Every summer the same pattern repeats: the temperature rises, the streets fill with tourists and, almost without us noticing, air quality in cities gets worse. It’s not a coincidence. Heat speeds up the formation of tropospheric ozone in the atmosphere, and on top of that comes the extra traffic that peak season brings. In some areas, you also have to factor in haze or smoke from nearby wildfires, two phenomena that have become quite a bit more frequent in recent summers than we’d like.
As a result, July and August tend to be the months with the most poor air quality episodes in cities, right when the most people are out enjoying the good weather. That’s why more and more city councils are turning to real-time environmental monitoring, instead of relying on isolated measurements that don’t tell the full story.
A problem made worse by the heat
High temperatures don’t just make summer harder to bear. They also speed up chemical reactions in the atmosphere that drive up concentrations of tropospheric ozone, one of the most harmful pollutants for respiratory health. Unlike other pollutants that come directly from an emission source, tropospheric ozone forms in the air itself, through a reaction between other gases and sunlight. That means it can show up even far from where the problem originated, and its peaks almost always coincide with the sunniest, hottest days.
And right when this happens, the city sees more visitors and more road traffic, so the problem feeds itself: more cars, more ozone precursors, higher concentrations during the middle of the day.
What air quality sensor networks change
Installing a network of sensors across the city, instead of relying on two or three fixed stations, changes things quite a bit. For years, an entire city’s air quality has been summed up by the reading from a single monitoring station, usually placed at one specific spot that doesn’t always reflect what most of the population actually breathes. With a distributed IoT sensor network, that blind spot disappears.
You get a much more accurate picture of what’s happening neighborhood by neighborhood, not just a citywide average. A narrow street with heavy traffic and a park five hundred meters away can have very different pollution levels, and until now that difference was invisible.
It becomes possible to issue early warnings when pollution rises, which is especially useful for older adults, children, or anyone with respiratory conditions, who can adjust their routines before things get worse.
City councils gain objective data to base decisions on. For example, whether it’s worth restricting traffic during a specific episode — rather than relying on estimates or public perception.
Historical data builds up over time, making it possible to check whether a mobility measure or an urban planning change has actually worked, something that used to be almost impossible to prove with hard data.
From perception to evidence
Before this sensor network existed, air quality was judged somewhat by feel, or using data from stations that only covered one very specific spot in the city. If the air smelled off one day, or visibility was worse than usual, people assumed pollution was high, but there was no easy way to know to what extent, or in which areas exactly.
Now, data makes it possible to move past that perception and work with real evidence. A municipal technician can check in real time how a pollutant’s concentration is evolving at different points in the city, cross-reference it with the time of day or recorded traffic, and make decisions backed by that data. This helps public policy rely on up-to-date information rather than assumptions, and it also helps communicate more clearly to the public what’s happening and why.
It’s not just about the environment, it’s public health
Ultimately, keeping an eye on air quality in summer isn’t just an environmental issue: it’s a public health one. Episodes of high tropospheric ozone have been linked to a rise in respiratory and cardiovascular emergencies, particularly among the most vulnerable populations. Having this information in real time makes it possible to act early, issue warnings before the problem becomes noticeable, and ultimately reduce that impact on health.
Cities that have access to this information can respond sooner, and that makes a real difference exactly when their population needs it most. It’s not just about measuring for the sake of it, but about turning that data into decisions that make a tangible difference day to day: less traffic during a critical episode, a timely warning for those who need it, or a mobility policy that, over the years, proves it has improved the air we breathe. At Nealis Tech, we help cities and public authorities deploy this kind of environmental sensor technology.
