Alkylphenol Polyethoxylates Research Articles

Toxicity of 4-nonylphenol in spiked sediment to three populations of Chironomus riparius

Nonylphenols (NPs) are the primary stable metabolites of alkylphenol polyethoxylates (APEs), a family of compounds widely used in industry and in some domestic products. As NPs accumulate in sediments in aquatic environments, the risk to benthic organisms needs to be assessed. In this study 4NP-spiked sediments were tested on larvae of the dipteran Chironomus riparius. First instar larvae obtained from populations at three different sources were used. To spike the sediments, an equilibration procedure between water and sediment was adopted to avoid the use of solvents. Lower 10-d LC 50 values were determined for two populations of C. riparius from clean environments (315–465 and 315–350 μg g −1 d.w., respectively) than those of a strain deriving from a population collected in a polluted river (600–680 μg g −1 d.w.). Larval growth always decreased with increasing 4NP concentration but without any defined trend. The results of this study suggest that tolerance to the toxicant can be developed in populations of polluted environments and that testing procedures should be standardised.

Empirical studies of the effects of endocrine disrupting compounds on male reproductive physiology

Concerns have been raised about the potential adverse effects on reproductive health in farm animals, humans, and wildlife species from a range of environmental chemicals that disrupt normal hormonal actions. The alkylphenol polyethoxylates are non-ionic surfactants used in the manufacture of detergents, paints and herbicides. During sewage treatment, these compounds are broken down to short chain alkylphenol polyethoxylates, alkylphenol carboxylic acids and alkylphenols which bioaccumulate in the lipid of living organisms. The estrogenic nature of one of these compounds - octylphenol has been clearly demonstrated in cell culture, in a recombinant yeast screen with human estrogen receptor?and in animal studies. It is proposed that these endocrine disrupting compounds influence male adult reproductive potential by disrupting the development of the hypothalamic-pituitary-testicular axis during fetal life. We have recently identified that exposure to octylphenol for the second half of gestation decreases circulating concentrations of FSH during fetal life and the number of Sertoli cells of the testis and testis size at birth in comparison to control animals (Sweeney et al., 2000). However, the testes size, % interstitial space, semen volume, semen concentration and % live semen was similar in both treatment groups in the adult. In contrast animals exposed to octylphenol from birth to weaning (16 weeks of age) had a significantly greater number of primary and secondary abnormalities in comparison to controls and animals exposed to octylphenol for the second half of gestation. A number of the animals exposed to octylphenol from birth to weaning exhibited augmented sexual behaviour, while those exposed to octylphenol for the second half of pregnancy showed a suppression of sexual behaviour. The current data suggests the physiological effect of exposure to octylphenol is dependant on the time and duration of exposure. This has major implications for the determination of universal end-point measurements to assess exposure to endocrine disrupting compounds.

Simultaneous determination of alkylphenol polyethoxylate surfactants and their degradation products in water, effluent and mussel using gas chromatography-mass spectrometry

Alkylphenol polyethoxylate surfactants (APnEO) are used in many industrial, commercial and household applications. Their widespread use has raised public concern about these chemicals and their degradation products in rivers and waterways. A gas chromatography-mass spectrometry (GC-MS) method was developed to determine 4-nonylphenol, 4-tert-octylphenol, alkylphenolpolyethoxylates (n=1–16), nonylphenolmonoethoxycarboxylic acid and octylphenolmonoethoxycarboxylic acid in surface water, effluent, and mussels. The method is based on the derivatization of analytes with pentafluorobenzyl bromide (PFB-Br), followed by chromatography cleanup and GC-MS determinations. Method detection limits were in the range of 1 ng L−1 for surface water and effluent, and 3ng g−1 for mussel samples. Recovery of farget compounds ranged from 40–102% and 24–111% in water and mussel samples, respectively. Several non-ionic surfactants were detected at concentrations ranging from 0.009 to 10.324 μgL−1 in the St. Lawrence River (surface water and sewage effluent) and at 177 to 12440 ng g−1 in mussels, introduced in this river for 62 days.

