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Feminisation of fish 5. Occurrence of estrogens and xenoestrogens in sewage effluent and occurrence and fate in the aquatic environmentThe present section will describe the occurrence of estrogens and xenoestrogens in the sewage effluent and what is known about their occurrence and fate when they reach the aquatic environment. Some information on the actual concentrations in both final effluent and surface water has already been given in chapter 4 in relation to the in vitro estrogenicity of the water samples. Table 5.1 and 5.2 summarise additional concentrations which have been reported for natural and synthetic estrogens in effluent and surface water, respectively while concentrations for the alkylphenolic compounds and bisphenol A are given in Table 5.3-5.6. Since a range of studies as shown in the previous section has pinpointed natural and synthetic estrogens to be the primary causes of the observed estrogenic activity of sewage effluent in many countries these will receive the largest attention in the following section compared to alkylphenols and bisphenol A. The fate of the estrogens in the sewage treatment works and the influence of different treatment processes on the removal rate of these compounds from the sewage will be covered in Chapter 11 and 12. An important thing which has to be remembered whenever concentrations of estrogens are mentioned in the present report is, however, that it seldom is specified whether the chemical analysis measures only free or both free and conjugated estrogens. There must probably also be expected to be larger uncertainties related to measurements of estrogen concentrations in influent than in effluent due primarily to interference from large contents of organic matter (matrix effect).Further, the detection limits of the analyses, especially for ethinylestradiol, are close to and sometimes even above the concentrations which have been demonstrated to cause reproductive disturbances in fish. 5.1 Estrogens5.1.1 Occurrence in sewage effluentWhen comparing the estrogen concentrations in sewage effluent from numerous countries mentioned throughout this report it is apparent that the levels can vary a lot. Levels of < 0.1 – 88 ng/l 17ß-estradiol, < 0.1 – 220 ng/l estrone, and < 0.053 – 62 ng/l ethinylestradiol have been detected (Table 5.1 and Chapter 4). The typical range of the steroids is in the range of 1-10 ng/l and 5-20 ng/l for estradiol and estrone, respectively, while ethinylestradiol often is below detection limits (0.1 –1 ng/l). When detected, it is mostly below 10 ng/l. Estrone is the most frequently detected of the natural estrogens and often detected in all samples which might reflect the relatively fast conversion of 17ß-estradiol to estrone (see chapter 5.1.3.1). Estriol could be expected at higher concentrations than estrone since this is excreted in higher concentrations from women. The relatively few measurements which exist on the effluent concentrations of this steroid have detected it in the range of < 0.1 – 42 ng/l estriol. Due to the relatively sparse material on effluent concentrations of estriol it is not possible to say whether these are representative. The steroid concentrations which have been measured in Danish sewage effluent lie within the typical range of the steroid estrogens which have been reported from other European countries. Large differences in effluent concentrations from a single sewage treatment plant are often observed when concentrations are followed over time. This might be caused by different weather conditions (sunshine and dryness, dilution by rainfall, temperature) in the sampling period, differences in the residence time of the sewage, microbial activity and varying composition of the influent water (138;139). The differences in steroid hormone concentration between effluent from different treatment works will also depend on the type of treatment processes used by the plant. This will be discussed in Chapter 13. Repetitive samplings of sewage effluent might therefore be necessary in order to get a true picture of the range of estrogen concentrations being released with sewage effluent. It also has to be kept in mind when relating the estrogen concentrations in sewage effluent to known lowest observed effect concentrations (LOECs) and no observed effect concentration (NOECs) for endocrine disrupting effects on fish that the reported concentrations often are measured in 24 hour samplings which gives the average steroid concentration being released to the water phase. It is known, however, that there is en early morning surge of sewage into the STPs (140) and there might therefore be higher peak values released to the environment at certain hours of the day. Table 5.1 Table 5.2. 