Unlike the criteria pollutants, toxics do not have National Ambient Air Quality Standards (NAAQS) making evaluation of their impacts more subjective. Because there are no standards established for Mobile Source Air Toxics (MSAT) not a lot of policy and guidance documents are available. Note that the interim guidance nor the frequently asked questions document are not a substitute for any laws or regulations, thus do not impose legally binding requirements on EPA, DOT, states, or the regulated community.