Mike, I'm not a chemist but I do know that if you have ever eaten a cheesburger under the Golden Arches, washed your clothes or even eaten Canadian bacon, you have injested or used TSP. The molecule consists of sodium, oxygen and phosphorus and it is a very common inorganic background chemical. You might want to check further on your favorite search engine. About the only point of controversy about TSP is as a source of phosphates in lakes to cause alga increases. There are scientists on both sides of this issue but if you fertilized your lawn recently, you certainly put more phosphates in the ground water that washing your driveway would do. Many scientists seem to consider it among one of the better alternatives for clothes washing from an environmental point of view.