The challenge posed by endocrine-disrupting chemicals

Estrogenic hazards of short chain phthalates and bisphenols found in cosmetic products

For several years, environmental exogenous agents, called endocrine disruptors, are suspected to interfere with the essential functions of reproduction and development in many living organisms. In this study, endocrine disruptors including five phthalates and two bisphenols contents in finished products were assayed and their estrogenic activity were measured by using the Yeast Estrogen Screen system with respect to human and trout estrogen receptors hERα and rtER_S. Independently of the estrogen receptor, only short-chain phthalates (DBP and BBP) and the two bisphenols exhibited an estrogenic activity. Besides, the risk of three end-products (agro-food, cosmetics, and pharmaceutical) was evaluated before and after forced aging. Only two cosmetics the face cream and the perfume presented a hazard which increases with aging. These results are consistent with the compounds identified by Gas chromatography-mass spectrometry. These findings confirmed that the YES system can be routinely used to evaluate the estrogenic hazards within finished products.

Multi-approach assessment for the evaluation of spatio-temporal estrogenicity in fish from effluent-dominated surface waters under low instream flow

Current practices employed by most wastewater treatment plants (WWTP) are unable to completely remove endocrine disrupting compounds (EDCs) from reclaimed waters, and consistently discharge these substances to receiving systems. Effluent-dominated and dependent surface waters, especially during low instream flows, can increase exposure and risks to aquatic organisms due to adverse biological effects associated with EDCs. Given the ecological implications that may arise from exposure to such compounds, the present a multi-approach study examined spatio-temporal estrogenic potential of wastewater effluent to fish in East Canyon Creek (ECC), Utah, USA, a unique urban river with instream flows seasonally influenced by snowmelt. Juvenile rainbow trout (Oncorhynchus mykiss) were caged at different upstream and downstream sites from an effluent discharge during the summer and fall seasons. In the summer, where approximately 50% of the streamflow was dominated by effluent, fish from the upstream and a downstream site, located 13 miles away from the effluent discharge, presented significantly elevated concentrations of plasma vitellogenin (VTG). Similarly, significantly high 17β-estradiol to 11-ketotestosterone ratios were measured in the summer across all sites and time points, compared to the fall. In the laboratory, juvenile fish and primary hepatocytes were exposed to concentrated effluent and surface water samples. Quantification of VTG, although in significantly lower levels, resembled response patterns observed in fish from the field study. Furthermore, analytical quantification of common EDCs in wastewater revealed the presence of estriol and estrone, though these did not appear to be related to the observed biological responses, as these were more significant in sites were no EDCs were detected. These combined observations suggest potential estrogenicity for fish in ECC under continuous exposures and highlight the advantages of following weight-of-evidence (WoE) approaches for environmental monitoring, as targeted analytically-based assessments may or may not support the identification of causative contaminants for adverse biological effects.

Competitive effects of humic acid and wastewater on adsorption of Methylene Blue dye by activated carbon and non-imprinted polymers

Natural organic matter (NOM), present in natural waters and wastewater, decreases adsorption of micropollutants, increasing treatment costs. This research investigated mechanisms of competition for non-imprinted polymers (NIPs) and activated carbon with humic acid and wastewater. Three different types of activated carbons (Norit PAC 200, Darco KB-M, and Darco S-51) were used for comparison with the NIP. The lower surface area and micropore to mesopore ratio of the NIP led to decreased adsorption capacity in comparison to the activated carbons. In addition, experiments were conducted for single-solute adsorption of Methylene Blue (MB) dye, simultaneous adsorption with humic acid and wastewater, and pre-loading with humic acid and wastewater followed by adsorption of MB dye using NIP and Norit PAC 200. Both the NIP and PAC 200 showed significant decreases of 27% for NIP (p=0.087) and 29% for PAC 200 (p=0.096) during simultaneous exposure to humic acid and MB dye. There was no corresponding decrease for NIP or PAC 200 pre-loaded with humic acid and then exposed to MB. In fact, for PAC 200, the adsorption capacity of the activated carbon increased when it was pre-loaded with humic acid by 39% (p=0.0005). For wastewater, the NIP showed no significant increase or decrease in adsorption capacity during either simultaneous exposure or pre-loading. The adsorption capacity of PAC 200 increased by 40% (p=0.001) for simultaneous exposure to wastewater and MB. Pre-loading with wastewater had no effect on MB adsorption by PAC 200.

The chemical disruption of human metabolism

BACKGROUND

Recent evidence highlights the reality of unprecedented human exposure to toxic chemical agents found throughout our environment - in our food and water supply, in the air we breathe, in the products we apply to our skin, in the medical and dental materials placed into our bodies, and even within the confines of the womb. With biomonitoring confirming the widespread bioaccumulation of myriad toxicants among population groups, expanding research continues to explore the pathobiological impact of these agents on human metabolism.

METHODS

This review was prepared by assessing available medical and scientific literature from Medline as well as by reviewing several books, toxicology journals, government publications, and conference proceedings. The format of a traditional integrated review was chosen.

RESULTS

Toxicant exposure and accrual has been linked to numerous biochemical and pathophysiological mechanisms of harm. Some toxicants effect metabolic disruption via multiple mechanisms.

CONCLUSIONS

As a primary causative determinant of chronic disease, toxicant exposures induce metabolic disruption in myriad ways, which consequently result in varied clinical manifestations, which are then categorized by health providers into innumerable diagnoses. Chemical disruption of human metabolism has become an etiological determinant of much illness throughout the lifecycle, from neurodevelopmental abnormalities in-utero to dementia in the elderly.

Use of sub-micron sized resin particles for removal of endocrine disrupting compounds and pharmaceuticals from water and wastewater

Endocrine disrupting compounds (EDCs) and pharmaceuticals pose a challenge for water and wastewater treatment because they exist at very low concentrations in the presence of substances at much higher concentrations competing for adsorption sites. Sub-micron sized resin particles (approximately 300nm in diameter) (SMR) were tested to evaluate their potential as a treatment for EDCs including: 17-β estradiol (E2), 17-α ethinylestradiol (EE2), estrone (E1), bisphenol A (BPA), and diethylstilbestrol (DES) as well as 12 pharmaceuticals. SMR were able to remove 98% of spiked E2, 80% of EE2, 87% of BPA, and up to 97% of DES from water. For a 0.5ppm mixture of E2, EE2, E1, BPA and DES, the minimum removal was 24% (E2) and the maximum was 49% (DES). They were also able to remove the pharmaceuticals from deionized water and wastewater. Overall, SMR are a promising advanced treatment for removal of both EDCs and pharmaceuticals.

