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PubMed1987

Mutagenicity of halogenated and other substituted dinitrobenzenes in Salmonella typhimurium TA100 and derivatives deficient in glutathione (TA100/GSH-) and nitroreductase (TA100NR).

In a previous study, it was shown that 1-chloro-2,4-dinitrobenzene (CDNB) was less mutagenic in a glutathione (GSH)-deficient derivative of Salmonella typhimurium TA100 (TA100/GSH-) than in TA100 itself, suggesting that the mutagenicity of the compound is dependent on GSH, possibly mediated by the action of a bacterial nitroreductase(s) on the CDNB-GSH conjugate. In the present study a series of mutagenicity tests were performed to determine how CDNB could be activated after reaction with GSH. In liquid preincubation assays, strains TA100, TA100/GSH- and TA100NR, a nitroreductase-deficient derivative of TA100, were treated with CDNB and its fluoro and bromo analogues (FDNB and BDNB), further with its GSH conjugate (S-GSH-DNB) and possible metabolic products, such as S-cysteine-dinitrobenzene (S-Cys-DNB) and S-methyl-dinitrobenzene (S-methyl-DNB), and with 2 more analogues, O-methyl-dinitrobenzene (O-methyl-DNB) and dinitrobenzene (DNB). CDNB, FDNB and BDNB were found to be mutagenic in TA100 and TA100NR, while TA100/GSH- was much less sensitive to the mutagenic action of these halogenated dinitrobenzenes. DNB, O-methyl-DNB, S-methyl-DNB and S-Cys-DNB induced equal numbers of His+ revertants in TA100 and TA100/GSH-, but were not mutagenic in TA100NR. S-GSH-DNB showed no mutagenic activity in any of the 3 strains under the present experimental conditions. These results suggest that the halogenated aromatics may react with bacterial DNA and produce pre-mutagenic alterations according to 2 mechanisms: direct attack on the DNA through nucleophilic substitution (SN2) of the halogen atoms; activation through GSH conjugation and subsequent nitroreduction of the conjugate or its metabolic products to more reactive intermediates.

Bacterial Proteins↗

PubMed1995

A catalytic triad is required by the non-heme haloperoxidases to perform halogenation.

The bacterial non-heme haloperoxidases are highly related to an esterase from Pseudomonas fluorescens, at structural and functional levels. Both types of enzymes displayed brominating activity and esterase activity. The presence of the serine-hydrolase motif Gly-X-Ser-X-Gly, in the esterase as well as in all aligned haloperoxidase sequences, strongly suggested that they belong to the serine-hydrolase family. Sequence alignment with several serine-hydrolases and secondary structure superimposition revealed the striking conservation of structural features characterising the alpha/beta-hydrolase fold structure in all haloperoxidases. These structural predictions allowed us to identify a potential catalytic triad in haloperoxidases, perfectly matching the triad of all aligned serine-hydrolases. The structurally equivalent triad in the chloroperoxidase CPO-P comprised the amino acids Serine 97, Aspartic acid 229 and Histidine 258. The involvement of this catalytic triad in halogenation was further assessed by inhibition studies and site-directed mutagenesis. Inactivation of CPO-P by PMSF and DEPC strongly suggested that the serine residue from the serine-hydrolase motif and an histidine residue are essential for halogenation, similar to that demonstrated for typical serine-hydrolases. By site-directed mutagenesis of CPO-P, Ser-97 was exchanged against alanine or cysteine, Asp-229 against alanine and His-258 against glutamine. Western blot analysis indicated that each mutant gene was efficiently expressed. Whereas the mutant S97C conserved a very low residual activity, each other mutant S97A, D229A or H258Q was totally inactive. This study gives the direct demonstration of the requirement of a catalytic triad in the halogenation mechanism.

Amino Acid Sequence↗

PubMed1987

Rapid halogenated hydrocarbon toxicity in isolated hepatocytes is mediated by direct solvent effects.

