6U.S. EPA (U. S. Environmental Protection Agency). Rules and Implementation [ EB/OL ]. http://www, epa. gov/ttn/atw/ eparules, html.
7Axelrada D A, Morello-Froschb R A, Woodruff T J, et al. Assessment of estimated 1990 air toxics concentrations in urban areas in the United States[ J]. Environmental Science & Policy, 1999, 2(4-5) :397-411.
8U. S. EPA ( U. S. Environmental Protection Agency). National Air Toxics Program: the integrated urban strategy; notice [ EB/ OL ]. http ://www. epa. gov/ttn/atw/area/fr19jy99, pdf.
9U. S. EPA. List of urban HAPs for the integrated urban air toxics strategy [ EB/OL ]. http ://www. epa. gov/ttn/atw/area/list33.html.
10U. S, EPA. List of 70 Area Source Categories[ EB/OL]. http :// www. epa. gov/ttn/atw/area/'701ist, pdf.