Estrogenic metabolites of alkylphenol polyethoxylates in secondary sewage effluents and rivers

Degradation products of nonionic surfactants of the nonylphenol polyethoxylate type (NPnEO) were reported recently to be estrogenic to fish at low microgram per litre concentrations. These estrogenic metabolites, including nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) as well as their corresponding carboxylic acids (NP1EC and NP2EC), were measured during 1997 and 1998 in sewage effluents and ambient waters in Switzerland in order to assess the effects of risk reduction measures introduced in 1986. Lipophilic metabolites (NP+NP1EO+NP2EO) were found in the examined secondary sewage effluents mostly at concentrations from 1 to 5 μg/L, while elevated levels were found in those sewage treatment plants which receive industrial effluents from textile finishing plants. The concentrations of the lipophilic nonylphenolic compounds in rivers ranged mainly from 0.05 to 0.3 μg/L with NP being most abundant. The total concentration of the nonylphenoxy carboxylic acids was significantly higher than that of the lipophilic metabolites. Despite a significant decrease of the environmental exposure levels of all nonylphenolic compounds subsequent to the introduction of risk reduction measures, the total concentration of estrogenic metabolites often exceeded the predicted no effect concentration (PNEC) of 0.33 μg/L proposed in a risk assessment report to the European Union.

Metabolic responses to acute toxicity of alkylphenols and alkylphenol polyethoxylates in Elliptio complanata measured by calorespirometry

AbstractAlkylphenol ethoxylates (APEs) are important contaminants of world water systems with effects on aquatic life. Metabolic responses to short‐term acute toxicities of alkylphenol and alkylphenolethoxylates were investigated in the freshwater bivalve mollusk Elliptio complanata using isothermal batch microcalorimetry and respirometry. Metabolic heat rates were altered following short‐time exposure of the gill tissue to these compounds over the concentration range of 10−6 to 10−3 M. There was a time and concentration dependence of the effects of alkylphenol and alkylphenolethoxylates on metabolic heat rates. In general, treatment with alkylphenols and alkylphenolethoxylates at concentrations ranging from 10−6 to 10−4 M caused stimulation of metabolic heat rates, possibly due to uncoupling of oxidative metabolism. Higher concentrations subsequently caused inhibition of metabolic activity and thus decreased heat rates. Rates of oxygen consumption by the gill tissue exposed to the surfactants, as a measure of effects on electron flux through mitochondria, showed a similar pattern of respiratory rate stimulation at low concentration and inhibition at higher concentration. Therefore, the batch calorespirometric method proved to be a useful technique to assess the toxicity of a group of surfactants on the control of energy flux in gills of a freshwater bivalve mollusk.

Metabolism and organ distribution of nonylphenol in Atlantic salmon ( Salmo salar)

Nonylphenol (NP) is a breakdown product of alkylphenol polyethoxylates (APEs), an important class of non-ionic surfactants that are widely used in many detergent formulations and plastic products for industrial and domestic use. A complex microbial degradation pattern, characterized by the formation of several metabolic products that are more toxic than the parent compound, has been established for APEs. We have studied the in vivo metabolism and organ distribution of NP in juvenile salmon. Fish were exposed to a single oral dose of [ 3H]-4-n-NP (1295 KBq, 25 μg) and sampled at 24, 48 and 72 h after exposure. Metabolites were separated by radio-high-performance liquid chromatography and tentatively identified by co-chromatography with standards characterized by mass spectrometry. Our results show that 4-n-NP was mainly metabolized in vivo to its corresponding glucuronide conjugate and to a lesser extent to various hydroxylated and oxidated compounds. Biliary excretion at 72 h after dosing amounted to 2.83±0.75% of the administered radioactivity. Kinetic analysis shows that NP-glucuronide accounted for 83, 95 and 81% of total radioactivity in the HPLC-injected bile sample at 24, 48 and 72 h, respectively, after exposure. The half-life of residues in carcass and muscle was between 24 and 48 h after exposure.

