2004 Progress Report: The Environmental Occurrence, Fate, and Ecotoxicity of Selective Serotonin Reuptake Inhibitors (SSRIs) in Aquatic EnvironmentsEPA Grant Number: R829006
Title: The Environmental Occurrence, Fate, and Ecotoxicity of Selective Serotonin Reuptake Inhibitors (SSRIs) in Aquatic Environments
Investigators: Black, Marsha C. , Armbrust, Kevin L. , Henry, Theodore B. , Kwon, Jeong-Wook
Current Investigators: Black, Marsha C. , Armbrust, Kevin L.
Institution: University of Georgia , Mississippi State University - Main Campus , University of Tennessee - Knoxville
Current Institution: University of Georgia
EPA Project Officer: Page, Angela
Project Period: September 1, 2001 through August 31, 2004 (Extended to April 30, 2007)
Project Period Covered by this Report: September 1, 2003 through August 31, 2004
Project Amount: $522,892
RFA: Drinking Water (2000) RFA Text | Recipients Lists
Research Category: Drinking Water , Water Quality , Water
Pharmaceutical chemicals can enter aquatic environments after their prescribed use and lead to negative effects on aquatic organisms. For most pharmaceutical chemicals, the environmental fate and ecotoxicological characteristics are unknown. Of particular concern are drugs that are hormonally active because disruption of physiological processes in aquatic organisms can occur at low environmental concentrations. Selective serotonin reuptake inhibitors (SSRIs) are among the most commonly prescribed drugs. SSRIs are hormonally active and low concentrations have been shown to affect aquatic organisms. There also is evidence that they can be present in effluents from wastewater treatment plants.
The objective of this research project is to characterize the occurrence, environmental fate, and ecotoxicity of five SSRI drugs (fluoxetine, fluvoxamine, paroxetine, citalopram, and sertraline) and their relevant metabolites. Investigations on the environmental chemistry of these five compounds will be used to identify the specific compounds that pose the greatest risk of becoming contaminants in aquatic ecosystems and to assess their persistence in aquatic environments. Routine sampling of a wastewater treatment plant combined with market information on the numbers of prescriptions for specific SSRIs will be used to gauge the potential environmental exposure of specific compounds. Acute and chronic toxicity testing with Ceriodaphnia dubia followed by determination of chronic effects on mosquitofish, Gambusia affinis, will help characterize their effects on key components of aquatic ecosystems.
Analyses of SSRI chemicals showed high water solubilities (3,022-15,460 mg/L) and relatively low octanol-water partition coefficients (log Kows ranged from 1.12-1.39). Adsorption coefficients were determined using two sediments (0.16% organic matter and 0.65% organic matter). Values of Kf, Kd, and Koc ranged from 50.7 to 419.1, from 87.6 to 1,304.0, and from 225.4 to 4,907.4, respectively, indicating very high sorption coefficients for all SSRIs. Similar results were obtained for soil adsorption coefficients. Kd and log Kom ranged from 39 to 18,342, from 60 to 42,579, and from 3.6 to 6.3, respectively, indicating very high soil sorption coefficients for all SSRIs. Hydroxyl radical rate constants, measured by competition kinetic methods, were conducted for SSRIs and ranged from 1.41 × 1012 to 1.99 × 1013 M-1 h-1. Paroxetine was the most reactive molecule measured by this method, followed by fluvoxamine, citalopram, fluoxetine, and sertraline. No significant hydrolytic degradation was detected for any drug in any aqueous solution.
