It turns out there’s lead (and arsenic, and other stuff) in those LED holiday lights, and maybe others as well.
This result was found through leaching tests performed by researchers at Univ. of California, Irvine. Because it appears that leaching was required to mobilize these compounds for quantifying their presence, I suspect that the immediate health implications of this result are not too serious. However, this is the kind of waste material that probably ought not be sold and then thrown in landfills, because over time hazardous chemicals can indeed leach out.
Similar results were obtained back in 2004 for other things like cell phones, computers, etc.:
“The bottom line is that when we tested these devices, in many cases they met the EPA definition for regulated hazardous waste” …
So, it’s not surprising to find this issue exists for other electronic items such as LED light bulbs.