Decay of endocrine-disrupting chemicals in aerobic and anoxic groundwater

Biodegradation and adsorption of selected endocrine-disrupting chemicals (EDCs), namely oestrogens (E2 and EE2) and phenolic compounds (BPA, 4-t-OP and 4-n-NP), in aquifer materials was investigated in the laboratory in order to understand the behaviour and fate of these chemicals associated with reclaimed water during managed aquifer recharge. Biodegradation experiments were conducted in microcosms with aquifer material and groundwater mixture, or with aquifer material and effluent mixture in the presence of glucose under both aerobic and anoxic conditions. All five selected compounds were degraded by microorganisms in both types of aquifer material-water mixtures under aerobic and anoxic conditions. Under aerobic conditions, EE2 was found to degrade faster in the aquifer material supplemented with effluent with a half-life of 15 days compared with that of 26 days in the aquifer material and groundwater microcosm. No significant difference between the two aquifer material-water mixtures was found for the other four compounds with half-lives ranging between 0.2 and 4.1 days. Under anoxic conditions, however, little biodegradation was observed for the selected EDCs except for E2, which degraded in the aquifer material in the presence of both water types.     

北京污水厂进、出水中内分泌干扰物的分布

以三种酚类化合物(4-OP、4-n-NP、BPA)、五种雌激素(E1、E2、E3、17α-E2、EE2)为目标物,对其在北京市三个污水处理厂进、出水中的浓度及工艺流程中的分布、迁移进行了研究.结果表明,污水处理厂出水中浓度最高的物质是BPA、EE2,分别为(56～140)、(78～115)ng/L.BPA和天然雌激素(17α-E2除外)主要被生物降解去除,而对EE2的去除主要发生在初级处理过程,去除率约为63%.两种烷基酚在污水处理厂并不能被有效去除.与欧美国家、日本等相比,北京市污水处理厂进、出水中的内分泌干扰物浓度偏高,尤其是出水中的雌激素浓度较高,具有一定的环境风险.     

Fate and removal of selected endocrine‐disrupting compounds in sewage using activated sludge treatment

The variation and fate of four endocrine‐disrupting compounds (EDCs) composed of 4‐n‐nonylphenol (4‐n‐NP), bisphenol A (BPA), 17β‐estradiol (E2) and 17α‐ethinylestradiol (EE2) were investigated along treatment units in a sewage treatment plant (STP), China with anaerobic, anoxic and aerobic activated sludge processes. The mean concentrations were 64.8 ng/L (E2), 115.3 ng/L (4‐n‐NP), 171.5 ng/L (EE2), and 920.7 ng/L (BPA) in the influents, and 22.8 ng/L (E2), 50.9 ng/L (4‐n‐NP), 49.9 ng/L (EE2), and 84.3 ng/L (BPA) in the effluents. The biological treatment was more effective in removing NP, BPA and E2 from the aqueous phase than the primary treatment, while the latter could effectively remove EE2. Their possible removal mechanisms during the biological treatment with activated sludge were further explored through spiked batch experiments under three oxygen‐supplying conditions (anaerobic, anoxic and aerobic). The batch experiments showed that 4‐n‐NP, E2 and BPA were removed from the aqueous phase through biodegradation. The combination of sludge sorption and biodegradation accounted for the removal of EE2. Anoxic activated sludge showed the most rapid degradation of 4‐n‐NP, while E2 could be removed most effectively by aerobic activated sludge, and sludge sorption had a remarkable effect on its removal within the initial 15 min of the experiments under three oxygen‐supplying conditions.     

The aqueous degradation of bisphenol A and steroid estrogens by ferrate

The aqueous reactivity of five prominent endocrine disrupting chemicals (EDCs) with potassium ferrate has been studied. The degradation kinetics and reaction pathways for bisphenol A (BPA) have been considered in detail, and the reaction rate constants for 17alpha-ethynylestradiol (EE2), estrone (E1), beta-estradiol (E2), and estriol (E3) have been determined, from tests carried out in the pH range of 8-12 and at different reactant molar ratios. The rate constants were determined by a kinetic model incorporating the various species equilibria for the EDC compounds and ferrate, using observations of the temporal reduction in EDC and ferrate concentrations. In agreement with other studies, the oxidation of the EDCs was found to be greater for mono-protonated ferrate, HFeO(4)(-), than for non-protonated ferrate, FeO(4)(2-). Among the five EDCs, all of which have phenol moieties, the ferrate oxidation of the four steroid estrogens (each incorporating the cyclopentanoperhydrophenanthrene ring) had higher reaction rates than BPA. The by-products of BPA degradation by ferrate were analyzed by liquid chromatography/mass spectrometry-mass spectrometry (LC/MS-MS) and gas chromatography/mass spectrometry-mass spectrometry (GC/MS-MS) and nine specific compounds were identified, including p-isopropylphenol, 4-isopropanolphenol, p-isopropenylphenol, and some dicarboxylic acids, etc. It is concluded that ferrate oxidation could be an effective treatment method for the purification of waters containing these particular EDCs.     

