Atmospheric testing of nuclear bombs releases all the radioactive consequences of an explosion that occurs in the air or on the surface of the ground. This type of testing involves fixing the nuclear device on top of a tower, dropping it from an airplane, or transporting it to the atmosphere by a balloon. The device is usually placed in a drilled hole or tunnel, between 200 and 800 m (650 and 2600 ft) below the surface and several meters wide. Studies and evaluations have estimated that cancer deaths due to global radiation doses from nuclear test programmes in the atmosphere of the five nuclear-weapon States amount to hundreds of thousands.
The preamble of the treaty banning nuclear weapons acknowledges the disproportionate impact of nuclear weapons activities on indigenous peoples. The International Campaign to Abolish Nuclear Weapons (ICAN) is a coalition of non-governmental organizations in one hundred countries that promote adherence to and implementation of the United Nations Treaty on the Prohibition of Nuclear Weapons. In 1996, recognizing that even underground tests were causing serious damage, and eager to end the era of nuclear testing, the international community adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT). This treaty prohibits any nuclear-weapon test explosion or any other nuclear explosion, and established an international system for monitoring and verifying tests.
However, it has not yet entered into force. Venting, which is the release of radiation from an underground nuclear explosion, would give clues to the technical composition and size of a country's device and, therefore, to its nuclear capacity.