EPO Level

[Siemowit]

Natural EPO concentrations in the blood increase when someone is exposed to pollution or second-hand smoke.

But does it come back to it's natural level, when a person spends some time away from pollution and smoke ?

[auden]

yes.

It's a feedback system based on oxygenation of the EPO-secreting cells in the renal parenchyma. The smoke or pollution increase % CO in the blood and therefore reduce O2 carriage, so resulting in relative hypoxia. This increases the production of EPO by a rather nifty bit of reverse coupling of some ion channel or other.

When you remove the smoke/pollution from the environment, the CO% goes down (over a period of days) and therefore the O2 supply to the cells rises and the EPO output falls. I can't remember the t1/2 for EPO so I'm afraid I can't help with how long this takes but think it is of the order of days following the removal of the stimulus.