MIB and the irregular sesquiterpene geosmin together account for the majority of biologically-caused taste and odor outbreaks in drinking water worldwide.

[1] MIB has a distinct earthy or musty odor, which most people can easily smell.

The odor detection threshold of MIB is very low, ranging from 0.002 to 0.02 micrograms per liter in water.

MIB is produced by various blue-green algae (cyanobacteria) and filamentous bacteria in the class Actinomycetia, and also some other prokaryotes and eukaryotes.

[3][4] They give a musty or earthy odor that can be quite strong if an algal bloom is present.