It's on the mass effect wiki timeline. So maybe worth two grains of salt, but it's there. And one of the talk pages has a former writer for the first game clarifying the devkit timeline they were using when writing the game. So again, maybe canon, maybe not.
iirc, that's only from biotic shepards, non biotics don't have element zero exposures, or at least they didn't when I checked the timelines in-game.
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though, that was a while ago.
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I've just checked the ingame timelines in all 3 games, there is no mention of shepard's element zero exposures, primary or secondary, even with a biotic shepard. checked other codex entries as well, no dice.