The news of black rain falling on Tehran felt all too familiar to Iranian researcher Nejat Rahmanian. On March 8, he was scrolling through alerts on social media feeds, trying to contact relatives. Israeli drone strikes had hit giant oil depots and refineries on the outskirts of the Iranian capital a few hours earlier.
The strike had set fuel on fire, releasing columns of black smoke that mixed with rain clouds. Later in the day, those clouds would pour toxic chemicals onto the city.
The descriptions reminded Rahmanian of a similar event he experienced in the city 35 years ago. It was surreal, recalled Rahmanian, a professor of chemical and petroleum engineering at the University of Bradford in the United Kingdom.
Clothes hanging out to dry got stained and the air felt heavy. No one knew why. Later, they learned that around 1,290km (801 miles) away in Kuwait, Iraqi forces battling US and allied forces in the Gulf War had set hundreds of oilfields ablaze.
Plumes of soot, hydrocarbons and sulphur dioxide blew over Iran, polluting everything in their path. It also accelerated the melting of glaciers in the Himalayas, according to a 2018 study led by Jiamao Zhou at the Chinese Academy of Sciences.
The latest war in the region has unleashed pollutants similar to those. It will have an even greater impact on Tehran and its wider metro area, home to around 18.5 million people, because they were released so close by, experts say.
“We always see oil facilities being attacked in conflicts,” said Doug Weir, CEO at the Conflict and Environment Observatory, or CEOBS, “but it’s extremely rare for them to be close to a large city like Tehran”.
CEOBS is a UK-based charity that aims to raise awareness about the environmental and humanitarian consequences of war. It identified over 300 incidents involving environmental risks resulting from the ongoing hostilities, according to the latest available data.
Missiles and bombs contain heavy metals and other toxic pollutants, which are released into the air, soil and water when they explode and crash, often lingering for decades and posing health risks. Clean-up is difficult and expensive.
“A lot of people are exposed to pollution and will continue to be,” Weir said.
The Israeli strike that hit the oil depots outside Tehran has been this war’s single biggest pollution incident so far, he added.
Iranian authorities initially advised residents to stay indoors, warning that acidic rain could cause chemical burns to the skin and damage the lungs. This was in accordance with the UN’s World Health Organization, which made the same recommendation.
But senior Iranian officials and state television later urged people to go outdoors and join state-organised rallies, including an annual pro-Palestine march in central Tehran.
“I would expect acute impacts on respiratory health,” said David J.X. Gonzalez, an assistant professor at the University of California, Berkeley. He added that young children and pregnant women are especially vulnerable to the air pollutants.
An Iranian engineer, who asked not to be identified due to fear of repercussions, said his relatives were planning to remain in Tehran despite the bombing but had fled to the country’s north.
Already before this war, Tehran was heavily polluted. Researchers, including Rahmanian, have detected high levels of fine particulate matter and heavy metals like lead, cadmium, chromium and nickel in the city’s water and air.
They have also found toxic substances that are released when fossil fuels and rubbish are burned, such as sulphur dioxide.
A high number of car engines and heavy industries near the city were the main cause, according to Dimitris Kaskaoutis, a physicist at the National Observatory of Athens, who has studied air and dust pollution in the country for over a decade.
Tehran lies at the base of the Alborz Mountains. The range blocks air circulation and creates a thermal inversion that traps pollutants, leading to episodes of poor air quality that can last for weeks and even months.
Normally, rain washes the pollution away, but on March 8, it might have made things worse, Kaskaoutis said.
“The combination of the catastrophic oil fires with rainfall makes them much more unhealthy and toxic for human health,” he said. “These pollutants diluted in the water are much more toxic and can easily be absorbed into our bodies – the nervous system, the blood system, and might affect kidneys, liver and other organs.”
Phone and internet communications in Iran have been cut since the US and Israel began their military campaign on February 28. Without sampling, it is impossible to know the scale of the pollution.
For now, damage needs to be documented, according to Nazanine Moshiri, an Iranian-born senior adviser on climate and peace at the Berghof Foundation in Berlin. “It’s necessary for accountability and clean-up when the conflict ends,” she said.