Photolysis is a potential route of degradation for several SSRIs. Fluoxetine was relatively resistant to photolysis at all pH ranges and degradation was generally less than 10 percent over a 10-day period, with no detectable degradation products, because of the very low degradation rate. Paroxetine was completely photodegraded, however, within 4 days after exposure to simulated sunlight and photodegradation was accelerated by increasing pH (to pH 9). Photolysis of sertraline at pH 5 and 7 was very slow, yet at pH 9 this drug was completely degraded by simulated sunlight within 10 days. Slower degradation of sertraline was observed in humic acid-containing water or natural waters compared with pure water, suggesting that the fate of sertraline in aqueous environments may be different in the laboratory than in real aqueous environments. Photolysis of citalopram also was slow at pH 5 and 7; however, at pH 9 citalopram was moderately degraded. Degradation was faster in synthetic humic water than in pH 9 buffer or in two lake waters. Two photoproducts were detected over the irradiation period and their structures were identified. Fluvoxamine was moderately degraded by simulated sunlight and degradation kinetics were biphasic.
Experiments to determine water/sediment degradation for sertraline, fluoxetine, and fluvoxamine were conducted according to U.S. Environmental Protection Agency methods. Although free sertraline in the aqueous phase was degraded when compared to dark controls, sertraline appears to be stable once it is absorbed to sediments. After 30 days of treatment, more than 80 percent of the compound remained in the sediments, indicating that the sediments are an important sink for sertraline. Fluoxetine appears stable to light in water. Sediments also are an important sink for fluoxetine, as it rapidly adsorbed to pond and creek sediments and sorbed concentrations decreased minimally within 30 days. Nor-fluoxetine, a major degradation product/metabolite, was not detected in any sample. Dissipation rates of fluvoxamine from the water phase varied according to light conditions and types of water. The results indicate that fluvoxamine is somewhat susceptible to light, and the properties of natural water affect the degradation of fluvoxamine in water. The highest amounts of fluvoxamine residues in sediments were detected in all treatments between days 1 and 3, indicating fast adsorption patterns. Nearly constant fluvoxamine residues in sediments indicate that fluvoxamine likely is stable to microorganisms in sediments. One photoproduct, a photoisomer of fluvoxamine, was detected in water and sediment under light conditions but decreased to negligible amounts by day 14.
Ready biodegradability by wastewater treatment was tested for three of the SSRI compounds, with an inoculum from an activated sludge collected from a wastewater treatment plant in Columbus, Mississippi. No degradation was observed in paroxetine, fluvoxamine, and sertraline within the test period of 28 days. Thus, it can be concluded that none of these drugs may be classified as readily biodegradable in wastewater treatment plants.
Methods for the determination of five SSRIs in surface water samples have been developed, and one sample collected from the secondary treatment tank of a wastewater treatment facility was analyzed. Citalopram and fluoxetine were detected at the concentrations of 0.029 μg/L and 0.033 μg/L, respectively. Additional sampling of wastewater treatment plant influents and effluents will measure the potential environmental exposure of specific SSRI compounds. Market surveys also will be conducted at the same time to attempt to correlate the amounts of SSRI drugs prescribed with their appearance in wastewaters.
Experiments with Ceriodaphnia dubia have determined the acute and chronic toxicity of each of the five SSRIs. C. dubia mortality increased with the increasing concentration of each SSRI, and the 48-hour LC50 values ranged from 0.14 mg/L for sertraline to 3.18 mg/L for citalopram. The LC50 values for other SSRIs were: fluoxetine, 0.47 mg/L; paroxetine, 0.59 mg/L; and fluvoxamine, 1.26 mg/L. In chronic tests, the SSRI with the lowest concentration to affect the mean number of neonates (lowest observable effect concentration [LOEC]) was sertraline (0.045 mg/L), whereas the highest LOEC was measured upon exposure to citalopram (4 mg/L). The time to first brood was not affected significantly after exposure to any of the SSRIs tested; however, the number of broods was reduced after exposure to fluvoxamine, fluoxetine, and paroxetine but not by the other SSRIs at the concentrations tested.
Acute and chronic toxicity tests with fluoxetine HCl indicated that toxic effects are not expected in C. dubia at environmentally relevant concentrations. A major concern for the ecotoxicology of pharmaceuticals, however, is that exposure to low concentrations of biologically active compounds may exert negative effects on aquatic organisms after multiple generations of exposure. To investigate this issue, C. dubia were exposed to concentrations of 0, 10, or 100 ppb fluoxetine HCl and reproduction was evaluated over four generations. Although results indicated more lethargic swimming in C. dubia exposed to fluoxetine HCl, no differences in the number of neonates produced or the time to first brood were detected among generations.
