good news is you won't need to worry about fallout if you're within
three kilometres of ground zero. The bad news is you won't worry
because you'll be dead. Depending on the bomb and its yield the
biggest dangers you face will be the immediate release of a
tremendous amount of heat and energy. The lesson is don't be close to
where a nuclear bomb is going to go off.
worst part is that a lot of the data we have uses a model where one
nuclear device is used, most current nuclear strategy (at least what
is known) says depending on where you live you could expect to see
multiple mushroom clouds on the horizon.
the long run, and remember you won't have to worry about the long run
if you're close enough so lucky you, the amount of nitric oxides
created by sudden heat and rapid cooling of a blast which in turn can
diminish ozone levels increasing the amount of ultra violet radiation
from reaching the earth, great! More radiation.
After several blasts
with nuclear weapons the earth may also be subject to nuclear winter
and nuclear famine - thus far these phenomena are unproven and
theoretical but the science behind both are pretty sound; they remain
theoretical because we've never had a chance to test the hypothesis.
And hopefully we never will.