Biodegradation of endocrine disrupting compounds in harbour seawater and sediments

The biodegradation of three endocrine disrupting compounds was examined using samples of seawater and sediment collected from Halifax Harbour, Nova Scotia, Canada, an urbanized harbour impacted by over two centuries of anthropogenic contamination. Flask experiments, where the samples were mixed to form a slurry were used to monitor the aerobic biodegradation of the synthetic plasticizer bisphenol A (BPA), the natural hormone 17β-estradiol (E2), and the pharmaceutical and contraceptive ethinylestradiol (EE2). Degradation rates followed the order E2 > EE2 > BPA with half-lives of up to 1, 5 and 14 days in seawater, respectively. A rapid initial degradation rate for all three compounds with no apparent lag phase indicated the ability of the microbial community to readily catabolise the chemicals. The formation of unidentified non-persistent intermediate metabolites was observed during the E2 degradation experiments. These degradation rates are more rapid and complete than reported in previous studies, indicating the adaptation of native microbial communities to these contaminants.     

Occurrence and fate of endocrine disrupters in Greek sewage treatment plants

The occurrence of five endocrine-disrupting compounds (EDCs), namely 4-n-nonylphenol (4-n-NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), triclosan (TCS) and bisphenol A (BPA), was assessed in the raw, treated wastewater and sewage sludge of eight sewage treatment plants (STPs) in Greece. The analytes were extracted by solid-phase extraction (dissolved phase) or sonication (solid phase). Qualitative and quantitative analyses were performed by gas chromatography-mass spectrometry (GC-MS). The average concentrations in the raw and treated wastewater ranged from 0.23 (4-n-NP) to 5.76microgL(-1) (NP1EO) and from 0.15 (BPA) to 1.84microgL(-1) (NP2EO), respectively. A great part of the detected EDCs was sorbed on suspended solids. In sewage sludge, the average concentrations ranged between 0.17 (4-n-NP) and 12.3microgg(-1)dw (NP1EO). Analysis of daily mass flows in STP of Athens showed that, with the exception of 4-n-NP, all other EDCs were significantly removed (>85%) during wastewater treatment. Regarding the fate of these compounds, a significant part ranging from 45% (for TCS) to more than 70% (for NP1EO, NP2EO and BPA) was transformed by abiotic or biotic mechanisms, while the rest was accumulated in sewage sludge or disposed to the environment via the effluents. Calculation of risk quotients showed the existence of possible threat due to the presence of certain EDCs in treated wastewater and sludge.     

Significance of biomass support particles in laboratory studies on microbial degradation of organic chemicals in aquifers

In degradation studies of xenobiotics in groundwater environments from where only water samples can be obtained (e.g. established deep groundwater wells, inhomogeneous formations as boulder aquifers, or consolidated aquifers), solids might be added as biomass support materials. The importance of biomass support materials as quartz sand, rock wool and crushed tiles on the degradation of 8 aromatic hydrocarbons (benzene, toluene, o-xylene, 1,2-dichlorobenzene (1,2-DCB), 1,4-dichlorobenzene (1,4-DCB), naphthalene, biphenyl and nitrobenzene) was investigated in experiments with groundwater collected from two aerobic aquifers (Vejen and Grindsted, Denmark). Experiments with only groundwater as well as groundwater suspensions with aquifer sediment were run as references. It was impossible to adjust pH to the desired level in the experiments with crushed tiles, where also substantial sorption of the test compounds and server clogging of filters used in sampling occurred, and this material was therefore useless as biomass support material. Presence of rock wool supported growth of bacteria and increased the degradation (in terms of rates and number of compounds degraded) compared with experiments with groundwater only. However, the degradation was less and the degradation patterns varied more than in the presence of aquifer sediment. Quartz sand gave the most promising results with respect to growth of bacteria, and the degradation patterns of most of the compounds were similar to those obtained in experiments including aquifer sediments, although the latter showed the most substantial degradation. This study suggests that in case aquifer sediment is not available, quartz sand should be added as biomass support material in studies on degradation of organic xenobiotics in groundwater environments.     

