “We really don’t know why it is high.”

The Department of Ecology is launching a study this week with support from the Benton Clean Air Agency to figure out the mystery.

Ozone in the earth’s upper atmosphere is good, shielding people from harmful ultraviolet radiation.

But high levels near the ground are a health hazard. It can aggravate asthma, inflame and scar lung tissue, and make people more susceptible to bronchitis and pneumonia.

Children, the elderly, people with lung disease and those who work hard or exercise outdoors are most at risk.

Too much ozone also can lead to increased federal regulation for this area.

The Tri-Cities, with just one year of official data on ozone levels, has come close to exceeding the federal limit. If the limit is exceeded for three years in a row, the state will be required to develop a compliance plan that could be subject to federal oversight for the next 20 years.

Among other requirements, businesses would find it more difficult and more expensive to comply with stringent permitting rules for any expansion that might add to the community’s ozone levels.

But by determining more about the sources of the ozone, steps could be taken to stay within federal standards.

Ozone levels are usually highest in the Tri-City area on hot and sunny days with little breeze, said Robin Priddy, executive director of the Benton Clean Air Agency. But staff also have noticed that when there is a slight breeze from the north or northwest, ozone levels sometimes rise.

That gives credence to a theory that air flowing from the north across the Tri-Cities is pooling up against the Horse Heaven Hills on hot summer days, giving ozone time to develop.

Three things are needed to create ozone: nitrogen oxide, volatile organic compounds and the right weather. When the two types of pollutants mix and then are baked in sunlight on hot days, ozone is created.

Typically, cars and industry contribute to ozone, and the Tri-Cities is growing. But it is still far from the scale of Seattle, Dhammapala said.

Trees also play a role in increasing ozone by releasing isoprene, a volatile organic compound. Eastern Washington’s shrub steppe landscape is not known for trees, but the area does have tree farms. The fast growing trees picked for the farms give off particularly large amounts of isoprene.

Hanford also might be a contributor of nitrogen oxide, with its many trucks and diesel generators.

Adding to the conundrum is that Hermiston, on the other side of the Horse Heaven Hills, also has recorded some high levels of ozone, although not as high as the Tri-Cities.

Three weeks of pollutant data collection is planned to start Friday in the Tri-Cities, with a parallel effort across the state line planned by the Oregon Department of Environmental Quality working with Portland State University and the Confederated Tribes of the Umatilla Indian Reservation.

The Washington State Department of Ecology has contracted for assistance or equipment from the Washington State University at Pullman and RJ Lee Group. The state is spending about $150,000 on contracts, in addition to the staff time of the state and the Benton Clean Air Agency.

The Tri-City study will collect data at the Benton Clean Air Agency in Kennewick, the Burbank High School and at Mesa, where data is expected to show what is flowing into the Tri-Cities from the north. Mobile equipment also will be used to take readings on roadways.

Whether high ozone readings are a recent or long-term phenomenon for the Tri-Cities is not known.

In 2012 Washington State University modeling of ozone levels showed potentially high levels in the Tri-Cities, Priddy said.

That surprising prediction was followed with data collection using a temporary ozone monitor in 2013 and 2014. The monitoring showed some surprisingly high levels of ozone, she said.

A permanent monitor then was installed at the Benton Clean Air Agency office on Steptoe Street, with one year of data collected.

“It has not violated federal standards, but it is kind of getting too close for comfort,” Dhammapala said.

Study results are due in the summer of 2017.

While the source of the Tri-Cities high ozone levels may not be known yet, residents can help keep ozone levels in check.

The state has some tips beyond the obvious, such as driving less and turning off cars rather than letting them idle.

Summertime activities like mowing the lawn and barbecuing add to ozone levels. Residents may consider passing on those activities on the hottest summer days.

They also can use an electric mower or mow in the evening, and use propane rather than charcoal to barbecue, according to the Department of Ecology and Environmental Protection Agency

This story was originally published July 27, 2016 at 2:58 PM with the headline "Solving a mystery: Why Tri-City ozone levels rival Seattle area."