Experiments were conducted to determine the acute and chronic toxicity of fluoxetine to the western mosquitofish Gambusia affinis. In 7-day acute toxicity tests with neonate (age 24-36 hours) G. affinis, the LC50 for fluoxetine HCl was 614 μg/L. A 91-day chronic test was conducted with neonate (age 24-48 hours) G. affinis based on toxicity data obtained from the acute test, and fish were exposed to 6, 0.6, and 0.06 μg/L fluoxetine HCl. Chronic exposure to fluoxetine did not significantly affect survival, sex ratio, or morphology of the male gonopodium. A second chronic test was conducted in larger tanks (100 L), beginning with older juvenile fish (age 5-6 weeks), and continued until fish were age 140-145 days. At the high exposure concentration (60 μg/L fluoxetine HCl), expression of mature sexual characteristics (gonopodium, male fish; black spot on abdomen, female fish) was significantly delayed in western mosquitofish exposed to 60 ppb fluoxetine HCl.
In 2004, additional experiments were conducted in the laboratory to investigate the effects of fluoxetine on the development of western mosquitofish exposed during specific stages of development. Fish were exposed to 0, 6, or 60 ppb fluoxetine HCl in three experiments. In experiment 1, fish were exposed from neonates (age 24-48 hours) to an age of 11 days, and then exposure to fluoxetine was ended and fish were allowed to develop to an age of 96 days. In experiment 2, fish were exposed from neonates (age 24-48 hours) to age 43 days, and then exposure to fluoxetine was ended and fish were allowed to develop to an age of 96 days. In experiment 3, fish were exposed for 164 days from an age of 38-42 days to age 202-206 days, at which time the experiment was ended. At preselected times during each experiment, fish were sampled randomly from treatments for evaluation of morphological features and preserved for histological examination.
The results indicate that mortality was highest among fish exposed early in development (neonates); however, exposure to fluoxetine did not significantly delay development of adult sexual morphology under any exposure scenario. A minor decrease in the growth of fish exposed to 60 ppb fluoxetine HCl was observed in experiment 3; however, this decrease was not significant. A potential explanation for the lack of effect on development of mature sexual characteristics was the low water temperature. Water temperature of the laboratory exposures was 18-21°C, which considerably slows development of western mosquitofish and impedes our ability to compare with the results of experiments conducted under natural temperature conditions (25-32°C) in 2003. Currently, histological examination is underway to determine the presence of lesions in fish exposed to fluoxetine and to confirm sex identification based on external characteristics.
We will continue to identify SSRI compounds in wastewater effluents, coupled with acute and chronic toxicity determinations. Patient surveys of SSRI drugs prescribed in Starkville, Mississippi, will be conducted in an attempt to correlate the amounts of SSRI drugs prescribed with their appearance in wastewaters. Fish tissues from chronic exposures conducted in 2003 and 2004 will be examined histologically to determine if external morphological indicators of delayed sexual maturity correlate with similar delays in gonad maturation.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
|Other project views:||All 44 publications||11 publications in selected types||All 9 journal articles|
||Henry TB, Kwon J-W, Armbrust KL, Black MC. Acute and chronic toxicity of five selective serotonin reuptake inhibitors to Ceriodaphnia dubia. Environmental Toxicology and Chemistry 2004;23(9):2229-2233.||
||Kwon J-W, Armbrust KL. Hydrolysis and photolysis of paroxetine, a selective serotonin reuptake inhibitor, in aqueous solutions. Environmental Toxicology and Chemistry 2004;23(6):1394-1399.||
||Kwon J-W, Armbrust KL. Photo-isomerization of fluvoxamine in aqueous solutions. Journal of Pharmaceutical and Biomedical Analysis 2005;37(4):643-648.||