The period was characterized by a chemistry-driven toxicology approach linking molecular properties and solution-phase behavior to observed toxicity across metals and organics, using indices and thermodynamic concepts to predict effects. Metal- and inorganic-contaminant ecology studies showed antagonism and joint toxicity, revealing how mixtures modify health of freshwater and marine organisms and shaping early risk assessment frameworks. Ecological and environmental-system research extended toxicity studies to fouling organisms, sewage purification, and marine biota, illustrating contaminant effects on community dynamics and biogeochemical cycles. Public health and industry contexts emphasized surveillance of toxicants such as DDT, benzene, fluoride, and methyl mercury in environmental and occupational settings, foregrounding risk communication and regulatory concerns. Historical Significance: This era established early quantitative methods for evaluating combined toxicity and began tying chemical constitution to biological effects, laying foundations for modern risk assessment and regulatory frameworks. The introduction of physico-chemical ecotoxicology, linking solution pressures and metal properties to aquatic toxicity, anticipated later structure-activity and mechanism-based approaches. The attention to oxygen toxicity, radium exposure, and carcinogenic hydrocarbons fostered safety standards and medical guidelines, cementing a chemico-biological bridge in environmental health.