Relevance of drinking water as a source of human exposure to bisphenol A.

A comprehensive search of studies describing bisphenol A (BPA) concentrations in drinking water and source waters (i.e., surface water and groundwater) was conducted to evaluate the relevance of drinking water as a source of human exposure and risk. Data from 65 papers were evaluated from North America (31), Europe (17), and Asia (17). The fraction of drinking water measurements reported as less than the detection limit is high; 95%, 48%, and 41%, for North America, Europe, and Asia, respectively. The maximum quantified (in excess of the detection limit) BPA concentrations from North America, Europe, and Asia are 0.099 µg/l, 0.014 µg/l, and 0.317 µg/l. The highest quantified median and 95th percentile concentrations of BPA in Asian drinking water are 0.026 µg/l and 0.19 µg/l, while high detection limits restricted the determination of representative median and 95th percentile concentrations in North America and Europe. BPA in drinking water represents a minor component of overall human exposure, and compared with the lowest available oral toxicity benchmark of 16 µg/kg-bw/day (includes an uncertainty factor of 300) gives margins of safety >1100. Human biomonitoring data indicate that ingestion of drinking water represents <2.8% of the total intake of BPA.

Early life-stage and multigeneration toxicity study with bisphenol A and fathead minnows (Pimephales promelas).

Regulatory guidelines for long term testing to assess the toxicity of xenobiotic compounds such as bisphenol A (BPA) with fish have focused on survival, growth, and development in early life stages. Early life stages are critical windows of exposure, but do not address later phases in the life cycle, such as reproduction, that are equally important for the continued survival of the organisms. Residual amounts of BPA are released to surface water. BPA has, therefore, been the subject of considerable toxicity testing with fish and other aquatic organisms. A long term multigeneration test with fish has been conducted to better interpret the environmental relevance of detectable levels of BPA. Fathead minnow (Pimephales promelas) were exposed for 444 days over the course of three generations that included F0 reproducing adults, F1 eggs grown to be reproducing adults, and F2 eggs. Endpoints included survival, growth, reproduction, and vitellogenin concentrations. Concentrations tested ranged from 1 to 1,280 µg/L. No observed effect concentrations (NOEC) of 640 µg/L and higher for growth parameters show few differences between age or generation. Reproductive NOEC in F0 and F1 breeding pairs were 640 and 160 µg/L, respectively. The lowest NOEC related to survival, growth and development or reproduction was 16 µg/L for F2 hatching success. This long term study covered both early life and adult reproduction stages that allowed examination of all critical windows of exposure. Overall, NOEC ranging from 16 to 1,280 µg/L were found, which are well above median and upper 95th percentile concentrations of BPA in fresh waters in North America and Europe (0.081 and 0.47 µg/L and 0.01 and 0.035 µg/L, respectively). The likelihood is low that measured concentrations of BPA in surface water would affect fish, even if exposed over more than one generation.

Occurrence of nonylphenol ethoxylates and their metabolites in municipal wastewater treatment plants and receiving waters.

Nonylphenol ethoxylates (NPEs) are surfactants often used in applications that result in their disposal and treatment in wastewater treatment plants (WWTPs). In this study, three municipal activated sludge WWTPs, receiving primarily residential wastewater, were monitored, with their receiving waters, to determine the occurrence of NPEs and their biodegradation metabolites, including nonylphenol (NP), low-mole and higher-mole nonylphenol ethoxylates (NPE1, NPE2-8, and NPE > or =9), and nonylphenol ether carboxylates (NPECs). The facilities were moderately sized and operating normally when influent and effluent samples were taken. Treatment efficiencies, taking into account concentrations of the parent ethoxylate and metabolites, ranged from 97.2 to 99.8%. Samples of receiving stream water, sediment, and pore water were collected upstream, downstream at the end of the mixing zones, and farther downstream from the WWTP discharges, to determine the occurrence of NPE and their metabolites and to assess the potential effect on the receiving stream ecosystems. Concentrations of nonylphenol or total nonylphenol equivalents measured upstream (<0.02 to 1.29 microg/L), at the end of the mixing zone (0.2 to 3.15 microg/L), and farther downstream (<0.02 to 1.84 microg/L) were compared with the recently established national ambient water quality chronic criteria of 6.6 mcirog/L. On the basis of this analysis, the likelihood of adverse effects on aquatic species within the three receiving streams is low.

