That is something that has always concerned me with carp anglers using PVA bags in lakes! Al least in a river it gets washed downstream and out into the sea, where eventually it is degraded to form naturally occuring carboxylic acids.I've been always very wary about using any chemical product on anything that comes into contact with water. Being a lifelong ecologist I contented myself with river mud and my own spit to break the surface tension with thin tippets. It usually worked well for me and I didn't bother about the continuous repeating. The trouble it takes eased my conscience and didn't compromise my respect for water and everything living in or of it. May sound far fetched, but all the manmade alternatives definitely were from my point of view. Each to their own of course.