Several experiments have measured the radiative climate forcing of the Pinatubo aerosols. Pinatubo's cloud caused about 1.7 times the global radiative forcing of El Chichon , making the estimated cooling of 0.5 degrees C a more robust figure. Vog , as well as acid rain , forms when sulfur dioxide reacts with atmospheric moisture. Vog aggravates respiratory problems, and acid rain damages crops and corrodes metal. On the Island of Hawai'i, the drinking water of many homes with rain-water catchment systems has been contaminated by lead leached by acid rain from roofing and plumbing materials.
Volcanoes emit gases during eruptions .
Even when a volcano is not erupting, cracks in the ground allow gases to reach the surface through small openings called fumaroles. Other common volcanic gases are carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, and fluorine. Sulfur dioxide gas can react with water droplets in the atmosphere to create acid rain , which causes corrosion and harms vegetation. Carbon dioxide is heavier than air and can be trapped in low areas in concentrations that are deadly to people and animals. Fluorine, which in high concentrations is toxic, can be adsorbed onto volcanic ash particles that later fall to the ground.