Fresh laboratory data from environmental authorities has revealed alarming levels of sulfur in the diesel supplied to major power plants in Tehran, Alborz, and Qazvin—levels in some cases hundreds of times higher than permitted standards.
The findings raise serious questions about fuel quality oversight in Iran and point directly to failures within the National Iranian Oil Refining and Distribution Company (NIORDC), the entity responsible for producing and delivering standard-compliant fuel.
According to ISNA and based on measurements released by Iran’s Department of Environment, sulfur concentrations in diesel used by power plants such as Rey, Parand, Pakdasht, and Shahriar ranged from 520mgkg to over 6,600mgkg. The national standard is 50mgkg—meaning some batches exceeded the limit by more than 130 times.
The situation is even more alarming in Alborz Province. At the Montazer-e Qaem power plant, both diesel and mazut samples carried extremely high sulfur content. One mazut sample registered 28,451mgkg, a figure that underscores the scale of the problem.
In Qazvin’s Shahid Rajaei power plant, sulfur levels ranged from 2,067 to 12,942mgkg, again far beyond legal thresholds.
These numbers make one fact unavoidable; the crisis lies not in the power plants—mere end-users—but in the quality of fuel entering the system. Yet it is the power plants that face public blame for emissions, despite having no authority over the type or quality of fuel they receive.
High-sulfur fuel drastically increases emissions of SO₂ and secondary particulate matter—pollutants that intensify smog, especially during cold, stagnant weather.
The resulting air pollution imposes severe public-health costs, exacerbating respiratory disease, heart conditions, and premature mortality. Cities like Tehran and Karaj, already burdened with chronic pollution, bear the brunt of these failures.
Under Iranian law, NIORDC is legally responsible for supplying low-sulfur, standard-compliant fuel. The newly revealed data suggests the organization has repeatedly failed to meet this obligation. It now faces growing pressure to explain why such contaminated fuel is being produced, how it is entering the distribution chain, and what corrective measures—if any—are being implemented.
A transparent action plan is urgently needed. Without an immediate shift toward cleaner fuel production and strict monitoring, Iran risks deeper environmental damage, escalating health costs, and further erosion of public trust in its fuel-quality governance.
