Atmospheric testing releases all the radioactive consequences of a nuclear bomb that explodes in the air or on the surface of the ground. In these tests, the nuclear device can be fixed on top of a tower, dropped from an airplane, or transported to the atmosphere by a balloon. The nuclear device is placed in a drilled hole or tunnel, typically between 200 and 800 m (650 and 2600 ft) below the surface and several meters wide. Some studies and evaluations, including an evaluation by Arjun Makhijani of the health effects of nuclear weapons complexes, estimate 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.
In its preamble, the treaty banning nuclear weapons recognizes 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. Recognizing that even underground tests were causing serious damage, and eager to end the era of nuclear testing, the international community adopted in 1996 the Comprehensive Nuclear-Test-Ban Treaty. The CTBT, which prohibits any nuclear-weapon test explosion or any other nuclear explosion, and established an international system for monitoring and verifying tests, has not yet entered into force.
The release of radiation from an underground nuclear explosion, an effect known as venting, would give clues to the technical composition and size of a country's device and, therefore, to its nuclear capacity.