Radiation

From Fallout - Wiki on Neoseeker

Radiation is caused by entering irradiated zones or by consuming certain food and drink. As your Radiation level increases some of your S.P.E.C.I.A.L stats will drop until you reach 1000 rads and die. You can check your current radiation level by looking under Status on your Pip-Boy

Entering the water anywhere in the Capital Wasteland will result in +1 rad per second and the majority of the food and drink will give you around +2 rads. There are a few places that are so highly irradiated that you'll likely die within seconds of entering. Walking to the main entrance of Vault 87 can result in over 3000 rads pers second, however, unless you're carrying a large amount of Rad-X and Rad Away it's likley that you'll die long before you can reach the entrance. Trying to obtain the GECK from the chamber in Vault 87 without Fawkes' help would be another suiside mission, by the time you reach the GECK you'll have around 400 rads per second. The water in the Capital Wasteland may only get you +1 rad per second but the water surrounding the bridge in The Pitt can go up to +600 rads per second.

Rads	Level	Effect
0-199	No Effect
200-399	Minor Radiation Poisoning	-1 END
400-599	Advanced Radiation Poisoning	-2 END, -1 AGL
600-799	Critical Radiation Poisoning	-1 STR, -3 END, -2 AGL
800-999	Deadly Radiation Poisoning	-2 STR, -3 END, -2 AGL
1000+	Lethal Radiation Poisoning	Death

There are 3 ways to remove Radiation from your body:

Rad Away - The amount of rads removed depends on your Medicine skill.
Doctors - Any of the Capital Wasteland's doctors can remove all of your rads for 100 Caps
My First Infirmary - This can be brought from either Moira Brown in Megaton or Lydia Montenegro in Tenpenny Tower depending on how you ended The Power of the Atom quest. It will remove all of your rads.