Biodegradation of a nonylphenol ethoxylate by the autochthonous microflora in lake water with observations on the influence of light

Alkylphenol polyethoxylates (APE) are routinely used as additives in pesticide formulations. Biodegradation of APEs results in the accumulation of persistent short chain mono-, di- and tri-ethoxylates (AP1EO, AP2EO AP3EO) that are more toxic than the parent compounds and potentially oestrogenic. Accumulation of persistent APE metabolites in shallow or ephemeral waters may pose a hazard to aquatic fauna. This study has followed the degradation and formation of individual oligomers in freshwater in static die-away tests with and without illumination. Over 33 days in darkness there was a progressive and complete loss of long chain oligomers (NP8-17EO), transient increases and subsequent loss of short to medium chain oligomers (NP4-7EO), and large persistent increases (∼1000%) in short chain oligomers (NP1-3EO). In the presence of illumination, biodegradation was retarded and heterotrophic bacterial proliferation was inhibited. After 33 days there was complete loss of long chain oligomers (NP9-17EO), incomplete loss of medium chain oligomers (NP6-8EO) and increases in short chain oligomers (NP1-5EO).

Formation of the metabolic intermediate 2,4,4-trimethyl-2-pentanol during incubation of a Sphingomonas sp. strain with the xeno-estrogenic octylphenol.

Degradation of branched octylphenol was studied in a bacterial culture of a Sphingomonas sp. strain. Octylphenol is considered to be the most stable degradation intermediate formed from the corresponding nonionic octylphenol polyethoxylates surfactants during biological wastewater treatment. Since octylphenol can exert estrogenic effects in wildlife, a detailed study of its biodegradation is warranted. The aerobic microbiological transformation of octylphenol was examined with and without the addition of the easily assimilable sodium acetate. In both cases the formation of the metabolite 2,4,4-trimethyl-2-pentanol, representing the intact alkyl chain as a tertiary alcohol, was observed. Since the octylphenol degradation rate was not affected by the presence of acetate, this strain did not show any diauxic metabolic behaviour when incubated with octylphenol and sodium acetate as the sources of carbon and energy. As a result of the biotransformation of octylphenol, its estrogenic potency was removed because it is the phenolic moiety that interacts with the estrogen receptors. This feature opens perspectives for the use of this strain in the framework of an adequate treatment of wastewater with high levels of alkylphenol polyethoxylates.

Linear Alkylbenzene Sulfonates and Intermediate Products from their Degradation are not Estrogenic

A number of natural and man-made chemicals possess estrogenic activity, i.e., they induce receptor-mediated estrogen dependent responses in vertebrates. Recently, high concentrations of linear alkylbenzene sulfonates (LAS) and intermediate products of LAS biodegradation, sulfophenyl carboxylates (SPC), have been found in the Bay of Cádiz, Spain. Due to their similar chemical properties with the estrogenic alkylphenolpolyethoxylates (APnEO) it has been speculated that LAS and their metabolites have estrogenic effects. The present work addresses the question upon the possible estrogenicity of LAS and LAS metabolites by two in vitro assays: the yeast estrogen receptor assay and the vitellogenin assay with cultured trout hepatocytes. With both bioassays no estrogenic effects were observed for any of the compounds tested.

Review of the Aquatic Toxicity, Estrogenic Responses and Bioaccumulation of Alkylphenols and Alkylphenol Polyethoxylates

