The document summarizes the effects of the atomic bombs dropped on Hiroshima and Nagasaki in August 1945. It provides data on the numbers killed and injured at different distances from the bomb explosions, as well as population figures. It then explains the main types of damage caused by a nuclear explosion - the blast shock wave, direct nuclear radiation, thermal radiation, and radioactive fallout. It notes the wind speeds and building damage from shock waves, the penetrating ability of neutrons and gamma rays, the burns caused by thermal radiation at different distances, and how fallout enters the atmosphere and environment.

1. Atomic Bomb

3. Little Boy Fat Man
Hiroshima Nagasaki
August 6, 1945 August 9, 1945

4. Distance from
Killed Injured Population
Ground Zero (km)
0 -1.0 86% 10% 31,200
1.0 - 2.5 27% 37% 144,800
2.5 - 5.0 2% 25% 80,300
Total 27% 30% 256,300

5. Distance from
Killed Injured Population
Ground Zero (km)
0 - 1.0 88% 6% 30,900
1.0 - 2.5 34% 29% 27,700
2.5 - 5.0 11% 10% 115,200
Total 22% 12% 173,800

6. Explosive Blast
Much of the damage inflicted by a nuclear explosion is
the result of its shock wave. There are two components
to a blast's shock wave. First, there's the wall of pressure
that expands outward from the explosion. It is this
pressure, measured in psi (pounds per square inch), that
blows away the walls from buildings. A typical two-story
house subjected to 5 psi would feel the force of 180 tons
on the side facing the blast. (Download the Quicktime
movie entitled house to see an example of a building
subjected to this type of pressure.) Additionally, the blast
creates a 160 mile-an-hour wind. And that's only at 5 psi.
The wind speed following a 20 psi blast would be 500
mph!

7. Direct Nuclear Radiation
A nuclear detonation creates several forms of nuclear, or
ionizing, radiation. The nuclear fission (atom splitting)
and nuclear fusion (atom combining) that occur to
produce the explosion release, either directly or
indirectly, neutrons, gamma rays, beta particles, and
alpha particles. Neutrons are heavy particles that are
released from atoms' nuclei. These tiny "missiles" can
easily penetrate solid objects. Another penetrating form
of radiation is gamma rays, which are energetic photons.
Both of these types of radiation can be deadly. Beta and
alpha particles are less dangerous, having ranges of
several meters and several centimeters, respectively.
Alpha particles can cause harm only if they are ingested.

8. Thermal Radiation
If you're seven miles away from a one
megaton explosion, the heat emanating
from the fireball will cause a first-degree
burn (equivalent to a bad sunburn ) to any
exposed skin facing the light. If you're six
miles away, it will cause second-degree
burns. And if you're five miles away, the
thermal radiation will cause third-degree
burns -- a much more serious injury that
would require prompt medical attention.

9. Fallout
You've seen the image: a mushroom cloud created by a
nuclear explosion. Produced with a detonation at or near
the earth's surface, this type of explosion results in far-
ranging radioactive fallout. Earth and debris -- made
radioactive by the nuclear explosion -- rises up, forming
the mushroom cloud's stem. Much of this material falls
directly back down close to ground zero within several
minutes after the explosion, but some travels high into the
atmosphere. This material will be dispersed over the earth
during the following hours, days, months. In fact, some of
the particles rising up through the mushroom will enter the
stratosphere, where they could remain for tens of years.

10. Distance: 30 miles
Much more than a lethal dose of radiation. Death can occur within hours of
exposure. About 10 years will need to pass before levels of radioactivity in
this area drop low enough to be considered safe, by U.S. peacetime
standards.
Distance: 90 miles
A lethal dose of radiation. Death occurs from two to fourteen days.
Distance: 160 miles
Causes extensive internal damage, including harm to nerve cells and the
cells that line the digestive tract, and results in a loss of white blood cells.
Temporary hair loss is another result.
Distance: 250 miles
Causes a temporary decrease in white blood cells, although there are no
immediate harmful effects. Two to three years will need to pass before
radioactivity levels in this area drop low enough to be considered safe, by
U.S. peacetime standards.