Black rain fell in Iran’s capital after airstrikes on oil facilities sent up dark clouds of toxic smoke. Health officials warned of serious risks to anyone who breathes or comes into contact with it. Soot, toxic chemicals and acidic gases combined with water droplets in the atmosphere, then fell back to Earth when it rained. Experts say microscopic soot particles can lodge deep in the lungs and enter the bloodstream, causing breathing and heart problems that can lead to premature death. Some toxic substances can increase cancer risk.