Don't worry about me washing mushrooms too much, I'm too lazy, I was just suggesting that PeterMac could avoid yet another issue by using the 'dirty' ones and then washing them. It may ruin a good conspiracy, but I have heard stories that they grow them in chemtrail dregs at an attempt to subdue us all.
Me, I just rinse them, slice them up, saute them with a bit of butter, add a little milk, and pour on to steak! Yum!