Critical influences of metal compounds on the formation and stabilization of environmentally persistent free radicals

Abstract

Environmentally persistent free radicals (EPFRs) are emerging organic pollutants found widely in environmental media, which can induce reactive oxygen species generation and DNA damage. EPFRs have lifetimes of hours, days, or even months. EPFRs form through chemical bonds of organic compounds (e.g., phenols and hydroquinones) rupture or through electron transfer between organic compounds and metal ions during thermal-related processes. Metal compounds play critical roles in EPFR formation and stabilization. Different metal compounds and concentrations catalyze the formation of EPFRs and give different EPFR lifetimes. Information on EPFR catalysis by different metal compounds is important for understanding EPFR formation mechanisms. The influences of metal compounds at different species, concentrations and in different crystal forms on EPFRs are systematically summarized here. Information on the roles metal compounds play in EPFR formation and stabilization is important to understanding EPFR characteristics during thermal processes involving different metals, and will therefore allow effective strategies to be developed to control EPFRs and certain persistent organic pollutants intermediated by EPFRs.