Smallest microorganisms

Mycoplasma genitalium

Explanation

,a bacterium which lives in the primate bladder, is the smallest known organism capable of independent growth. With a size of approximately 200 to 300 nm, M. genitalium is small enough to easily passes through bacterial filters

i believe you meant to say air rather than hair so the answer is below ")

the dead sea, the lowest place on earth at 430 metres (1,410 ft) below sea level, has a correspondingly high typical atmospheric pressure of 1065 hpa.

b brown mice / white sand dunes