Which are the most polluting countries in the world?

Which country pollutes the most?

China pollutes the most by total CO2 emissions, producing 31.8% of the world total in 2024. Qatar emits the most CO2 per person (41.3 tonnes a year), while Chad has the world’s dirtiest air, with PM2.5 pollution more than 18 times above the WHO guideline. Which country is "the most polluting" therefore depends on the metric you choose.

The most polluting countries by total CO2 emissions

Measured by the sheer volume of carbon dioxide released, China leads by a wide margin: it emitted 12,289 million tonnes of fossil CO2 in 2024, almost a third of the world total. The United States (12.7%) and India (8.3%) complete the podium — together, the three countries generate more than half of global fossil CO2 emissions, according to the Global Carbon Budget 2025.

The most populous, most industrialised countries dominate the list: China concentrates the world’s manufacturing and still relies heavily on coal, the United States is the largest economy, and India’s emissions are growing as the country develops. These emissions are the main driver of the man-made greenhouse effect and, with it, of global warming.

The most polluting countries per capita: the other side of the ranking

The ranking looks completely different once you divide emissions by population. The countries that emit the most CO2 per person are small oil and gas states: Qatar tops the list with 41.3 tonnes per person per year — almost nine times the world average of 4.7 t. Kuwait, Brunei, Bahrain and Trinidad and Tobago follow.

This metric overturns some common assumptions. China, the largest absolute emitter, drops to a far more modest position with 8.7 t per person, and India does not even reach half the world average (2.2 t). The average American, meanwhile, emits 14.2 t a year — three times the global mean. Two factors explain why small petrostates dominate:

1. the enormous weight of the oil and gas industry in their economies;
2. their small populations, which spread those emissions across very few people.

Historical emissions: who is responsible for climate change?

CO2 stays in the atmosphere for centuries, so today’s climate reflects cumulative emissions since the Industrial Revolution, not just last year’s. On this metric, the biggest polluter is the United States: it has emitted around 435 Gt of CO2 since 1750, close to a quarter of the historical world total.

This is the metric of climate justice: the countries that industrialised first put most of the carbon that is in the atmosphere today. China has already overtaken every individual European country and, according to Carbon Brief, is closing in on the EU-27 bloc — but the US cumulative total remains far ahead. It is the central argument of developing countries at IPCC negotiations and climate summits: those who emitted the most historically should shoulder the biggest cuts and financing efforts.

The most polluted countries by air quality

CO2 is not what makes air unbreathable — fine particulate matter (PM2.5) is. On this measure, the "dirtiest" country in the world is Chad, whose air averaged 91.8 µg/m³ of PM2.5 in 2024 — more than 18 times the WHO annual guideline of 5 µg/m³ — according to the IQAir World Air Quality Report 2024. Bangladesh, Pakistan, the Democratic Republic of the Congo and India complete the top five.

The air-quality map barely overlaps with the CO2 map. Chad and the DR Congo emit almost no carbon dioxide, but suffer from Saharan dust, open waste burning and cooking with solid fuels. Of 138 countries analysed, 126 (91.3%) exceeded the WHO guideline in 2024 — only seven met it, among them Australia, New Zealand, Estonia and Iceland — and just 17% of the world’s cities breathed air within the recommended limit. Delhi was the most polluted capital city on Earth for the sixth year running, ahead of N’Djamena in Chad, both averaging over 90 µg/m³.

Why the metric matters: territorial, per capita, historical or consumption

There is no single ranking of the most polluting countries: each metric tells a different story, and it pays to know which one is being used before drawing conclusions:

• Absolute territorial emissions: what is emitted within each country’s borders. This is the metric of official inventories, and China leads it;
• Per capita emissions: absolute emissions divided by population. They reflect the average lifestyle and are led by the Gulf petrostates;
• Cumulative historical emissions: responsibility for the warming already caused, led by the United States and Europe;
• Consumption-based emissions: they reassign to each country the CO2 embedded in what it imports. On this measure, part of China’s emissions shifts to consumers in Europe and the United States, whose figures rise by around 6-10%, according to Our World in Data;
• Air quality (PM2.5): the pollution people actually breathe, dominated by Chad, Bangladesh and Pakistan rather than the big CO2 emitters.

There is an even broader indicator, the ecological footprint, which measures all the pressure a lifestyle puts on the planet’s resources (not just CO2) and is calculated by the Global Footprint Network: at current consumption levels, humanity would need 1.7 Earths — which is why Earth Overshoot Day falls earlier almost every year.

What are the biggest polluters doing about it?

The climate commitments of the largest emitters are moving at very different speeds:

• China has pledged to peak its emissions before 2030 and reach carbon neutrality before 2060. In September 2025 it also announced its first absolute target: cutting emissions by 7-10% from the peak by 2035 and expanding wind and solar capacity to 3,600 GW, according to Carbon Brief;
• the United States withdrew from the Paris Agreement for the second time: the exit became effective on 27 January 2026, leaving the world’s second-largest emitter without a federal climate target;
• India maintains its goal of net-zero emissions by 2070, announced at COP26, while investing massively in renewable energy;
• the European Union is aiming for climate neutrality by 2050 under the European Green Deal, with a cut of at least 55% in emissions by 2030 compared with 1990.

While governments negotiate, individuals and businesses can act too: cut their consumption, choose green energy and offset their carbon footprint by funding projects such as the Gandhi Project, the wind farm Selectra supports in India to replace coal-fired generation.