Simultaneous quantitation of testosterone, estradiol, ethinyl estradiol, and 11-ketotestosterone in fathead minnow fish plasma by liquid chromatography/positive atmospheric pressure photoionization tandem mass spectrometry.

In the present work, for the first time, a rapid and sensitive liquid chromatography/positive atmospheric pressure photoionization tandem mass spectrometry (LC/APPI-MS/MS) method has been developed and validated for the simultaneous quantitation of testosterone, estradiol, ethinyl estradiol, and 11-ketotestosterone in fathead minnow fish plasma using no more than 10 microL of plasma. Compounds present in plasma were directly derivatized with dansyl chloride and 25 microL of the derivatized mixture was injected into the LC/APPI-MS/MS system. The gradient chromatographic elution was achieved on an Agilent Zorbax SB-C18 analytical column (2.1 mm x 50 mm, 1.8 microm particle size) with mobile phases consisting of acetonitrile, water and acetic acid. The flow rate was 0.5 to 0.7 mL/min and the total run time was 11.5 min. The lower limits of quantitation for testosterone, estradiol, ethinyl estradiol, and 11-ketotestosterone and were 1, 1, 1, and 2.5 ng/mL, respectively. Intra-batch precision was less than 19.4% and inter-batch precision was less than 11.7% for all four analytes. Accuracy was within 83.5-115.4% of nominal concentrations. This method is used for quantitation of sex steroid levels in fathead minnow tested in endocrine disruptor screening experiments.

Exposure analysis of bisphenol A in surface water systems in North America and Europe.

This study was conducted to develop a statistical understanding of exposures to bisphenol A (BPA) in aquatic environments in North America and Europe. Concentrations of BPA have been reported by 89 investigations published between 1997 and 2007. On the basis of an analysis of weighted observations (n = 1068 and 848 for North America and Europe, respectively), BPA was reported at concentrations above the detection limit in 20-51% of freshwater samples. Median BPA concentrations for fresh surface waters for North America and Europe were 0.081 and 0.01 microg/L, respectively, while 95th percentiles were 0.47 and 0.35 microg/L, respectively. In contrast to fresh surface waters, only limited data are available for sediments and less for marine ecosystems. For freshwater sediments in North America (n = 71), the median and 90th percentile concentration (the 95th percentile was not calculable) were 0.6 and 3.4 ng/ g-dw, respectively, while the median and 95th percentile concentration in Europe (n = 249) were 16 and 256 ng/g-dw, respectively. To assess the potential ecological significance, we compared exposure concentrations with available regulatory criteria. The results suggest the frequency of locations in which concentrations are likely to cause adverse effects on aquatic ecosystems is low, with the exception of sediments collected from some highly urbanized and industrial locations.

Introduction to special series: science-based guidance and framework for the evaluation and identification of PBTs and POPs.

There is a growing sense of urgency among scientists and environmental policy-makers concerning the need for improving the scientific foundation supporting international regulations for identifying and evaluating persistent, bioaccumulative, and toxic (PBT) substances and persistent organic pollutants (POPs) in the environment. The current national and international regulations define PBTs and POPs in terms of fairly strict criteria that are based on the state of the science in the late 1970s and early 1980s. Since then, an evolution in the state of the science has produced new insights into PBT substances and an array of new methods to identify PBT chemicals. The development of regulatory criteria has not kept up with the rapid development in environmental chemistry and toxicology, and as a result, scientists often find themselves in the situation where guidance on PBT and POPs criteria is limited and, in some respects, out of date. With this background, a Society of Environmental Toxicology and Chemistry (SETAC) Pellston Workshop brought together experts from academia, government, and industry to reach consensus on the significance of advancements in our understanding of the behavior and potential impact of POPs and PBTs in the environment, the current understanding of the state of the science, as well as recommendations for policy-makers to improve and coordinate national and international regulations on this issue. The workshop builds on the outcome of a previous Pellston workshop, held in 1998, which focused on the evaluation of persistence and long-range transport of organic chemicals in the environment, and is linked to other recent Pellston workshops, among them the Tissue Residue Approach for Toxicity Assessment workshop held in 2007. The results of this workshop are conveyed in a series of 9 articles, published in this issue of Integrated Environmental Assessment and Management, and describe the coordination of science, regulation, and management needed to more effectively achieve a common goal of managing chemicals on our planet.

