Black Rain

News: The World Health Organization has warned about health risks from “black rain” reported in Iran after oil facility fires.

About Black Rain

• It is uncommon atmospheric phenomenon where rain becomes contaminated during its passage through the atmosphere, particularly in highly contaminated atmospheric layers.
• It contains dark, often black, grey, or oily droplets.
• How it happens: 
  • Rain forms when water vapour condenses around tiny particles called condensation nuclei (dust, salt, pollen, pollutants).
  • Normally, raindrops carry very little material. When the air contains large amounts of ash or particles, raindrops collect them while falling. This process is called atmospheric scavenging.
  • If particle concentration is very high, the rainwater appears black, brown, or reddish depending on the particles present. 
  • In explosion affected regions, explosions releases significant quantities of toxic hydrocarbon compounds, sulfur, and nitrogen oxides into the air. As rain moved through the pollutant-saturated skies, it absorbed these chemicals and fell back down as black rain.
• Impact: It may cause several environmental problems such as contamination of soil, lakes, rivers, and groundwater. It can also cause human health problems like skin and respiratory issues due to contact with contaminated water and air.