In addition to the deadly blast and heat effects of the primary detonation, nuclear bombs result in deadly gamma rays and other radiation. Exposure to intense radiation causes sickness and death in humans, especially in the form of cancer. In addition to the 80,000 people who instantly died in Hiroshima, another 60,000 people perished by the end of 1945 due to radiation sickness. Those who survived beyond that were at a much higher risk of cancer years later.
Fallout is another danger of nuclear weapons. Radioactive particles spread out in the atmosphere after being dispersed by the mushroom cloud. These materials can travel around the world before precipitating along with rain, snow, and fog. Most fallout dissipates within days, but several elements continue to release harmful radiation over a long period of time and may render the area uninhabitable.
Even testing of nuclear weapons can have great detrimental effects. Nuclear testing in the United States in the 1950s and 1960s generated radioactive fallout that resulted in 17,000 cancer deaths, according to some expert estimates. Millions of residents in Kazakhstan who lived upwind of Soviet nuclear tests have been afflicted with cancer, birth defects, and weakened immune systems. This has lead for the push for a Comprehensive Test Ban Treaty.
Many experts theorize that nuclear explosions have the potential to cause massive weather changes and global environmental damage.