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Hazardous air pollutants (HAPs) are air pollutants that are known to cause or suspected to cause serious, adverse health effects. They come from a wide variety of industrial, residential, and mobile sources.
The Division of Air Quality (DAQ) conducted a year-long pilot study in 2015 to learn more about HAPs in the Salt Lake and Utah valleys. HAPs found along the Wasatch Front are commonly found in other urban environments.
DAQ compiled and analyzed the data from the study into a Hazardous Air Pollutant Report (4.5 MB). The report’s data analysis shows a significant decrease in one hazardous pollutant and periodic increases for three other HAPs, two of which — formaldehyde and methylene chloride — warrant further study. The highest concentrations of these two HAPs were observed in Bountiful, and the data show that the periodic increases for these particular pollutants are relatively recent.
All other HAPs detected in the study were found to be below threshold levels.
DAQ consulted with its toxicologist and the Utah Department of Health regarding possible health impacts from these specific HAPs. State health officials concluded that while poor air quality is always a health concern, it is unlikely that anyone would experience symptoms or harm to their health from exposure to these pollutants at these levels.
Exposure to HAPs at these levels isn’t zero-risk. DAQ believes strongly that ongoing study is needed to better understand these periodic increases and identify the causes and/or sources of these HAPs so the agency can apply appropriate emission controls. DAQ has developed a Scope of Work that outlines next steps in the study process. The division has also applied for funding from the Environmental Protection Agency (EPA) to conduct a follow-up study. The proposed study would involve intensive sampling at three different sites in Bountiful over a two-week period in the winter and summer.
Health Effects
The Clean Air Act does not set a health “standard” for HAPs, but rather assesses health risks based on thresholds for lifetime exposure. According to the Utah Department of Health, exposure to the formaldehyde and methylene chloride levels observed in the monitoring data are not likely to result in lasting harm to the health of residents in the study area. DAQ’s toxicologist has put the short-term exposure risks, even with the spikes in readings, far below the acute exposure threshold, even for the highest peaks in the study. Those living in the area are unlikely to experience symptoms.
HAPs Study History
Since 2002, Utah has conducted HAPs monitoring as a part of the National Air Toxics Trends Stations (NATTS) program. In 2013, the division conducted a rigorous analysis of HAPs data collected at the Bountiful monitoring site between 2002 and 2012. DAQ scientists decided to conduct a follow-up study after observing some atypical readings that raised possible concerns.
Legislative funding in 2014 provided DAQ with the opportunity to conduct a year-long HAPs study with more frequent sampling at the Bountiful monitoring site and two temporary sites in West Valley City and Lindon to collect additional data.
Study Observations
Monitoring data showed high formaldehyde levels along the Wasatch Front, but the Bountiful site had the highest concentrations, particularly in the winter. All three sites showed short-term spikes of formaldehyde. Formaldehyde levels tend to be higher during the summer, but elevated levels in the winter are unusual and merit further study.
The West Valley City monitor showed slightly elevated lead concentrations as compared to the Lindon and Bountiful monitors, perhaps due to past smelting and mining activity in the area, but not at levels that would show a health impact. The West Valley City monitor also showed a 70 percent reduction in benzene levels over the past fourteen years, likely the result of cleaner automobile technology.
Pollutant Characteristics
- Formaldehyde is used in the manufacture of resins for particleboard and is a byproduct of combustion. It can also be formed in the atmosphere from precursor pollutants. Many chemical compounds break down and become formaldehyde before they dissipate in the atmosphere.
- Methylene Chloride is not formed in the environment naturally. It is released by a number of industrial and residential sources. The most common is as a solvent in paint-stripping or as a cleaning agent in electronics production. It is also used as a propellant for aerosols, polyurethane foams, and paints.
- Lead is commonly emitted during mining operations and smelting activities.
- Benzene is commonly observed in urban areas and is associated with vehicle exhaust.