Fourth of July 🇺🇸, Canada Day 🇨🇦, Bastille Day 🇫🇷… seems like half the world is out celebrating this month! And where there’s a festival, there are fireworks-and where there are fireworks, there’s smoke! So how badly do fireworks affect air quality? 🎆

Our in-house Atmospheric Scientist ran the numbers in Los Angeles, Houston, Chicago, and New York this Independence Day. The graphs above show some moderate to high ozone pollution that afternoon – reasonably common in summer. The big spikes in the evening though? Particulate matter. Likely due to smoke from this year’s displays.

While this means those with sensitivities should take extra care during fireworks shows, most of us shouldn’t sweat it too much. Pollution above 100 on our Plume Index only becomes harmful if breathed in for more than an hour. Cumulative exposure is what’s important, and the peak is mostly gone by morning!

However, an extra PM peak can conspire with existing pollution cycles to ruin what would otherwise be a fresh air moment. For example, take a look at the graph below showing our overall Plume AQI for LA – it takes its value from the pollutant most affecting your health at any given moment. You can see that a cumulative effect begins to stack up.

What can we expect to see in Paris on Bastille Day this year? Here’s a look at the pollution trends from July 14th 2019.

Paris pollution July 14th 2019

Similar to the trends in US cities, we see a massive spike in particulate matter lining up perfectly with the fireworks display. What’s really interesting about this graph is the low levels of PM2.5 when we compare it with the high levels of the larger PM10.

This is a result of the hyper-local nature of pollution. There was only one ground station in Paris showing the massive spike in Particulate matter (Champs Elysées) and that particular station does not have a PM2.5 sensor! So what you are seeing in the average city level of PM2.5.

Firework peaks also depend on the weather. For example, it rained in Washington DC this 4th of July in 2017, so any fumes from the fireworks were quickly washed away.