No.

Many people want cars to stop using lead acid batteries, not due to concern about the lead, but because technology has advanced and there are better materials.

If this occurs, then the recycling stream will stop as there is now nowhere to reuse the lead. This is an option for a new way to reuse the lead.

>Instead of adding more lead to the environment

Of course the number of lead atoms on earth is pretty much constant and they are out there in the environment somewhere. The idea is to have them somewhere harmless rather in us. Leaded fuel was a bit of a disaster from that point of view hence the decline in the graph as leaded fuel was banned. (Still available in Algeria, Iraq, Yemen, Myanmar, North Korea according to Wikipedia). I think the solar panels could be done without net lead ending up in people if handled properly. Incidentally there's a probably a fair bit of lead a few mm from you in the solder of your electronic gadget but it doesn't do any harm there as it's had to get it from solder in to people. Hopefully the panels would have similar stability and not be like lead based paints which are a problem.

There are some similar question marks with cadmium based solar panels of which First Solar have installed 8GW worth. I think I might worry slightly about those too, probably more that lead. Indeed I think First Solar have only done industrial installations for power companies rather than domestic so the recycling can be done properly.

Actually, the number of lead atoms is not constant. It is steadily increasing, due to U and Th decay.

That's a pretty suggestive graph. If you look a bit more closely you'll see the opposite of what it suggests, we're halfway into the third decade without change in 'level of concern'. That doesn't mean there even is a safe level, it does seem to mean that we are definitely not approaching '0' by 2020.

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.

Its the usual argument for green products "ours produces 25% less blah". Doesn't stop the existing products being on the market, in fact it often looks like more products so likely more environmental damage.