These studies focused on causes of toxicity that may be common to paper mill discharges: use of toxic additives in paper manufacturing (e.g. biocides), residual wood derivatives released from repulping (e.g. resin acids), toxic wastewater treatment chemicals (e.g. polymers), and incomplete treatment of mill wastewaters. The role of the chemical additives in pulp and paper effluents can be readily determined through bench-scale testing using the U.S. Environmental Protection Agency’s (USEPA) toxicity identification evaluation (TIE) procedures. Other causes of toxicity such as organic compounds (either formed in the bleaching process or released in repulping) may be reduced through improvements in water management and biological treatment. Additional TRE examples are noted based on experience at similar U.S. industries.