A layer of haze spread over the planet's surface, seen from the International Space Station.
Blue Initiative

Air quality

We share one atmosphere. What rises from a chimney on one continent settles into lungs and seas on the others.

NASA

Every day each of us breathes about eleven thousand litres of air. We cannot choose which air, and we cannot filter it with our eyes: the most dangerous pollution is invisible. The atmosphere is also the ocean’s partner. Much of what we put into the air ends up in the sea, changing its chemistry in ways that were measured long before they were understood.

What is in the air

  • Fine particles (PM2.5) are specks smaller than 2.5 micrometres, from burning fuel, wood, crops and waste, and from dust and chemical reactions in the air. They are small enough to pass deep into the lungs and into the bloodstream.
  • Coarse particles (PM10) come from dust, construction and road wear. They lodge in the nose and airways.
  • Nitrogen dioxide comes mostly from vehicles and power stations, and helps form ozone and particles.
  • Ground-level ozone is created when sunlight cooks other pollutants. It inflames the lungs and damages crops.
  • Sulphur dioxide comes from burning coal and heavy fuel oil, including in ships.
  • Household smoke from cooking and heating with wood, coal, dung or kerosene is one of the largest exposures of all, mostly borne by women and children.
A traditional mud and brick cookstove beside a house wall, with firewood, dried dung cakes and coconut shells piled in front of it.
A chulla, a traditional cookstove in rural Tamil Nadu, India, fired with branches, scrap wood, dried dung and coconut shells. Smoke from fires like this is one of the largest air-pollution exposures in the world. Photo: McKay Savage, CC BY 2.0

Public health

The World Health Organization estimates that the combined effects of outdoor and household air pollution are associated with 6.7 million premature deaths every year, through strokes, heart disease, lung cancer, chronic lung disease and infections. In 2019, 99 percent of the world’s population lived in places where the WHO’s air quality guideline levels were not met. In 2021 the WHO halved its guideline for yearly average PM2.5, from 10 to 5 micrograms per cubic metre, because the evidence showed harm at lower levels than previously thought.

6.7 millionpremature deaths a year from outdoor and household air pollution combined (WHO)
99%of people lived where WHO guideline levels were not met (WHO, 2019 data)
5 µg/m³WHO annual guideline for PM2.5 since 2021 (WHO)
A dust storm over the Sahara on the border of Algeria and Niger.
Desert dust crosses whole oceans: Saharan dust fertilises the Atlantic and the Amazon, and worsens air quality downwind. Credit: NASA

The air changes the ocean

The ocean has absorbed roughly a quarter of the carbon dioxide humanity has emitted. That has slowed climate change, at a price: dissolved CO2 forms carbonic acid, and the surface ocean has become about 30 percent more acidic since the industrial revolution, a fall of about 0.1 pH units. More acidic water makes it harder for corals, oysters, mussels and some plankton to build their shells and skeletons, and it reaches the base of the ocean food web.

Other air pollutants rain into the sea as well. Nitrogen from exhausts and fertilisers adds to the nutrient load that feeds dead zones. Mercury from burning coal and from small-scale gold mining settles into the ocean, where microbes turn it into methylmercury, which builds up in large fish such as tuna and swordfish, and in the people who eat them (UNEP Global Mercury Assessment 2018).

The ocean has been quietly cleaning our air for two centuries. The bill is arriving in its chemistry.

Proven solutions

Dirty air is one of the problems people have already solved, in places, many times over. Where clear rules, public money and cleaner technology come together, the air improves within a few years, and it keeps improving as long as the effort continues. These are measured results, not promises.

The United States. Between 1970 and 2024, total emissions of the six main pollutants regulated under the Clean Air Act fell by 79 percent, while the economy grew by 338 percent (US EPA). Clean air and a growing economy turned out to be compatible.

Acid rain, capped and traded. The 1990 amendments to the Clean Air Act set a national cap on sulphur dioxide from power stations and let companies trade permits under it, the first national cap-and-trade scheme. Power stations in the programme cut their sulphur dioxide by 96 percent between 1990 and 2023. Wet sulphate deposition, the usual measure of acid rain, fell by more than 70 percent between the early 1990s and the early 2020s, and the number of monitored lakes and streams receiving more acid than they can absorb fell by 81 percent (US EPA; US EPA).

A ridge of dark green spruce and fir trees with many dead, bare grey trunks standing among them, on a hazy mountain summit.
Damaged spruce and fir on the summit of Mount Mitchell, North Carolina, in 2006. High mountain forests like these were harmed by acid rain as well as by an introduced insect pest. Photo: SquareWave, CC BY-SA 3.0

Europe’s sulphur cuts. Between 2005 and 2023, emissions of sulphur oxides in the European Union fell by 84 percent, nitrogen oxides by 53 percent and fine particles by 38 percent. Ammonia, which comes mostly from farming, fell by only 17 percent, which shows where the next effort is needed (European Environment Agency).

