Uniform design ray in the assessment of combined toxicities of multi-component mixtures

Multi-component mixture (MCM) is a complicated chemical system that contains a great deal of mixture rays with various mixture ratios, and each ray includes many mixtures with different concentration levels. Currently, in combined toxicity field, almost all studies on MCM focus on the mixtures designed by the equivalent-effect concentration ratio (EECR) procedure. However, the EECR mixtures cannot represent the whole mixture system because the EECR mixtures are located on one mixture ray in concentration space formed by multiple components. In our view, some optimal experimental design such as the uniform design (UD) should be used to effectively select many representative mixture rays from the MCM system, instead of single EECR ray. The uniform design ray (UD-ray) integrating UD idea with fixed-ratio ray design can systematically and comprehensively measure the combined toxicity changes in the MCM system. This review introduces the operation method, construction of uniform table and corresponding usable table, and some cases of application of the UD-ray to help readers easily use UD-ray in their MCM toxicity assessment.