my feet really get black at the drying area as well. I don't believe there are that many chemicals that are harmful. I've been doing it for 30+ years and don't have any problems, so I wouldn't sweat it.
I find that my soles tend to become charcoal black after a trip into the city. Places that are frequented by tourists tend to leave my feet their blackest! Humidity also plays a big role when determining the color of my soles. On a hot summer night, my soles can turn jet black with little to know effort at all. Once autumn comes it seems to take much more of an effort to get my soles black. And by winter, it's times to keep my little pigly wiglys warm, so, I reach for a pair of comfortable shoes
Mine are always black from walking around. I think my feet are stained for life with a light hint of black. lol
April, in your gallery there are some pics of your dirty feet... where were they taken and how did they get so black? do you have any more pics?