Dieldrin reduces male production and sex ratio in Daphnia galeata mendotae

We used the sex ratio of neonate Daphnia, as well as the more standard endpoints of adult survivorship and fecundity and neonatal morphology, as an assay for detecting the effects of the insecticides endosulfan and dieldrin. Dieldrin caused a decrease in sex ratio (number of males/number of males plus females); we observed no endosulfan effect. We estimated (by extrapolation) that the sex ratio was reduced by dieldrin from concentrations of about 30 ppb and higher, based on a linear decrease in sex ratio with log dieldrin concentrations from 50 to 600 ppb. Neither insecticide significantly affected adult survival or clutch size. Because sex ratio changed but total neonate production did not change, the data suggest that the effect of dieldrin was on the sex-determining system during embryogenesis. Neither insecticide caused morphological abnormalities. Mixtures of the two pesticides produced only additive effects.

Size does matter! Label-free detection of small molecule-protein interaction

This review is focused on methods for detecting small molecules and, in particular, the characterisation of their interaction with natural proteins (e.g. receptors, ion channels). Because there are intrinsic advantages to using label-free methods over labelled methods (e.g. fluorescence, radioactivity), this review only covers label-free techniques. We briefly discuss available techniques and their advantages and disadvantages, especially as related to investigating the interaction between small molecules and proteins. The reviewed techniques include well-known and widely used standard analytical methods (e.g. HPLC-MS, NMR, calorimetry, and X-ray diffraction), newer and more specialised analytical methods (e.g. biosensors), biological systems (e.g. cell lines and animal models), and in-silico approaches.

A real-time PCR assay for differential expression of vitellogenin I and II genes in the liver of the sentinel fish species Lipophrys pholis

Abstract The recent advances in molecular biology techniques have prompted the use of vitellogenin (VTG) gene expression as a sensitive and reliable indicator of estrogenic chemicals (EC) exposure. However, data on the dynamic response of the different VTGs genes upon EC exposure is still poorly understood, particularly in sentinel fish species used in field monitoring studies. Hence, the present study aimed at developing a sensitive real-time PCR assay for determining the response of VTG I and II in the recently proposed marine sentinel species Lipophrys pholis upon exposure to the model EC 17α-ethinylestradiol (EE2). The findings of the laboratory study indicate that L. pholis VTG I proved to be not only more inducible but also more sensitive to EE2 exposure than VTG II, for the same range of concentrations. In fact, VTG I gene induction was 475-fold higher than VTG II at 15 ng/L EE2, and 13-fold at 5 ng/L EE2. Overall, the findings of the present study indicate that in the field, expression of VTG I in L. pholis should be preferentially used in the screening of EC exposure because of its higher sensitivity. Furthermore, the present study favors L. pholis integration in monitoring programs associated with EC's pollution within the European water policy legislation.

Application of molecularly imprinted and non-imprinted polymers for removal of emerging contaminants in water and wastewater treatment: a review

Over the past decade, several studies have reported trace levels of endocrine disrupting compounds, pharmaceuticals, and personal care products in surface waters, drinking water, and wastewater effluents. There has also been an increased concern about the ecological and human health impact of these contaminants, and their removal from water and wastewater has become a priority. Traditional treatment processes are limited in their ability to remove emerging contaminants from water, and there is a need for new technologies that are effective and feasible. This paper presents a review on recent research results on molecularly imprinted (MIP) and non-imprinted (NIP) polymers and evaluates their potential as a treatment method for the removal of emerging contaminants from water and wastewater. It also discusses the relative benefits and limitations of using MIP or NIP for water and wastewater treatment. MIP, and in particular NIP, offer promising applications for wastewater treatment, but their toxicity and possible health effects should be carefully studied before they are considered for drinking water treatment. More research is also required to determine how best to incorporate MIP and NIP in treatment plants.

Ligand- and structure-based pregnane X receptor models

The human pregnane X receptor (PXR) is a ligand dependent transcription factor that can be activated by structurally diverse agonists including steroid hormones, bile acids, herbal drugs, and prescription medications. PXR regulates the transcription of several genes involved in xenobiotic detoxification and apoptosis. Activation of PXR has the potential to initiate adverse effects by altering drug pharmacokinetics or perturbing physiological processes. Hence, more reliable prediction of PXR activators would be valuable for pharmaceutical drug discovery to avoid potential toxic effects. Ligand- and protein structure-based computational models for PXR activation have been developed in several studies. There has been limited success with structure-based modeling approaches to predict human PXR activators, which can be attributed to the large and promiscuous site of this protein. Slightly better success has been achieved with ligand-based modeling methods including quantitative structure-activity relationship (QSAR) analysis, pharmacophore modeling and machine learning that use appropriate descriptors to account for the diversity of the ligand classes that bind to PXR. These combined computational approaches using molecular shape information may assist scientists to more confidently identify PXR activators. This chapter reviews the various ligand and structure based methods undertaken to date and their results.

Elimination of persistent toxicants from the human body

There is compelling evidence that various chemical agents are important determinants of myriad health afflictions--several xenobiotics have the potential to disrupt reproductive, developmental, and neurological processes and some agents in common use have carcinogenic, epigenetic, endocrine-disrupting, and immune-altering action. Some toxicants appear to have biological effect at miniscule levels and certain chemical compounds are persistent and bioaccumulative within the human body. Despite escalating public health measures to preclude further exposures, many people throughout the world have already accrued a significant body burden of toxicants, placing them at potential health risk. As a result, increasing discussion is underway about possible interventions to facilitate elimination of persistent toxicants from the human organism in order to obviate health affliction and to potentially ameliorate chronic degenerative illness. An overview of the clinical aspects of detoxification is presented with discussion of established and emerging interventions for the elimination of persistent xenobiotics. Potential therapies to circumvent enterohepatic recirculation and a case report highlighting a clinical outcome associated with detoxification are also presented for consideration.

