Smoke plumes caused by oil depot and refinery strikes drifted across Tehran on Monday, satellite images show, as the World Health Organization (WHO) warned that attacks on oil facilities could pose serious health risks to residents.
Since the US-Israeli attacks on Iran began on 28 February, we have confirmed strikes on at least four oil facilities around the capital.
Residents said smog and pollution have blocked out the Sun and left a strong smell of burning in parts of the city, while experts warn the scale of some of the pollutants released could be “unprecedented”.
The spike in air pollution appears to focus near the damaged oil sites around the capital – a city with a population of nearly 10 million, with millions more in the surrounding areas.
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The latest satellite pictures, captured on 9 March and reviewed by BBC Verify, show two major oil facilities in Tehran still on fire, following reported air strikes overnight on Saturday.
The images also show smoke coming from Shahran depot in the north-west of the Iranian capital and the Tehran oil refinery, in the south-east. Verified video of the moments after Saturday’s strike showed huge fireballs illuminating the night sky at the refinery.
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The combination of cloud and smoke plumes from the ongoing fires mean that we are unable to assess the extent of the damage at either oil facility hit over the weekend yet.
But images taken at Shahran on Sunday morning showed emergency workers inspecting burned out oil tankers, blackened buildings and blazing fires.
The Israel Defense Forces (IDF) said it hit “fuel depots” near Tehran in a post on X on 7 March, which included a photograph showing damage to the Tehran oil refinery. BBC Verify provided the coordinates of this facility, along with three other locations we identified, to the IDF and the Pentagon for comment. The Pentagon did not reply, while the IDF said there were “no IDF strikes at those sites”. We have asked for clarification.
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Strikes at oil refineries have the potential to bring significant air pollution because they contain a huge variety of chemicals.
When there is incomplete burning of oil – 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 sulphur and nitrogen oxides, which can form acids if they dissolve in rainwater, as well as other harmful hydrocarbons, metallic compounds and droplets of oil.
How bad is the air pollution?
A Tehran woman in her 20s said that she could “smell the burning” caused by the attacks on oil facilities.
“I can’t see the Sun. There is a horrible smoke. It’s still there. I’m very tired,” she told BBC Persian on Saturday.
A precise assessment of air pollution is challenging because there are no ground-based measurements available – and satellite data is hard to interpret due to winds, clouds and other factors.
But given the mix of chemicals likely released from the damaged oil sites, scientists have little doubt that the pollution is harmful and extreme – and very different to the smog seen in cities like Beijing or Delhi.
“What has happened [in Iran] is definitely unprecedented because it’s all coming in from missiles dropping in and airstrikes on oil refineries,” said Dr Akshay Deoras, 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 “definitely unusual”, he added.
Eloise Marais, professor of atmospheric chemistry and air quality at University College London, agreed.
She said that in most circumstances this kind of pollution would only be seen from “a very, very severe industrial accident where an entire refinery explodes”.
What is ‘black rain’ and what causes it?
On Sunday, Tehran residents reported downpours of “black rain”.
Black rain is the informal term for rainfall contaminated with pollutants, turning it dark.
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It is normal for pollutants to be “washed out” of the air by rainfall, but black rain is rare and typically is the result of high levels of soot and other air pollutants, scientists have 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’s being described as ‘black rain’,” explained Deoras.
It is also possible that some larger particles may have fallen out of the air without rain.
What might the impacts be?
The head of the WHO has already expressed “great concerns” for the impacts of the conflict on people’s health.
Damage to oil facilities “risks contaminating food, water and air – hazards that can have severe health impacts especially on children, older people, and people with pre existing medical conditions”, said Dr Tedros Adhanom Ghebreyesus.
“These very intense exposures of particulates 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 afterwards, on both respiratory systems and increasing cancer risk.”
Doug Weir, director of the Conflict and Environment Observatory, noted that “what’s unusual about Tehran is we haven’t observed these attacks in such a densely populated area before”.
“Often these oil field 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.
BBC Weather forecasts suggest spells of rain on Tuesday and again from Thursday onwards, as well as a stronger breeze. That should help to disperse and wash pollutants away.
But that does not mean the risks of the pollutants disappear. They can enter rivers and other waterways, or if they settle and the ground dries then winds can pick them up and they can become resuspended in the air.
This story has been updated with a statement from the IDF which was received after publication.
Additional reporting: Ghoncheh Habibiazad, Paul Brown, Rollo Collins, Shayan Sardarizadeh, Farida Elsebai and Daniel Wainwright
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