Acute and chronic toxicity testing of bisphenol A with aquatic invertebrates and plants.

Bisphenol A (BPA, 4,4'-isopropylidine diphenol) is a commercially important chemical used primarily as an intermediate in the production of polycarbonate plastic and epoxy resins. Extensive effect data are currently available, including long-term studies with BPA on fish, amphibians, crustaceans, and mollusks. The aim of this study was to perform additional tests with a number of aquatic invertebrates and an aquatic plant. These studies include acute tests with the midge (Chironomus tentans) and the snail (Marisa cornuarietis), and chronic studies with rotifers (Brachionus calyciflorus), amphipods (Hyalella azteca), and plants (Lemna gibba). The effect data on different aquatic invertebrate and plant species presented in this paper correspond well with the effect and no-effect concentrations (NOECs) available from invertebrate studies in the published literature and are within the range found for other aquatic species tested with BPA.

Plasma sampling and freezing procedures influence vitellogenin measurements by enzyme-linked immunoassay in the fathead minnow (Pimephales promelas).

The present study compared three different methods for measuring plasma vitellogenin (VTG) in fathead minnow (FHM; Pimephales promelas): A procedure using liquid chromatography with electrospray ionization combined with tandem mass spectrometry (LC/ESI-MS/MS), and two commercial enzyme-linked immunoassay (ELISA) kits using either anti-carp or anti-FHM antibodies. The influence on plasma VTG measurements of using the protease-inhibitor aprotinin during blood sampling and of submitting the plasma samples to a freeze-thaw cycle before analysis also was evaluated. The addition of aprotinin to the blood during sampling significantly reduced the plasma VTG concentrations measured by ELISA, whereas the VTG values measured after plasma samples were submitted to a freeze-thaw cycle were significantly higher than those measured before freezing. This inflating effect of freezing on VTG measurements made by ELISA could be prevented if plasma samples were frozen diluted in citrate buffer containing 16 mg/ml of polyethylene glycol (PEG). In contrast, measurements of VTG made by LC/ESI-MS/MS were unaffected by freezing and, conceptually, are independent from enzymatic degradation. Although the use of aprotinin and PEG effectively reduced the influence of enzymatic and physical degradation caused by freezing and thawing on VTG measurements made by ELISA, it did not improve agreement between the three analytical techniques evaluated. More information is needed regarding the molecular structure and the existence of possible multiple forms of VTG before this protein can be measured adequately in FHM.

Potentiation of the vitellogenic response to 17alpha-ethinylestradiol by cortisol in the fathead minnow Pimephales promelas.

The effects of elevated plasma cortisol levels on vitellogenin (VTG) induction were examined in the fathead minnow (Pimephales promelas) in an attempt to evaluate the potential influence of stress on this commonly used biomarker of estrogenicity. Two separate experiments were conducted in which fish plasma cortisol was elevated to various levels for 14 d by noninvasive additions of cortisol to the aquaria water. Fathead minnows were exposed to either cortisol alone, 17alpha-ethinylestradiol (EE2) alone, or a combination of the two hormones, and plasma levels of VTG as well as liver expression of VTG mRNA were measured. Both experiments gave similar results, with an exposure to 4 ng/L of EE2 resulting in significantly greater levels of plasma VTG in the presence of, compared to that in absence of, cortisol, whereas exposure to cortisol alone at concentrations between 144 and 800 microg/L had no effect on plasma VTG levels. This potentiation of the EE2-induced vitellogenesis by cortisol was dose-dependent, with plasma VTG reaching 125, 167, and 295% of the values obtained with EE2 alone when 144, 360, and 800 microg/L of cortisol, respectively, were added to the water. Liver mRNA results were consistent with plasma VTG, although they generally were more variable. The present study demonstrates that cortisol does not independently induce vitellogenesis but can potentiate estrogen-induced VTG synthesis in fathead minnow. The implications of these findings for the use of VTG as a biomarker of estrogenicity are discussed.

