"The first section introduces the background and significance of combined toxicity, covering degradation, oxidation, absorption, distribution, biotransformation, and excretion of compounds in the environment and organisms. The second section examines the primary sources and enrichment mechanisms of chemical mixtures, detailing biological exposure pathways. The third section presents classical and emerging toxicological research models, including cell and in vivo models, with case studies. It explores the combined molecular toxicity mechanisms of heavy metals, pesticides, POPs, PPCPs, PAEs, microplastics, and flame retardants. The fourth section introduces computer modeling methods for hazard assessment of mixtures. The final section discusses the challenges and future trends in this field."-- Provided by publisher.