5.1.2 Occurrence in surface waterThe concentrations of estrogens which have been measured in surface water also show a large variability and concentrations of < 0.05 – 15.5 ng estradiol/l, < 0.1 – 17 ng estrone/l and < 0.053 – 30.8 ng/ ethinylestradiol/l have been detected (Table 5.2 and Chapter 4). Very few results exist again for estriol which has been detected at concentrations of < 0.1 – 3.4 ng/l. Though single very high concentrations of the estrogens have been detected they are generally found at concentrations of less than 5 ng/l for estradiol and estrone and less than 1 ng for ethinylestradiol. As for sewage effluent estrone is the most and ethinylestradiol the least frequently detected of the estrogens. More studies are needed to assess the estrogen concentrations of surface waters since the use of the dilution factor in the receiving stream does not always give the right estimate of the actual surface water concentration when trying to estimate from sewage effluent concentrations. Kuch et al. 2001 found a dilution factor of only 2-6 of estrogens in the Danube River downstream of effluent discharge based on chemical analysis of the compounds though the effluent was diluted 100 times. This indicated that the river already contained a steroid load. In Denmark estrogen levels have only been measured in surface water in a few streams and lakes which have served as reference locations and which did not receive or received sewage effluent in very low amounts (2). In these waters low levels of estrone could be detected in all samples in the range of 0.2 – 3.0 ng/l. Estradiol was detected less frequently at 4 of 5 sites at concentrations of 0.2 – 0.8 ng/l and a single detection of ethinylestradiol (1.5 ng/l) has also been made. Estrone has been detected in upstream locations and in presumptive clean location in other studies (139). This indicates the need for also considering other sources of estrogens to the environment besides sewage effluent. 5.1.3 Fate and behaviour in the environmentWhen effluent is discharged to surface waters the aqueous concentration of estrogens will be reduced due to dilution, degradation and sorption of the compounds (150). Not much is yet known, however, about the fate, behaviour and persistence of steroidal estrogens following their discharge to the environment. Recent studies have begun to answer some of these questions (35;36;150). 5.1.3.1 Degradation in river water Microorganisms in the environment are capable of degrading the estrogens. Using river water from urban/industrial and rural environments in England, the speed of biodegradation of estradiol and ethinylestradiol has been estimated. Estradiol was rapidly transformed to estrone under aerobic conditions in river water with a half-life of 0.2 – 8.7 days (at 20 ° C) (35;36). Estrone was further degraded to non-estrogenic products at a similar halflife of 0.1 – 10.9 days. Mean half-lives of estradiol have been calculated to 2.8 days while mean half-life for estrone (calculated from 25 separately collected water samples) was 3.0 days (35). The biodegradation rate of estradiol was temperature dependent and the fastest degradation was obtained with water samples collected in the summer (half-lives of 4 – 5 hours). Incubation of river water at temperatures of 10 and 20 ° C also demonstrated that half-life of estradiol was approximately twice as long at the lower temperature (36). The bacterial fauna will also influence the degradation rate. The rate of removal seems to be independent of the estrogen concentration since the same rate was found for 100 ng/l to 100 mg/l of estradiol. Estadiol at 20 ng/l was also rapidly degraded indicating that low concentration of the hormone also will be metabolised even though high background levels of other organic carbon sources are present. Some studies have also indicated that degradation of estradiol is even faster at lower concentrations (36;144). Ethinylestradiol is less biodegradable in aerobic river water and was shown to have a half-life of approximately 10 times that of estradiol under the same incubation conditions. In a comparison study, the half-life of estradiol and ethinylestradiol was assessed to 1.2 and 17 days, respectively (35;36). All steroids have a low vapour pressure and are unlikely to volatilise from aquatic environments (37). Degradation by photolysis can, however, take place at slow rates and photolysis has been demonstrated to degrade estradiol and ethinylestradiol with a half-life of approximately 120 hours for both. Assuming 12 hours of bright sunlight this would equal 10 days. Photolysis of estradiol is slow compared to the microbial degradation and considered unimportant for removal of this steroid in English rivers which are characterised by short transit time of the water (36). For ethinylestradiol this degradation pathway might play a larger role considered the slower biodegradation of this synthetic steroid. 