The TRI was federally mandated by the emergency planning and community right-to-know act(EPCRA)title 3 of the superfund amendments and reauthorization act(SARA)of 1986. all manufacturing facilities in SIC codes 20-39 must report their discharges if they have '' 10 or more full-time employees and meet the established thresholds for manufacturing ,process,or (are)otherwise using listed chemicals'' (U.S Environmental protection agency (EPA),1994:14).thresholds for manufacturing and processing are currently "25000 pounds for each listed chemical,while the threshold for otherwise use is 10000 pounds per chemical'' (U.S. EPA,1994:14).
Griffin(1996) and logsdon(1995) have carefully reviewed the limitations in this database , and it will not be repeated here .logsdon does suggest,however,that researchers using the TRI database " focus on one or only a few industries, or at least report results by industries" (P.650).