Aerobic and anaerobic biodegradation of phenol derivatives in various paddy soils

Microbiological degradation of phenol and some of its alkyl-derivatives (p-cresol, 4-n-propylphenol, 4-i-propylphenol, 4-n-butylphenol, 4-sec-butylphenol, 4-t-butylphenol, and 4-t-octylphenol) was examined under both aerobic and anaerobic conditions in seven Japanese paddy soils. Aerobic biodegradation of phenol derivatives was detected in all the paddy soils examined. The half-lives ranged from 2 to 19 days. The aerobic degradation rate of 4-t-octylphenol was correlated inversely with the total carbon contents of paddy soils, and there were significant inverse correlations between the aerobic degradation rate and the size of alkyl groups of alkylphenols. Anaerobic biodegradation of phenol and p-cresol was detected in three soils with the half-lives ranging from 24 to 260 days for phenol and from 11 to 740 days for p-cresol, respectively. The three soils were characterized by low contents of nitrate and iron oxides. Other soil properties did not show any significant correlations with the anaerobic degradation rates. In one soil, we found for the first time anaerobic biodegradation of 4-n-propylphenol. However, the other five compounds (4-i-propylphenol, 4-n-butylphenol, 4-sec-butylphenol, 4-t-butylphenol and 4-t-octylphenol) were not degraded over 224 days of incubation. These results suggest that phenol and all the alkylphenols were degraded within several days when paddy soil is not flooded and so under aerobic conditions. Under flooded and anaerobic conditions, 4-n-propylphenol would be degraded as well as phenol and p-cresol while alkylphenols with long and branched alkyl chains were hardly degraded at all.     

Selected personal care products and endocrine disruptors in biosolids: an Australia-wide survey

Personal care products (PCPs) and endocrine disrupting compounds (EDCs) are groups of organic contaminants that have been detected in biosolids around the world. There is a shortage of data on these types on compounds in Australian biosolids, making it difficult to gain an understanding of their potential risks in the environment following land application. In this study, 14 biosolids samples were collected from 13 Australian wastewater treatment plants (WWTPs) to determine concentrations of eight compounds that are PCPs and/or EDCs: 4-t-octylphenol (4tOP), 4-nonylphenol (4NP), triclosan (TCS), bisphenol A (BPA), estrone (E1), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2). Concentration data were evaluated to determine if there were any differences between samples that had undergone anaerobic or aerobic treatment. The concentration data were also compared to other Australian and international data. Only 4tOP, 4NP, TCS, and BPA were detected in all samples and E1 was detected in four of the 14 samples. Their concentrations ranged from 0.05 to 3.08 mg/kg, 0.35 to 513 mg/kg, < 0.01 to 11.2 mg/kg, < 0.01 to 1.47 mg/kg and < 45 to 370 μg/kg, respectively. The samples that were obtained from WWTPs that used predominantly anaerobic treatment showed significantly higher concentrations of the compounds than those obtained from WWTPs that used aerobic treatment. Overall, 4NP, TCS and BPA concentrations in Australian biosolids were lower than global averages (by 42%, 12% and 62%, respectively) and 4tOP concentrations were higher (by 25%), however, of these differences only that for BPA was statistically significant. The European Union limit value for NP in biosolids is 50 mg/kg, which 4 of the 14 samples in this study exceeded.     

Fate simulation and risk assessment of endocrine disrupting chemicals in a reservoir receiving recycled wastewater

A fugacity based model was applied to simulate the distribution of three endocrine disrupting chemicals (EDCs), namely estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) in a reservoir receiving recycled wastewater in Australia. At typical conditions, the majority of estrogens were removed by degradation in the water compartment. A sensitivity analysis found that the simulated concentrations of E1, E2 and EE2 were equally sensitive to the parameters of temperature (T), reservoir water volume (V) and equivalent biomass concentration (EBC), but E1 was more sensitive to estrogen concentration in the recycled water (C_e) and recycling rate (F_r). In contrast, all three estrogens were not sensitive to reservoir water releasing rate (F_d). Furthermore, a probabilistic health risk assessment showed that the simulated concentrations were below fish exposure threshold value (ETV) and human public health standard (PHS). Human equivalent dose of EDCs from fish consumption was about 10 times higher than that from drinking water consumption. The highest risk quotient among the three estrogens was found for EE2 with less than 9.5 × 10⁻², implying negligible health risks.     

