Data Summary

Air Quality Data Summary for 2019

Fine particles and smog (ozone) are our greatest concerns in Puget Sound. These types of air pollution cause heart attacks, strokes, and even premature death. Air pollution is especially dangerous for children, the elderly, and people with lung or heart diseases.

In 2017 and 2018, we saw a lot of wildfire smoke with the highest ever recordings of fine particles since we started monitoring for them in 1999. Fortunately, we did not have any wildfire smoke in 2019, which kept the air quality much healthier. We also had a mild winter, with less wood smoke compared to past winters. Most days were in the GOOD air quality category, some MODERATE days, and three days that were UNHEALTHY FOR SENSITIVE GROUPS. The table below shows the air quality health categories over 2019 by county.   

2019 Air Quality, Days by Health Category

CountyGoodModerateUnhealthy for Sensitive Group
King280 days85 days0 days
Kitsap363 days2 days0 days
Pierce286 days77 days2 days
Snohomish272 days92 days1 days


Fine particles

Fine particles are tiny, microscopic pieces of pollution which are even smaller than a hair. These can easily enter the deepest part of your lungs and cause breathing and heart problems. In our region, they mainly come from wood smoke from home heating, vehicles, wildfires, and industry.

The graph below shows that all the sites had fine particle levels within the EPA standard (of 35 micrograms per cubic meter) on the majority of days in 2019. However, studies have shown significant health impacts below the EPA standard as well. Therefore, Agency has a health goal (of 25 micrograms per cubic meter), which was exceeded up to 5 days in winter months at various sites.  


Black Carbon

Fine particles that come specifically from diesel exhaust is our greatest concern as they carry the most health risks, but we can’t directly measure them and there is no EPA standard for them. Although not a perfect measurement, we use a “black carbon” monitor to estimate our impacts from diesel pollution. Diesel exhaust represents over 70% of the potential cancer risk from air pollution in the Puget Sound area. Most of the diesel exhaust in the region comes from four transportation sectors: maritime, off-road equipment, on-road vehicles, and rail. The graph below shows a reducing trend for black carbon since 2002. The levels have remained low in summer and higher in the winter, when the air is typically more stagnant. 


Ozone (also called “smog”)

Unlike fine particles and black carbon, ozone (smog) is created on hot summer days by chemical reactions with different types of air pollution from vehicles, industry, paints, solvents, and gasoline fumes. 

The graph shows that the ozone levels have been well within the EPA standard for the past few years. In 2019, we had a mild summer, which resulted in lower ozone levels.


National and local air pollution reduction programs

Nationally, large reductions in diesel exhaust are expected to continue thanks to the newer diesel fuel and truck engine standards that took effect in 2007. The newer trucks are 50 to 60 times cleaner than the older, dirtier trucks.  In 2011, an international agreement required incoming ships to use the cleanest shipping fuels along US coastlines (called an Emission Control Area) also reduces diesel exhaust in our area. EPA continues to develop rules to reduce air toxics emitted from large and small industrial sources, which we ensure are implemented by the industries in our four counties through our compliance program. 

Our Agency has also been working to further reduce air pollution on a local scale. With our Diesel Solutions program and the Western Washington Clean Cities Coalition, we partner with private and government organizations to reduce diesel exhaust. Through our wood stove replacement program, and continuing to ensure wood heating burn ban compliance, we’ve seen levels of wood smoke come down in our region over the years. We continue to pursue other opportunities to lower air pollution in the region, including greenhouse gas reductions.