Nothing on the island is quite comparable to anything in the 'outside world' but let's keep in mind that same medicine can both be a good drug and a bad drug, the cure and the poison without contradiction (ex: chemotheraphy or radiotheraphy) My point is: could not the exceptional power of the island-magnetism, just as well lead to anomaly in cell growth, aka tumor formation? If longer exposure to this magnetism could trigger such an effect, it makes all the sense that someone born and lived on the island all his life (like Ben claims to be) would be harmed sooner or later.. What do you say?

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"Bear...? Is that you?"-- Hurley S03E4