The aquarium silicone sealant will be the product that caused the warning. It seems that almost any product sold in the US ends up with that ridiculous warning on it. If you think about it, breathing the fumes that come off of uncured silicone sealant can't be good for your health and somehow California has a requirement for that caution on most uncured chemicals, even if the chemical is in its cured state by the time you see it as a consumer. As Tolak said, I have seen the warning on things intended for use with food.