The toxicity of several halogenated and non-halogenated hydrocarbons (CH2Cl2, CHCl3, CCl4, C6H14, C8H10) in isolated rat hepatocytes were compared. Release of aspartate aminotransferase (AST) activity was rapid and concentration-dependent. Fractional AST release plateaued at 10-60 min following hydrocarbon exposure. Enzyme leakage at 60 min correlated with the oil/water partition coefficient (pi) of the compounds. All compounds, except n-hexane, also caused an immediate inhibition of the rate of cellular respiration. Inhibition of cell respiration also correlated with pi and was reversible. The recovery of cellular oxygen consumption was examined in detail for CCl4 and correlated with evaporation of the compound. These data suggest that acute hydrocarbon-induced injury in isolated hepatocytes is mediated by concentration-dependent direct solvent effects. Since halogenated hydrocarbons are widely used to induce general anesthesia, the clinical implications of possible direct effects by halocarbons on liver function in vivo and the potential relationship to liver injury are discussed.

Animals↗

PubMed1996

Nephrotoxicity of N-(3-bromophenyl)-2-hydroxysuccinimide: role of halogen groups in the nephrotoxic potential of N-(halophenyl) succinimides.

Among N-(halophenyl)succinimides. N-(3,5-dichlorophenyl)succinimide (NDPS) is a potent nephrotoxicant as well as an agricultural fungicide. Although two chloride groups on the phenyl ring are essential to induce optimal nephrotoxicity, the role of halogen groups in NDPS nephrotoxicity is not clear. In this study, N-(3-bromophenyl)-2-hydroxysuccinimide (NBPHS) was prepared as a monohalophenyl derivative of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), an oxidative and nephrotoxicant metabolite of NDPS. The nephrotoxic potential of NBPHS was evaluated in vivo and in vitro to determine the role of halogen groups in N-(halophenyl)succinimide nephrotoxicity. Male Fischer 344 rats (four/group) were administered a single intraperitoneal (i.p.) injection of NBPHS (0.1, 0.4 or 0.8 mmol/kg) or vehicle (25% dimethyl sulfoxide in sesame oil) and renal function monitored for 48 h. Administration of NBPHS (0.8 mmol/kg) induced nephrotoxicity, while very mild changes or no changes in renal function were observed following administration of 0.4 mmol/kg or 0.1 mmol/kg of NBPHS, respectively. Nephrotoxicity induced by NBPHS (0.8 mmol/kg) was characterized by diuresis, transiently increased proteinuria, glucosuria and hematuria elevated kidney weight and reduced tetraethylammonium (TEA) uptake by renal cortical slices, and was not as marked as nephrotoxicity induced by NDHS (0.1 mmol/kg) or NDPS (0.4 mmol/kg). In the in vitro studies the effects of NBPHS on organic ion accumulation, pyruvate-stimulated gluconeogenesis, and lactate dehydrogenase (LDH) release were measured using renal cortical slices. NBPHS decreased p-aminohippurate (PAH) and TEA accumulation at NBPHS bath concentrations of 0.05 mM and 0.5 mM and 0.5 mM or greater, respectively. Renal gluconeogenesis was inhibited by NBPHS at 1 mM bath concentration, while LDH leakage was not increased at NBPHS bath concentrations up to 1 mM. The results demonstrate that NBPHS is a mild nephrotoxicant in vivo and in vitro, but does not have cytotoxic effects to renal tissues at the concentrations tested. From these results, it appears that halogen groups are essential to the nephrotoxic potential of N-(halophenyl)-2-hydroxysuccinimides or N-(halophenyl)succinimides and play an important role in the mechanism of NDPS nephrotoxicity following NDHS formation.

Analysis of Variance↗

PubMed1989

Selective radiosensitization and cytotoxicity of human melanoma cells using halogenated deoxycytidines and tetrahydrouridine.