Abstract A review of the available information on the toxicity and bioaccumulation of alkyphenols (AP) and their polyethoxylates (APE) and polyethoxycarboxylates (APEC) was conducted in support of their assessment as Priority Substances under the Canadian Environmental Protection Act. This included an examination of the acute and chronic toxicity of these compounds in a wide variety of aquatic organisms as well as an examination of their potential effects on endocrine function in fish and aquatic invertebrates. Although the data in the literature are scattered among many species, different test methods and chemicals, there is a consistent pattern in the toxicity. Nonylphenol (NP) and octylphenol (OP) are both acutely toxic to fish (17-3000 µg/L), invertebrates (20-3000 µg/L) and algae (27-2500 µg/L). In chronic toxicity tests no observable effect concentrations (NOEC) are as low as 6 mg/L in fish and 3.7 µg/L in invertebrates. There is an increase in the toxicity of both NPEs and OPEs with decreasing EO chain length. NPECs and OPECs are less toxic than corresponding APEs and have acute toxicities similar to APEs with 6-9 EO units. APs and APEs bind to the estrogen receptor resulting in the expression of several responses both in vitro and in vivo, including the induction of vitellogenin. The threshold for vitellogenin induction in fish is 10 µg/L for NP and 3 µg/L for OF. APEs also affect the growth of testes, alter normal steroid metabolism, disrupt smoltificaton and cause intersex (ova-testes) in fish. The available literature suggests that the ability of AP and APEs to bioaccumulate in aquatic biota in the environment is low to moderate, BCFs and BAFs in biota, including algae, plant, invertebrates and fish range from 0.9 to 3400. Although there are relatively few data available for OP or OPEs, their potential to bioaccumulate is expected to be similar to that of corresponding NP and NPEs.

Concentrations of alkyphenol polyethoxylates entering UK estuaries

Concentrations of the weakly oestrogenic degradation products of alkylphenol polyethoxylate (APE) surfactants (nonylphenol, octylphenol, nonylphenol monoethoxylate and nonylphenol diethoxylate) were measured in water and sediments from British rivers and estuaries collected during 1994 and 1995. In addition, a series of samples of tissues of wild fish from the River Aire, and from a laboratory dosing experiment were analysed for alkylphenols, to assess the degree of bioaccumulation of these compounds. Measurable concentrations of APE residues were recorded in the River Aire (15–76 μg/l total extractable alkylphenols), the River Mersey (6–11 μg/l) and the Tees estuary (up to 76 μg/l). These levels exceed, or are close to, the no observed effect concentration for the induction of vitellogenesis in caged trout (5–20 μg/l total extractable alkylphenols), and may be sufficient to exert an oestrogenic effect on fish populations in these areas. A sediment sample from Bingley on the River Aire contained 15 μg/g (dry weight) nonylphenol, and concentrations in sediments from the Tees and Mersey estuaries exceeded 1 μg/g. These rivers receive a variety of trade waters via sewage treatment works (STW) effluents containing significant concentrations of APE. Elsewhere, concentrations in water and sediments were near or below limits of detection and biological effects are unlikely, suggesting that any oestrogenic effects observed in sewage outfalls and rivers not directly impacted by APE-containing trade-waters may be caused by other chemicals. Analysis of samples of trout muscle taken from a tank dosed at 65 μg/l nonylphenol indicated a bioaccumulation factor of between 90 and 125 after 3 weeks exposure. Samples of wild fish from the River Aire contained up to 0.8 μg/g nonylphenol in the muscle, a tissue bioaccumulation factor of approximately 50 relative to measured concentrations in water samples. A series of fish samples taken from offshore for food quality assurance purposes contained no detectable levels of APE residues (0.05–0.1 μg/g nonylphenol).

Assessment of Environmental Toxicities of Linear Alkylbenzenesulfonates (LAS) Including LAS Complexes (LAS-C), Alkylphenolpolyethoxylates, and Their Biodegradation Products

Linear alkylbenzenesulfonates (LAS) and alkylphenolpolyethoxylates (APE) are shown to belong to a major group of surfactant as ingredients of detergents and are normally present in raw sewage. Many biodegradation products of these surfactants, such as sulfophenyl-carboxylic acids, nonylphenol (NP) and nonylphenoldiethoxylate (NP2EO) etc., and LAS complexes (LAS-C) with cationic surfactants are also present in river water, sediment and/or effluent. Recently, the estrogenic properties of the biodegradation products of APE, NP and NP2EO etc., have a great interest for us. In order to assess the risks of LAS and APE for an aquatic environment, the following are required to be cleared ; (1) exposure concentrations of these compounds, including their biodegradation products and LAS-C, (2) behaviors on their biodegradation, adsorption, and the rate of removal in the wastewater treatment plant, (3) toxic and estrogenic effects on aquatic organisms and eosystem. In this review, the recent trends of studies on LAS, APE and their biodegradation products, and LAS-C are discussed.

