Air strikes cause black rain and ‘unprecedented’ pollution in Tehran, scientists say
Plumes of smoke caused by strikes at oil depots and refineries drifted over Tehran on Monday, satellite images showed, as the World Health Organization (WHO) warned that attacks on oil installations could pose serious health risks to residents.
Since the US-Israeli attacks on Iran began on February 28, we have confirmed strikes against at least four oil facilities around the capital.
Residents said smog and pollution had blocked out the sun and left a strong burning smell in parts of the city, while experts warned the scale of some of the pollutants released could be “unprecedented”.
The spike in air pollution appears to be concentrated near damaged oil sites around the capital – a city of nearly 10 million people, with millions more in surrounding areas.
The latest satellite images, taken on March 9 and reviewed by BBC Verify, show two major oil installations in Tehran still on fire, following airstrikes reported overnight on Saturday.
The images also show smoke coming from the Shahran depot, northwest of the Iranian capital, and the Tehran oil refinery, to the southeast. Verified video of the moments after Saturday’s attack shows huge fireballs lighting up the refinery’s night sky.
The combination of clouds and plumes of smoke from the ongoing fires means we are not yet able to assess the extent of the damage at the two oil installations affected this weekend.
But images taken in Shahran on Sunday morning showed rescue workers inspecting burning oil tankers, blackened buildings and blazing fires.
The Israel Defense Forces (IDF) said it had struck “fuel depots” near Tehran in a March 7 post on X, which included a photograph showing damage to Tehran’s oil refinery. BBC Verify provided coordinates for this facility, as well as three other locations we identified, to the IDF and the Pentagon for comment. The Pentagon did not respond, while the IDF said there were “no IDF strikes on these sites.” We asked for clarification.
Strikes at oil refineries can potentially lead to significant air pollution because they contain a wide variety of chemicals.
When oil combustion is incomplete – when there is not enough oxygen – carbon monoxide and soot particles can be released instead of carbon dioxide and water.
Oil fires can also release oxides of sulfur and nitrogen, which can form acids if they dissolve in rainwater, as well as other harmful hydrocarbons, metal compounds and oil droplets.
How bad is air pollution?
A woman in her 20s in Tehran said she could “smell the burning smell” from attacks on oil installations.
“I can’t see the sun. There is horrible smoke. It’s still there. I’m very tired,” she told the Persian BBC on Saturday.
Accurate assessment of air pollution is difficult because there are no ground-based measurements available and satellite data are difficult to interpret due to winds, clouds and other factors.
But given the mix of chemicals likely released from damaged oil sites, scientists have no doubt that the pollution is harmful and extreme — and very different from the smog seen in cities like Beijing or Delhi.
“What happened [in Iran] is undoubtedly unprecedented, as this all comes from missile attacks and airstrikes on oil refineries,” said Dr Akshay Deoras, a research scientist at the University of Reading.
Many conflicts cause high levels of dust and particle pollution – but the “basket” of different chemicals in this case is “quite unusual”, he added.
Eloise Marais, professor of atmospheric chemistry and air quality at University College London, agrees.
She said that in most cases this type of pollution would only show up in a “very, very serious industrial accident where an entire refinery explodes.”
What is “black rain” and what causes it?
Tehran residents reported “black rain” downpours on Sunday.
Black rain is the informal term for precipitation contaminated with pollutants, making the atmosphere dark.
It’s normal for pollutants to be “washed” from the air by precipitation, but black rain is rare and is usually the result of high levels of soot and other air pollutants, scientists told BBC Verify.
“The raindrops acted like little sponges or magnets, collecting whatever was in the air as they fell, which is why residents observed what is described as ‘black rain,'” Deoras explained.
It is also possible that larger particles fell from the air without rain.
What could be the impacts?
The head of the WHO has already expressed “great concerns” about the impacts of the conflict on the health of the population.
Damage to oil installations “risks contaminating food, water and air – hazards that can have serious health consequences, particularly for children, the elderly and people with pre-existing health conditions,” said Dr. Tedros Adhanom Ghebreyesus.
“These very intense exposures to particles have immediate impacts on the lungs,” added Anna Hansell, professor of environmental epidemiology at the University of Leicester.
“But they can also have quite long-lasting effects over many years, both on the respiratory system and by increasing the risk of cancer.”
Doug Weir, director of the Conflict and Environment Observatory, noted that “what is unusual about Tehran is that we have never seen these attacks in such a densely populated area before.”
“Often these oil sites are quite far out in the countryside. People in Tehran are exposed to a huge range of substances in this black rain – not just oil,” he said.
The BBC weather forecast suggests spells of rain on Tuesday and again from Thursday, as well as a stronger breeze. This should help disperse and remove pollutants.
But this does not mean that the risks linked to pollutants disappear. They can enter rivers and other waterways, or if they settle and the ground dries, winds can pick them up and they can be resuspended in the air.
This story was updated with an IDF statement received after publication.
Additional reporting: Ghoncheh Habibiazad, Paul Brown, Rollo Collins, Shayan Sardarizadeh, Farida Elsebai and Daniel Wainwright
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