Iran is increasingly blending hazardous petrochemicals into its gasoline supply to address a growing shortfall in domestic fuel production, risking environmental damage and endangering public health, according to confidential documents reviewed by Iran Open Data (IOD).
Among the additives is methyl tert-butyl ether (MTBE), a chemical known for its role in groundwater contamination and listed as a potential carcinogen.
Though banned or heavily restricted in numerous countries such as the US, MTBE is reportedly being used in substantial volumes—even in gasoline marketed under European emissions standards, such as Euro 4 and Euro 5.
Unacknowledged chemicals in ‘euro-standard’ fuel
The documents reviewed by IOD detail a system-wide reliance on off-site chemical additives to raise the octane rating of base gasoline. These include MTBE and aromatic octane boosters, which are not derived from conventional refining processes.
Iran’s Shazand refinery, the country’s largest producer of Euro-grade gasoline, blends approximately 350,000 liters of MTBE daily, while the Esfahan refinery adds 325,000 liters per day, according to the data. Both refineries label their fuel as Euro 4 or Euro 5 compliant.
The use of restricted additives contradicts environmental standards associated with the Euro classification, which are designed to reduce emissions and limit pollutants.
Production gap and fuel demand
Iran produced an average of 101 million liters of base gasoline per day in 2024, rising to 121 million liters per day after incorporating roughly 20 million liters of off-site additives. However, daily domestic demand stands at 123.5 million liters, leaving a shortfall of 2.5 million liters.
The shortfall, coupled with economic constraints and sanctions limiting imports and refinery upgrades, has prompted a quiet return to petrochemical-derived gasoline—first adopted during international sanctions in 2010.
Refining limitations and aging infrastructure
In spite of owning the world's second largest natural gas reserves, Iran’s refining infrastructure remains massively underdeveloped resulting from both sanctions and macroeconomic policies in Iran. No new refinery has been commissioned since 2017, and six of the ten major facilities predate the 1979 Islamic Revolution.
The Persian Gulf Star refinery, Iran’s largest by volume, produces 39 million liters/day, but none of its output qualifies for Euro-grade certification.
According to IOD, one-third of Iran’s gasoline is officially labeled Euro 4 or Euro 5, but internal documents indicate that even these fuels often contain high-risk chemical additives.
Health and environmental risks
MTBE is widely banned in Europe, the US, and other countries due to its high solubility in water and persistence in the environment. Even trace contamination of groundwater can lead to environmental damage and health risks for the population, making its use in consumer fuels controversial.
In 2014, a Tehran city health official warned that non-standard fuels could increase airborne benzene levels up to 35 times the safe limit.
A 2023 environmental review by Iranian authorities said that just 38% of gasoline met domestic quality standards. The IOD report suggests the problem has since worsened.
Iran maintains one of the world’s lowest gasoline prices—second only to Libya—due to heavy state subsidies, currency depreciation, and the impact of international sanctions.
Officials frequently cite low fuel prices as a driver of excessive consumption and cross-border smuggling, but attempts to increase prices have been shelved amid fears of social unrest.
The government has not publicly addressed the use of MTBE or other additives, and internal reports avoid naming specific chemicals, instead using general terms such as “aromatic octane boosters” or “off-site petrochemical inputs.”
Iran Open Data warns that Iran’s increasing dependence on petrochemical additives, without parallel investment in refining capacity, poses significant long-term risks to public health, environmental safety, and economic sustainability.
“The growing reliance on high-risk additives has become a cornerstone of fuel supply, in the absence of refinery upgrades,” the report said. “This strategy could carry severe health, environmental, and economic consequences.”
Officials from Iran’s Ministry of Petroleum and the Department of Environment did not immediately respond to requests for comment.