5.1.3.2 Sorption to and degradation of estrogens in the sediment When estrogens are released with effluent to the river water, a partitioning between the water phase and the sediment will take place (150). Sorption to suspended particles is also a removal route (35;36;150). The log octanol-water partitioning coefficient (Kow values) of estradiol, estrone and ethinylestradiol have been reported in the range of 3-4 and a little lower for estriol (<3) (37;150). A slightly higher Kow value of the synthetic steroid has been detected (150) and these values therefore indicate medium sorption potential to organic matter in the following decreasing rank order: ethinylestradiol > estradiol = estrone > estriol (37). Studies using natural sediments from three English rivers have also demonstrated the sorption of both estradiol and ethinylestradiol to both suspended and bed sediments with a slightly higher partition coefficient for ethinylestradiol (35). The amount and rate of sorption to the suspended material depend on its total organic contents and it is generally agreed that smaller particle size and higher organic content result in an increased sorption. The suspended sediment has been demonstrated to have a higher sorption efficiency than bed sediments (150). However, in English rivers less than 1 % of the present steroid are predicted to be removed from the water phase by suspended sediments when considering their concentration. Despite the lower sorption potential of the bed sediment, this might still be an important sink considering the available quantity (35). The persistence of steroids in the bed sediment phase will depend on the oxygenation conditions. River bed sediments from heavily polluted rivers might often be partly or completely anaerobic. Under anaerobic conditions estradiol has been shown to be rapidly converted to estrone. Using bed sediments from two English rivers, estradiol was degraded to estrone with a half-life of 8-16 hours. Estrone, on the other hand, seemed very persistent and no reduction was seen in the bed sediment concentration of this hormone over a period of 48 hours (35;36). If this results in a build-up of estrone in the sediment needs further investigation. The conversion of estradiol in aerobic sediments was faster compared to the degradation taking place under anaerobic conditions with an approximately three times shorter half-life (36). The degradation of ethinylestradiol under anaerobic conditions have been shown to be poor and this, together with the slightly higher sorption coefficient compared to that of estradiol, has led to speculations of whether ethinylestradiol might accumulate in bed sediments (36). Sediments from an English sewage effluent receiving river have had concentrations that were 700-1700 fold higher than that of the overlying river water. This supports the suggestion that sediments are a major sink but also a source of estrogenic pollution (151). Measurements of estrogens in the sediment of the English river Nene gave bed sediment concentration of estrone between 34 and 386 ng/kg while neither estradiol and ethinylestradiol were detected above the detection limit (100 ng/kg). The concentrations of estrone not only differed between sites but also at the same site on different days. Further studies on exact quantified sediment concentrations of estrogens are sparse. 5.2 Alkylphenols5.2.1 Concentrations in sewage effluentConcentrations of nonylphenol and octylphenol, the two most frequently encountered alkylphenols in sewage effluent, are in comparison with the natural and synthetic estrogens which are detected in the ng-range, in general detected at higher concentrations which sometime reaches µg/l levels (Table 5.3). Concentrations between 0.025 and 330 µg/l have been reported for nonylphenol and between 0.0022 and 73 µg/l for octylphenol although both, in general, mostly are found at concentrations below 10 µg/l. Levels below 4 µg/l have been detected in samples of effluent from Danish STPs whereas octylphenol seldom is detected at all (2). Table 5.3. 5.2.2 Concentrations in surface waterHigh levels of nonylphenols have been detected in some rivers in England, Switzerland and Spain in which concentrations between 45 and 644 µg/l have been reported (14;152;155). Most other reports on surface water concentrations of alkylphenols in European waters have not exceeded 1 µg/l (Table 5.4). Octylphenol is typically detected at lower concentrations in surface water with a maximum reported concentration of 13 µg/l in English river water (152). Table 5.4. 