Influência da matéria orgânica e da interação de estrogênios na quantificação de atividade estrogênica e sua interferência em matrizes ambientais

Abstract

The presence of estrogenic endocrine disruptors in aquatic environmental matrices has been a concern during the last decades and bioassays are recommended tools for their monitoring. However, the occurrence of mixture of different substances, their physical-chemical properties and the environmental matrix characteristics may influence the resultant response. This study aimed to assess this influence on the estrogen receptor transcriptional activation assay Yeast estrogen Screen (YES). A binary mixture analysis of 17β-estradiol (E2), 17α-ethinylestradiol (EE2), estrone (E1) and estriol (E3) was performed with partial fixed-ratio design, whose results were adjusted to a concentration addition model and further extended to synergism/antagonism, dose level and dose ratio dependent deviation models. Mixtures of E2 and humic acid (HA) were evaluated through the Schild approach in order to investigate the interactions of estrogens and dissolved organic matter (DOM). Environmental samples from municipal landfill leachate and wastewater treatment plant (WWTP) influent and effluent were screened with the YES assay for (anti)estrogenic activity at both dissolved and particulate phases and results were statistically confronted with physical-chemical parameters of samples through principal component analysis (PCA) Synergism deviations were obtained for all estrogen mixtures, except from EE2+E1, mainly at the lowest test concentrations. Despite (non)interaction at the environment, in vitro synergism may be recurrent in estradiol-equivalent (E2-Eq) results of enriched samples. The HA test concentrations deeply reduced the E2 response in the assay, even at low levels. Humic substances may not only reduce the estrogen bioavailability, but also interfere within the assay mechanism through enzymatic inhibition thus masking the sample estrogenic potential. Landfill leachate had total E2-Eq in the rage 1282–2591 ng L-1, while WWTP influent and effluent were in the range 12,1–41,4 e <DL–2,3 ng L-1 and the average estrogenicity reduction was 92 %. The contribution of particulate phase to total E2-Eq were 33% to 100% between matrices, though cytotoxicity recurrently occurred in extracts from suspended solids > 0,7 μm. Antiestrogenic activity was also observed in dissolved and particulate phases and might also have masked the estrogenic potential of samples. The PCD did not resulted in positive correlations that supported a multiphase distribution pattern of estrogenic compounds and it is supposed that physical-chemical parameters are not predictive for that. Nevertheless, the solids and organic matter characteristics supported the data interpretation and more robust studies may be performed towards it. In conclusion, the in vitro YES assay is subjected to factors intrinsic to the environmental sample that can influence on the estrogenic potential obtained by the assay. Therefore, the interpretation of results is recommended to be performed together with organic matter characterization parameters, cytotoxicity and antiestrogenic activity.