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Scientists at Utah's Division of Air Quality are zeroing in on a few key chemicals after a newly released study of toxic air pollutants found elevated levels of hazardous substances on the Wasatch Front.

The year-long effort, which looked at 86 of the more than 180 substances classified by the Environmental Protection Agency as "hazardous air pollutants," or air toxics, identified four areas of concern — airborne lead particles, particularly on the western side of the Salt Lake Valley; localized concentrations in Bountiful of a carcinogenic solvent known as methylene chloride; and concentrations of formaldehyde and acetaldehyde, both probable carcinogens, across the Wasatch Front.

But the study also comes bearing good news: concentrations of benzene — a carcinogenic pollutant associated with leukemia, reproductive abnormalities, and blood disorders such as aplastic anemia — dropped nearly 70 percent between 2002 and 2016 in West Valley City. Bryce Bird, director of the DAQ, said emissions of benzene — primarily released by automobiles, gas stations and the combustion of other fossil fuels — have decreased as motor fuels have become cleaner.

On the other hand, concentrations of formaldehyde and the similar acetaldehyde are increasing, Bird said. Both are related to combustion, but are also emitted by everything from plants to large industrial sources. The two chemicals were elevated at all three of the study's sample sites — Lindon, West Valley and Bountiful — and there's no immediately obvious source, Bird said. The results suggest that there are both localized and widespread air quality issues that Bird said will require additional research.

Cancer risk • While several pollutants were found to exceed thresholds the EPA believes are associated with adverse health outcomes, Alan Matheson, executive director of the Utah Department of Environmental Quality, said he did not see "anything that causes real concern."

"We feel an obligation to give people information that is meaningful," he said. "We don't want to create an unnecessary panic, but we don't want to downplay things either."

Matheson pointed out that the thresholds used by the EPA are based on statistical probabilities — cancer-related thresholds, for example, are based on the concentration at which exposure to a substance is believed to cause 1 in 1 million individuals to develop cancer. Overall, Utah's risk for these outcomes is low. A separate report released last December by the EPA, based on data from 2011, found that hazardous air pollutants will cause about 29 of every 1 million Utah residents to develop cancer in their lifetime, Matheson said.

That report identified Salt Lake as the county with the greatest risk associated with air toxics. The EPA estimates about 43 of every 1 million Salt Lake County residents will develop cancer due to exposure to harmful air pollutants. So, based on the county's 2010 census population of 1,029,655, the EPA's figures suggest these specific pollutants will cause 45 individuals in Salt Lake County to experience cancer.

In comparison, the EPA estimated that in Los Angeles County, air toxics could cause about 43 cases of cancer per every 1 million residents. Though that's roughly the same as Salt Lake County's risk rate, Los Angeles had some neighborhoods where the local cancer risk was as high as 114 cases of cancer per 1 million residents. Salt Lake County's most at-risk neighborhood, in downtown Salt Lake City, had a risk factor of 58 cancers per 1 million residents.

And for residents of Utah's many rural counties, the cancer risk associated with air toxics is considerably smaller. Based on the EPA's risk factors and the 2010 census, air toxics are estimated to be responsible for less than one incidence of cancer in every county except Cache, Washington, Weber, Davis, Utah and Salt Lake.

Matt Pacenza, executive director of HEAL Utah, praised the state for pursuing an independent analysis of air toxics data, which he said allows the state to consider in greater detail how air quality may vary from one area to the next.

"I think people tend to think, 'I live near this one giant factory so I should be worried,' but it could be proximity to much smaller facilities that you may not think about" or could be related to factors such as airflow and elevation, Pacenza said. "This study should really send a message of 'gosh, we need to be looking carefully in all kinds of places to see what kinds of concerns are out there."

Toxic unknowns • But Pacenza said the limited scope of the state's study — and its inability to identify the source of some of the pollutants, including formaldehyde — had him wondering whether there are other, potentially larger concerns that were not detected.

At all three of the report's sites, concentrations of formaldehyde were found to exceed not only the EPA's cancer threshold but also a higher standard that's associated with non-cancerous health effects.

