Charred, soot-covered buildings, vehicles and roads, billows of dense, black and oily rain, toxic air inflaming the lungs, sore and raw lips, and burning eyes – this was the grim reality for the residents of Tehran and its surrounding areas last week.

This was due to US-Israeli airstrikes on Iran’s oil infrastructures, which resulted in vast clouds of poisonous smoke being released into the atmosphere.

These hazardous clouds subsequently returned to earth as deadly ‘black rain’ – a situation so severe it has led international health bodies such as the WHO (World Health Organisation) to issue warnings about the health risks to the public.

The IDF confirmed in a statement that they had “struck a number of fuel storage facilities in Tehran” which they believed were being utilised by the Islamic Republic of Iran’s military “to operate military infrastructure, including military entities in Iran”.

Following the strikes last week, Tehran residents reported difficulties breathing and burning eyes as oily and pitch-black precipitation descended upon and around the Iranian capital, due to several oil refineries and fuel oil depots being targeted by US-Israeli forces, reports the Mirror.

The strikes coincided with a warning from US President Donald Trump who posted “today Iran will be hit very hard” on Truth Social.

Terrifying clouds of dense and heavy black smoke have also been observed over other areas in the Middle East as Iran’s conflict with the United States and Israel continues, with the Islamic Republic retaliating by targeting several Gulf countries. If the situation further escalates, Iranians won’t be the only ones endangered by ‘black rain’.

Specialists are issuing urgent health alerts to those who have encountered ‘black rain’, as exposure to this toxic phenomenon can result in short- and long-term risks.

Since the US-Israeli attacks on Iran began on February 28, the BBC has confirmed at least four strikes on Iran’s oil facilities around its capital city of Tehran.

Tehran is home to nearly 10 million people, with millions more residing in the surrounding regions.

Following the strikes on Iranian oil refineries and depots near Tehran, the city’s inhabitants complained of thick smog and pollution which they claimed was “blocking out the sun”, leaving a potent smell of burning in various parts of the capital city.

Experts quickly warned that the volume of pollutants already released into the atmosphere could be “unprecedented” as they highlighted the deadly health risks to individuals.

The surge in air pollution was reportedly primarily around the areas around Tehran, where oil facilities were targeted and damaged.

Dr Akshay Deoras, a research scientist at the University of Reading, told the BBC: “What has happened [in Iran] is definitely unprecedented because it’s all coming in from missiles dropping in and airstrikes on oil refineries.”

Tehran’s residents ‘can’t breathe’

Leila, a 27-year-old teacher in Tehran, told TIME that the air had become “unbreathable” following the initial US-Israeli overnight strikes on Iran’s oil infrastructures on 7 March.

She said: “Today I was in the car for just 15 minutes, breathing this air. I don’t even know what it is, and now I have a headache. The skin on my face, especially my lips, is sore and raw. It burns and feels like diluted tear gas is in the air. It irritates my eyes, and I keep needing to clear my throat.”

Another woman in her 20s from Tehran told BBC Persian: “I can’t see the Sun. There is a horrible smoke. It’s still there. I’m very tired.”

Negin (name changed) shared with The Guardian: “The situation is so frightening it’s hard to describe. Smoke has covered the entire city. I have severe shortness of breath and burning in my eyes and throat, and many others feel the same. But people still have to go outside because they have no choice.”

What is ‘Black Rain’?

Residents of Tehran reported experiencing “black rain” downpours after last week’s strikes on the city’s oil facilities.

So, what exactly is ‘Black Rain’?

It’s the colloquial term for rainfall that has been contaminated with a high concentration of pollutants, causing it to turn dark or ‘black’.

Whilst typically pollutants are ‘washed out’ of the air when it rains, the rare phenomenon of ‘black rain’ occurs when high levels of soot, ash, and toxic chemicals mix with water droplets in the atmosphere and fall back to Earth without being ‘washed out’.

Dr Deoras explained to 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’.”

It is also possible that some of the larger pollutant particles fell out of the air even without precipitation.

Black rain can occur after oil refineries or oil fields ignite, and can also be a result of volcanic eruptions, wildfires and industrial-grade pollution.

Speaking to the BBC, Peter Adams, a professor of civil and environmental engineering at Carnegie Mellon University, explained how in the case of Iran, microscopic soot was formed as a result of the incomplete burning of hydrocarbons in the fuel oil that was struck.

The burning oil also led to the formation of compounds called polycyclic aromatic hydrocarbons (PAHs) and toxic gases like nitrogen oxides and sulfur dioxide (which cause acid rain), according to the professor.

Following the strikes, the Red Crescent Society in Iran cautioned residents living in Tehran and neighbouring areas that the subsequent rainfall could be “highly dangerous and acidic”, potentially resulting in “chemical burns of the skin and serious damage to the lungs”.

The microscopic soot – particles of which are roughly 40 times smaller than the typical width of a strand of human hair – can become embedded deep within the lungs and penetrate the bloodstream, which could trigger fatal respiratory and cardiac problems and may even lead to premature death according to experts, as reported by AP. Cancer risk, asthma, pulmonary conditions and heart disease may also be heightened due to exposure to PAHs.

The head of WHO, Tedros Adhanom Ghebreyesus, said in an urgent statement issued after the strikes: “Damage to petroleum facilities in Iran 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.”

Professor of environmental epidemiology at the University of Leicester, Anna Hansell, told the BBC that “these very intense exposures of particulates have immediate impacts on the lungs”, as she explained that this ‘black rain’ could also have “quite long lasting effects over many years afterwards, on both respiratory systems and increasing cancer risk”.

Whatever the outcome of this destructive war, one thing remains certain: the highest price of war is always paid by ordinary people.