In the past, cities have primarily used a handful of automatic stations to monitor air quality. They are large, static, and expensive. Today, experts agree that data generated from these so-called ‘reference’ stations is insufficient because it fails to capture differences in air pollution levels across neighbourhoods.
Air pollution is the leading cause of premature death worldwide. Therefore, it’s crucial that cities are able to address the complexity of air pollution sources. One way to do so is by increasingly relying on their residents for community-led monitoring.
In this aspect, affordability is critical. Most initiatives collected by the CitiMeasure project on the CitiAIR tool – a comparability tool collecting organisations implementing participatory air quality monitoring – use diffusion tubes or lower-cost sensors. Both are small, inexpensive, movable, and intuitive.
Diffusion tubes and lower-cost sensors
Running without power, diffusion tubes can be deployed in remote locations. They gather pollutants whose concentration is later determined in a laboratory.
A major benefit is their accessibility. In the CitiAIR inventory, prices start as low as €7. Interreg used around 600 of these tubes to measure indoor air quality in Flanders, while CurieuzenAir even distributed 6,000 across Brussels.
Salviamo l’aria: NO2 NO Grazie – an Italian initiative for better air in Milan, Naples, Brescia, and Rome – used a model more suitable for assessing outdoor air quality, which comes at a slightly higher price, €18.
Unlike diffusion tubes, lower-cost sensors use electrical signals to identify pollutant concentrations and convert them into concentration values. Because they are more technically advanced, they are slightly more expensive.
Smart Citizen, a self-funded project by Fab Lab Barcelona, has developed a sensor kit for anyone interested in environmental monitoring for €100. Their kits travel well beyond Barcelona. I-CHANGE, a CitiAIR initiative implemented by 16 organisations from 12 countries, acquired 80 Smart Citizen kits to promote changes towards more sustainable behaviour.
The Sensor Community kit has had a similar impact. For €50, it can be used in various contexts, including school projects. One example is the CitiMeasure pilot project led by Senzorvzduchu, an NGO based in Prague. They introduced the kit to four schools to promote air quality monitoring and student awareness.
Both kits had the additional effect of being used as a learning tool too. People who had little to no expertise in environmental monitoring now know how to collect and interpret data and show a more substantial interest in protecting the environment and urban natural assets.
It comes as no surprise, then, that cities increasingly explore the untapped potential of lower-cost monitoring.
The Mayor of London launched the Breathe London network in 2021. Lower-cost sensors were set up at over 100 locations. Its Community Programme mainly targets groups for whom air quality monitoring has long been a pipe dream. Extra efforts are made to reach low-income households and communities of colour in neighbourhoods hardest hit by polluted air.
In Paris, a network of lower-cost sensors was established in 2019 to gather school air quality data. 138 sensors were installed in 44 schools, the data of which was combined with diffusion tubes and 16 reference stations across the city. The results revealed that air pollution in schoolyards was significantly lower than in surrounding roads. This helped strengthen public acceptance of the Mayor’s decision to further pedestrianise streets around schools.
In Warsaw, too, lower-cost sensors played a role in bringing about greater awareness. Inspired by the Breathe London initiative, 164 sensors were installed in many locations. Using microsensors, Warsaw is building one of Europe’s largest air quality monitoring systems in Europe. Its population closely follows air quality developments and Warsovians make their frustration known on social media on particularly polluted days.
Lower-cost measuring devices are powerful tools. For cities new to air quality monitoring, affordable devices can help initiate the fight against polluted air. Their inaccuracy should not discourage decision-makers; some data is still better than no data. At a later stage, they can be combined with richer data from reference stations. Cities such as Warsaw have been at the forefront of such hybrid approaches.
Perhaps most importantly, these devices can help democratise science and provide historically under-served or vulnerable communities with an instrument to push for systemic change. Hyperlocal data on exposure to air pollution will likely create greater awareness of the issue.
In years to come, progress in lower-cost monitoring is urgently needed. Only then can we realise cities with cleaner air for all.
CitiAIR is the first online inventory of participatory air quality initiatives in Europe. Many projects – which can be submitted here – are enthusiastic about one solution in particular: lower-cost monitoring.