Sounds like an explosive combination of common sense
Point is stuff that was common place and hardly hazardous has been legislated out of existence, or red taped to death because of a select few morons (how about CARB compliant gas cans) or a politician who assumed a duty to protect us from ourselves where no problem existed. We ridicule "them" when a serious issue appears like a single ***** (like the McDonalds coffee burn lawsuit that resulted in the temp warnings on the cups) because the media reports sensationalism over facts (the McD's was repeatedly cited and fined for serving coffee at extreme temp - over 212* IRRC and the woman was scalded and had serious burns requiring hospitalization. We've all spilled coffee on ourselves, I'm sure no one got 3rd degree burns from it.)
Lead is one of many chemicals on the prop 65 warning and one of many in that extension cord. Examine the life an extension cord (especially this particular one will have) - if there is lead in the PVC jacket - contact with skin is minimal (wash your hands after touching it if it bothers you - that's all we shooters to after leaving the gun range and believe me I've got more lead residue and powder chemicals on my hands after a single round is fired than anyone will handling the cord). If it's in doors and not sitting in a window exposed to constant daily UV it's not going to break down like the blinds did. I've got several cords that have lived outside most of their life and the jackets are still not breaking down after several years of 6 months or outside at a stretch running battery chargers, maintainers, and block heaters.
I now heavy metal poisoning is no joke - friends son had it from their apartment with lead paint several years ago. He is hyper sensitive as the average person would not be affected. We all used to play with toys that had lead paint when we were kids - still got some Matchbox cars with the lead paint mostly gone - chipped off and probably ingested many years ago, never mind the high lead content in the casting metal they were made from.
Yes, I take my work clothes off before I come in the house, I leave chemical covered clothes and shoes from yard work (poison and fertilizer) outside to keep it away from the kids, I stay away from Asbestos and do my best not to chew on the trim and windows in my home which undoubtedly has lead paint in it's layers. think of it like the Saccharin debate from years ago which caused the cancer warning on food with the sweetener in it. Lab tests were done by many, especially in the FDA where several people there over the hundred years plus it's been around have felt it was a dangerous product with no evidence to back it.
The last ones in 1977 caused the warning (which was removed in 2000) that it was shown to cause cancer in test animals... not humans - lab animals. Of course we all know it was lab Rats which have little relation to humans. We also generally know the tests were forced because the amount of saccharin the rats were fed would be equivalent to an adult consuming several rail road box cars full of it in a day. Consumption would kill you long before cancer...which it turns out was never there. See, scientists forgot to take into consideration that Rats are not humans and don't act like humans behaviorally or genetically. The cell growth they found in the rats was caused by something else but they had attributed it to the saccharin testing, which is why the warning labels were removed.
If you want to believe something you will believe it regardless of the evidence and facts right in front of you. so many believe autism is caused by vaccinations even tho the evidence shows otherwise and the single study supporting it was proven falsified and created to push an idea not just once, but multiple times. Society believes the multivitamins we swallow daily are helping keep us healthy when numerous studies have shown the absorption rates for those compounds in the multivitamins are miniscule in the form and dosages in the pils while many believe vitamin C helps the immune system (a hold over from the same doctor who instilled the daily vitamin belief and who's career was destroyed over the insistence on vit C) with absolutely zero scientific results proving it.
I don't remember his name, but I'm sure google will yield info for anyone interested in learning more (or fact checking me)
If you really really don't want a cord subject to Prop 65 you're probably out of luck due to the previously mentioned brass plug terminals, but there are plenty sources of rubber jacketed cordage out there. Be prepared to replace it regularly since rubber is so UV sensitive. I have had to replace rubber jacketed power cords on several tools (porter cable of Pentair days) almost annually.