Iran’s network of aging oil tankers used to move crude under sanctions is increasingly being flagged as an environmental and maritime safety risk, with experts warning that a serious accident could trigger a catastrophic spill, The Guardian reported on Tuesday.
The Guardian said Pole Star Global assessed 29 Iran-linked vessels that “went dark” by switching off satellite identification systems, and found that about half were older than the recommended 20-year safe service life. Analysts said the ships are believed to be poorly maintained and may fail to meet international safety standards because they operate outside normal scrutiny.
Seven of the 29 vessels were placed in an “extreme risk” category because they were over 25 years old, and three were more than 30 years old. It added that five of the ships were both aging and very large crude carriers, capable of holding about 300,000 tons of oil, meaning a single accident could dwarf past disasters, the report noted.
The Guardian cited more than 50 reported incidents involving shadow tankers globally in recent years, ranging from collisions to spills, and said nine oil slicks between 2021 and 2024 were attributed to Russian “dark fleet” vessels. It said the Iranian fleet has drawn less scrutiny, despite analysts warning that its age profile is among the worst observed.
The report said shadow-fleet tankers are typically uninsured, which could leave coastal states bearing cleanup and compensation costs if a spill occurs. It cited an estimate that puts the potential bill between $860 million and $1.6 billion.
The warning comes as US enforcement pressure on Iran’s oil export ecosystem continues to expand. Reports last week said the administration is weighing seizing additional Iranian oil tankers to pressure Tehran, while US officials warned such steps could prompt “near-certain retaliation,” including seizures of allied shipping or disruption in the Strait of Hormuz.
Other recent US actions have focused on disrupting the networks supporting oil shipments. In January, the State Department announced it was offering rewards of up to $15 million for information leading to the identification of entities or individuals involved in oil sales by the Islamic Revolutionary Guard Corps.
The Guardian said the global “dark fleet” now numbers many hundreds of vessels, with some estimates suggesting it accounts for about 17% of the world’s tanker fleet. Mark Spalding, president of the Ocean Foundation, was quoted as saying, “The question is not whether a major incident will occur, but when.”
MIRIAM SELA-EITAM and Reuters contributed to this report.