Degradation of the (R)- and (S)-enantiomers of the herbicides MCPP and dichlorprop in a continuous field-injection experiment

An aerobic field-injection experiment was performed to study the degradation and migration of different herbicides at trace levels in an aerobic aquifer at Vejen, Denmark. Mecoprop (MCPP) and dichlorprop monitored in a dense network of multilevel samplers were both degraded within a distance of 1 m after a period of 120 days. The study showed that no preferential degradation of the (R)- and (S)-enantiomers of MCPP and of dichlorprop took place as the enantiomeric forms of the phenoxy acids were degraded simultaneously in the aquifer.     

Removal of bisphenol A and 17α-ethinyl estradiol from landfill leachate using single-walled carbon nanotubes

In this study, the adsorption of bisphenol A (BPA) and 17α-ethinyl estradiol (EE2) from landfill leachate onto single-walled carbon nanotubes (SWCNTs) was investigated. Different leachate solutions were prepared by altering the pH, ionic strength, and dissolved organic carbon (DOC) in the solutions to mimic the varying water conditions that occur in leachate during the various stages of waste decomposition. The youngest and oldest leachate solutions contained varying DOC and background chemistry and were represented by leachate Type A (pH = 5.0; DOC = 2500 mg/L; conductivity = 12,500 μS/cm; [Ca²⁺] = 1200 mg/L; [Mg²⁺] = 470 mg/L) and Type E (pH = 7.5; DOC = 250 mg/L; conductivity = 3250 μS/cm; [Ca²⁺] = 60 mg/L; [Mg²⁺] = 180 mg/L). These solutions were subsequently combined in different ratios to produce intermediate solutions, labeled B-D, to replicate time-dependent changes in leachate composition. Overall, a larger fraction of EE2 was removed as compared to BPA, consistent with its higher log K_OW value. The total removal of BPA and EE2 decreased in older leachate solutions, with the adsorptive capacity of SWCNTs decreasing in the order of leachate Type A > Type B > Type C > Type D > Type E. An increase in the pH from 3.5 to 11 decreased the adsorption of BPA by 22% in young leachate and by 10% in old leachate. The changes in pH did not affect the adsorption of EE2 in the young leachate, but did reduce adsorption by 32% in the old leachate. Adjusting the ionic strength using Na⁺ did not significantly impact adsorption, while increasing the concentration of Ca²⁺ resulted in a 12% increase in the adsorption of BPA and a 19% increase in the adsorption of EE2. DOC was revealed to be the most influential parameter in this study. In the presence of hydrophilic DOC, represented by glucose in this study, adsorption of the endocrine disrupting compounds (EDCs) onto the SWCNTs was not affected. In the absence of SWCNTs, hydrophobic DOC (i.e., humic acid) adsorbed 15-20% of BPA and EE2. However, when the humic acid and SWCNTs were both present, the overall adsorptive capacity of the SWCNTs was reduced. Hydrophobic (π-π electron donor-acceptor) interactions between the EDCs and the constituents in the leachate, as well as interactions between the SWCNTs and the EDCs, are proposed as potential adsorption mechanisms for BPA and EE2 onto SWCNTs.     

Sources of endocrine-disrupting chemicals in urban wastewater, Oakland, CA

Synthetic endocrine-disrupting chemicals (EDCs) have been found in surface waters throughout the United States, and are known to enter waterways via discharge from wastewater treatment plants (WWTPs). Studies addressing EDCs in wastewater do not examine their specific sources upstream of WWTPs. Presented here are results of a pilot study of potential sources of selected EDCs within an urban wastewater service area. Twenty-one wastewater samples were collected from a range of sites, including 16 residential, commercial, or industrial samples, and five samples from influent and effluent streams at the WWTP. Samples were analyzed for the following known and suspected EDCs: five phthalates, bisphenol A (BPA), triclosan, 4-nonylphenol (NP), and tris(2-chloroethyl) phosphate (TCEP), using well-established methods (EPA 625 and USGS O-1433-01). Twenty of 21 samples contained at least one EDC. Phthalates were widely detected; one or more phthalate compound was identified in 19 of 21 samples. Measurement of two phthalates in a field blank sample suggests that the accuracy of sample detections for these two compounds may be compromised by background contamination. Triclosan was detected in nine samples, BPA in five samples, and TCEP in four samples; NP was not detected. The results of this and future source-specific studies may be used to develop targeted pollution prevention strategies to reduce levels of EDCs in wastewater.     

