[Siegmund]

If I could return us to Peru from the PNAC tangent...

It seems vastly more likely to me that the meteorite landed on top of something that smelled bad (vegetation buried 50 feet deep and slowly rotting, freshly exposed to air again), than that the meteorite itself introduced a harmful chemical.

Among other things, the timeframe is wrong: if the meteorite directly released a poisonous gas, it dissipates with the first breeze; if it spread heavy metal over the area or something, the poisoning won't show up for years. A condition that comes to light moderately soon after the event and persists for a few days is something that got dug up.