To put that in context, a shark can smell blood at one part per million. That means human noses are 200,000X more sensitive to geosmin, which is also the source of the earthy taste in some vegetables, than a shark is to blood. (American Council on Science and Health)

They came up with the idea of “olfactogenetics.” It’s similar in principle to optogenetics, an approach Potter had been trying with Drosophila but to underwhelming results. Rather than using light to stimulate a specific neuron, olfactogenetics uses an odor—geosmin. (nature)

Yet despite this substantial body of knowledge, geosmin and 2-MIB remain poorly understood throughout much of the water industry, and misconceptions which impede the prediction, treatment, and control of these volatile organic compounds (VOCs) persist. (ASM Journals)