Results from a Puget Sound Clean Air Agency study reveal emissions from Lafarge Cement are the likely source of an odor that has plagued and puzzled many residents of south Seattle for years.

Since 2001, residents in Highland Park, South Park, Burien and parts of West Seattle have complained of an odd smell that most described as bleach-like. Many contend the odor has caused scratchy throats, eye irritation and difficulty breathing.

Lafarge Cement, located on West Marginal Way just a few miles north from neighborhoods where most complaints stem from, has been a suspect in the past. But the plant is, and always has been, in compliance with air-quality standards, said Jim Nolan, compliance director for the Puget Sound Clean Air Agency. He added the agency's study did not find the odor to be a health hazard, only a nuisance.

Lafarge's cement-making process emits certain chemicals that can smell bleach-like, said Nolan.

A mixture of limestone, sand, iron, clay and other materials are heated in a kiln at about 3,000 degrees Fahrenheit. When the fuel is burned to heat the kiln, nitrogen oxide and sulfur dioxide are released into the air through Lafarge's smoke stack.

"These are both acid gases and they smell sort of acrid, a smell that can easily be described as bleach-like," Nolan said. A previous effort to locate the cause of the odor in the Duwamish area had ruled out bleach, chlorine and ammonia as possible sources.

The nearby Holnam cement plant uses a more modern chemical process to make its cement and has much lower emissions, said Nolan. It is not considered a source of the odor.

The agency used a technology called "open path." Ultraviolet sensors on monitor devices, located at the West Seattle Reservoir and in South Park, took samples of the air every few minutes from May to September for the past two years. They were tuned to detect sulfur dioxide and nitrogen oxide, said Nolan.

When they compared data from the devices with odor complaints reported from south Seattle neighborhoods, they found that when the wind blew from the north and high concentrations of nitrogen oxide and sulfur dioxide were detected, there were more odor complaints.

From a legal standpoint, there is no doubt that the smell is coming from Lafarge, said Nolan.

"All of the data we have indicates that when the wind blows from the north, complaints from these neighborhoods come flooding in," he said.

The previous year's study yielded similar results, said Mike Gilroy, manager of technical services for the agency.

But from a scientific perspective, Lafarge cannot be pinpointed as the source, said Gilroy.

"It is just impossible to trace a tiny nitrogen-oxide molecule back to one source" without considering other factors like emissions from automobiles or other facilities, he said

Russ Simonson, environmental manager for Lafarge, said it doesn't make sense that the odor could be coming from Lafarge.

The emissions are dispersed through the air, decreasing in percentage with distance, and Simonson said it is not likely people could smell such small percentages from a few miles away. Simonson also said he does not believe any of the 15 Lafarge plants in the U.S. have generated related complaints.

White Center resident Beth Lynch has been involved with tracking the odor investigation with Clear the Air, a community group that formed in 2002. She isn't so sure that it's just nitrogen oxide and sulfur dioxide that residents smell.

"I think it's more complicated than that," she said.

In 2002, the clean air agency issued Lafarge a notice of violation for emanating bleach-like odors.

"In this case we had evidence that Lafarge was the source of the odor because we could visually see the plume impacting the complainants," said Nolan.

In response to the violation, Lafarge hired Ron Hawks, an independent air-pollution specialist from Environmental Quality Management Inc. Hawks' study did detect chlorine coming from Lafarge, but the amount found was too low for humans to smell. Lafarge does not use chlorine in its cement-making process, so Hawks said it could have come from city water, which is treated with chlorine.

"The report, however, also showed that at times the Lafarge plume does touch down in the community," said Nolan. "When the plume impacts the ground the nitrogen oxides are above the odor threshold and are detectable."

As part of the settlement agreement to resolve the 2002 citation, Lafarge began installation of the Lucy Program last year. Lucy is a computer system that monitors emission levels and kiln operations. The system closely monitors the air, temperature and chemical levels within the kiln to prevent excess nitrogen- oxide emissions.

"It commands more gradual changes," said Simonson.

The new system is good from the air-quality standpoint and good for the plant because it makes its processes more efficient, said Nolan.

"We are always looking for ways to reduce negative impact on the environment," said Simonson. He said the plant's emission levels have decreased over the years but he doesn't attribute this to Lucy (that system is expected to be fully operational by the end of 2006). Changes in plant processes have lowered emissions, he said.

Citing the Hawks study, Lynch said Lafarge emissions may have decreased over the years. The study shows there were approximately 18 registered odor complaints in 2001, and that number rose to about 290 in 2002 and 250 in 2003, she said. Nolan said the agency registered 84 complaints in 2004, and 51 have been documented so far this year.

But the rise and dip in complaints could be attributed to residents getting burned out on calling in complaints, and not necessarily decreased odor occurrences, said Lynch.

Lafarge has recently applied for an "Order of Approval" from the clean-air agency to burn whole tires in its kiln, which the agency said could help reduce emission levels. The plant currently uses coal and petroleum coke as its primary fuel sources.

"Tires are better than coal because their chemical composition is more consistent than coal," said Nolan. "The kiln operates at over 3,000 degrees Fahrenheit and is capable of burning all the organics in the tires."

The Seattle plant also plans to add a new product called NewCem this year. This will require fewer raw materials, so Lafarge will be firing its kiln less. The plant expects emissions to drop during the high-heating process.

Results from the Puget Sound Clean Air Agency air monitoring study can be downloaded at www.pscleanair.org/spwsairmon. To report odor complaints call 343-8800.

Rebekah Schilperoort can be reached at rebekah@robinsonnews.com