Editorial Note: Phenylmercuric acetate is routinely added by some paint manufacturers to interior latex (water-based) paint as a fungicide and bactericide to prolong the paint's shelf-life. EPA permits interior latex paint to contain less than or equal to 300 ppm elemental mercury and exterior latex paint to contain less than or equal to 2000 ppm. However, neither the presence nor the concentration of mercury in the paint is required to be labeled on the paint can. Mercury may not lawfully be used in oil-based paint (1,2).
Cut and pasted from the below article.
http://www.cdc.gov/mmwr/preview/mmwrhtml/00001566.htm?mobile=nocontent