Oxidative transformation of 17beta-estradiol by MnO2) in aqueous solution

17beta-Estradiol (E2) is known as a natural endocrine disruptor and often found in municipal sewage. Batch experiments were conducted to assess the oxidative transformation of E2 in aqueous solutions by MnO2 and the probable degradation pathway. The results suggested that E2 could be degraded by MnO2, and the oxidation reaction deviated from pseudo-first-order kinetics due to the accumulation of reaction products in mineral surfaces and a gradual change of the surface site distribution toward less reactive sites. MnO2 dosage had a positive effect on oxidative transformation of E2, and both the initial reaction rate and the adsorption of E2 to oxide surfaces increased as the pH decreased. Two products, estrone and 2-hydroxyestradiol, were detected by gas chromatography coupled with mass spectrometry, and the probable degradation pathway was proposed. Results suggest that E2 can be oxidatively transformed by MnO2, which will provide some new insights into the interaction of estrogens with manganese oxides in natural soils and sediments.

Reuse of concentrated animal feeding operation wastewater on agricultural lands

Concentrated animal feeding operations (CAFOs) generate large volumes of manure and manure-contaminated wash and runoff water. When applied to land at agronomic rates, CAFO wastewater has the potential to be a valuable fertilizer and soil amendment that can improve the physical condition of the soil for plant growth and reduce the demand for high quality water resources. However, excess amounts of nutrients, heavy metals, salts, pathogenic microorganisms, and pharmaceutically active compounds (antibiotics and hormones) in CAFO wastewater can adversely impact soil and water quality. The USEPA currently requires that application of CAFO wastes to agricultural lands follow an approved nutrient management plan (NMP). A NMP is a design document that sets rates for waste application to meet the water and nutrient requirements of the selected crops and soil types, and is typically written so as to be protective of surface water resources. The tacit assumption is that a well-designed and executed NMP ensures that all lagoon water contaminants are taken up or degraded in the root zone, so that ground water is inherently protected. The validity of this assumption for all lagoon water contaminants has not yet been thoroughly studied. This review paper discusses our current level of understanding on the environmental impact and sustainability of CAFO wastewater reuse. Specifically, we address the source, composition, application practices, environmental issues, transport pathways, and potential treatments that are associated with the reuse of CAFO wastewater on agricultural lands.

Structure-activity relationship analysis of rat mammary carcinogens

Structure-activity relationship (SAR) models are powerful tools to investigate the mechanisms of action of chemical carcinogens and to predict the potential carcinogenicity of untested compounds. We describe here the application of the cat-SAR (categorical-SAR) program to two learning sets of rat mammary carcinogens. One set of developed models was based on a comparison of rat mammary carcinogens to rat noncarcinogens (MC-NC), and the second set compared rat mammary carcinogens to rat nonmammary carcinogens (MC-NMC). On the basis of a leave-one-out validation, the best rat MC-NC model achieved a concordance between experimental and predicted values of 84%, a sensitivity of 79%, and a specificity of 89%. Likewise, the best rat MC-MNC model achieved a concordance of 78%, a sensitivity of 82%, and a specificity of 74%. The MC-NMC model was based on a learning set that contained carcinogens in both the active (i.e., mammary carcinogens) and the inactive (i.e., carcinogens to sites other than the mammary gland) categories and was able to distinguish between these different types of carcinogens (i.e., tissue specific), not simply between carcinogens and noncarcinogens. On the basis of a structural comparison between this model and one for Salmonella mutagens, there was, as expected, a significant relationship between the two phenomena since a high proportion of breast carcinogens are Salmonella mutagens. However, when analyzing the specific structural features derived from the MC-NC learning set, a dichotomy was observed between fragments associated with mammary carcinogenesis and mutagenicity and others that were associated with estrogenic activity. Overall, these findings suggest that the MC-NC and MC-NMC models are able to identify structural attributes that may in part address the question of "why do some carcinogens cause breast cancer", which is a different question than "why do some chemicals cause cancer".

Establishing evidence for early action: the prevention of reproductive and developmental harm

Developmental and reproductive toxicants that cause serious disease and dysfunction, either lifelong or occurring late in life, can be initiated in the early life stages of human beings and other species. It is often the timing of the dose more than the dose itself that distinguishes harmful from harmless exposures to such toxicants. As much of the harm is irreversible, and sometimes multigenerational, the timing of actions to prevent such harm is also critical. In determining when there is a sufficiency of evidence to justify early prevention of harm, decision-makers need to take account of the implications of multicausality, the methodological biases within environmental sciences, and the need to take precautionary, as well as preventive actions to eliminate or reduce exposures. The widely used Bradford Hill causal 'criteria' are briefly reviewed in light of multicausality. Reaching agreement between stakeholders on a sufficiency of evidence for early action to reduce exposures to toxicants requires the consistent use of transparent definitions of the concepts and terms used to characterize the strength of evidence between causes and effects. Proposals are made to improve those in current use, including a definition of the precautionary principle.

Seven deadly sins of environmental epidemiology and the virtues of precaution

The potentials for error in planning, conducting, reporting, and utilizing epidemiologic results can be considered in terms of the traditional 7 deadly sins. To counter these sins, epidemiologic virtues should be inspired by the precautionary principle. The remedies emphasize acknowledgment and exploration of the impact of uncertainties, weight-of-the-evidence assessments that consider what could be known given the opportunities for research, and epidemiologic strategies that facilitate the use of tentative, though innovative, studies in decision-making.

