Radiation

You gain one "radiation point" every 2 seconds if you stay on the radiation areas.

it takes 6 in game hours to eliminate one point.

The "radiations" buff appears when you have more than 15 points, and disappears when you have less than 10 points.

If you just have the buff (if you didn't spend more time in the radiations), it should take 30 in game hours to eliminate the surplus of radiations.

(From Barinou's reply to a Forum query)