That's interesting. I stopped at a McDonald's very near Coalinga* and on the take out window it read verbatim:
"Chemicals known to the state of California to cause cancer, or birth defects or other reproductive harm may be present in foods or beverages sold or served here.
Such chemicals are also present in this area and in consumer products and other items sold, provided, and used here."
And wondered why this was on window. Now I know. Still decent cheeseburger though I don't care.
I don't live in California, but sometimes fly in for work. I've joked that the pilot should just announce as they are crossing the border that "The State of California is known by the State of California to cause cancer." and call it a day.
Another fun thing to do is to point the signs out to a California resident, who has probably long since completely edited them out of existence. It causes a "can't unsee!" reaction for about a week for certain people.
I bought some graphite a few years ago to lubricate a sticking lock. The label on the tube told me that graphite is known to the state of California as a carcinogen. I reflected on the pencils I and everyone else had sharpened over the years, and wondered what if any abatement measures are present in California classrooms.
Yeah, it's a warning that was passed by ballot initiative. If the initiative had said "Warning: this building is known to contain body thetans" then they'd have to print that on the sign. Welcome to California.
As a non-CA resident I've benefitted from these stickers. One time I was given a bar set which included a shaker which had a sticker on it that said something along the lines of "This product contains lead paint which the state of California has found to be hazardous…"
Unfortunately, a lot of the Prop 65 warning labels don't even say what particular substance they're warning you about. And I've even seen such stickers on pieces of solid wood, warning the consumer because wood dust is a _suspected_ carcinogen when inhaled.
To me, these labels are useless and dangerous for the same reason a lot of anti-drug education/propaganda is bad: it doesn't do anything to inform you about the relative level of danger. e.g. regardless of the affects of the drug itself, smoking a joint is _much_ less dangerous than injecting any substance with needles/syringes/etc which are not sterile.
It goes farther. Every single cable (USB, HDMI, ethernet... that kind of cable) you buy will come with the same label "this product contains lead, a chemical known to the state of California to cause birth defects etc etc etc". It might have more of an effect if there were any cables that didn't come with the warning.
"Chemicals known to the state of California to cause cancer, or birth defects or other reproductive harm may be present in foods or beverages sold or served here.
Such chemicals are also present in this area and in consumer products and other items sold, provided, and used here."
And wondered why this was on window. Now I know. Still decent cheeseburger though I don't care.
*https://www.google.com/maps/dir/Coalinga,+CA/McDonald's,+275...