Short Wave ‘Black rain’ in Iran and the environmental cost of war
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Mar 17, 2026 
Peter Ross, a toxicologist and senior scientist who studies environmental contamination, explains the fallout from Iran’s ‘black rain’. He breaks down what pollutants like soot, PAHs and benzene do to air, water and health. He discusses how rain can transport toxins, Tehran’s geography that worsens exposure, and why recovery from oil-related pollution can take decades.
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Black Rain Is A Toxic Chemical Soup
- Black rain results when explosions at oil facilities inject soot, sulfur and nitrogen oxides, metals, PAHs, benzene and other volatile toxicants into the atmosphere.
- Those pollutants mix with water vapor to form acidic, oily precipitation that burned throats and left oily residue across Tehran.
Stay Indoors When Black Rain Falls
- Authorities urged residents to stay indoors and the WHO warned about breathing high levels of toxic pollutants.
- Iran's deputy health minister warned the rain was contaminating soil and water, prompting immediate shelter-in-place guidance.
Explosions Turn Oil Into A Complex Airborne Hazard
- Explosions and fires at oil depots combust volatile gases and liquid fuels, releasing a complex mix of pollutants into neighborhoods.
- Peter Ross lists sulfur and nitrogen oxides, carbon monoxide, PAHs, benzene and toluene as acute airborne hazards.