Late lessons from early warnings: Toward realism and precaution with endocrine-disrupting substances

The histories of selected public and environmental hazards, from the first scientifically based early warnings about potential harm to the subsequent precautionary and preventive measures, have been reviewed by the European Environment Agency. This article relates the "late lessons" from these early warnings to the current debates on the application of the precautionary principle to the hazards posed by endocrine-disrupting substances (EDSs). Here, I summarize some of the definitional and interpretative issues that arise. These issues include the contingent nature of knowledge; the definitions of precaution, prevention, risk, uncertainty, and ignorance; the use of differential levels of proof; and the nature and main direction of the methodological and cultural biases within the environmental health sciences. It is argued that scientific methods need to reflect better the realities of multicausality, mixtures, timing of dose, and system dynamics, which characterize the exposures and impacts of EDSs. This improved science could provide a more robust basis for the wider and wise use of the precautionary principle in the assessment and management of the threats posed by EDSs. The evaluation of such scientific evidence requires assessments that also account for multicausal reality. Two of the often used, and sometimes misused, Bradford Hill "criteria," consistency and temporality, are critically reviewed in light of multicausality, thereby illustrating the need to review all of the criteria in light of 40 years of progress in science and policymaking.

Diazinon-induced endocrine disruption in bluegill sunfish, Lepomis macrochirus

An attempt to reveal endocrine disruption in bluegill fish (Lepomis macrochirus) upon exposure to diazinon was made. Fish blood serum was collected and estradiol levels were measured following times of exposure to 60 microg/L of diazinon. Samples were drawn from the fish during each exposure period of 24, 48, 72 and 96 h and 1 and 2 weeks. The sample estradiol levels were compared to those of a control. Ovarian tissue was examined. As necrosis increased within the ovaries, estradiol blood serum levels altered from those of the control sample (101 pg/mL). Histopathology within the follicles became apparent as exposure time to diazinon increased. The changes in the ovarian follicles can be correlated to the estradiol levels in the blood. Mean estradiol level for the control group was 101.53 pg/mL. Estradiol levels from the trial groups varied from those of the control (24 h, undetectable; 48 h, 74.04 pg/mL; 72 h, 57.16 pg/mL; 96 h; 39.15 pg/mL; 1 week, 66.50 pg/mL; 2 weeks, undetectable). It seems that the initial shock experienced by the fish after 24 h of exposure resulted in an undetectable level of estradiol. The level of estradiol initially ascended, but it began to decline and after 1 week of exposure it ascended a little and became undetectable after 2 weeks. Nevertheless, throughout the exposure period the level of estradiol was lower than normal. Severe damage to the mature oocytes may be the reason for undetectable levels of estradiol after 2 weeks of exposure.

Comparison of three extraction methods for 17beta-estradiol in sand, bentonite, and organic-rich silt loam

Extraction is an important procedure for samples that contain soil because other compounds in soil may affect analysis of estrogens. This study was conducted to evaluate three different extraction methods for 17beta-estradiol in soil. Sand, bentonite, and organic-rich silt loam were spiked with 1 mg kg(-1) of 17beta-estradiol as a model compound of estrogens. 17beta-estradiol and its metabolites, estrone and estriol, were extracted using (i) a modified Bligh and Dyer extraction, (ii) a pressurized fluid extraction, and (iii) a diethyl ether extraction, and measured by liquid chromatography tandem mass spectrometry. There were significant differences in the extraction efficiency for 17beta-estradiol among the extraction methods and the soils: the efficiencies ranged from 10% to 97%. Overall, the diethyl ether extraction method had the largest efficiency of 17beta-estradiol with 45% and 57% for bentonite and silt loam, respectively. Transformation of 17beta-estradiol to estrone and estriol in the different extraction methods was less than 3.6% during the extraction procedures. This study underlined the importance of sample preparation for estrogen analysis in soil samples.

Effect of agricultural antibiotics on the persistence and transformation of 17beta-estradiol in a Sequatchie loam

A laboratory incubation study was conducted to investigate the effect of agricultural antibiotics (sulfamethazine, tylosin, and chlortetracycline) on the persistence and transformation of 17beta-estradiol in Sequatchie loam. We measured concentrations of 17beta-estradiol and its primary metabolite (estrone) in soils spiked with antibiotics and 17beta-estradiol. Dehydrogenase activity (DHA) was also measured as an indicator of the total microbial activity of the soils. The presence of antibiotics significantly decreased transformation of 17beta-estradiol to estrone. There was a positive correlation between the DHA and the concentrations of estrone in soil spiked with 17beta-estradiol only, implying that the reaction is mainly catalyzed by dehydrogenases. However, the positive correlation was weakened in soil spiked with 17beta-estradiol and antibiotics together. We recommend that any study evaluating the fate and transport of estrogenic hormones in soil should include the effect of agricultural antibiotics because antibiotics and estrogenic hormones are commonly excreted together in environmental samples.

Smooth muscle actin and vimentin as markers of testis development in the harbour porpoise (Phocoena phocoena)

Testicular development in the harbour porpoise Phocoena phocoena was examined using animals (n = 192) stranded or by-caught off the coast of England, Wales and Scotland. Classification of animals according to their stage of sexual development was undertaken using gonadal morphology and the distribution of cytoskeletal proteins. Smooth muscle actin (SMA) and vimentin proved particularly useful in this respect; SMA was prominent in the myoid peritubular cells of the adult testis, and two stages of peritubular cell SMA expression could be recognized ('absent' or 'incomplete'). The initial appearance of SMA in peritubular cells was associated with significant increases in body length and body weight (P < 0.001), and occurred during the second year of life. Vimentin, which was prominent in prespermatogonia and spermatogonia, sometimes showed a polarized cytoplasmic distribution. This correlated with a developmental stage at which the seminiferous tubule epithelium becomes populated by germ cells (mean age 1.8 years). Several antibodies were tested for their utility as Sertoli cell markers, but none was found to be specific or useful. Nevertheless, immunohistochemical localization of desmin, GATA-4, Ki67 and androgen receptor was possible despite the poor quality of tissue preservation. This study showed that immunohistochemical classification of these individuals provides a robust basis for the recognition of key physiological stages of sexual development in the male harbour porpoise. This may provide an alternative to the estimation of age, body weight and body length in future analyses aimed at detecting possible adverse effects of environmental pollutants on the reproductive potential of wild marine mammals.