Alkylphenol Polyethoxylate Metabolites in Canadian Sewage Treatment Plant Waste Streams

Abstract Nonylphenol polyethoxylates and their refractory metabolites, including nonylphenol, are on the second Priority Substances List (PSL2) to determine if they are "toxic" as defined under the Canadian Environmental Protection Act. This study addresses the need for data on their occurrence in raw sewage, final effluents and sludge in Canada. Samples of raw sewage, final effluent and sludge were collected from 16 wastewater treatment plants across Canada in 1995 and 1996. These samples were analyzed for 4-nonylphenol (4-NP), nonylphenol ethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO) and 4-4-tert-octylphenol (4-t-OP). Measurable quantities of these chemicals were found in almost all raw sewage and sludge samples. In the raw sewage, concentrations ranged from <0.005 to 21 μg/L for 4-t-OP, from 0.69 to 155 μg/L for 4-NP, from 2.9 to 43 μg/L for NP1EO and from 0.26 to 24 μg/L for NP2EO. Sludge concentrations (based on dry weight) ranged from <0.010 to 20 μg/g, from 8.4 to 850 μg/g, from 3.9 to 437 μg/g and from 1.5 to 297 μg/g for 4-t-OP, 4-NP, NP1EO and NP2EO, respectively. Of the final effluent samples, 60% contained detectable amounts of 4-t-OP and concentrations ranged from <0.005 to 0.37 μg/L. Almost all of the final effluent samples had detectable levels of 4-NP, NP1EO and NP2EO. The 4-NP concentrations varied from <0.020 to 13 μg/L, NP1EO was found in the range of 0.072 to 26 μg/L and NP2EO was found in the range of 0.099 to 21 μg/L.

An updated review of environmental estrogen and androgen mimics and antagonists

For the last 40 y, substantial evidence has surfaced on the hormone-like effects of environmental chemicals such as pesticides and industrial chemicals in wildlife and humans. The endocrine and reproductive effects of these chemicals are believed to be due to their ability to: (1) mimic the effect of endogenous hormones, (2) antagonize the effect of endogenous hormones, (3) disrupt the synthesis and metabolism of endogenous hormones, and (4) disrupt the synthesis and metabolism of hormone receptors. The discovery of hormone-like activity of these chemicals occurred long after they were released into the environment. Aviation crop dusters handling DDT were found to have reduced sperm counts, and workers at a plant producing the insecticide kepone were reported to have lost their libido, became impotent and had low sperm counts. Subsequently, experiments conducted in lab animals demonstrated unambiguously the estrogenic activity of these pesticides. Man-made compounds used in the manufacture of plastics were accidentally found to be estrogenic because they fouled experiments conducted in laboratories studying natural estrogens. For example, polystyrene tubes released nonylphenol, and polycarbonate flasks released bisphenol-A. Alkylphenols are used in the synthesis of detergents (alkylphenol polyethoxylates) and as antioxidants. These detergents are not estrogenic; however, upon degradation during sewage treatment they may release estrogenic alkylphenols. The surfactant nonoxynol is used as intravaginal spermicide and condom lubricant. When administered to lab animals it is metabolized to free nonylphenol. Bisphenol-A was found to contaminate the contents of canned foods; these tin cans are lined with lacquers such as polycarbonate. Bisphenol-A is also used in dental sealants and composites. We found that this estrogen leaches from the treated teeth into saliva; up to 950 μg of bisphenol-A were retrieved from saliva collected during the first hour after polymerization. Other xenoestrogens recently identified among chemicals used in large volumes are the plastizicers benzylbutylphthalate, dibutylphthalate, the antioxidant butylhydroxyanisole, the rubber additive p-phenylphenol and the disinfectant o-phenylphenol. These compounds act cumulatively. In fact, feminized male fish were found near sewage outlets in several rivers in the U.K.; a mixture of chemicals including alkyl phenols resulting from degradation of detergents during sewage treatment seemed to be the causal agent. Estrogen mimics are just a class of endocrine disruptors. Recent studies identified antiandrogenic activity in environmental chemicals such as vinclozolin, a fungicide, and DDE, and insecticide. Moreover, a single chemical may produce neurotoxic, estrogenic and antiandrogenic effects. It has been hypothesized that endocrine disruptors may play a role in the decrease in the quantity and quality of human semen during the last 50 y, as well as in the increased incidence of testicular cancer and cryptorchidism in males and breast cancer incidence in both females and males in the industrialized word. To explore this hypothesis it is necessary to identify putative causal agents by the systematic screening of environmental chemicals and chemicals present in human foods to assess their ability to disrupt the endocrine system. In addition, it will be necessary to develop methods to measure cumulative exposure to (a) estrogen mimics, (b) antiandrogens, and (c) other disruptors.

