Everything has a does-response curve that, at one or both extreme, will kill you. Oxygen, water, nitrogen, pizza, everything. Since 1986, California has had a reporting law on the books with a very steep financial fine, so it's cheaper to slap a sticker on any product that may contain those chemicals than to run the risk of the fine. For things like furniture/matresses/clothes, it's usually off-gassing of flame retardants. Most foods have been exposed to herbicides/pesticides/fertilizers or are packaged in something that would qualify. Building materials are chock full of carcinogenic.

We're fairly good at keeping everything to safe doses for the general population, and making companies tell consumers about the crap isn't a bad thing. Think about it loke nutrition labels... most people don't care, but if you have a dietary restriction or an allergy, it's pretty helpful to know what's in it before you buy and eat it.