October 1987 | The Antarctic ozone expedition ends: findings indicate that chlorine chemicals are the primary cause of ozone depletion. |
November 1987 | A scientific conference confirms the findings of the Antarctic ozone depletion expedition. |
November 1987 | United States lawmakers call for new negotiations to strengthen the Montreal Protocol. |
February 1988 | Three United States senators ask DuPont to stop making CFCs. |
March 1988 | The chairman of DuPont denies the request to stop making CFCs. |
March 1988 | The United States ratifies the Montreal Protocol in a unaimous vote. |
March 1988 | The Ozone Trends Panel announces it has found ozone losses of 1.7 to 3 percent over the Northern Hemisphere. |
March 1988 | Three weeks after refusing to stop making CFCs, the DuPont Corporation announces it will cease manufacture of the chemicals as substitutes become available. |
April 1988 | Manufacturers of plastic foam food containers announce they will stop using CFCs. |
August 1988 | The EPA orders domestic CFC reductions that mirror the terms of the Montreal Protocol. |
October 1988 | Scientists meeting in the Netherlands confirm the Ozone Trends Panel findings of ozone losses in the Northern Hemisphere. |
March 1989 | European countries and the United States agree to faster CFC reductions but developing countries oppose the new timetable citing the costs of substitutes and scientific uncertainty. |
1990 | The United States Congress passes the amendments to the Clean Air Act. These amendments include Title VI , regulations concerning the protection of stratospheric ozone. |
1992 | Worldwide ozone levels in the stratosphere drop to lowest levels in recorded history. |