While short-term PM2.5 pollution is the only measure for which Eugene air quality fails to meet US Environmental Protection Agency (EPA) attainment, other pollution measures have room for improvement as well. Of neighboring cities, Eugene reported the highest PM2.5 levels in 2019 with an average annual concentration of 8.8 μg/m 3, but fared better than neighboring interior cities, such as Salem and Roseburg, in 2018, with a PM2.5 concentration of 7.1 μg/m 3. Both cities tied at #24 for worst short-term air pollution in the US out of 201 included cities according to the American Lung Association’s (ALA) 2018 State of the Air report. These high measured values are largely attributable to climatic conditions that trap emissions in the atmosphere rather than the increase in direct emissions.ĭenver air quality suffers from similar climatic conditions. In 2019, November and December were Eugene’s most polluted months respectively, with PM2.5 concentrations of 21.7 μg/m 3 and 16.8 μg/m 3, roughly 4 to 5 times summer levels. In Eugene, PM2.5 emissions tend to reach their highest levels during wildfire season in the late summer, early fall, and in the winter as a result of domestic wood burning. Thermal inversions in inland Oregon are particularly common during the winter when snow coverage, freezing conditions, and a lack of direct sunlight contribute to freezing ground-level air. When this happens, the cool ground-level air stagnates and is prevented from rising and dispersing, causing ground-level pollution emissions to accumulate. For example, when ground-level air is cooler than an air layer directly above it.
Thermal, or temperature, inversions occur when these conditions are disrupted. Under normal thermal conditions, temperatures decrease with gains in altitude. Temperature conditions can likewise play a similar role.
While wind and rain, for example, can disperse and tamp down particle pollution, a lack thereof can cause emissions to accumulate. This is because weather plays a critical role in pollution dispersion. While emissions are responsible for polluting the air with particles and gases, meteorological events such as wind, rain, and temperature conditions can significantly impact measured ambient air quality. To understand Eugene air quality, it’s important to understand the difference between air pollution emissions and measured air quality levels. PM2.5 pollution in Eugene comes from a combination of sources including vehicular and industrial emissions, wood and stubble burning, windblown dust and pesticides from agricultural land, pollen from the Willamette Valley grass seed farms, and transboundary pollution carried by wind from neighboring cities and states. In doing so, PM2.5 has the ability to affect a variety of organs, such as the heart and brain, among others. This is because PM2.5 describes matter so small that it’s able to cross the natural barriers in our airways and enter the bloodstream. Unlike gases and other commonly measured air pollutants, PM2.5 is defined by its size rather than its chemical makeup. PM2.5 includes a combination of airborne particulate matter including ash, soot, dust, dirt, pollen, and chemicals that measure 2.5 microns in diameter or smaller.
Eugene averages 6.2 unhealthy PM2.5 days per year, nearly double the federal allowance set at 3.2 unhealthy days per year. When it comes to clean air, short-term particle pollution (PM2.5) is of primary concern in Eugene, Oregon.
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