Identification of Alkylphenols and Other Estrogenic Phenolic Compounds in Wastewater, Septage, and Groundwater on Cape Cod, Massachusetts

As part of a larger effort to characterize the impacts to Cape Cod drinking water supplies from on-site wastewater disposal, we developed two analytical methods using HPLC and GC/MS for a range of compounds identified as endocrine-disrupting chemicals (EDCs), including the nonionic surfactants alkylphenol polyethoxylates (APEOs) and their degradation products. We analyzed samples for nonylphenol, octylphenol, and their ethoxylates up to the hexaethoxylate using an HPLC method, with detection limits ranging from 2 to 6 μg/L. A set of phenolic compounds including bisphenol A and nonylphenol were derivatized and analyzed by GC/MS with detection limits from 0.001 to 0.02 μg/L. Total APEOs in untreated wastewater and septage samples ranged from 1350 to 11 000 μg/L by the HPLC method. Nonylphenol was detected in all septage samples at concentrations above 1000 μg/L. Phenylphenol and bisphenol A were detected in septage and wastewater at about 1 μg/L. In groundwater downgradient of an infiltration bed for second...

名古屋市内の水環境中のアルキルフェノールポリエトキシレート（ＡＰＥ）および分解生成物の分布

Alkylphenol polyethoxylate (APE) and their metabolites were determined in the aquatic environment in Nagoya city. The persistent metabolites of APE, namely nonylphenol tetra-,tri -,di- and monoethoxylate(NPI-4EO), nonylphenol(NP) and octylphenl(OP) were determined in effluents of municipal sewage-treatment plants and river waters by HPLC. In many samples NP1-4EO concentrations were higher than NP. It seems that a predominant source of the invesitigated compounds in river waters was the effluents of municipal sewage-treatment plants. Nonylphenol polyethoxylate (NPnEO : n≥5) was not detected in effluents of municipal sewage-treatment plants, but was detected only in river water receiving untreated municipal wastewaters.NPnEO, NP1-4EO, NP and OP were found in sediments at concentration levels of a few hundreds times higher than those levels in river waters, indicating their accumulation in sediments. NP concentrations were higher than NP1-4EO concentrations in sediments.These metabolites, particularly NP, are more toxic to aquatic organisms than the parent compounds, consequently there are public concerns about their environmental effects. This research demonstrates that further investigation on the behaviour of APE and their metabolites is necessary.

DISTRIBUTION OF ALKYLPHENOL COMPOUNDS IN GREAT LAKES SEDIMENTS, UNITED STATES AND CANADA

Alkylphenol polyethoxylates are a major class of nonionic surfactants that are microbially degraded in sewage treatment plants (STPs) and sediments to more toxic and hydrophobic alkylphenols. Recent data on the estrogenic activity of alkylphenols has prompted interest in the distribution of these compounds in the aquatic environment. Sediment samples were collected from several sites (n = 28) at industrialized and pristine regions of Lake Huron, Lake Erie, and Lake Ontario, USA and Canada, and analyzed for concentrations of 4-nonylphenol (NP) and 4-(tert)-octylphenol (OP). Also, sludge samples were taken from a secondary STP in Whitby, Ontario, Canada. Sediment and sludge samples and analytical standards were prepared for analysis by gas chromatography–mass spectrometry in selected ion mode by combined acetylation and supercritical fluid extraction. Concentrations of NP were up to 37 μg/g in sediments and >300 μg/g in the sewage sludge. Concentrations of OP were up to 23 μg/g in sediment and 21 μg/g in the sewage sludge. These data indicate that alkylphenols are distributed widely in sediments in the lower Great Lakes. However, concentrations of NP were present at high (μg/g) levels only in sediments near urban and industrialized centers.

