WHO Warns Iran's Toxic 'Black Rain' Threatens Respiratory Health After Oil Strikes

Black, oil-laden rain began falling on Tehran and parts of Iran after strikes on oil storage facilities and refineries ignited massive fires, and the World Health Organization issued an urgent health warning, backing calls for residents to remain indoors.

"The black rain and the acidic rain coming with it is indeed a danger for the population, respiratory mainly," WHO spokesperson Christian Lindmeier said at a press briefing in Geneva on Monday. The agency said it had received multiple reports of oil-laden rainfall that week and was in direct contact with Iranian hospitals and health authorities.

The fires, described by Reuters as part of a U.S.-Israeli campaign targeting Iran's domestic energy infrastructure, sent thick black smoke over Tehran on Monday after an oil refinery was struck. Scientists identified the primary pollutants released as toxic hydrocarbons, sulfur oxides, and nitrogen compounds, along with soot and unburnt hydrocarbons carried aloft by the blazes and then deposited by rainfall. Inhaling or touching the smoke and particles can cause headaches, skin and eye irritation, and difficulty breathing; longer-term exposure to some of the compounds increases the risk of certain cancers.

A video shared with Reuters by a WHO staff member showed a cleaner mopping up dark liquid outside the WHO office entrance in Tehran on March 8, though Reuters could not independently verify the footage.

Akshay Deoras, a research scientist at the University of Reading, said the visible precipitation had brought the danger into sharp focus for the public. "The rain was an eye-opener to people," he said. But he warned that the more persistent threat was airborne, not meteorological: long-term exposure to toxic air was likely more of a health risk, which people could protect themselves from by staying indoors, wearing masks, and covering their skin outdoors. Weather forecasts at the time suggested dry conditions for the rest of the week, which Deoras said should allow air quality to gradually improve. "The risk of exposure goes down provided we don't see fresh strikes," he said. "If we get fresh strikes, that is going to be problematic."

The WHO backed Iran's official advisory urging residents to stay indoors, a recommendation the agency said was fully justified given the scale of contamination. Iran's health authorities have been placed on alert, and the WHO's existing office in Tehran has positioned the agency to coordinate directly with the government on the public health response.

Beyond the immediate health emergency, the strikes are drawing scrutiny over their legality. UN Human Rights office spokesperson Ravina Shamdasani said the health and environmental impacts raise "serious questions as to whether the proportionality and precaution obligations under international humanitarian law were met," adding that the sites struck "do not appear to be of military exclusive usage."

The Nivaran Foundation, an advocacy organization monitoring the crisis, called for urgent distribution of respiratory protective equipment, establishment of medical facilities equipped to treat pollution-related illness, access to clean drinking water, and sustained public health surveillance to track respiratory disease, skin conditions, and waterborne illness in the weeks ahead.

Critical gaps remain. No independent air quality measurements, particulate concentration figures, or hospital admission data linked to the black rain had been reported as of Monday. Deoras noted explicitly that data on ground-level air quality was lacking, making a full assessment of population exposure impossible without systematic monitoring that has yet to be confirmed.