Satellites now show the change from orbit. A study led by Norway’s NILU research institute compared satellite measurements of nitrogen dioxide from 2019 to 2024 with economic growth in 2,475 cities around the world whose pollution had clearly changed, and found that almost 80 percent of them had grown richer while their air became cleaner; 390 cities grew richer with more nitrogen dioxide (ESA, 2026; Hassani et al., 2026).

Tower blocks fading into a thick grey haze over Beijing, seen from a hotel window.
Beijing under a haze of pollution in October 2006, seven years before the city's clean-air action plan began. Photo: David Barrie, CC BY 2.0

Beijing, China. In 2013 Beijing’s yearly average of fine particles (PM2.5) was 89.5 micrograms per cubic metre, nearly eighteen times what the WHO now recommends. Under a five-year clean-air action plan, from 2013 to 2017 the city removed coal boilers with a combined capacity of 39,000 steam tonnes, took 2.17 million old vehicles off its roads and closed 1,992 polluting factories, while the surrounding provinces cut coal as well. PM2.5 fell to 58 by 2017 and to 27.0 in 2025, 70 percent lower than in 2013. Days of heavy pollution fell from 58 in 2013 to 2 in 2024. The work is not finished: 27 is still more than five times the WHO guideline (Beijing Ecology and Environment Bureau; China Daily, 2025).

London’s Ultra Low Emission Zone. Since 2019, drivers of the most polluting vehicles pay a daily charge to drive in London. The zone began in the centre in 2019 and grew to cover inner London in 2021 and the whole city in 2023. The Mayor of London estimates that in 2024 roadside nitrogen dioxide was 54 percent lower in central London and 27 percent lower across the whole city than it would have been without the zone. These are modelled estimates, which compare real measurements with a calculated “no zone” scenario (Mayor of London, ULEZ one-year report).

A green Ultra Low Emission Zone sign and a Congestion Charge sign on a pole in central London, with a red double-decker bus behind.
Congestion Charge and Ultra Low Emission Zone signs on the Euston Road in central London, April 2019, the month the zone began. Photo: citytransportinfo, CC0

Cleaner ships. In 2020, the International Maritime Organization cut the limit for sulphur in ships’ fuel from 3.5 to 0.5 percent worldwide (IMO).

Satellite view of long, bright criss-crossing lines in a sheet of low clouds over the Pacific off the western United States.
Ship tracks off the western United States, 1 November 2013: bright lines of cloud that form on particles in ships' exhaust, drawing the routes of the ships across the sky. Credit: NASA/Jeff Schmaltz, MODIS Land Rapid Response Team

The lesson from all of these is the same. Measure the air in public, set limits in law, give people and companies a cleaner option, and keep going for years. Clean cooking, electric transport, and wind and solar power go one step further: they remove the source instead of cleaning up after it.

Organisations doing this work

These non-profits have a public record of results. Take a look at what they do, and if their work speaks to you, consider donating to them directly through their own websites. The Local Solar System Foundation has no affiliation with any of them and receives nothing from them. Before you give, read each organisation’s latest annual report and accounts, as you would with any charity.

  • ClientEarth is an environmental law charity (registered in England and Wales, charity number 1053988). It uses the courts to make governments keep their own clean-air laws: in 2015, in a case it brought, the UK Supreme Court ordered the government to draw up new plans to meet legal limits for nitrogen dioxide (UK Supreme Court, 2015).
  • OpenAQ is a non-profit that gathers air quality measurements from around the world, from government monitors since 2015 and from low-cost sensors since 2021, and makes them free and open for anyone to use. Communities, journalists and researchers use it to see the air they breathe, especially in countries with few official monitors.
  • Clean Air Fund is a UK registered charity (number 1183697) that funds and connects campaigners, researchers and governments working on air pollution, with programmes in India, Indonesia, Ghana, South Africa, the United Kingdom and the European Union. Its website lists its funders and the grants and projects it supports.
A fenced air monitoring station with instruments and a sign reading EPA Air Monitoring Station on a grassy site.
An air monitoring station run by EPA Victoria in Morwell, Australia. Public monitors like this one, and low-cost sensors, feed the open data that anyone can check. Photo: Environment Protection Authority Victoria, CC BY 4.0

How you can help

  • Check the air where you live. Many cities publish real-time air quality; low-cost sensors let communities map their own streets. Share what you find.
  • Burn less. Avoid burning garden waste, plastics or treated wood; if you heat with wood, use dry, seasoned wood in a modern stove.
  • Walk, cycle, share or go electric for short trips, and switch off idling engines, especially near schools.
  • Ask for clean streets. Support low-traffic neighbourhoods, school streets and clean-air zones in your area; write to local representatives about monitoring near schools and hospitals.
  • Choose clean power where your supplier allows it, and support clean cooking programmes for families who still cook over open fires.
  • Help us explain it. Translate this page or build a local air map through the contribution board.

Sources and further reading