Background and purposeThe ubiquitous dissolved organic matter (DOM) is actually not inert as we always think, and the hormone-like effects of DOM have been reported. The objective of this study was to investigate the estrogenic effects of DOM and its impact on the activity of the natural estrogen 17β-estradiol (E2).Materials and methodsDOM of three different sources, HA sodium salt, Suwannee River natural organic matter (NOM), and Nordic Reservoir NOM, were used. The estrogenic activity was detected by using the yeast estrogen screen (YES) assay. Estrogenic effects of DOM without and after solar irradiation were tested. Influences on the action of E2 by DOM were also investigated.ResultsNo direct estrogenic effects of the DOM used were observed in the YES assay. However, the estrogenic activities after 24 h of irradiation increased to 0.0288, 0.0178, and 0.0195 μM of E2 equivalents for HA sodium salt, Suwannee River NOM, and Nordic Reservoir NOM, respectively. After incubation of DOM, the estrogenic activity of E2 was increased by low concentrations (8.33 and 83.3 μM) of DOM while decreased by higher concentrations (8.33 × 102 and 8.33 × 103 μM) of DOM.ConclusionsThough direct estrogenic effects of DOM were not observed, increase in the estrogenic activity of DOM after irradiation was significant. DOM shows amphoteric influence on the natural estrogen E2, which depends on the concentration of DOM used. Because of its ubiquity, DOM may be of great ecological significance, playing an important role in regulating the reproduction of aquatic organisms.