I do not know. I assume they come from the manufacture of the plastic panels. You’d have to look that one up.
Apparently in some parts of the country like Missouri that are subject to violent storms, some panels get damaged and whatever is inside the panel itself is carried off by the rain to the ground.
Not only are we growing food to put in gas tanks, but we are systematically making prime (rated 1-5) farmland unusable forever.
Panels are made of silicon and then they're usually doped with boron and phosphorous to create positive and negative charges,respectively, and then whatever frame they're set in, so some type of probably aluminum frame and the clear polycarbonate top. The worst thing in them would be some lead solder