We explain the Air Quality Stripes - a visualisation of how air quality has changed since 1850.
It can be hard to tell when the air we’re breathing is polluted. One young person told the Royal College of Paediatrics and Child Health in 2024: “It’s hard to know what my local air quality is … we assume that we have good air”. However, its estimated that 99% of the world’s population – over 8 billion people – could be living with unhealthy air.
Even if we have lots of data, they can be hard to interpret. Helping people to see and understand air pollution were the main goals of a group of academics and organisations when they launched the Air Quality Stripes last year.
Image source: airqualitystripes.info
What are the Air Quality Stripes?
The Air Quality Stripes are a visualisation of how air quality has changed since 1850. Specifically, the coloured stripes shows annual levels of PM2.5 in each of 176 cities. PM2.5 refers to tiny particles (particulate matter) which are smaller than 2.5 micrometres in size. Particulate matter is released from vehicles, indoor heating, and industrial processes. It has serious health effects, mainly because the particles can reach deep into the lungs.
The Air Quality Stripes take after Professor Ed Hawkins’s Climate Stripes, which have become instantly recognisable. Published in 2019, the Climate Stripes also use vertical coloured lines and illustrate global average temperature changes since 1850. The image is a startling representation of the progression of the climate crisis and has been shared and featured widely. The project has identical objectives to the Air Quality Stripes: initiating conversations around a pressing environmental and social issue.
Image source: showyourstripes.info
Did you know that climate change and air quality are linked? Common air pollutants are not only dangerous to our health, but also our climate. Ozone, a harmful air pollutant, is also a potent greenhouse gas, trapping the sun’s radiation in the atmosphere, while particulate matter, by darkening surfaces and reducing the reflection of sunlight back into space, has similar climate-warming effects. In the opposite direction, climate change can exacerbate poor air quality. For example, hotter, drier days will limit the dispersal of pollutants, causing them to build up. Fortunately, these links mean that efforts to tackle one issue will lead to improvements in the other. In particular, because some highly-warming air pollutants are also very short-lived, interventions to reduce them can have rapid climate benefits.
Where are the data from?
For stripes since 2000, the team used a dataset consisting of ground-level and satellite observations of PM2.5 concentrations, created by academics in the US and Canada. However, there aren’t satellite observations of PM2.5 for before 1998, so the team used computer models to determine historical trends. Modelling global concentrations of pollutants is very challenging, and it’s important to continuously evaluate and finetune the outputs of the models by comparing them with recent, real observations. You can view the dataset yourself here.
Joining forces with artists
The Air Quality Stripes show how creativity can bring about environmental action. The team collaborated with artist Ethan Brain to find colours for the stripes that were resonant and meaningful. Ethan searched “air pollution” on Google Images and analysed 200 of the results. Images of pollution were dominated by dark reds, browns, and greys, whereas clean air was associated with light, clear blues. Final colours were hand-picked from this selection and integrated into a gradient of increasing colour values.
Aren’t things improving?
Over recent years, for many cities, the stripes have become blue, indicating improvements in air quality. However, as you can see below, London’s PM2.5 levels still exceed the WHO’s Air Quality Guidelines. Furthermore, the Air Quality Stripes creators also warn that PM2.5 can have significant health effects even at low levels. Elsewhere in the world, the situation is critical. The image further below shows the Air Quality Stripes for Delhi, India. We wrote about Licypriya Kangujam’s campaign to improve air quality in Delhi here.
Image source: airqualitystripes.info
Inspiring students
Uniquely vulnerable, more than 90% of the world’s children under the age of 15 years (1.8 billion children) breathe air that puts their health and development at risk every day. A fantastic example of visual storytelling, the Climate Stripes, and hopefully now the Air Quality Stripes too, are being used to raise awareness of air pollution amongst students. At Enviro Technology, we want to help improve air quality for young people.
Take a look at some of our insights for schools:
