The Environmental Protection Agency is responding to a rulemaking petition requesting amendments to the Non-Hazardous Secondary Materials (NHSM) regulations, which establish standards and procedures for identifying whether non-hazardous secondary materials are solid wastes when used as fuels or ingredients in combustion units. The petition requested the following amendments: 1) change from mandatory to "should consider" the legitimacy criterion for comparison of contaminants in the NHSM to the traditional fuel the unit is designed to burn; 2) remove associated design to burn and other limitations for creosote treated railroad ties; and 3) revise the definition of paper recycling residuals (PRRs) that can be burned as non-waste to include non-fiber materials. EPA issued a proposed response that would deny the petition but revise the definition of PRR on January 28, 2022 (87 FR 4536).