The halogenated pyrimidines 5-chloro-2'-deoxycytidine (CldCyd) and 5-bromo-2'-deoxycytidine (BrdCyd) can act as radiosensitizers and cytotoxic agents. It was hypothesized that tumor cells and normal cells might use different metabolic pathways to incorporate these halogenated deoxycytidines into DNA. This difference could potentially be exploited to produce selective radiosensitization and cytotoxicity of human tumor cells compared to normal human fibroblasts. This hypothesis was tested using two human melanoma cell lines and two normal fibroblast cell lines. Either CldCyd or BrdCyd alone caused both cytotoxicity and radiosensitization of tumor and normal cells. The addition of the cytidine deaminase inhibitor tetrahydrouridine (H4U) significantly protected the normal cells but had relatively little effect on the tumor cells. These data indicate that it may be possible to exploit differences between the pyrimidine metabolism of normal cells and melanoma cells to improve the therapeutic index of halogenated pyrimidines both as radiosensitizers and as cytotoxic agents.

Antineoplastic Agents↗

PubMed1990

The dependence of halogenated pyrimidine incorporation and radiosensitization on the duration of drug exposure.

The influence of the duration of exposure to the halogenated pyrimidines iododeoxyuridine (IdUrd) and bromodeoxyuridine (BrdUrd) on incorporation into DNA and the resulting radiosensitization was studied in cultured human colon cancer cells. Cells were incubated with either 10 microM BrdUrd or IdUrd for periods up to 7 days. They were also assessed for up to 4 days after removal of drug from the medium. Replacement of thymidine by fraudulent bases was measured using a sensitive gas chromatographic, mass spectrometric (GC/MS) assay. Incorporation of BrdUrd and IdUrd plateaued at 35% and 30%, respectively, after 4 days of exposure. Prolonging the time of exposure to 7 days increased cytotoxicity without affecting either incorporation or radiosensitization. Incorporation remained constant for 1-2 days after removal of drug from the medium. Radiosensitization was linearly related to incorporation throughout the range of conditions assessed. These data suggest that it may be possible to develop a predictive assay for radiosensitization based on measurements of halogenated pyrimidine incorporation in a tumor biopsy specimen. They also suggest that a clinical approach based on repeated short exposures to halogenated pyrimidines may present certain advantages over the current practice of prolonged continuous exposure. A Phase I/II trial using IdUrd and external beam irradiation for the treatment of patients with poor prognosis soft tissue sarcomas has been initiated based on this concept.

Bromodeoxyuridine↗

PubMed1995

Enzymic- and thiol-mediated activation of halogen-substituted diaziridinylbenzoquinones: redox transitions of the semiquinone and semiquinone-thioether species.

Activation of 2,5-diaziridinyl-1,4-benzoquinones bearing halogen (Cl, Br, or F) substituents at C3 and C6 by NADPH-cytochrome P450 reductase and glutathione nucleophilic substitution was examined in terms of free radical production and DNA strand scission. A semiquinone species was observed by direct ESR in aerobic conditions during: (a) NADPH-cytochrome P450 reductase-catalyzed reduction of the above quinones. (b) The interaction of these quinones with GSH entailing primarily reactivity of halogen substituents toward sulfur substitution. (c) NADPH-cytochrome P450 reductase-catalyzed activation of products resulting from the quinone/GSH interaction. The semiquinone ESR signal observed during enzymic catalysis was suppressed by superoxide dismutase and was not affected by catalase. ESR studies in conjunction with the spin trapping technique on the autoxidation of the semiquinones formed by the above reaction pathways indicated the formation of superoxide radicals. In addition, thiyl radicals were formed during the reactions following glutathione necleophilic substitution of the above quinones. The ESR signals of both superoxide and thiyl radicals were abolished by superoxide dismutase. No hydroxyl radicals were formed in solution during the redox transitions of these halogen-containing diaziridinylbenzoquinones. Bioreductive activation of these compounds via NADPH-cytochrome P450 reductase or sulfur nucleophilic substitution was associated with the formation of DNA strand breaks. This process was substantially inhibited (74-86%) by superoxide dismutase and to a lesser extent (23-31%) by catalase. It is suggested that DNA strand breakage proceeds in a manner entailing a semiquinone-dependent reduction of metal-ligands bound at the DNA surface and leading to site-specific, hydroxyl radical production.

