"The environmental radioactivity is increased." That's it?

Polonium and especially radon contribute to the natural environmental radioactivity.

Milton H Feldman has written:

'Environmental trace materials' -- subject(s): Trace elements, Radioactivity

K. Beach has written:

'Marine environmental radioactivity surveys at nuclear submarine berths 2003' -- subject(s): Charts, diagrams, Charts, diagrams, etc, Measurement, Nuclear submarines, Radioactive pollution of the sea, Radioactivity

A half-life is the time taken for the radioactivity of a material to fall to half its original value. A material can undergo infinite half-lives because each time it falls to half the next half-life falls to half of that half:

No half-lives have elapsed when radioactivity is at the original amount; 1/1.

1 half-life is when radioactivity is at 1/2

2 half-lives is when radioactivity is at 1/4.

3 half-lives is when radioactivity is at 1/8.

4 half-lives is when radioactivity is at 1/16.

And so on.