Environmental factors influencing public health and medicine: policy implications

Environmental health threats are increasing throughout the United States, particularly in low-income populations and in communities of color. Environmental science researchers are investigating plausible associations between the environment and human health. As a result, the role and responsibility of the primary care physicians and other health care providers are changing. This paper highlights selected lines of evidence suggesting that clinicians should now consider interactions between humans and their environment as central to providing effective primary care. Subject areas include: exposure to environmental agents, reproductive toxicity, pulmonary disease, neurobehavioral toxicity, endocrine disruptors, mechanisms of environmental disease, and cultural competence. Concerns about these and other environmentally related issues influence the manner in which primary care is practiced now, and will be practiced in the future. Biomedical technology and community awareness demand that physicians pay more attention to advances in environmental medicine. Ironically, one of the least taught subjects in medical school is environmental medicine. To effectively respond to growing concerns about the role of the environment in human health, clinicians, researchers, educators, public policy officials, and the general public must join together to reduce the risk of environmental health threats and improve quality of life.

Persistence of estrogenic hormones in agricultural soils: I. 17Beta-estradiol and estrone

The persistence and pathways of dissipation of 17beta-estradiol and estrone in soil were established in laboratory microcosm incubations. [4-14C]-17beta-Estradiol dissipation and mineralization rates were determined over a range of temperatures and moistures, and this compound was rapidly removed in soil conditions typical of a temperate growing season. 17beta-Estradiol was oxidized to estrone in both autoclaved and nonsterile loam, silt loam, and sandy loam soils, suggesting an abiological transformation. In contrast, estrone was stable in autoclaved soil, suggesting that its removal was microbially mediated. Both [4-14C]-17beta-estradiol and [4-14C]-estrone formed non-extractable residues, and soil-bound residues were only slowly mineralized, suggesting that their bioavailability was low. Determination of total estrogenicity in soil extracts by means of a recombinant yeast assay indicated that there were no other estrogenic compounds produced during 17beta-estradiol dissipation, and that total estrogenicity was rapidly dissipated below the detection limit. We suggest that environmental studies evaluating the movement and persistence of estrogenic hormones from animal wastes should include estrone in their analyses.

Ecological risk assessment of endocrine disruptors

The European Centre for Ecotoxicology and Toxicology of Chemicals proposes a tiered approach for the ecological risk assessment of endocrine disruptors, integrating exposure and hazard (effects) characterization. Exposure assessment for endocrine disruptors should direct specific tests for wildlife species, placing hazard data into a risk assessment context. Supplementing the suite of mammalian screens now under Organization for Economic Cooperation and Development (OECD) validation, high priority should be given to developing a fish screening assay for detecting endocrine activity in oviparous species. Taking into account both exposure characterization and alerts from endocrine screening, higher tier tests are also a priority for defining adverse effects. We propose that in vivo mammalian and fish assays provide a comprehensive screening battery for diverse hormonal functions (including androgen, estrogen, and thyroid hormone), whereas Amphibia should be considered at higher tiers if there are exposure concerns. Higher tier endocrine-disruptor testing should include fish development and fish reproduction tests, whereas a full life-cycle test could be subsequently used to refine aquatic risk assessments when necessary. For avian risk assessment, the new OECD Japanese quail reproduction test guideline provides a valuable basis for developing a test to detecting endocrine-mediated reproductive effects; this species could be used, where necessary, for an avian life-cycle test. For aquatic and terrestrial invertebrates, data from existing developmental and reproductive tests remain of high value for ecological risk assessment. High priority should be given to research into comparative endocrine physiology of invertebrates to support data extrapolation to this diverse fauna.

WISP-2 as a novel estrogen-responsive gene in human breast cancer cells

In order to search for novel estrogen-responsive genes, we performed serial analysis of gene expression (SAGE) for estrogen-treated MCF-7 human breast cancer cells. SAGE analysis of 31,000 and 30,856 tags from non-treated and 17 beta-estradiol (E2)-treated cells for 24 h, respectively, facilitated the identification of 15,037 different transcripts. Comparison of these two SAGE libraries indicated a remarkable similarity in expression profiles. Among the identified transcripts, four genes were found to be markedly increased for E2-treated cells compared with control cells. Three of the transcripts were cathepsin D, pS2 and high mobility group 1 protein, which have been described as estrogen-inducible genes. The fourth gene was WISP-2 (Wnt-1 inducible signaling pathway protein 2) which has recently been reported as an up-regulated gene in the mammary epithelial cell line C57 MG transformed by the Wnt-1 oncogene. The increase in WISP-2 mRNA was completely prevented by co-incubation with a pure anti-estrogen ICI 182,780, but not by coincubation with cycloheximide, indicating that WISP-2 is directly regulated by the estrogen receptor. The WISP-2 gene was also induced by treating with environmental estrogens, such as bisphenol-A or nonylphenol. This study represents the first comprehensive gene expression analysis of estrogen-treated human breast cancer cells.

Validation of in vitro and in vivo methods for assessing endocrine disrupting chemicals

The concepts that require validation in terms of the subject of endocrine disruption are listed and discussed. The main mechanisms by which endocrine disruption can occur are identified, and the assays required for the detection of adverse endocrine disruption toxicities associated with these mechanisms are discussed. The process of assay validation is considered. The validation of structure-activity relationships, the need for reference chemicals, and the problems recently encountered when attempting to reproduce endocrine disruption data are also explored. The most important conclusions derived from this analysis are that given the immature state of research into endocrine disruption toxicity, testing strategies and the types of assay employed should be kept under constant review; inevitably researchers need to accept the fact that future revision of each assay will be required. Second, given the current absence of any chemical that is universally accepted to be devoid of endocrine toxicity, assay specificity will be difficult to assess, and that imposes the need for alternative objective criteria for assessing the value of individual assays.