Animals↗

PubMed2006

C3-halogenation of cytisine generates potent and efficacious nicotinic receptor agonists.

Neuronal nicotinic acetylcholine receptors subserve predominantly modulatory roles in the brain, making them attractive therapeutic targets. Natural products provide key leads in the quest for nicotinic receptor subtype-selective compounds. Cytisine, found in Leguminosae spp., binds with high affinity to alpha4beta2* nicotinic receptors. We have compared the effect of C3 and C5 halogenation of cytisine and methylcytisine (MCy) on their interaction with native rat nicotinic receptors. 3-Bromocytisine (3-BrCy) and 3-iodocytisine (3-ICy) exhibited increased binding affinity (especially at alpha7 nicotinic receptors; Ki approximately 0.1 microM) and functional potency, whereas C5-halogenation was detrimental. 3-BrCy and 3-ICy were more potent than cytisine at evoking [3H]dopamine release from striatal slices (EC50 approximately 11 nM), [3H]noradrenaline release from hippocampal slices (EC50 approximately 250 nM), increases in intracellular Ca2+ in PC12 cells and inward currents in Xenopus oocytes expressing human alpha3beta4 nicotinic receptor (EC50 approximately 2 microM). These compounds were also more efficacious than cytisine. C3-halogenation of cytisine is proposed to stabilize the open conformation of the nicotinic receptor but does not enhance subtype selectivity.

Alkaloids↗

PubMed2003

Molecular volume determines the activity of the halogenated alkane bromoform at wild-type and mutant GABA(A) receptors.

The GABA(A) receptor is an important target for a variety of general anesthetics, including halogenated ethers such as isoflurane and halogenated ethers such as chloroform. Bromoform is a halogenated alkane that exhibits anesthetic properties and has been shown by X-ray crystallography to bind to model anesthetic targets. In this study we report the ability of bromoform to potentiate GABA-induced current in recombinant GABA(A) receptors composed of alpha(1)beta(2)gamma(2s) subunits. Recent studies have shown that specific point mutations in the transmembrane (TM) region of the GABA(A) receptor alpha-subunit can selectively abolish the modulatory activity of specific general anesthetics, and that molecular volume is a key determinant of anesthetic activity. The action of bromoform was examined in a series of mutant receptors and compared with the activity profiles of three other volatile anesthetics. The pharmacological profile of bromoform at the mutant receptors used in this study was similar to that seen with halothane, and distinct from that observed for isoflurane and chloroform. The molecular volume of bromoform is closest to that of halothane, and therefore our data are consistent with the idea that molecular volume is an important determinant of inhaled anesthetic activity at the GABA(A) receptor.

Anesthetics, Inhalation↗

PubMed1999

Androgenic and anti-androgenic effects of progesterone derivatives with different halogens as substituents at the C-6 position.

