Interesting. The following is taken from the news story linked in the first post:
[“As part of the law, businesses selling products to people in California must provide clear and reasonable warnings” before knowingly exposing people to any chemical on the list, unless the expected level of exposure would pose no significant cancer risk. This warning is often in the form of a label on the product or its packaging.
The law defines “no significant risk” as a level of exposure that would cause no more than 1 extra case of cancer in 100,000 people over a 70-year lifetime. So a compound can be unlabeled if a person exposed to the substance at the expected level for 70 years is estimated to have a 1 in 100,000 chance or less of getting cancer due to that exposure. The law also has similar strict cutoff levels for birth defects and reproductive harm.]
So it appears that the burden lies on the manufacturer or seller to determine the risk level, which, at least in the case of the seller, they are neither educated nor equipped to do. The chance of causing cancer cited in that text is so minuscule that it seems to me other environmental factors would cause much greater threats, and the influence of a nickel-plated object would be unmeasurable and unprovable.
In such a case, the smart thing to do to avoid frivolous or opportunistic lawsuits would seem to be to label darn near everything.
An allergic reaction to nickel is quite different from a cause of cancer (as far as I know), but there may even be some charlatan who is ready to argue that A can lead to B.
This appears to me to be one of those well-meaning laws that will require a number of cases to move through court in order to establish enough case law that those making and selling a variety of products have some level of guidance about where the need for labeling exists and where it does not. I don't view it as "them damn environmentalists agin," although if the article is accurate, I think the law is poorly and vaguely written in terms of the evidence of harm required.