Nonylphenol in the environment: A critical review on occurrence, fate, toxicity and treatment in wastewaters

Environmental fate of alkylphenols and alkylphenol ethoxylates--a review

http://www.beamreach.org/data/101/Science/processing/Nora/Papers/Fate,%20behavior%20and%20effects%20of%20surfactants%20and%20their%20degradation%20products%20in%20the%20environment.pdf

Fate, behavior and effects of surfactants and their degradation products in the environment

This study was designed to test for synergism (increased stress) or antagonism (decreased stress) among multiple environmental stressors using additive, multiplicative, and simple comparative effects models. Model predictions were compared to empirical results of laboratory experiments measuring interactions among thermal stress, toxin exposure, and low food on reproduction and survival of two species of cladoceran zooplankton. Stress was defined operationally as a reduction in reproduction or survival relative to optimal conditions over a 7-d period. These experiments are particularly applicable to episodic stresses such as those associated with short-term heat waves. Toxin or low food in combination with 30°C temperatures were generally more harmful than high temperature alone. However, most multiple stress effects were antagonistic, in that effects in combination were not as severe as predicted based on the sum or the product of their individual effects. In rare cases, interaction among stressors even diminished effects of the worst single stressor. Optimal conditions for reproduction and survival occurred at 25°C, high food and 0 mg liter ' toxin (a surfactant, sodium dodecyl sulfate). Suppressive effects of stressors examined individually ranked: high temperature (30°C) > SDS (10 mg liter -1 ≥ low food (∼100 μg C liter -1 ) > low temperature (20°C). Daphnia pulex isolated from a pond which experiences high summer temperatures throughout was more tolerant of 30°C conditions than Daphnia pulicaria isolated from a lake with a cold-water refuge. Differences were observed in individuals exposed as either adults or as 24-h neonates.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1999.44.3_part_2.0864

Synergism and antagonism among multiple stressors

Biodegradation of poly(vinyl alcohol) based materials

Bacterial scission of ether bonds.

The global response of Escherichia coli to the broad-spectrum biocide polyhexamethylene biguanide (PHMB) was investigated using transcriptional profiling. The transcriptional analyses were validated by direct determination of the PHMB-tolerance phenotypes of derivatives of E. coli MG1655 carrying either insertionally inactivated genes and/or plasmids expressing the cognate open reading frames from a heterologous promoter in the corresponding chromosomally inactivated strains. The results showed that a wide range of genes was altered in transcriptional activity and that all of the corresponding knockout strains subsequently challenged with biocide were altered in tolerance. Of particular interest was the induction of the rhs genes and the implication of enzymes involved in the repair/binding of nucleic acids in the generation of tolerance, suggesting a novel dimension in the mechanism of action of PHMB based on its interaction with nucleic acids.

The response of Escherichia coli to exposure to the biocide polyhexamethylene biguanide.

There is growing concern that the perceived reductions in the human male sperm count in the second half of this century, the increased incidence of testicular cancer (5, 32, 35), and the feminization of species inhabiting aquatic freshwater environments (30), may be attributable to endocrine-disrupting chemical pollutants in the environment. In addition to the identified need for studies on epidemiology and for toxicity-testing strategies and methods (6, 27), environmental risk assessments will be required for products from which endocrine disrupters (xenoestrogens) may be derived. Among the sources of putative xenoestrogens are the nonylphenol polyethoxylates (NPEOx [see below]) (Fig. ​(Fig.1),1), which are commercially important surfactants with industrial, agricultural, and domestic applications. They are comprised of a phenol nucleus that is o, m, or p substituted with one of a variety of hydrophobic, branched, isomeric nonyl moieties, and with a hydrophilic polyethylene glycol (ethoxylate) chain ether linked at the phenolic oxygen. As a result of the mode of synthesis from ethylene oxide monomers, the ethoxylate chains in commercial preparations are polydisperse, with lengths ranging from 1 to typically 50 or more ethylene glycol units; this variation is reflected in the designation NPEOx where x is the number of ethylene glycol (EO) units in the molecule and NP stands for nonylphenol. The combined annual production for the United States, western Europe, and Japan is estimated at about 0.35 Mt, and thus these compounds are common constituents of municipal wastewaters (2). While the higher homologs of NPEOx lack estrogenic activity, the shorter NPEOx homologs and nonylphenol itself are known to exert estrogenic effects in aquatic organisms (18, 19, 39) and in mammals and birds (10, 33, 39). 



FIG. 1

Typical structure of a highly branched isomer of NPEOx in which x may range from 2 to about 50. Commercial mixtures may also contain, in addition to the structure shown, other isomeric C9 branched chains as well as o- and m-substitution patterns.



