Researchers tested the lead levels of 10 sets of indoor/outdoor Christmas lights, some recently purchased in Nebraska and New York, others from the 1970s. The researchers found detectable levels of lead in all of them; and all were above EPA/HUD regulatory limits for equivalent areas of windowsills and floors. They also found no significant differences in lead levels among manufacturers, year of purchase, or how many years the lights had been used.

Lead is used in the polyvinyl chloride (PVC) jacketing of the Christmas light cords, said Laquatra, to prevent them from cracking or crumbling and to make them resistant to heat, light and moisture damage. Lead makes up 2-5 percent of PVC jacketing in different types of wires, he said.

"While some products are starting to have warning labels, there is no coordinated drive to encourage manufacturers to pursue alternatives," Laquatra said.

"Consumers should be aware that lead is in all appliance cords," he said, noting that although American manufacturers have been moving away from using lead as a PVC stabilizer in the last five years, at present there is no way to know how much lead exists in jacketing or in various products without independent testing.

While I knew lead was used in solder, I had no idea how prevalent lead was in PVC wiring. For sure, anything PVC is pretty god awful to burn -- it smells so nasty, it producing toxic byproducts, it's just nasty. But at lower temperatures it does actually put out fire, and is quite restive to corrosion, cracking, and conducting electricity.