Armin Sorooshian
The Conversation / March 16, 2026
The waves of U.S. and Israeli bomb strikes in Tehran and Beirut, and Iran’s missile and drone attacks on neighbouring countries in response, are damaging more than buildings – they are sending toxic debris into the air in cities that are home to millions of people.
Military strikes have hit Iran’s missile stockpiles, nuclear facilities and oil refineries. When a strike set fire to an oil depot, it sent toxic black clouds billowing over Tehran and created oily rain that settled on buildings, cars and people. Residents described having headaches and difficulty breathing.
As a chemical and environmental engineer who studies the behaviour and effects of airborne particles, I have been following the damage reports to understand the health risks residents are facing as toxic materials get into the air. The risks come from many sources, from heavy metals in the munitions themselves to the materials sent airborne by what they blow apart.
The invisible enemy during war: air pollution
A disaster’s effects on air quality and public health depend in large part on what is being destroyed.
The terrorist attacks on New York City’s World Trade Center on Sept. 11, 2001, were localized, but they ejected massive bursts of pollutants into the air. These included gases such as volatile organic compounds and particulates – often called aerosols – containing a myriad of substances, such as dust, polycyclic aromatic hydrocarbons, metals, asbestos and polychlorinated biphenyls.
These pollutants can harm the lungs, making breathing difficult, and worsen cardiovascular problems, contributing to heart attacks, among other health damage. Tiny particles smaller than 2.5 micrometers, called PM2.5, are especially harmful because they can travel deep into the human respiratory system. But larger particles can also bring major airborne health risks.
When buildings are heavily damaged or collapse, the rubble often contains crushed concrete, gypsum and carcinogenic fibrous materials, such as asbestos. Even after the initial dust settles, wind and other disturbances, including efforts to find survivors or clear the rubble, can send those materials back into the air, putting more people at risk.
Many rescue and recovery workers who responded to the World Trade Center collapse in 2001 developed chronic respiratory problems. That’s also a risk for people searching for survivors in bombed buildings after military strikes and later when cleaning up the debris.
Fires create additional hazards as vehicles, buildings and the chemicals and other materials in them burn. The January 2025 fires in Los Angeles sent a stew of dangerous particles and gases into the lower atmosphere. Studies have shown how lead particles that fell to the ground were kicked back up into the air again where people could inhale them, along with other contaminants.
Munitions and oil facilities
Military attacks degrade air quality in other ways. The Gaza Strip, Iraq, Kuwait, Ukraine and most recently Iran and surrounding countries have all faced extensive damage from munitions, which contain toxic materials. Bombs and artillery often contain explosives and heavy metals, such as lead and mercury, which also contaminate soil, water and the environment.
When oil storage facilities and pipelines are damaged, they emit an especially harmful cocktail of pollutants. This chemical blend includes airborne soot particles, which darken the sky and contribute to the “black rain” observed in Iran.
During the Gulf War in 1991, downwind countries experienced similar polluted rain as Kuwait’s oil fields burned. The U.S. Department of Defense found that the smoke plumes contained sulphur dioxide and nitrogen oxides, among other gases and soot.
The severe consequences of environmental pollution during wars prompted the U.S. National Academies of Science, Engineering, and Medicine to publish a series of reports on Gulf War military veterans’ health, starting in the early 2000s. They documented illnesses soldiers suffered after being exposed to chemicals and heavy metals, including from oil well fires. They also examined scientific evidence on potential associations between pollution in war and reproductive and developmental effects in the veterans’ children.
Getting pollution out of the air
Nature, including rain and wind, can help reduce the pollution levels in the air.
Rain helps pull particles out of the air, depositing them back on the ground and surfaces. The raindrops form around particles and also collect more particles as they fall. However, rain has occurred only sporadically since the military attacks began in Iran.
And rain also contributes to runoff into streams, and pollutants can damage crops and contaminate waterways, soil and vegetation.
Wind can help blow pollutants out of an area, though at the expense of downwind sites.
Tehran has another challenge when it comes to pollution because of its terrain. The city is surrounded by mountains and prone to the effects of low-altitude temperature inversions in the wintertime, which concentrates pollutants even more by holding them closer to the ground. These attacks have been slightly outside the coldest periods for Tehran, allowing for deeper mixing of air, but the inversion still has an effect.
Can people in war zones protect their health ?
People in war zones, where they are already under stress, can reduce their health risks by staying indoors in the days after military attacks, if possible. Keeping windows and doors closed can help reduce the amount of polluted ambient air that comes inside.