Natural attenuation of chlorinated solvents at Area 6, Dover Air Force Base: characterization of microbial community structure.

A polyphasic approach based on cultivation and direct recovery of 16S rRNA gene sequences was utilized for microbial characterization of an aquifer contaminated with chlorinated ethenes. This work was conducted in order to support the evaluation of natural attenuation of chlorinated ethenes in groundwater at Area 6 at Dover Air Force Base (Dover, DE). Results from these studies demonstrated the aquifer contained relatively low biomass (e.g. direct microscopic counts of < 10(7) bacteria/g of sediment) comprised of a physiologically diverse group of microorganisms including iron reducers, acetogens, sulfate reducers, denitrifiers, aerobic and anaerobic heterotrophs. Laboratory microcosms prepared with authentic sediment and groundwater provided direct microbiological evidence that the mineralization of vinyl chloride and cis-dichloroethene as well as each step in the complete reductive dechlorination of tetracloroethene to ethene can occur in the Area 6 aquifer. Enrichment cultures capable of the oxidative degradation of cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) were obtained from groundwater across the aquifer demonstrating the possible importance of direct, non-cometabolic oxidation of cis-DCE and VC in natural attenuation. Culture-independent analyses based upon recovery of 16S rRNA gene sequences revealed the presence of anaerobic organisms distributed primarily between two major bacterial divisions: the delta subdivision of the Proteobacteria and low-G + C gram positive. Recovery of sequences affiliated with phylogenetic groups containing known anaerobic-halorespiring organisms such as Desulfitobacterium, Dehalobacter, and certain groups of iron reducers provided qualitative support for a role of reductive dechlorination processes in the aquifer. This molecular data is suggestive of a functional linkage between the microbiology of the site and the apparent natural attenuation process. The presence and distribution of microorganisms were found to be consistent with a microbially driven attenuation of chlorinated ethenes within the aquifer and in accord with a conceptual model of aquifer geochemistry which suggest that both reductive and oxidative mechanisms are involved in heterogeneous, spatially distributed processes across the aquifer.

Natural attenuation of chlorinated solvents at Area 6, Dover Air Force Base: groundwater biogeochemistry.

Monitored natural attenuation (MNA) has recently emerged as a viable groundwater remediation technology in the United States. Area 6 at Dover Air Force Base (Dover, DE) was chosen as a test site to examine the potential for MNA of tetrachloroethene (PCE) and trichloroethene (TCE) in groundwater and aquifer sediments. A "lines of evidence" approach was used to document the occurrence of natural attenuation. Chlorinated hydrocarbon and biogeochemical data were used to develop a site-specific conceptual model where both anaerobic and aerobic biological processes are responsible for the destruction of PCE, TCE, and daughter metabolites. An examination of groundwater biogeochemical data showed a region of depleted dissolved oxygen with elevated dissolved methane and hydrogen concentrations. Reductive dechlorination likely dominated in the anaerobic portion of the aquifer where PCE and TCE levels were observed to decrease with a simultaneous increase in cis-1,2-dichloroethene (cis-DCE), vinyl chloride (VC), ethene, and dissolved chloride. Near the anaerobic/ aerobic interface, concentrations of cis-DCE and VC decreased to below detection limits, presumably due to aerobic biotransformation processes. Therefore, the contaminant and daughter product plumes present at the site appear to have been naturally atteuated by a combination of active anaerobic and aerobic biotransformation processes.