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.

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.

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.

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.

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.

There is a horrible smoke.

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.

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".

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

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