TCA (2,4,6 trichloroanisole) is a bacterial contamination in certain natural, or pressed corks. It is in no way harmful, except to your sense of smell. TCA, and its little brother TCB, will generally be described as smelling like moldy newspaper. It is not as easy to distinguish this on the cork itself, as much as in the wine. Once an infected cork has been placed in the bottle, the wine is effectively tainted, permanently. There is no way to remove the smell once it is there. It is such a problem because it can be picked up at levels as low as 10 parts-per-TRILLION! Because of its tiny effective levels, there is no point in dumping out a glass which has contained a "corked" wine, a new, or well rinsed glass is needed, otherwise you are just going to "infect" the new wine poured.

There are conflicting reports as to the percentage of wine that is affected by TCA/TCB. I have read everything from 1% to 15%, but the number that I see most often is between 6-7%. In the past 3 days, I have pulled the cork on 3 different bottles with TCA, from a $10 bottle of South American white to a $40 California Red.