The pharmacological activities of four pregnane derivatives: 17alpha-hydroxy-16beta-methylpregna-4,6-diene-3,20-dio ne (7), 17alpha-acetoxy-16beta-methylpregna-4,6-diene-3,20-dio ne (8), 17alpha-acetoxy-6-bromo-16beta-methylpregna-4,6-diene- 3,20-dione (10), and 17alpha-acetoxy-6-chloro-16beta-methylpregna-4,6-diene -3,20-dione (11), were determined. The derivatives were evaluated on gonadectomized male hamster flank organs and seminal vesicles. The results indicate that topical applications of testosterone (T) on the flank organs increased the diameter of the pigmented spot. Similarly, the same phenomenon occurred on the glands treated with compound 11, whereas compound 10 decreased the size of the spot significantly. In this study, we determined the effects of several new steroids on the conversion of T to DHT in flank organs and seminal vesicles. The results show that compound 10 inhibited T conversion to DHT, but compound 11, at a dose of 200 microg, stimulated T conversion in both flank organs and seminal vesicles. However, when 2 mg of compound 11 was applied, it inhibited the conversion of T to DHT, suggesting that this compound also represses gonadotropin release. The difference between compounds 10 and 11 involves the electronegativity of the halogen at the C-6 position of the progesterone skeleton. These data clearly indicate that by decreasing the electronegativity of the halogen at C-6 (compound 10), 5alpha-reductase is inhibited in both tissues and at different pHs. On the other hand, when the electronegativity of the halogen atom was increased (11), there was a much lower inhibitory effect on the conversion of T to DHT.

Androgen Antagonists↗

PubMedDate not supplied

Elution of leachable components from resin composites after plasma arc vs standard or soft-start halogen light irradiation.

OBJECTIVES: To determine the release of leachable components from resin based composites (RBC) after plasma arc vs. standard or soft-start halogen curing. METHODS: The tested RBC were the fine hybrids Herculite XRV (Kerr), Solitaire 2 (Kulzer) and Z250 (3M), the micro-fill Silux Plus (3M) and the polysiloxane-containing Definite (Degussa). The irradiation protocols included halogen standard irradiation at three different intensities (TriLight, ESPE), ramp curing (dito), step curing (HiLight, ESPE), pulse polymerization (VIP Light, BISCO) and plasma curing (Apollo 95E, DMDS; PAC Light, ADT). Initial solubility was determined applying RBC into simulated cavities (molds of 6mm inner diameter and 2mm height fabricated from pressed ceramics) and eluting 24h in demineralized water at 37 degrees C. Medium-term solubility was evaluated using plain RBC specimens of equivalent dimensions stored dark (37 degrees C, 24h) and extracted in 50% CH(3)OH (37 degrees C, 72 h). After drying the specimens to constant weight, solubility and sorption were determined gravimetrically. RESULTS: Medium-term solubility/sorption were higher than initial ones. Irradiation at reduced intensity increased solubility and sorption, whereas ramp curing, step curing and pulse polymerization (for most materials) maintained low values. Plasma arc curing worked well for Z250 and Herculite XRV, compared to medium or low intensity halogen irradiation for Silux Plus and Definite and produced moderately (PAC Light) or very (Apollo 95E) high solubility for Solitaire 2. CONCLUSIONS: Reducing irradiation intensity does and soft-start protocols do not compromise solubility and sorption. The efficiency of plasma arc curing depends markedly on the types of photo-initiators used.

Analysis of Variance↗

PubMed2002

Microwave-assisted (radio)halogenation of nitroimidazole-based hypoxia markers.

Microwave-assisted radiohalogenation for the production of short-lived radiopharmaceuticals has now been applied to the synthesis and radiolabelling of azomycin nucleosides. (Radio)halogens were incorporated either by nucleophilic substitution of a leaving group or by halogen-halogen exchange, in the synthesis of IAZA, IAZP and FAZA. A comparison of conventional labelling and microwave-assisted labelling procedures reflects a clear advantage of the microwave technique.

Biomarkers↗

PubMed2001

FTIR studies of intermolecular hydrogen bonding in halogenated ethanols.

