Top-10 Most Polluted and Least Polluted Countries in the World in 2025

Pollution is a serious problem in many parts of the world. It harms the air we breathe, the water we drink, and the environment around us. Some countries suffer from very high pollution levels, while others enjoy clean and fresh air. In this article, we will learn about the most and least polluted countries in the world in 2024-25.

Polluted Countries of the World

Air pollution is one of the biggest problems for health all over the world. The World Health Organization (WHO) says it causes 1 in every 9 deaths. One of the most dangerous parts of air pollution is PM2.5 – tiny particles in the air that can damage our heart, lungs and even affect children’s growth.

Recent reports show a big difference between countries with clean air and those with dirty air. Let’s look at the top-10 most polluted and least polluted countries in 2024-25, based on average PM2.5 levels.

What is PM2.5?

PM2.5 stands for ”particulate matter” that is 2.5 micrometers or smaller in size. These particles are so tiny that we cannot see them with our eyes, but they can go deep into our lungs and even into our blood.

Most Polluted Countries in the World in 2025

According to the 2024-25 IQAir report, South Asia remains one of the most polluted regions in the world. Bangladesh, Pakistan and India are among the top five most polluted countries. Bangladesh is ranked second, Pakistan third and India fifth. India showed a small improvement, with its PM2.5 level dropping to 50.6 μg/m³ from 54.4 in 2023. Pakistan’s air quality is still very poor, with a high PM2.5 level of 73.7 μg/m³.

Top-10 Most Polluted Countries in the World in 2025

As of 2025, Chad stands as the most polluted countries in the world with the PM2.5 concentration of 91.8 μg/m³, followed by Bangladesh, Pakistan and Democratic Republic of the Congo.

Here is the list of top-10 most polluted countries in the world in 2025:

Least Polluted Countries in the World in 2025

The Bahamas ranked as the least polluted country in the world, with very clean air and a PM2.5 level of just 2.3 μg/m³. It has become a global example for fresh air. While South Asia has the most polluted countries, Nordic nations like Iceland, Finland and Sweden are among the cleanest due to strong environmental laws. In the Southern Hemisphere, New Zealand (4.3 μg/m³) and Australia also have clean air, helped by their mild climate and focus on clean living.

Top-10 Least Polluted Countries in the World in 2025

Bahamas stands as the least polluted country in the world as of 2025 with a PM2.5 concentration of 2.3 μg/m³, followed by French Polynesia, Barbados and Grenada.

Here is the list of top-10 least polluted countries in the world in 2025: