We now know the answer: air quality was very poor the evening of July 4th and the immediate morning hours, in some locations as bad or worse than previous years. Personal fireworks are clearly the mainstay of the air quality disaster of July 4th.
Let me prove this to you. Consider an image that will shock and awe…but in a bad way… showing the EPA Air Quality Index (AQI) at 4:30 AM Sunday (July 5) morning (PDT). Just scary. The U.S. really stands out with reds and even purples–from unhealthy to hazardous (the EPA AQI scale is shown below). Some of the worst air quality in the world. Very bad for folks with asthma and respiratory/heart issues.
AQI Map Courtesy of PurpleAir.com
Now, let’s zoom into the U.S. for the same time. The West Coast is particularly bad, with some locations getting into the hazardous zone (301 or more on the AQ scale). No issues in Canada.
Some areas in Los Angeles were crazy bad, with several locations getting above 400. Such values will make even healthy people feel unwell. Such levels can be sickening in vulnerable people.
Moving to Puget Sound at 4:15 AM, unhealthy conditions (red and darker) were widespread, but not as bad as LA.
And turning to a summary for the Seattle metro region, one can view the extraordinary degradation to hazardous level that occurred after 10 PM July 4th.
No wonder sunrise this morning in Seattle brought a smoky haze, as viewed by the Seattle PanoCam.
Not a morning to take a deep breath.
An important issue is how this year, without big community events, compares to last year, when the usual community fireworks displays were taking place.
Consider the Puget Sound Clean Air Agency site in South Park (south Seattle). Below are plots of concentrations of PM2.5–small particles that can move deep into your lungs–for this year and last. The values last year got to roughly 102 (micrograms per cubic meter of hour, one-hour average values. Clearly in the unhealthy range.
This year? It went even higher… around 120.
This comparison was no outlier. 2020 was worse than 2019 at many locations.
Thus, a reasonable conclusion is that personal fireworks and other home-based activities (like barbecuing) are a far more important source of July Fourth air pollution than the community displays.
Why was this year worse than last? The meteorology was favorable, but perhaps more important was that personal firework usage were up–at least the media were reporting this. And the personal fireworks bought at local “boom cities” appears to be larger and higher flying than in the past. Certainly, at my location in north Seattle the explosive concussions were the worst I have experienced and the rockets going up from Mathews Beach park were extraordinary–some almost professional level. My little dog was terrorized.
A question that is often asked is why don’t Seattle Police enforce the fireworks ban in the city on July 4th? Air quality declines to very unhealthy levels, animals are scared, homes and apartments are set afire (like the apartment complex in Tacoma), and kids are getting hurt. Maybe this is an issue for which we need more police, not less.