The effect of halogen substitution on intermolecular hydrogen-bonding in ethanol is studied. Specifically, Fourier-transform infrared (FTIR) spectra of ethanol, 2,2,2-trifluoroethanol (TFE), and 2,2,2-trichloroethanol dissolved in carbon tetrachloride are reported as a function of temperature and concentration. The spectral intensities corresponding to monomer, dimer, and multimer formation are used to determine the effect of halogen substitution on intermolecular hydrogen-bonding. The enthalpy for dimerization was found to evolve from -4.2+/-0.3 kcal/mol in ethanol to -6.8+/-1.0 kcal/mol in TFE. An opposite trend was observed for multimer formation with enthalpies of -3.7+/-0.5 in ethanol and -2.1+/-1.4 kcal/mol in TFE. The majority of this evolution is assigned to the ability of ethanols to form intramolecular hydrogen bonds involving the hydoxyl proton and the halogen substituents.

Dimerization↗

PubMed2003

Development of a multiple-class high-resolution gas chromatographic relative retention time model for halogenated environmental contaminants.

A predictive model for the relative gas chromatographic retention times (GC-RRTs) of the following nine classes of halogenated environmental contaminants was developed: polybrominated diphenyl ethers (PBDEs); polychlorinated diphenyl ethers (PCDEs); polychlorinated biphenyls (PCBs); polychlorinated naphthalenes (PCNs); polychlorinated dibenzo-p-dioxins (PCDDs); polychlorinated dibenzofurans (PCDFs); polybrominated dibenzo-p-dioxins (PBDDs); polybrominated dibenzofurans (PBDFs); and organochlorine pesticides. MOPAC calculated physicochemical properties and structural descriptors in the model include molecular weight, square root of the number of halogen substituents, ionization potential, dipole moment, and the number of ortho, meta, and para halogen substituents. Using these variables, individual models for each of the contaminant classes were combined into a multiple class model incorporating the GC-RRTs of the 375 compounds of interest. The individual and multiclass GC-RRT models had acceptable fits between observed and predicted GC-RRTs (r2 = 0.9741-0.9990 for PBDEs, PCDEs, PCBs, PCNs, PCDD/Fs, and PBDD/Fs; r2 = 0.9250 for pesticides; and r2 = 0.9631 for the multiclass model) over a wide range of retention times and molecular structures. The combined model was tested on known GC-RRTs of hydroxylated PCBs and chlorinated phenoxyphenols and provided satisfactory results, demonstrating the strength of the model in predicting GC-RRT windows for contaminant classes not used in constructing the model. Such models will be useful in predicting the GC retention characteristics of novel environmental contaminants and their degradation products, for which analytical standards may not be available.

Journal Article↗

PubMed2004

Development of a chemical ionization ion trap mass spectrometric method for trace level determination of molecular halogens.

An ion trap mass spectrometric technique using negative ion chemical ionization has been developed for the quantitative determination of the molecular halogen species Br(2), Cl(2), and BrCl. The technique utilizes NO(2)(-) as a chemical ionization reagent in an electron-transfer reaction to form the corresponding molecular anions of the halogen species, lending excellent selectivity to the measurement. Reaction rate experiments performed in the ion trap yield a rate constant for Br(2) + NO(2)(-) --> Br(2)(-) + NO(2) of (1.4 +/- 0.6) x 10(-)(9) cm(3) molecule(-)(1) s(-)(1), determined relative to published data for Cl(2) + NO(2)(-) --> Cl(2)(-) + NO(2). This paper describes a mass spectrometer pinhole inlet design and cryogenic preconcentration system for detection of the molecular halogens at atmospherically relevant concentrations. Linear calibration curves were obtained for Cl(2) and Br(2) over 3 orders of magnitude and indicate limits of detection of 50 and 8 pmol for 3.8- and 5.1-L samples, respectively, corresponding to 220 and 50 parts per trillion (mole/mole). Quantitation is based on the total signal at m/z values of 70, 72, and 74 for Cl(2) and 158, 160, and 162 for Br(2). The effects of water vapor on the cryogenic preconcentration step are quantitatively assessed.

Journal Article↗

PubMed1983

Stereoselectivity of chloroperoxidase-dependent halogenation.

