Iran, one of the world’s richest countries in oil and gas reserves, is today home to tens of millions of people who breathe some of the most polluted air on the planet. Every winter, cities like Tehran, Isfahan, Karaj, Ahvaz and Tabriz are trapped under a suffocating dome of sulfur dioxide, soot, and ultrafine particles. What should sustain life instead poisons it — a reality that many residents increasingly describe as living inside a “12-million-person gas chamber.”
This is not an exaggeration. It is the predictable outcome of energy policies that prioritize economic survival and exports over the health, dignity, and fundamental rights of Iran’s population.
This report explains why Iran burns mazut, how this fuels a nationwide air-toxicity crisis, and why the issue must now be recognized as a human rights concern — not merely an environmental one.
What Is Mazut and Why Is It So Dangerous?
Mazut, or heavy fuel oil, is the dirtiest residue left after refining crude oil. It contains extremely high levels of sulfur and, when burned, releases a toxic mixture of:
- Sulfur dioxide (SO₂)
- Nitrogen oxides
- Heavy metals
- PM2.5 ultrafine particles
According to ScienceDirect, heavy fuel oil combustion is a major global source of sulfur dioxide — a gas directly linked to respiratory failure, cardiovascular disease, and smog formation. In many countries, mazut is banned or strictly controlled because of its devastating health impacts.
In Iran, however, it has become a winter reality.
Why Does Iran Burn Mazut?
The answer lies in a combination of outdated infrastructure, economic pressure, and political decision-making.
1. Aging refineries that overproduce mazut
Iran’s refineries lack modern cracking units capable of converting heavy residue into cleaner fuels. As a result, a disproportionately large portion of crude oil becomes mazut — a product with limited export value and high domestic environmental cost.
2. Exporting cleaner fuels is more profitable
Under sanctions and economic stress, the government prioritizes exporting gasoline, diesel, and lighter refined products to earn revenue.
What remains — the low-value mazut — is burned at home in power plants, cement factories, and industrial zones, often located near densely populated cities.
3. Seasonal gas shortages force a switch to mazut
Despite possessing the world’s second-largest natural gas reserves, Iran faces chronic winter shortages due to systemic mismanagement. When gas supplies are diverted to households, industries and power plants are ordered to burn mazut — no matter how catastrophic its emissions may be.
The Human Cost: Living in a “12-Million Gas Chamber”
When mazut is burned, its pollutants settle in the cold winter air during inversion episodes. These conditions transform Iranian megacities into toxic basins where:
- Children experience worsening asthma and developmental harm
- Elderly populations face increased cardiac and respiratory hospitalizations
- Cancer risks rise due to long-term exposure
- Thousands of premature deaths occur annually
- Daily life becomes a struggle for clean breath
The World Health Organization identifies PM2.5 as one of the leading global killers. In Tehran, winter levels regularly exceed WHO limits by more than 10 to 15 times.
This is not merely an environmental crisis — it is a violation of the right to health, the right to life, and the right to live in dignity, enshrined in international human rights standards.
Join our Campaign
The Iranian population cannot fight this alone.
We call on:
- Environmental organizations,
- Human rights bodies,
- International institutions,
- Media outlets, and
- Concerned citizens worldwide
to recognize this crisis and support efforts to document, expose, and challenge the policies that have turned Iranian cities into hazardous zones.
Your donations help us amplify the voices of those living under toxic skies and strengthen international advocacy for their protection.*
Together, we can turn global attention toward a crisis that costs thousands of lives each year — and demand accountability for the right to breathe.
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