Identification and steroid receptor activity of products formed from the bromination of technical nonylphenol

Chlorination of Emerging Contaminants for Application in Potable Wastewater Reuse: Disinfection Byproduct Formation, Estrogen Activity, and Cytotoxicity

With increasing water scarcity, many utilities are considering the potable reuse of wastewater as a source of drinking water. However, not all chemicals are removed in conventional wastewater treatment, and disinfection byproducts (DBPs) can form from these contaminants when disinfectants are applied during or after reuse treatment, especially if applied upstream of advanced treatment processes to control biofouling. We investigated the chlorination of seven priority emerging contaminants (17β-estradiol, estrone, 17α-ethinylestradiol, bisphenol A (BPA), diclofenac, p-nonylphenol, and triclosan) in ultrapure water, and we also investigated the impact of chlorination on real samples from different treatment stages of an advanced reuse plant to evaluate the role of chlorination on the associated cytotoxicity and estrogenicity. Many DBPs were tentatively identified via liquid chromatography (LC)- and gas chromatography (GC)-high resolution mass spectrometry, including 28 not previously reported. These encompassed chlorinated, brominated, and oxidized analogs of the parent compounds as well as smaller halogenated molecules. Chlorinated BPA was the least cytotoxic of the DBPs formed but was highly estrogenic, whereas chlorinated hormones were highly cytotoxic. Estrogenicity decreased by ∼4-6 orders of magnitude for 17β-estradiol and estrone following chlorination but increased 2 orders of magnitude for diclofenac. Estrogenicity of chlorinated BPA and p-nonylphenol were ∼50% of the natural/synthetic hormones. Potential seasonal differences in estrogen activity of unreacted vs reacted advanced wastewater treatment field samples were observed.

Halogenated ingredients of household and personal care products as emerging endocrine disruptors

The everyday use of household and personal care products (HPCPs) generates an enormous amount of chemicals, of which several groups warrant additional attention, including: (i) parabens, which are widely used as preservatives; (ii) bisphenols, which are used in the manufacture of plastics; (iii) UV filters, which are essential components of many cosmetic products; and (iv) alkylphenol ethoxylates, which are used extensively as non-ionic surfactants. These chemicals are released continuously into the environment, thus contaminating soil, water, plants and animals. Wastewater treatment and water disinfection procedures can convert these chemicals into halogenated transformation products, which end up in the environment and pose a potential threat to humans and wildlife. Indeed, while certain parent HPCP ingredients have been confirmed as endocrine disruptors, less is known about the endocrine activities of their halogenated derivatives. The aim of this review is first to examine the sources and occurrence of halogenated transformation products in the environment, and second to compare their endocrine-disrupting properties to those of their parent compounds (i.e., parabens, bisphenols, UV filters, alkylphenol ethoxylates). Albeit previous reports have focused individually on selected classes of such substances, none have considered the problem of their halogenated transformation products. This review therefore summarizes the available research on these halogenated compounds, highlights the potential exposure pathways, and underlines the existing knowledge gaps within their toxicological profiles.

Estrogen agonistic/antagonistic activity of brominated parabens

The estrogen agonistic/antagonistic activity of 16 brominated by-products of parabens was assessed by using a yeast two-hybrid assay transfected with the human estrogen receptor α. Characterization of synthetic compounds including novel brominated parabens was performed using ¹H-NMR spectroscopy and high-resolution mass spectrometry. For the agonist assay, five C₃-C₄ alkylparabens exhibited significant activity (P < 0.05) relative to that of 17β-estradiol, ranging from 3.7 × 10^-5 to 7.1 × 10^-4. In contrast, none of the brominated alkyl parabens exhibited agonistic activity. In the antagonist assay, 12 brominated alkylparabens and butylparaben exhibited significant antagonistic activity (P < 0.05). Their antagonistic activity relative to 4-hydroxytamoxifen ranged from 0.11 to 2.5. The antagonist activity of C₁-C₄ alkylparabens increased with the number of bromine substitutions. Benzylparaben exhibited both agonistic and antagonistic activity, and these activities dissipated or were weakened with increased bromination. Thus, increased bromination appeared to attenuate the estrogen agonistic activity of most parabens such that it resulted in increased antagonistic activity, a feature of parabens that had not been previously described.

Screening for potential endocrine disruptors in fish: evidence from structural alerts and in vitro and in vivo toxicological assays

BACKGROUND

The European chemicals' legislation REACH aims to protect man and the environment from substances of very high concern (SVHC). Chemicals like endocrine disruptors (EDs) may be subject to authorization. Identification of (potential) EDs with regard to the environment is limited because specific experimental assessments are not standard requirements under REACH. Evidence is based on a combination of in vitro and in vivo experiments (if available), expert judgement, and structural analogy with known EDs.

OBJECTIVES

The objectives of this study are to review and refine structural alerts for the indication of potential estrogenic and androgenic endocrine activities based on in vitro studies; to analyze in vivo mammalian long-term reproduction studies with regard to estrogen- and androgen-sensitive endpoints in order to identify potential indicators for endocrine activity with regard to the environment; to assess the consistency of potential estrogenic and androgenic endocrine activities based on in vitro assays and in vivo mammalian long-term reproduction studies and fish life-cycle tests; and to evaluate structural alerts, in vitro assays, and in vivo mammalian long-term reproduction studies for the indication of potential estrogenic and androgenic endocrine disruptors in fish.