Modeling the effects of sodium chloride on degradation of chloramphenicol in aquaculture pond sediment

Sodium chloride was added to aquaculture pond sediment to determine effects of different salinities on degradation of chloramphenicol (CM). In this experiment, freshwater (0 ppt salinity) eel pond sediment slurries (10% w/v) were amended with sodium chloride to obtain salinities of 12, 24 and 36 ppt. There were no significant differences in sorption rate either between aerobic and anaerobic conditions or among various salinities. Degradation of CM fitted well to the decaying exponential curve. The degradation rates under anaerobic conditions were significantly greater than those under aerobic conditions. As salinity increased, the degradation rates decreased under both aerobic and anaerobic conditions. The differences in degradation rates either between aerobic and anaerobic conditions or among various salinities were attributed to the effects of microbial activities under different environments.     

Optimierter mikrobiologischer Abbau von Chlorbenzen in <Emphasis Type="Italic">In situ</Emphasis>-Grundwasserreaktoren (SAFIRA)

In two reactors of the SAFIRA pilot plant, the microbial degradation of chlorobenzene (CB) by indigenous bacteria in native aquifer sediment were tested under oxic and anoxic conditions. Under anoxic conditions, no definite degradation was observed. Adding hydrogen peroxide (2.94 mM) and nitrate (2 mM) in one of the two reactors caused the degradation of CB (0.2–0.3 mM) in the lower part of the reactor, accompanied by a clear increase of the number of cultivable aerobic CB-degrading bacteria. After decreasing the hydrogen peroxide concentration to 0.88 mM, the CB concentrations increased in the lower part of the reactor, but decreased later, starting after approximately 100 days, finally under the detection limit again. Less than four mole oxygen were needed for the degradation of one mole CB. No accumulating compounds were determined, which could indicate an incomplete aerobic degradation of CB. These results point out that the oxygen released from hydrogen peroxide was almost completely consumed by bacteria for CB degradation. Nitrate disappeared uniformly during the reactor flow path.     

Removal and degradation characteristics of natural and synthetic estrogens by activated sludge in batch experiments

The removal and degradation characteristics of natural and synthetic estrogens by activated sludge were investigated by a series of batch experiments using the activated sludge samples of four actual wastewater treatment plants and synthetic wastewater spiked with estrogen. The rapid removal and degradation of 17β-estradiol (E2) and estrone (E1) were observed by the activated sludge samples of the oxidation ditch process which operated at higher solids retention time (SRT). On the other hand, E1 tended to remain both in the water phase and the sludge phase in the activated sludge samples of the conventional activated sludge process which operated at lower SRT. The anoxic condition was considered to be not favorable to the effective removal of estrogens as compared with the aerobic condition. The removal and degradation of EE2 showed the lag phase, which neither E2 nor E1 showed, but EE2 was finally removed and degraded completely after 24 h. The removal of estrogens in the water phase did not follow the first-order-rate reaction because a large part of the spiked estrogen was immediately removed from the water phase to the sludge phase by adsorption.     

Fate of N-nitrosodimethylamine in recycled water after recharge into anaerobic aquifer

Laboratory and field experiments were undertaken to assess the fate of N-nitrosodimethylamine (NDMA) in aerobic recycled water that was recharged into a deep anaerobic pyritic aquifer, as part of a managed aquifer recharge (MAR) strategy. Laboratory studies demonstrated a high mobility of NDMA in the Leederville aquifer system with a retardation coefficient of 1.1. Anaerobic degradation column and ¹⁴C-NDMA microcosm studies showed that anaerobic conditions of the aquifer provided a suitable environment for the biodegradation of NDMA with first-order kinetics. At microgram per litre concentrations, inhibition of biodegradation was observed with degradation half-lives (260 ± 20 days) up to an order of magnitude greater than at nanogram per litre concentrations (25-150 days), which are more typical of environmental concentrations. No threshold effects were observed at the lower ng L⁻¹ concentrations with NDMA concentrations reduced from 560 ng L⁻¹ to <6 ng L⁻¹ over a 42 day ¹⁴C-NDMA aerobic microcosm experiment.Aerobic ¹⁴C-NDMA microcosm studies were also undertaken to assess potential aerobic degradation, likely to occur close to the recharge bore. These microcosm experiments showed a faster degradation rate than anaerobic microcosms, with a degradation half-life of 8 ± 2 days, after a lag period of approximately 10 days.Results from a MAR field trial recharging the Leederville aquifer with aerobic recycled water showed that NDMA concentrations reduced from 2.5 ± 1.0 ng L⁻¹ to 1.3 ± 0.4 ng L⁻¹ between the recharge bore and a monitoring location 20 m down gradient (an estimated aquifer residence time of 10 days), consistent with data from the aerobic microcosm experiment. Further down gradient, in the anaerobic zone of the aquifer, NDMA degradation could not be assessed, as NDMA concentrations were too close to their analytical detection limit (<1 ng L⁻¹).     