5.2.3 Fate and behaviour in the environment5.2.3.1 Degradation in river water The alkylphenols, NP and OP are generally considered to be readily degradable by aerobic biotransformation in river water (161-163). Staples et al. 1999,2001 have reported biodegradation half-lives of 7 – 28 days (162;163). A lag time of approximately 2-3 days has been observed (162;164). A range of half-lives of 7 – 50 days was found when studying the biodegradation rate of OP in water from three English rivers (161). The fastest degradation was observed at urban/industrialised stretches of the rivers (half-lives of 8-13 days). As has been demonstrated for the estrogens, little difference in degradation rates was found for OP over a range of concentrations (20 – 100 µg/l) and OP is therefore not more persistent at low concentrations. Higher temperatures result in higher degradation (163;165). 5.2.3.2 Sorption to and degradation of alkylphenols in the sediment Compared to estrogens, alkylphenols have a stronger affinity for bed sediments and therefore a higher tendency to accumulate in the sediment. The log Kow has been reported to be 4.48 for nonylphenol and 4.12 for octylphenol which means that nonylphenol is most strongly absorbed to sediment and suspended particles (166). For octylphenol it has been demonstrated that the higher organic content and the greater proportion of clay and silt, the larger proportion of the alkylphenol will be sorbed to the sediment. This is also in agreement with what has been demonstrated for estrogens. In rivers with large amounts of organic aggregates, as has been seen at industrial reaches of English rivers, suspended sediments seem to play a large role in the fate of the octylphenol distribution. Here the suspended sediments absorbed 5-35 times more octylphenol than the bed sediments on a carbon-to-carbon basis and they had the potential to absorb 30-40 % of the octylphenol. In areas with low river velocity or large sedimentation rate as in estuaries the amount bound to the suspended particles will add to the concentration of the bed sediments. The degradation in the sediment of alkylphenols has been reported to be very slow to practically non-existing in anaerobic environments (117). The half-life of nonylphenol in marine sediments in a Canadian study was estimated to be greater than 60 years. Long persistence has been shown in experiments where the amount of nonylphenol remaining after 440 days of addition was similar to the amount present in the sediment after 2 days (38). In agreement with the high affinity to and the low degradability in sediment, high sediment concentrations for nonylphenol and octylphenol have been reported from numerous countries. In Swiss rivers, sediment concentrations of nonylphenol between 190 – 13,100 µg/kg dry weight have been detected (155). Sediment in a Korean bay which received industrial and municipal wastewater from two cities contained 113 – 3890 µg NP/kg dry weight and 3.97 – 179 µg OP/kg (167) and concentrations of <2.9 – 2960 µg NP/kg have been reported for sediment in US rivers. In UK estuarine sediments from highly industrialised areas concentrations of 1600 – 9050 µg nonylphenol and 30 – 340 µg OP/ kg dry weight were found (168) while sediment nonylphenol concentrations of 10-259 µg/kg dry weight and octylphenol concentrations of < 0.5 – 8 µg/kg have been reported from German rivers (158). Bottom living fish which burrow in or feed on sediment therefore might be at higher risk towards exposure to alkylphenols than pelagic species. 5.3 Bisphenol A5.3.1 Concentrations in sewage effluentExisting reports on the level of bisphenol A in sewage effluent are not as numerous as seen for estrogens and alkylphenols. Levels of less than 1 ng to 6,2 µg/l have been reported but levels below 1 µg/l are most frequently encountered (Table 5.5). In Aarhus County, Denmark levels of 1 ng/l to 4 µg/l in sewage from high technology sewage treatment works and up to 6,2 µg/l in sewage from plants with lower technology treatment steps have been found (2). This is within the range reported from other countries. Table 5.5.
1 The figure in parenthesis is the median concentration5.3.2 Concentrations in surface waterConcentrations of bisphenol A in surface water are generally lower than in sewage effluent and have generally been detected in the range of < 0.001 – 1 µg/l (Table 5.6). Downstream of sewage from manufacturers levels up to 8 µg/l have been found. The levels seen in Danish streams were within the typical range reported for other European countries. Table 5.6.
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