Degradation of poly(ethylene glycol) based nonionic surfactants by different bacterial isolates from river water

Different bacterial strains able to attack polyoxyethylene-type nonionic surfactants were isolated by enrichment procedure from the surface waters of the Arno River. Alkylphenol polyethoxylates and alkyl polyethoxylates, as well as polyethylene glycols, were degraded and assimilated by bacterial strains in axenic cultures. Degradative routes of polyethyleneoxide chains were investigated by matching each bacterial isolate with several types of nonionic surfactants and polyethers and by the identification of their degradation products isolated during aerobic digestion experiments. In accordance with previous reports, the first attack led to the shortening of the poly(oxyethylene) chains of the nonionic surfactants. It was found that the strains able to degrade PEG segments of nonionic surfactants possess enzymatic systems unable to degrade free PEGs, whereas those degrading the latter substrates cannot degrade PEG segments coupled to hydrophobic moieties.

Reproductive health in humans and wildlife: are adverse trends associated with environmental chemical exposure?

In recent years, evidence from disparate observations has indicated adverse changes in the reproductive health and fecundity of animals and humans. In humans, there is strong evidence for such trends in the incidences of testicular and female breast cancer, and concern has also been expressed regarding semen quality, cryptorchidism, hypospadias and polycystic ovaries. Laboratory studies have indicated that some chemicals in the environment, both natural and synthetic, have the potential to disrupt the endocrine system and that these could, at least theoretically, be partly responsible for the observed changes. Chemicals thus identified include the naturally occurring steroid hormones, phyto- and myco-estrogens, and anthropogenic chemicals such as synthetic hormones, organotins, organochlorine pesticides, polychlorinated biphenyls, dioxins, alkylphenol polyethoxylates, phthalates and bisphenol-A. While there is no direct evidence from human studies to confirm a causal link between exposure and effect, concern exists and is strengthened by reports of adverse reproductive and developmental effects in wildlife, possibly mediated via endocrine disruptive pathways. The development of imposex in neogastropod molluscs exposed to tributyltin has been attributed to such a mechanism and in wild populations of fish, alligators and birds, instances of masculinisation or feminisation in polluted areas have been noted. Among mammals, disturbed fertility of Florida panthers and some marine species has also been reported. A concentrated research and monitoring programme is required to clarify the nature and extent of effects on reproductive health in humans and wildlife, and to assess human and wildlife exposure to relevant naturally occurring or anthropogenic endocrine disrupting substances. This will enable a more robust evaluation of the contribution that environmental chemical exposure may have on adverse trends in the reproductive health of humans and wildlife.

Identification of Metabolites from the Biological Transformation of the Nonionic Surfactant Residue Octylphenoxyacetic Acid and Its Brominated Analog

The aerobic biological transformation of octylphenoxyacetic acid (OP1EC) and its brominated analog (BrOP1EC) by groundwater enrichment cultures was studied, and persistent metabolites were identified by GC/MS. OP1EC is a representative of the class of alkylphenol ethoxycarboxylates (APEC), formed from alkylphenol polyethoxylate nonionic surfactants during sewage treatment. BrOP1EC is a byproduct formed during chlorine disinfection in the presence of bromide. The metabolite 2,4,4-trimethyl-2-pentanol was detected in stoichiometric quantities in OP1EC-metabolizing enrichment cultures, representing the intact alkyl side chain as a tertiary alcohol. BrOP1EC was transformed by the OP1EC-utilizing cultures only if OP1EC was simultaneously metabolized, suggesting a cometabolic mechanism of transformation. Brominated intermediates were also detected: brominated octylphenol and a compound tentatively identified as 2-aminomethoxy-3-bromo-5-(1,1,3,3-tetra- methylbutyl)phenol.