Biological assessments of a mixture of endocrine disruptors at environmentally relevant concentrations in water following UV/H2O2 oxidation

Numerous studies have investigated degradation of individual endocrine disrupting compounds (EDCs) in lab or natural waters. However, natural variations in water matrices and mixtures of EDCs in the environment may confound analysis of the treatment efficiency. Because chemical based analytical methods cannot represent the combined or synergistic activities between water quality parameters and/or the EDC mixtures at environmentally relevant concentrations (microg L(-1)-ng L(-1)), bioanalytical assessments of residual estrogenic activity in treated water were used to evaluate the performance of the UV based advanced oxidation process for estrogenic contaminants in water. Four EDCs including estradiol (E(2)), ethinyl estradiol (EE(2)), bisphenol-A (BPA) and nonylphenol (NP) were spiked individually or as a mixture at mug L(-1)-ng L(-1) in laboratory or natural river water. The removal rates of estrogenic activity were quantitatively evaluated by in vitro yeast estrogen screen (YES) and in vivo Vitellogenin (VTG) assays with Japanese medaka fish (Oryzias latipes). UV in combination with 10 ppm H(2)O(2) as an oxidation process was capable of decreasing in vitro and in vivo estrogenic activity, however, in vivo estrogenic activity of the EDC mixture in natural water was not completely removed at UV fluence up to 2000 mJ cm(-2). The removal rates of in vitro estrogenic activity of the EDC mixtures were lower than those observed for single compounds, and slower in natural waters, likely due to lower steady-state concentrations of hydroxyl radicals (*OH) in the presence of *OH scavengers from the water matrix and EDC mixture.     

我国饮用水中内分泌干扰物的去除研究进展

对我国水源水中内分泌干扰物（EDCs）的存在现状以及采用常规饮用水处理工艺、深度处理工艺和高级氧化技术去除EDCs的研究现状和进展进行了综述。我国水源水已受到EDCs的严重污染，其中主要包括农药类、壬基酚、双酚A、邻苯二甲酸酯类以及多氯联苯类等；常规饮用水处理工艺对EDCs的去除非常有限；饮用水深度处理工艺可降解一定的EDCs；生物处理技术具有成本低、可去除多种EDCs的特点，具有很好的应用前景。     

Photochemical induced changes of in vitro estrogenic activity of steroid hormones

Steroid estrogens are endocrine disrupting contaminants frequently detected in natural waters. Because these estrogens can elicit significant biological responses in aquatic organisms, it is important to study their rates and pathways of degradation in natural waters and to identify whether the transformation products retain biological activity. Photochemical kinetics experiments were conducted under simulated solar light for the hormones 17β-estradiol (E2), 17α-ethinylestradiol (EE2), estrone (E1), equilin (EQ), and equilenin (EQN) under direct and indirect photolysis conditions. All of these hormones were susceptible to direct photodegradation, with half-lives ranging from 40 min for E1 to about 8 h for E2 and EE2. Indirect photolysis experiments with added Suwannee River fulvic acid (SRFA) lead to faster degradation rates for E2, EE2, and EQ. Added SRFA caused slower photodegradation rates for E1 and EQN, indicating that it acts primarily as an inner filter for these analytes. The well-established yeast estrogen screen (YES) was used to measure the estrogenicity of the analytes and their photoproducts. Results of YES assay experiments show that only the direct photolysis of E1 gave estrogenic products. Lumiestrone, the major E1 direct photolysis product, was isolated and characterized. It formed in 53% yield and exhibited moderate estrogenic activity. When photolysed in the presence of perinaphthenone, a potent synthetic sensitizer, E1 degraded via an indirect photolysis pathway and did not produce lumiestrone or any other active products. These results suggest that under typical natural water conditions photochemical reactions of E2, EE2, EQ, and EQN are expected to produce inactive products while E1 will give the estrogenic product lumiestrone in moderate yield.