RESULTS

Screening for potential endocrine activities in fish via estrogenic and androgenic modes of action based on structural alerts provides similar information as in vitro receptor-mediated assays. Additional evidence can be obtained from in vivo mammalian long-term reproduction studies. Conclusive confirmation is possible with fish life-cycle tests. Application of structural alerts to the more than 33,000 discrete organic compounds of the EINECS inventory indicated 3585 chemicals (approx. 11%) as potential candidates for estrogenic and androgenic effects that should be further investigated. Endocrine activities of the remaining substances cannot be excluded; however, because the structural alerts perform much better for substances with (very) high estrogenic and androgenic activities, there is reasonable probability that the most hazardous candidates have been identified.

CONCLUSIONS

The combination of structural alerts, in vitro receptor-based assays, and in vivo mammalian studies may support the priority setting for further assessments of chemicals with potential environmental hazards due to estrogenic and androgenic activities.

Biotransformation of halogenated nonylphenols with sphingobium xenophagum bayram and a nonylphenol-degrading soil-enrichment culture

When discharged in chlorinated wastewater, alkylphenol ethoxylate metabolites (APEMs) are often discharged in halogenated form (XAPEMs, X = Cl, or Br). The potential environmental impact of XAPEM release was assessed by studying the biotransformation of halogenated nonylphenol by Sphingobium xenophagum Bayram and a soil-enrichment culture. S. xenophagum Bayram transformed chlorinated nonylphenol (ClNP) slowly and nearly completely to form nonyl alcohol; the monobrominated nonylphenol (BrNP) and dibrominated nonylphenol were transformed cometabolically with nonylphenol (NP) as the primary substrate. The presence of either ClNP or BrNP in the S. xenophagum Bayram cultures retarded the transformation of nonhalogenated NP. NP-degrading soil cultures transformed nonhalogenated NP to a mixture of nonyl alcohols but were not capable of transforming either ClNP or BrNP. The presence of either ClNP or BrNP retarded the transformation of nonhalogenated NP in the soil cultures, as was observed in S. xenophagum Bayram cultures. Predicting the environmental fate of alkylphenol ethoxylate residues requires considering APEM halogenation during effluent chlorination and inhibitory effects as well as the refractory nature of halogenated metabolites.

Profiles and some initial identifications of (anti)androgenic compounds in fish exposed to wastewater treatment works effluents

Exposure of fish to wastewater treatment works (WwTWs) effluents can result in reproductive anomalies consistent with exposure to estrogenic compounds. However, UK WwTWs effluents also contain compounds with androgen receptor activities which may contribute to reproductive dysfunction in fish. A toxicity identification and evaluation (TIE) approach was used to profile (anti)androgenic compounds in bile of fish exposed to two WwTWs effluents. Extracts of bile from exposed fish and effluent were fractionated by liquid chromatography and tested for (anti)androgenic activity using a yeast androgen receptor transcription screen (YAS). A number of bile fractions contained (anti)androgenic activity unique to the effluent-exposed fish. Some of these fractions contained di(chloromethyl)anthracene or dichlorophene, and these contaminants showed antagonistic activity in the YAS when tested as pure compounds. No androgenic activity was detected in the effluents, but TIE analysis of bile revealed a number of androgenic fractions which contained testosterone metabolites that were unique to effluent-exposed fish. This is the first work reported on the nature of some of the (anti)androgenic compounds that bioaccumulate in fish from WwTWs effluents and indicates that other contaminants, besides estrogenic substances, need to be considered for their potential to contribute to the disruption of reproductive system of fish in UK waters.

Formation of estrogenic brominated ethinylestradiol in drinking water: implications for aquatic toxicity testing

17alpha-Ethinylestradiol (EE2) is a synthetic estrogen which is thought to contribute the feminisation of fish exposed to wastewater effluents. During laboratory exposure studies of fish to EE2, it was observed that the estrogen in the aquarium water was rapidly transformed (within 10 min) to mono- and di-brominated A-ring products. Exposure of roach (Rutilis rutilus) to 30 ng L(-1) EE2 resulted in accumulation of dibrominated EE2 in ovaries (apparent bioconcentration factor, BCF 130) and liver (apparent BCF 7894) at concentrations which were 18-67-fold greater than the test EE2 compound. The estrogenic activities of brominated EE2 compounds were tested in an in vitro yeast recombinant estrogen receptor transcription screen (YES). All the brominated products of EE2 were estrogenic, however monobrominated isomers of EE2 were 18-105-fold less estrogenic, and dibrominated EE2 2058-fold less active in the YES than EE2 itself. This study reveals the importance of using chemical methods to verify exposure concentrations of waterborne test chemicals and suggests that bromination of estrogens may occur during water treatment, potentially resulting in the formation of bioavailable estrogenic environmental contaminants.