Indoor air quality is just as important as the air outside. For example, infants crawling on floors can be exposed to deposited particles with toxic materials that are tracked in or blow in under sills and doors, similar to wildfire smoke exposure.
As buildings continue to smoulder and clearing debris sends harmful particles back into the air, the pollutants can also contaminate agriculture and waterways. People can try to avoid crops, water and seafood that were likely to have been affected by toxic airborne pollutants. However, getting information about risks gets harder in a time of war, and scarcity can leave people with few choices.
Armin Sorooshian – Professor of Chemical and Environmental Engineering, University of Arizona
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What is the ‘acid rain’ in the wake of US bombings in Iran? An atmospheric scientist explains
Gabriel da Silva
The Conversation / March 9, 2026
Reports are emerging of black rain falling over parts of Iran in the hours after US-Israeli airstrikes on oil depots on the weekend, with some outlets describing it as “acid rain”.
Iranian residents have reported headaches, difficulty breathing, and oil-contaminated rain settling on buildings and cars. Iran’s Red Crescent Society warned rainfall following the strikes could be “highly dangerous and acidic.”
As an atmospheric chemist and chemical engineer who researches air pollution, these reports are very worrying, and indicate much more than just acid rain.
This rain would include acids but also likely a host of other pollutants that are harmful to humans and the environment in the short and long term. It may even be worse than the term “acid rain” conveys.
More broadly, the thick clouds of toxic smoke over densely populated areas in Iran are also a major problem for anyone breathing this air right now.
What could this ‘acid rain’ be ?
One of the primary ways air pollutants are removed from the atmosphere is through rain. When you have significant levels of pollutants in air they will be collected by falling water droplets and “rain out” of the atmosphere.
That’s why we are getting these reports of black rain falling from the sky after the oil depots were struck – evidence of just how contaminated the local air must be.
To me, this black rain indicates toxic pollutants such as hydrocarbons, ultrafine particles known as PM2.5, and carcinogenic compounds called polycyclic aromatic hydrocarbons (PAHs) have made their way into the rain.
On top of this there would be a mix of other unknown chemicals, likely including heavy metals and inorganic compounds from the building materials and everything else caught up in the initial explosions and the ensuing fires.
The smoke from the bombed oil depots would also contain sulphur dioxide and nitrogen dioxide, which are precursors to forming sulfuric acid and nitric aid in the air. This acid then makes its way into water droplets, and is responsible for what we conventionally label acid rain.
The acid rain we heard so much about in past decades was primarily caused by sulphur dioxide produced by burning fossil fuels. Sulphur is naturally present in crude oil but is now mostly removed at the refining stage.
Aside from the rain, it’s worth remembering that all smoke is toxic; if you can smell it, it can be at levels that are harming you.
So that level of black smoke seen over densely populated areas in Iran is extremely worrying and can cause chronic short- and long-term health problems.
What are the potential health risks ?
In the short term, people exposed to this black smoke in Iran might have headaches or difficulty breathing, especially if they have asthma or lung disease.
Vulnerable populations – such as older people, young children and people with disabilities – are more at risk. Exposure to toxic air pollution during pregnancy can also lead to lower birth weights.
In the longer term, exposure to the compounds in the air and in this black rain is potentially increasing people’s cancer risk. When ultrafine particles (PM2.5) are inhaled, they can get into your bloodstream. This has been linked to a range of health impacts including cancers, neurological conditions (such as cognitive impairment), and various cardiovascular conditions.
Once these heavily polluted plumes of air have their pollutants rained into natural waterways, they can also start to affect aquatic life, as well as human drinking water sources.
Another issue is that this black rain is depositing these compounds on buildings, roads and surfaces, which means they can make their way back into the air when disturbed by strong winds.
A legacy of war
There has been growing attention on the environmental impact of conflict worldwide. Part of this has emerged in the wake of past wars in Iraq and Kuwait, where there was large-scale deconstruction of oil wells and the use of burn pits.
We now know there are long-term health impacts on returning service people, including Australians. So we can assume local populations are also profoundly affected.
In the short term, people exposed to this smoke and black rain in Iran should try to wear masks or face coverings, seek refuge from it, stay indoors, close doors and windows, and try to keep the air out. It is also important to clean hard surfaces where possible, particularly indoors, to reduce exposure to deposited pollutants.
On the ground, of course, this may be very difficult to achieve in the chaos of war.
Gabriel da Silva – Associate Professor of Chemical Engineering, The University of Melbourne