Permanent effects of neonatal estrogen exposure in rats on reproductive hormone levels, Sertoli cell number, and the efficiency of spermatogenesis in adulthood

This study aimed to identify the mechanism(s) for impairment of spermatogenesis in adulthood in rats treated neonatally with estrogens. Rats were treated (days 2-12) with 10, 1, or 0.1 microg diethylstilbestrol (DES), 10 microg ethinyl estradiol (EE), 10 mg/kg of a GnRH antagonist (GnRHa), or vehicle and killed in adulthood. DES/EE caused dose-dependent reductions in testis weight, total germ cell volume per testis, and Sertoli cell volume per testis. Sertoli cell number at 18 days of age in DES-treated rats was reduced dose dependently. GnRHa treatment caused changes in these parameters similar to those in rats treated with 10 microg DES. Plasma FSH levels were elevated (P < 0.001) to similar levels in all treatment groups regardless of differences in Sertoli cell number and levels of inhibin B; the latter reflected Sertoli cell number, but levels were disproportionately reduced in animals treated with high doses of DES/EE. Neonatal estrogen treatment, but not GnRHa, caused dose-dependent reductions (40-80%) in plasma testosterone levels in adulthood, but did not alter LH levels. Preliminary evidence suggests that the decrease in testosterone levels in estrogen-treated rats is not due to reduced Leydig cell volume per testis. GnRHa-treated rats exhibited a significant increase in germ cell volume per Sertoli cell and a reduction in germ cell apoptosis, probably because of the raised FSH levels. Despite similar raised FSH levels, rats treated with DES (10 or 1 microg) or EE (10 microg) had reduced germ cell volume/Sertoli cell and increased germ cell apoptosis, especially when compared with GnRHa-treated animals. The latter changes were associated with an increase in lumen size per testis, indicative of impaired fluid resorption from the efferent ducts, resulting in fluid accumulation in the testis. Rats treated neonatally with 0.1 microg DES showed reduced germ cell apoptosis comparable to that in GnRHa-treated animals. The changes in apoptotic rate among treatment groups occurred across all stages of the spermatogenic cycle. It is concluded that 1) neonatal estrogen treatment results in dose-dependent alterations in Sertoli cell numbers, germ cell volume, efficiency of spermatogenesis, and germ cell apoptosis in adulthood; 2) the relatively poor spermatogenesis in estrogen-treated animals is most likely due to altered testis fluid dynamics and/or altered Sertoli cell function; 3) as indicated by FSH (LH) and testosterone levels, the hypothalamic-pituitary axis and Leydig cells are probably more sensitive than the Sertoli cells to reprogramming by estrogens neonatally; and 4) elevated FSH levels in adulthood may improve the efficiency of spermatogenesis.

Specific issues in health risk assessment of endocrine disrupting chemicals and international activities

Specific issues in health risk assessment of EDCs and correlated international activities thereof are discussed. Risk characterization is a synthesis of all information including hazard assessment, dose-response relationship, and exposure information to identify clearly the strengths and weaknesses of the database, the criteria applied to evaluation and validation of all aspects of methodology, and the conclusions reached from the review of scientific information. In the case of EDCs, new models need to be developed taking into account possible new kinds of information, e.g., effects of EDCs on gene activation in response to hormonal challenge or effects on receptor expression. Such models should also account for homeostatic adaptive responses and consider the possibility of having windows of exposure for given effects. Work to compile and harmonize the definitions and terms appropriate to endocrine disruption will be conducted within the joint IPCS/OECD project on harmonization of risk/hazard assessment terminology reviews. The ICPS is the process of preparing a "State of the Science" report, and is implementing a global inventory of ongoing research on ECDs.

Mechanism for biotransformation of nonylphenol polyethoxylates to Xenoestrogens in Pseudomonas putida

A strain of Pseudomonas putida isolated from activated sewage grew aerobically on the xenoestrogen precursor, nonylphenol polyethoxylate (NPEOx, where x is the number of ethoxylate units) as sole carbon source. Comparative growth yields on NPEOav6, NPEOav9, and NPEOav20 (mixtures with average ethoxylate numbers as indicated) were consistent with utilization of all but two ethoxylate units, and the final accumulating metabolite was identified by gas chromatography-mass spectroscopy as nonylphenol diethoxylate (NPEO2). There was no growth on nonylphenol or polyethylene glycols, and there was no evidence for production of carboxylic acid analogs of NPEOx. Biodegradation kinetics measured by high-pressure liquid chromatography (HPLC) for each component in NPEOx mixtures showed that biodegradation proceeded via successive exoscission of the ethoxylate chain and not by direct scission between the second and third ethoxylate residues. The NPEOx-degrading activity was inducible by substrate, and cell extracts of NPEOav9-induced cells were also active on the pure alcohol ethoxylate, dodecyl octaethoxylate (AEO8), producing sequentially, under either aerobic or anaerobic conditions, AEO7, AEO6, AEO5, etc., thus demonstrating that the pathway involved removal of single ethoxylate units. HPLC analysis of 2,4-dinitrophenylhydrazone derivatives revealed acetaldehyde (ethanal) as the sole aldehydic product from either NPEOav9 or AEO8 under either aerobic or anaerobic conditions. We propose a mechanism for biotransformation which involves an oxygen-independent hydroxyl shift from the terminal to the penultimate carbon of the terminal ethoxylate unit of NPEOx and dissociation of the resulting hemiacetal to release acetaldehyde and the next-lower homolog, NPEOx-1, which then undergoes further cycles of the same reaction until x = 2.

Polychlorinated biphenyls affect the activities of gluconeogenic and lipogenic enzymes in rat liver: is there an interference with regulatory hormone actions?

