[kragen]

They typically contain copper, silver, lead, and tin, but those don't leach out of them at a significant rate, and of those four heavy metals, only lead is a real toxicity risk even if you digest the panels in acid instead of leaving them out in the rain. Another comment suggests that the dopants in the silicon are the relevant heavy metals, but those are present at parts-per-million levels, locked inside the silicon's diamond-structures crystalline lattice, and passivated with silicon dioxide, so that's not plausible either.

The most likely explanation is that this is a lie.