[the_solution]

I agree that the argument about keeping lead out of the environment is weak. As for using lead in any products I think it comes down to whether its possible that the lead leaks out into the environment in any way. That is very unlikely with car batteries (assuming they are recycled correctly) and remains to be shown for these solar panels. If the lead in them is bound in a way that makes it impossible to leak out (despite being exposed to weather or broken in a storm etc) I think it's a fair tradeoff.