1. The effects of dietary polychlorinated biphenyls (PCBs) (30-2000 ppm) on activities of gluconeogenic (phosphoenolpyruvate carboxykinase-PEPCK, and fructose 1,6-bisphosphatase-FdPase) and lipogenic enzymes (fatty acid synthase-FAS, ATP citrate lyase-ACL, malic enzyme-ME, glucose 6-phosphate dehydrogenase-G6PDH, and 6-phosphogluconate dehydrogenase-PGDH) were studied in livers of the female Sprague-Dawley and Wistar rat. 2. PCB amounts accumulating in the liver reflected the extent of dietary exposure. The Wistar strain was more sensitive to PCBs than the Sprague-Dawley strain. Of the Clophentype PCBs those containing 60 and 64% chlorine displayed the most pronounced effects. 3. Activities of gluconeogenic enzymes (PEPCK and FdPase) were dose-dependently decreased by PCBs, PEPCK being considerably more sensitive. This decrease was also found under conditions where the activity of PEPCK was induced (administration of adrenalin, glucagon or cAMP, feeding high protein diets, starvation). 4. Activities of lipogenic enzymes were induced by PCBs. The increase was much greater with ME, G6PDH and PGDH (up to 10-fold) than with FAS and ACL (approximately 2-fold). PCB effects were dose-dependent, but transient. 5. In cultured hepatocytes basal activities of lipogenic enzymes were induced by PCBs in the absence of hormones. With saturating levels of insulin or triiodothyronine, enzyme activities were also induced, but addition of PCBs resulted in an additive effect. 6. These results suggest that in the female rat PCBs can mimic the actions of certain hormones by affecting either hormone levels, hormone receptor systems or regulatory systems.

Stepping backward to improve assessment of PCB congener toxicities

Polychlorinated biphenyls (PCBs) are ubiquitous global contaminants that have been intensively investigated for three decades. They are broad-acting toxicants occurring in complex mixtures and accurate risk assessment has proven to be elusive. Focusing on a limited set of end points and emphasizing a fixed set of congeners have led to more streamlined data sets that are meant to expedite hazard characterization and risk assessment for the most potent congeners--aryl hydrocarbon receptor (AhR) agonists. Unfortunately, this has made it impossible to confirm or deny significant contributions from the more prevalent components of the mixtures. PCBs may be only coincidentally present, rather than causal, in some diseases. Still, attempts to determine associations with incomplete residue data may lead to erroneous conclusions and make accurate risk assessment even more elusive. Responses not mediated through the AhR are presented and emphasize large data gaps. Dissimilar analytical reports emphasize that selection of analytes is not consistent. Collectively, these data confirm that AhR-focused objectives unintentionally created the impression that nonplanar PCBs have little if any potential for hazards to humans and wildlife. Near steady-state exposure of healthy adults are probably of minor consequence except for emerging correlations with non-Hodgkin's lymphoma; however, pulses of exposure to more labile mixtures may contribute to developmental effects without leaving a residue record. More broadly based criteria are suggested and harmonization of data collection and presentation are desirable. A more comprehensive list of PCB congeners is proposed that would provide more adequate data upon which to base associations with adverse outcomes.

Validating new toxicology tests for regulatory acceptance

Before a new or revised toxicology test is considered acceptable for safety evaluation of new substances, the test users and the industrial and regulatory decision makers must feel comfortable with it, and the decisions it supports. Comfort with, and the acceptance of, a new test comes after knowing that it has been validated for its proposed use. The validation process is designed to determine the operational characteristics of a test, that is, its reliability and relevance, in addition to its strengths and limitations. The reliability of a test is measured by its reproducibility. Its relevance is judged by its mechanistic relationship to the health effects of concern, and its ability to predict or identify those effects. The U.S. government has recently formed the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) to work with federal agencies and test developers to coordinate the evaluation and adoption of new test methods. The ICCVAM will provide guidance to agencies and other stakeholders on criteria and processes for development, validation, and acceptance of tests; coordinate technical reviews of proposed new tests of interagency interest; facilitate information sharing among agencies; and serve as an interagency resource and communications link with parties outside of the federal government on matters of test method validation. Copyright 1998 Academic Press.

Stepping backward to improve assessment of PCB congener toxicities

Polychlorinated biphenyls (PCBs) are ubiquitous global contaminants that have been intensively investigated for three decades. They are broad-acting toxicants occurring in complex mixtures and accurate risk assessment has proven to be elusive. Focusing on a limited set of end points and emphasizing a fixed set of congeners have led to more streamlined data sets that are meant to expedite hazard characterization and risk assessment for the most potent congeners--aryl hydrocarbon receptor (AhR) agonists. Unfortunately, this has made it impossible to confirm or deny significant contributions from the more prevalent components of the mixtures. PCBs may be only coincidentally present, rather than causal, in some diseases. Still, attempts to determine associations with incomplete residue data may lead to erroneous conclusions and make accurate risk assessment even more elusive. Responses not mediated through the AhR are presented and emphasize large data gaps. Dissimilar analytical reports emphasize that selection of analytes is not consistent. Collectively, these data confirm that AhR-focused objectives unintentionally created the impression that nonplanar PCBs have little if any potential for hazards to humans and wildlife. Near steady-state exposure of healthy adults are probably of minor consequence except for emerging correlations with non-Hodgkin's lymphoma; however, pulses of exposure to more labile mixtures may contribute to developmental effects without leaving a residue record. More broadly based criteria are suggested and harmonization of data collection and presentation are desirable. A more comprehensive list of PCB congeners is proposed that would provide more adequate data upon which to base associations with adverse outcomes.

Subchronic toxicity (90-day) study with para-nonylphenol in rats

As a component to the risk assessment process for para-nonylphenol (NP; CASRN 84852-15-3), a 90-day study was conducted in rats following U.S. EPA TSCA guidelines and Good Laboratory Practice regulations. NP was administered to four groups of rats at dietary concentrations of 0, 200, 650, or 2000 ppm which corresponded to approximate dietary intakes of 0, 15, 50, or 150 mg/kg/day, respectively. There were 25 rats/sex/group in the control and high-dose groups and 15 rats/sex/group in the low- and middose groups. Ten of the 25 rats/sex in the control and high-dose groups were designated as recovery animals and were maintained on control diets for 4 weeks after completion of the 90-day exposure period to assess the reversibility of any effects which might be observed. To evaluate for the possible weak estrogen-like activity that has been reported for NP in a number of screening assays, estrous cyclicity was monitored using vaginal cytology during Week 8 of the study, and sperm count, motility, and morphology were evaluated at termination. In-life effects from NP exposure were limited to small decreases in body weight and food consumption in the 2000-ppm dose group. Postmortem measurements at Week 14 indicated a dose-related kidney weight increase in males and a decrease in renal hyaline globules/droplets in males from the high-dose group. The kidney weights showed complete recovery following the 4-week postdosing recovery period. Due to the small magnitude of the changes (i.e., all weights were within or near laboratory historical control values) and the lack of correlating clinical or histopathological changes, the kidney weight alterations were not considered toxicologically significant. The biological significance of reduced hyaline in the kidneys of male rats from the high-dose group is uncertain. Renal tubular hyaline is associated with the rat-specific protein, alpha-2u-globulin, and, therefore, this finding was not considered toxicologically relevant to humans. No other effects attributable to NP were observed. No changes were observed for estrous cycling, sperm evaluations, or effects on endocrine organs. NP, therefore, did not manifest any estrogen-like activity as measured in these parameters at dietary concentrations as high as 2000 ppm, the maximum dose administered in this study. Based on the minor findings for the 2000-ppm dose group, the NOAEL (no-observed-adverse-effect level) for NP in this study is considered to be 650 ppm in the diet, corresponding to an approximate intake of 50 mg/kg/day.