The stereoselectivity of chloroperoxidase halogenation of four substrates has been examined. Chloroperoxidase catalyzes the bromination, but not chlorination, of racemic 2-exo-methylbicyclo[2.2.1]hept-5-ene-2-endo-carboxylic acid (to the delta-lactone) and racemic bicyclo-[3.2.0]hept-2-en-6-one (to the 2-exo-bromo-3-endo-hydroxy-bromohydrin). These products are obtained in near quantitative yield and are racemic. The circumstances of the bromination strongly suggest that halogenation does not occur at the active site but rather by chloroperoxidase-catalyzed formation of Br2 and its release into solution. The inability of chloroperoxidase to halogenate these two alkenes at its active site most probably derives from a steric exclusion from the active site. The stereoselectivity of two additional substrates that undergo active site chlorination was determined. Methionine is quantitatively converted to a 50:50 ratio of the two methionine sulfoxide diastereomers. 2-Methyl-4-propylcyclopentane-1,3-dione is quantitatively chlorinated to 2-chloro-2-methyl-4-propylcyclopentane-1,3-dione. On the basis of optical rotation and proton nuclear magnetic resonance, this product is present as a 40:60 ratio of the racemic diastereomers. It is concluded that active site chlorination by chloroperoxidase proceeds without appreciable stereoselectivity.

Bromine↗

PubMedDate not supplied

Benchmarking of model core potentials: application to the halogen complexes of group 4 metals.

The reliability of the model core potential (MCP) method was probed in a systematic RHF and MP2 study of the geometries of the group 4 metal halogen complexes (MX4; M = Ti, Zr, Hf and X = F, Cl, Br, I). The computed bond lengths were compared with experimental values, as well as those predicted using effective core potentials. Provided that electrons from the outermost core shell of the metal atom are treated explicitly in the calculation, both the MCP and ECP methods predict M-X bond lengths within 0.02-0.03 A of experiment. The reaction energies for a simple set of halogen substitution reactions of the MX4 complexes leading to the mixed halogen complex, MX2Y2, were also studied. Although no experimental values are available for these reactions, comparison was made with the values computed using effective core potentials. The predictability of the different pseudopotential techniques and the importance of the metal atom valence basis set contraction scheme and polarization space are discussed.

Journal Article↗

PubMed2003

Occurrence and removal of estrogenic short-chain ethoxy nonylphenolic compounds and their halogenated derivatives during drinking water production.

The elimination of nonylphenol (NP), nonylphenol mono- and diethoxylates (NP1EO and NP2EO), nonylphenol carboxylates (NP1EC and NP2EC) and their brominated and chlorinated derivatives during drinking water treatment process in Sant Joan Despf waterworks in Barcelona was investigated utilizing a recently developed, highly sensitive LC-MS-MS method. The concentration of these potentially estrogenic compounds in raw water entering waterworks (taken from the Llobregat River, NE Spain) ranged from 8.3 to 22 microg/L, with NP2EC being the most abundant compound. Prechlorination reduced the concentration of short-chain ethoxy NPECs and NPEOs by about 25-35% and of NP by almost 90%. However, this reduction of concentrations was partially due to their transformation to halogenated derivatives. After prechlorination, halogenated nonylphenolic compounds represented approximately 13% of the total metabolite pool, of which 97% were in the form of brominated acidic metabolites. The efficiency of further treatment steps to eliminate nonylphenolic compounds (calculated for the sum of all short-chain ethoxy metabolites including halogenated derivatives) was as follows: settling and flocculation followed by rapid sand filtration (7%), ozonation (87%), GAC filtration (73%), and final disinfection with chlorine (43%), resulting in overall elimination ranging from 96 to 99% (mean 98% for four sampling dates). A few of the nonylphenolic compounds (NP, NP1EC, and NP2EC) were also identified in drinking water; however, the residues detected were generally below 100 ng/L, with one exception for NP2EC in November 2001 when a concentration of 215 ng/L was detected.

Estrogens, Non-Steroidal↗