June 8, 2004 in City

2002 field smoke study encouraging

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PULLMAN – Volunteers exposed in 2002 to field smoke from burning wheat stubble at pollution levels lower than in the recent past showed no adverse health effects, a new study has found.

Researchers from the University of Washington and Washington State University released their $500,000 study Monday in Pullman and Spokane before an audience of wheat industry officials, state regulators, journalists and clean-air activists.

They warned their study of health impacts on 33 Pullman subjects with mild to moderate asthma had limitations – including that all the people studied were young adults in their 20s and did not include children or vulnerable elderly.

Also, researchers said the 2002 fall burning season didn’t have the big spikes in smoke pollution that occurred in 2000 and 2001 before wheat growers and the state agreed on stricter smoke curtailment practices.

“No adverse health effects were observed – but the results should be interpreted with caution,” said Sally Liu of UW’s EPA Northwest Research Center for particulate Air Pollution and Health.

“The news is basically good, but it doesn’t mean there are no further questions. It just narrows down the range of questions a bit,” said David Kalman, chairman of the UW’s Department of Environmental and Occupational Health Sciences.

The study results aren’t a surprise but they contribute more to what’s known about health effects in a range of exposures to field smoke, a Pullman clean-air activist said.

“This study was looking at the lower end of our exposures,” said Patti Gora, the founder of Safe Air for Everyone. Community exposures were up to five times higher in 2001, Gora said.

The researchers wanted to study the impacts of field smoke on young children, but Pullman school district officials declined, they said. “Ideally, we would have liked very old or very young subjects, but we weren’t able to do so,” Liu said. National asthma rates are highest in children and young adults.

Tiny particulates in field smoke are called PM 2.5 because they are less than 2.5 microns in diameter, a size that can easily lodge in the lungs. A smoke “episode” that triggered health examinations for the study participants consisted of five or more 30-minute average PM 2.5 levels of 40 micrograms per cubic meter over 24 hours. Smoke episodes in 2002 occurred Sept. 11-15, Sept. 25-26, Oct. 17-19 and Oct. 24-26, the researchers said.

A day after the smoke episodes, many of the study participants did show an increase in exhaled nitric oxide, a colorless gas in the lungs that increases when asthma gets worse, said Joel Kaufman, a UW professor who monitored them for health effects. But 84 percent of the volunteers showed no worsening of their breathing problems and only 1 percent got markedly sicker, Kaufman said.

“None called their doctors or missed class or work…. no statistically significant effect was observed for all the markers of lung disease,” Kaufman said.

The study volunteers recorded a diary every 10 minutes, writing down where they were and what they were doing. They all lived near Pullman and worked or studied on campus.

In another study, Liu’s team is looking at how much smoke 10 wheat farmers were exposed to when they lighted the stubble in their fields last September and October. The PM 2.5 emissions where they were torching their fields in 2003 were dramatically higher than in the smoke drifting into nearby communities in 2002 – between 100 to 7,000 micrograms per cubic meter, Liu said.

Those study results will be presented this Thursday at a 10 a.m. meeting of the state agricultural burning task force at the Washington Department of Ecology in Spokane.

“The peak exposures (to) farmers are much higher … they’ve chosen to be exposed, but they didn’t know how high the exposures were until we conducted this study,” Liu said.

Wheat stubble smoke is different from bluegrass smoke, which a recent North Idaho study shows emits four times more biomass than wheat stubble, said researcher Candis Claiborn of WSU.

“In North Idaho, the (bluegrass) concentrations have been much higher. They are not really comparable” to wheat stubble emissions, Claiborn said.

The 2002 particulate health study released Monday was an offshoot of a legal settlement between Ecology and Save Our Summers, a Spokane clean-air group that sued over smoke levels in the air. Ecology contributed $225,000 to the study and the U.S. Environmental Protection Agency gave $50,000.

State regulators also worked with wheat growers to better control smoke in 2002, including metering smoke emissions and agreeing to burn earlier in the day, said Ecology’s Grant Pfeiffer.

The UW-WSU study results are encouraging, he said.

“This study says the program we have now is working pretty well. Our complaints are way down,” he said.

Gretchen Borck, spokeswoman for the Washington Association of Wheat Growers, agreed that the industry is making progress in reducing emissions. The growers have signed a memorandum of agreement with the state to cut their emissions in half by June 2006, down from a baseline 229,000 acres. They’ve already reached the 50 percent emission reduction goal, she said.

“In cooperation with (Ecology), we’ve been doing a good job. We’ve been using best management practices, metering burns and educating the farmers. We’ve been able to get a handle on this without losing burning as a tool,” Borck said.

Ecology also plans to further tighten its stubble-burning rules this year – another condition of the SOS settlement.

“We want to look at ways our program could be better,” Pfeiffer said.

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