Sorry if this topic is already over-discussed (I'm new here), but I haven't seen another post saying THIS.
One of these days I was thinking about what the hell will happen in season six, whether they changed the timeline or not... And then I remembered that earlier in the series, when they were examining the Hatch's foundations, Sayid said the last time he saw something like that was Chernobyl (it was something like full of concrete).
Then, when Desmond got stuck on the Island, Kelvin was using a special suit and he said it was dangerous outside the hatch. Eventually, Desmond discovered it was not. At first, I thought that was because of the Purge and that letal gas, but what if Dharma folks (Kelvin and Radzinsky) were like afraid of the radiation? Either way, what about the Sayid-Chernobyl thing? (I think the episode was Everybody Hates Hugo).