4 1 chapter industry reporting to the toxics release inventory this provides an overview of 1997 tri data by sector for 20 manufacturing sectors required report as described in will expand include seven additional beginning with 1998 year box lists industries standard industrial classification sic code 2 explains codes and their use summarizes other waste management comparable overviews presented it then compares last three years 1995 1996 1988 recent because some types were not collected also reviews 1991 these multiple analyses correspond 3 discussion core chemical introduction is important accurate interpretation comparisons significant changes over time across all 21 490 facilities submitted 71 670 forms
