I have been reading about dryer lint as an effective kindling material, but I keep having the feeling that in some way it implies burning "plastic": all the artificial materials, coloring (although it might have been well washed out by then), detergents, chemically treated threads etc. Can it be considered as a polluting material, even just in such a small amount? (Wiki points it out as "one of the primary polluters in cave exploration") Can/should this amount of pollution be ignored because of the benefits of this kindling material?
I think that this is one of those things that has to be left to an individual's judgment. Some people would consider just starting the fire to be polluting even if it was done in accordance with Leave no Trace principles.
If this is something that bothers you, why not simply err on the conservative side and either use naturally occurring tinder or choose not to have a campfire?