Abstract: In the traditional sense, any material may produce biotoxicity as long as it reaches a certain quantity or concentration, while it doesn’t have the corresponding toxicity when it is lower than the safe threshold. For many years, toxicologists have believed that higher doses of chemicals will cause greater effects than lower doses, while multiple researches on xenoestrogens (XEs) have demonstrated that XEs are capable of eliciting biphasic dose responses (inverted U shape curve) with different endpoints at many organization levels, especially inducing lowdose and nonmonotonic interference effects. XEs are a class of typical environmental endocrine disruptors (EDCs), leading to disturbance of normal endocrine function mainly through simulating or interfering with the synthesis, metabolism and transport of body’s normal endogenous estrogen. XEs induce lowdose and nonmonotonic effects by the combination of genomic and nongenomic pathways. This paper summarized the lowdose estrogenic effects of XEs on individual organism and molecular cell levels. The estrogenic effect mechanisms (i.e., genomic and nongenomic effects) were presented, and the analysis methods of environmental XEs trace concentrations were described. Finally, the future research direction of the lowdose and nonlinearity effects was prospected, providing theoretical guidance for ecological safety and human health research of XEs.

Key words: phylogenetic tree, molecular identification, statistical classification, sequence character, DNA barcode, genetic similarity, genetic distance