Primary biodegradation of NPEOx in wastewater treatment plants is relatively efficient, but the resulting intermediates are more recalcitrant and ultimate degradation efficiency is significantly lower (2), so that degradation products, predominantly nonylphenol and lower homologs of NPEOx, are found in sewage treatment effluents (11, 14, 17), rivers (3, 14), estuaries (21, 22), and coastal waters (25). Thus, the biodegradation process converts the relatively benign surfactants into the more endocrine-disruptive components, and an understanding of this process will be an important component in the formulation of environmental risk assessments for this group of products.

Bacteria have been credited with three broad strategies for primary biodegradation of nonionic (polyethoxylate) surfactants (36): separation at the ether bond joining hydrophilic to hydrophobic moieties (central fission); ω/β-oxidative degradation of the hydrophobic group; and successive exoscission of the hydrophilic group. In mixed cultures, the first and second strategies fail for NPEOx due to, respectively, the proximity of the aryl nucleus and the presence of branching in the nonyl chain, leaving only the last mechanism (36). This is consistent with the observed accumulation of residues with intact nonylphenol moieties in natural environments.

Laboratory studies with mixed cultures (20, 23, 31) and pure cultures (15, 24, 26) have demonstrated that biodegradation results in the conversion of NPEOx to shorter homologs, usually nonylphenol diethoxylate (NPEO2) and/or its carboxylic acid analog, and it has been tacitly assumed that this is achieved by sequential removal of C2 ethoxylate units from the end of the chain. However, definitive evidence for the operation of this pathway in pure culture is lacking, and the nature of the ether scission reaction which it requires is unknown. The work now described was undertaken to isolate bacteria capable of growth on NPEOx surfactants, to confirm that growth was at the expense of only the ethoxylate moiety, and to elucidate the pathway and mechanism for ethoxylate removal.

Mechanism for Biotransformation of Nonylphenol Polyethoxylates to Xenoestrogens in Pseudomonas putida

Nonylphenol ethoxylate (NPEOx) homologs present in commercial mixtures were rapidly adsorbed to and desorbed from native river sediment. Adsorption isotherms, established using high-performance liquid chromatography analysis to monitor individual homologs NPEO3 to NPEO13 simultaneously, were linear for each component adsorbing to native sediment, organic-free sediment, and kaolinite, usually with small positive intercepts on the isotherms indicating an additional low-capacity, high-affinity binding site. The adsorption partition coefficients (Kd) for the native sediment decreased progressively from 1,460 L/kg for NPEO3 to 450 L/kg for NPEO10, then increased again slightly for higher homologs. In contrast, Kd values for organic-free sediment (range 230–590 L/kg) or kaolinite (190–490 L/kg) increased steadily from NPEO3 to NPEO13. Adsorptions to silica and alumina were very weak, but to sewage sludge all components adsorbed strongly (Kd values 12,000–33,000, with a maximum at NPEO7). The adsorption to sewage sludge was related to the low-capacity, high-affinity sites observed for native sediment. Dependence of Kd values on ethoxylate chain length was analyzed, in terms of both possible adsorption mechanisms, and the environmental fate and impact of NPEOxs as endocrine disruptors.

Environmental fate of nonylphenol ethoxylates: Differential adsorption of homologs to components of river sediment

Bacteria capable of metabolizing highly explosive and vasodilatory glycerol trinitrate (GTN) were isolated under aerobic and nitrogen-limiting conditions from soil, river water, and activated sewage sludge One of these strains (from sewage sludge) chosen for further study was identified as Agrobacterium radiobacter subgroup B A combination of high-pressure liquid chromatography and nuclear magnetic resonance analyses of the culture medium during the growth of A radiobacter on basal salts-glycerol-GTN medium showed the sequential conversion of GTN to glycerol dinitrates and glycerol mononitrates Isomeric glycerol 1,2-dinitrate and glycerol 1,3-dinitrate were produced simultaneously and concomitantly with the disappearance of GTN, with significant regioselectivity for the production of the 1,3-dinitrate Dinitrates were further degraded to glycerol 1- and 2-mononitrates, but mononitrates were not biodegraded Cells were also capable of metabolizing pentaerythritol tetranitrate, probably to its trinitrate and dinitrate analogs Extracts of broth-grown cells contained an enzyme which in the presence of added NADH converted GTN stoichiometrically to nitrite and the mixture of glycerol dinitrates The specific activity of this enzyme was increased 160-fold by growth on GTN as the sole source of nitrogen

Graham F. White

Papers

Bacterial scission of ether bonds.

The response of Escherichia coli to exposure to the biocide polyhexamethylene biguanide.

Mechanism for Biotransformation of Nonylphenol Polyethoxylates to Xenoestrogens in Pseudomonas putida

Environmental fate of nonylphenol ethoxylates: Differential adsorption of homologs to components of river sediment

Biodegradation of Glycerol Trinitrate and Pentaerythritol Tetranitrate by Agrobacterium radiobacter.