Development of a Tier I screening battery for detecting endocrine-active compounds (EACs)

One of the components of our research program is development of a mode-of-action screening battery to detect several different types of endocrine-active compounds (EACs). Our working hypothesis is that a comprehensive short-term in vivo/in vitro battery can be developed to identify endocrine toxicants using a collection of endpoints. The goals of this battery are that it be quick, cost effective, and predictive. The purpose of this battery is to identify potential EACs and to assess their potency in order to prioritize compounds for further study. Two in vivo screens (intact male and ovariectomized female rats) are being evaluated for their ability to detect several different types of endocrine activity. To validate this screen, 15 compounds with known endocrine activities are being used to evaluate a collection of different endpoints for their variability, stability over time, predictiveness, and dose dependency. These positive controls were chosen because they can modulate development, reproduction, or cancer. The advantage of an in vivo screen is that it utilizes a metabolically and physiologically intact system. The male in vivo battery will be used to assess several different types of endocrine activity, primarily by using a comprehensive hormonal battery. The female in vivo battery will be used to identify compounds which are either estrogenic/antiestrogenic or can alter the prolactin pathway. The in vitro portion of the screening battery consists of a yeast transactivation system (YTS). The YTS is being evaluated for its ability to identify compounds which are agonists or antagonists to the estrogen, androgen, or progesterone receptors. The expression of mammalian receptors in yeast allows for assessment of steroid-dependent transcriptional activators. The value of this system is that it can be used as a routine screen for compounds that interact with steroid receptors. Alterations in ligand binding to these receptors can be correlated with alterations in development via masculinization of females and/or feminization of males, decreases in reproductive success, or modulation of cancer incidence from in vivo tests. The in vivo and in vitro screens are designed to be run in parallel with built-in redundancy in order to reduce the probability of false-negative/ positive responses.

Assessing the risks of adverse endocrine-mediated effects: where to from here?

This article is based on the closing lecture (by J. Ashby) of the meeting held in Research Triangle Park on January 13-14, 1997-"Assessing the Risks of Adverse Endocrine-Mediated Effects." Several summaries of unpublished data from Zeneca CTL are presented to illustrate concerns over the present absence of agreed criteria for the assessment of endocrine toxicity data. Reference is also made to several points raised by others during the course of the meeting. It is concluded that the substantial challenges currently faced can be met only by strict adherence to the basic principles of good scientific practice, preeminent among which are the needs to confirm data and to respond to them in a cool and dispassionate manner. The wealth of expertise and enthusiasm being devoted to the task in hand, by both governmental and industrial interests, suggests that practical means by which to address the topic of the symposium will be forthcoming in the near future. However, moves to accelerate progress unduly-"to conduct science under the gun"-are already evident. Therefore, if external influences demand that short-cuts must be taken toward achievement of the goals set out in the Wingspread Statement (Colborn and Clement, 1992), such compromises should be clearly identified in order not to confuse the underlying progress that is already evident in this new branch of toxicology.

The rodent uterotrophic assay: critical protocol features, studies with nonyl phenols, and comparison with a yeast estrogenicity assay

The major protocol features of the immature rat uterotrophic assay have been evaluated using a range of reference chemicals. The protocol variables considered include the selection of the test species and route of chemical administration, the age of the test animals, the maintenance diet used, and the specificity of the assay for estrogens. It is concluded that three daily oral administrations of test chemicals to 21- to 22-day-old rats, followed by determination of absolute uterus weights on the fourth day, provide a sensitive and toxicologically relevant in vivo estrogenicity assay. Rats are favored over mice for reasons of toxicological practice, but the choice of test species is probably not a critical protocol variable, as evidenced by the similar sensitivity of rats and mice to the uterotrophic activity of methoxychlor. Vaginal opening is shown to be a useful, but nondefinitive, adjunct to the uterotrophic assay. The ability of test chemicals to reduce or abolish the uterotrophic response of estradiol is suggested to provide a useful extension of the uterotrophic assay for the purpose of detecting antiestrogens. The results of a series of studies on the environmental estrogen nonyl phenol (NP), and its linear isomer n-nonyl phenol, confirm that branching of the aliphatic side chain is important for activity. 17beta-Desoxyestradiol is shown to be of similar activity to estradiol in the uterotrophic assay and is suggested to represent the "parent" estrogen of NP. Benzoylation of NP and 17-desoxyestradiol did not affect their uterotrophic activity, in contrast to the enhancing effect of benzoylation on estradiol. Selected chemicals shown to be active in the immature rat uterotrophic assay were also evaluated in an in vitro yeast human estrogen receptor transactivation assay. Most of the chemicals gave similar qualitative responses to those seen in the uterotrophic assay, and the detection of the estrogen methoxychlor by the yeast assay evidenced a degree of intrinsic metabolic competence. However, the assay had a reduced ability (compared to rodents) to hydrolyze the benzoate ester of estradiol, and the estrogenic benzoate derivative of NP was not active in the yeast assay. These last results indicate that current metabolic deficiencies of in vitro estrogenicity assays will limit the value of negative data for the immediate future. The results described illustrate the intrinsic complexity of evaluating chemicals for estrogenic activities and confirm the need for rigorous attention to experimental design and criteria for assessing estrogenic activity.