Formaldehyde is associated with lung and nasal cancers, and has an inflammatory effect on the pulmonary system, said Steve Packham, a toxicologist with the Utah DAQ. It's of concern to individuals with chronic conditions — formaldehyde exposure can trigger an asthma attack, for example — and long-term exposure can affect healthy individuals as well.

Beyond the immediate health effect, Bird said, concentrations of formaldehyde on the Wasatch Front warrant additional attention from the state because it is a precursor chemical that contribute to two larger pollution problems in Utah — small particulates (classified as PM 2.5), and ozone.

Most of the Wasatch Front is considered a nonattainment area for failing to meet the EPA's health-based standards for exposure to PM 2.5. Much of the same area will likely fail to meet the EPA's new standards for ozone, Bird said.

Bird said the DAQ has applied for funding to collect more detailed air quality data to attempt to pinpoint possible sources of formaldehyde.

Pacenza said he'd urge state leaders to support these efforts. "They're doing a really good job ... but I think we can all agree that it's alarming to say that we have a problem [and] we don't know where it's coming from."

Investigations pending • Another mystery that has intrigued DAQ scientists is the sudden increase in concentrations of methylene chloride in Bountiful. Levels of the solvent were more or less normal there until 2008, when concentrations of methylene chloride jumped dramatically, pushing Bountiful above the level at which the EPA believes exposure to methylene chloride will cause cancer in approximately 1 in one million individuals.

The nature of the data suggests that a single source began emitting the chemical in 2008, and has continued to operate more or less 24/7 since, Bird said. But the source of the emissions has yet to be identified.

Methylene chloride is used in paint strippers, the manufacturing of pharmaceuticals and electronics, and in various aerosols, foams and paints. Bird said he was reasonably confident the chemical was not coming from a large industrial source, which would need a permit from the DAQ to release such chemicals, suggesting that the source in question may be a small business or even an in-home operation, such as an auto body shop.

The Davis County Health Department is also investigating possible sources, Bird said.

But the DAQ has no plans to further investigate airborne concentrations of lead, though the division's report found levels in West Valley and Bountiful at times approach or even exceed the EPA's action level of .015 micrograms of lead per cubic meter of air.

Bird said the overages did not appear to be a health concern. Most lead-related health effects documented in Utah are associated with exposures related to older homes and buildings with, for example, lead-based paint, he said, and the elevated levels of lead on the Wasatch Front are likely tied to historical mine activity in the region.

Brian Moench, president of Utah Physicians for a Healthy Environment, said he believes the state is downplaying the severity of its lead data, pointing out that Kennecott continues to emit lead into the Wasatch Front environment.

"Like most heavy metals, lead is not destroyed, does not degrade, and is not combustible," Moench said. "Therefore the lead exposure for the residents of the Salt Lake Valley slowly and steadily increases."

Utah Physicians for a Healthy Environment recently joined the American Medical Association in calling for more lead testing to identify children with elevated levels of the heavy metal in their blood. Only about 3 percent of Utah children are tested, despite recommendations from the CDC that all children ages 2-5 get screened.

Overall, Moench said, he was pleased to see the state taking on the issue of hazardous air pollutants.

"The air toxics component of our community's pollution problem does not get the attention it deserves, given the danger that these compounds represent to human health in causing cancer, impaired fetal development, and likely association with many chronic diseases. The findings prompt the call for more investigation, and we hope the Legislature will accept the need to fund follow-up studies."

Pacenza also called on state leaders to provide more funding for air quality and monitoring, and said he was discouraged by developments in the last legislative session, when the DAQ's request for funding to upgrade and expand its air monitoring network was only partially approved.

"We're doing better every year," he said, "but we still have a pretty crude picture of air quality and environmental health."

Bird said the DAQ has been working with the EPA to monitor air toxics from a site at Viewmont High School in Bountiful since 2003. That site, he said, was selected because of its proximity to several oil refineries and other industrial operations that could lead to exceptionally high concentrations of hazardous air pollutions in that neighborhood. In order to determine how the data from the Bountiful site relates to the rest of the Wasatch Front, the DAQ conducted an independent analysis of the Bountiful data and compared it to data from two additional sites in Lindon and West Valley.

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