Humans are super-sensitive to it as well. In fact, according to plant scientists at the U.K.'s John Innes Centre, we can detect it in as few as 100 parts per trillion – that's "trillion" with a "T" – which, as they vividly put it, means we're better at smelling it than sharks are at smelling blood.
— On geosmin, from We know what causes the scent of spring, but what's it actually for? at The Weather Network via Yahoo.
Super interesting (and relatively short) article. Thanks for posting.
Glad you enjoyed reading. I wish there had been some explanation of why humans are so sensitive to the smell!