almost 2 years ago - Regalis - Direct link
The radiation is explained quite poorly in the game at the moment (a lot of the lore we've written about it has currently only been published in the DLC Magazines), but that's going to change in future updates.

The radiation fields around Jupiter are a real-life phenomena caused by Jupiter's immense magnetic field. Because of it, the level of radiation on Europa's surface is high enough to be deadly (which explains why the colonists settled under the ice in Barotrauma).

The part made up for the game is that the intensity of that radiation is somehow increasing, and has already gotten so intense that it's affecting the outposts under the ice. Why exactly it's increasing is a mystery to the Europans as well. The reason why the society is not in a state of panic is that people don't know for sure how bad the situation is - they don't know how long it's going to keep increasing, or whether it's going to reach a level where shielding the outposts and/or migrating deeper down won't be enough to save humanity. Some people believe it's going to be the end of civilization, some think it's a minor inconvenience, some think it's some weird fluke that's going to pass. You could maybe draw some parallels to how the society is reacting to climate change in real life.

We've also implied (again, most of this is just mentioned in the DLC Magazines) that it may have something to do with the Eye of Europa, the ancient impact crater the outposts are built around, whose center you're travelling towards in the campaign and inside which the gravity is mysteriously stronger than it should be on Europa (close to Earth gravity).

But anyhow, we're going to be shedding some more light to this in future updates. Eventually, you'll be able to discover the cause and perhaps to find a way to stop it and save the Europan civilization. ;)