研究テーマ
DEGRADATION PRODUCTS OF NONYLPHENOL POLYETHOXYLATES: DETERMINATION AND TOXICITY
担当：Pham Hoai Manh
The occurrence and possible toxicity of some end degradation products of nonylphenol polyethoxylates (NPnEOs, n = number of ethoxy units) such as nonylphenol (NP), short ethoxy chain nonylphenols (NPnEOs, n = 1-3) and short ethoxy chain nonylphenol carboxylic acids (NPECs, n = 1-2, number of ethhoxy units plus an acetate) have been of great concern and received considerable attention. These chemicals were recognized to exhibit ubiquitous, lipophilic, refractory, and potential estrogenicity although the evidence is still fragmentary.
Further, in few researches concerned with the degradation products of the NPnEOs, the evidence on the formation of some halogenated derivatives such as XNP, XNPnEOs, and XNPnECs (n = 1-2, X = Cl or Br that is substituted on the ortho position of the aromatic ring) in the environmental compartments were reported. The occurrence of halogenated derivatives was recognized in effluent water and receiving river water after disinfection with chlorine in the presence of bromide ion in the wastewater treatment plants. They were reported in the range of hundreds ng/l to µg/l in water and of hundreds µg/kg in sludge and sediments of water treatment plants and receiving river. Study on the toxicity of these compounds are very rare comparing to their precursors, e.g. NP, short ethoxy chain NPnEOs. In few researches regarding the toxicology study, some halogenated derivatives showed potential low estrogenic activities but high antiestrogenic activities.
The dicarboxylic degradation products (CAPECs) were recently recognized to occur in different environmental compartments at relatively high, microgram per liter, levels. Particularly, those CAPECs that contain 5-8 C atoms and a carboxyl group in the alkyl chain (CA5-8P1ECs) are believed to be the most commonly occurring metabolites in an aqueous environment. The CA5-8P1ECs appeared to be extremely persistent species (remain even after 5 months following their generation on laboratory scale wastewater treatment unit), and accounted for between 60% and 63% of the total pool of degradation metabolites in river water and treatment plant effluents, respectively. Of the CAPECs class, the carboxyalkylphenol monoethoxycarboxylates (CAP1ECs) and carboxyalkylphenol diethoxycarboxylates (CAP2ECs) are the most common. The relatively high concentrations and possible persistence of the CAPECs in the environment have been of reasons for concern; however, the identification and quantifications of these compounds so far have been rather laborious and inaccurate due to the lack of commercially available standards. The levels of the CAPECs have only been semi-quantified based on the assumption that the response factors of the base ions of these compounds and specific internal standards, or NPnEOs and NPnECs.
The overall study including the occurrence, behavior and toxic implication on the halogenated derivatives and CAPECs is still very limited, of which the lack of standard reagents is one of the reasons. Because of their possible presence in the environment and potential toxicities, XNP, XNPnEOs, XNPnECs and CAPECs should be determined together with their precursors (NP, NPnEOs, NPnECs).
Developing standard reagents of the NPnEOs degradation products, after that using them for the development of the analytical methods for their determination in the environmental water samples as well as fully elucidating their toxicity are of my research plan. In this period, the study was successfully meet two main objectives as follows:
• Synthesis of standard reagents for the NPnEOs degradation products (short chain NPnEOs (1-3 ethoxy units), NPnECs (1-2 ethoxy units plus an acetate); XNP, XNP1EO, XNP1EC; and CAP1EC (5-8 carbon atoms in the alkyl chain)
• Development of routine analytical methods for the determination of those compounds in water samples using the developed standard reagents and evaluate their concentrations in some collected water samples
In addition, the examination of the toxicity (acute toxicity, mutagenicity, and estrogenicity, using Daphtoxkit (Creasel Ltd.), umu test system, and yeast two-hybrid system, respectively) of these chemicals was conducted to fully assess their possible impact into the environment.
研究テーマ一覧へ