Two atmospheric scientists have discovered that about 40,000 metric tons of chlorine were injected into the stratosphere during the eruption of the El Chichón volcano in Mexico in March and April 1982. According to the National Center for Atmospheric Research (NCAR), never before had chlorine in the stratosphere been conclusively traced to volcanic sources.

The NCAR scientists who made the discovery, William G. Mankin and M.T. Coffey, said the principle source of stratospheric chlorine was previously believed to be manmade fluorocarbons from activities at the Earth's surface. The presence of natural sources of stratospheric chlorine may change the overall view of the chemistry of the ozone layer.