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Pharmaceuticals Effects in the Environment
Pharmaceuticals Effects in the Environment C Ferna´ndez and EM Beltra´n, Laboratory for Ecotoxicology, Spanish National Institute for Agriculture and Food Research and Technology, Madrid, Spain JV Tarazona, Spanish Royal Academy of Veterinary Sciences, Spanish National Institute for Agriculture and Food Research and Technology, Madrid, Spain Ó 2014 Elsevier Inc. All rights reserved.
Introduction The presence of pharmaceutically active compounds (PhACs) in the environment can pose significant human and wildlife health threats. Pharmaceuticals were initially identified in the mid1970s associated with wastewater treatment plant (WWTP) effluents in the United States. During the 1980s, there has been only little interest in this type of contamination. It has not been until this last decade that social concern has been aroused for a potential risk to ecosystems. The increased concern on the ecological effects of PhACs was initiated largely as a result of a growing number of technical papers reporting detectable levels of pharmaceuticals in WWTP effluents, surface waters, drinking waters, and sediments. For instance, >100 pharmaceuticals and personal care products have been detected in effluents of WWTPs in several countries of the European Union. The current awareness of emergent pollutants is the result of new advances in analytical techniques capable of revealing the presence of these substances at very low levels. Presumably, they have been in the environment, undetected, since their use began. These compounds and their metabolites continuously enter the aquatic environment largely through effluents from WWTPs because of incomplete elimination or sporadic direct wastewater discharge. Even low concentrations of these substances may lead to unwanted effects in aquatic systems. Although pharmaceuticals are designed as bioactive molecules to treat diseases, they can affect nontarget organisms, with harmful effects reported at environmentally relevant concentrations. Concern is such that several reviews recently published have dealt with the exposure of humans or biota to pharmaceuticals. The environmental concerns about these compounds are linked to two main factors: (1) the bioactive property of pharmaceuticals and (2) their capacity to be routinely present in aquatic environments. This situation has resulted in their characterization as ‘pseudo’ persistent compounds. The scientific community is in broad agreement on the possibility that adverse effects not only for human health but also for aquatic organisms may arise from the presence of pharmaceuticals. Several almost negligible effects have been shown to occur from continuous exposure during the life cycle of aquatic vertebrates and invertebrates to subtherapeutic drug concentrations. These effects slowly accumulate and manifest themselves as a final irreversible condition that is frequently only noticed several generations later, affecting the sustainability of aquatic organism populations.
Sources of PhACs Environmental Contamination The main pathway for environmental contamination of medicines is via the metabolic excretion (nonmetabolized
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parent drug, parent–drug conjugates, and bioactive metabolites) in urine and faces, although other anthropogenic mechanisms should be assumed: a) Disposal of unused/outdated medication to sewage systems b) Release of treated/untreated hospital wastes to domestic sewage systems c) Release to private septic/leach fields: treated effluent from domestic sewage treatment plants discharged to surface waters d) Transfer of sewage solids (‘biosolids’) to land as amendments/fertilizers e) Direct release to open waters via washing, bathing, or swimming f) Discharge of regulated/controlled industrial manufacturing waste streams g) Direct release from aquaculture facilities (fish farming)
Environmental Fate In general, a wide-dispersive environmental release should be assumed. After human or animal treatment, most drugs are excreted partly nonmetabolized. Some, such as X-ray contrast media, are excreted as a parent drug. PhACs as well as disinfectants are used in medicine, which enter municipal sewage and WWTPs. Pharmaceuticals not readily degraded in WWTPs are being discharged in treated effluents, resulting in the contamination of surface waters, groundwater, and drinking water. In addition, the conjugated metabolites can be hydrolyzed, releasing the parent drug or Phase I metabolites. When sewage sludge is applied to agricultural fields, contamination of soil, runoff into surface water, and drainage may occur. In addition, veterinary drugs may enter aquatic systems via manure application to fields and subsequent runoff. Drugs used in animal husbandry as well as aquaculture are also discharged into the environment. Finally, PhACs reach groundwater via soil after manure or sewage sludge application as fertilizers (see Figure 1).
Environmental Concentrations Since 1976, when Garrison et al. reported the occurrence of clofibric acid, in the range 0.2–2 mg l1, in treated wastewater in the United States, pharmaceuticals have been detected in many countries around the world. In the last decade, specialized literature has supplied a lot of data on PhAC concentration in surface and groundwater, WWTP influents and effluents, soils, sediments, biosolids, biota, and so on. Environmental concentrations of pharmaceuticals have been mainly reported in WWTP effluents and surface water. WWTP effluent concentrations range from ng l1 to mg l1. In surface water, the level of contamination
Encyclopedia of Toxicology, Volume 3
http://dx.doi.org/10.1016/B978-0-12-386454-3.00571-6
Pharmaceuticals Effects in the Environment
PhACs for human use
Excretion (hospital effluents)
Excretion (WWTPs effluents)
Municipal effluents
845
PhACs for veterinary use
Disposal of unused/outdated medication Domestic sewage
Excretion
Manure
Agro industrial effluents WWTPs
Sewage sludges
Surface water
Aquaculture
Figure 1
Landfields
Soil
Groundwater
Drinking water Pharmaceutical Industry
Sources, distribution, and sinks of PhACs in the environment.
is in the range of ng l1. Data have been compiled up to 2006 and are reviewed by Fent et al., as shown in Figure 2. After reaching WWTPs, PhACs are degradated and partitioned in effluent and sewage sludge. Mean concentration levels of the PhACs ranged between 20 and 4000 mg kg1 dw, 15 and 1000 mg kg1 dw, 3 and 600 mg kg1 dw, and 10 and
1000 mg kg1 dw in primary, secondary, digested sludge, and compost, respectively. The highest ecotoxicological risk, in digested sludge and compost, was caused by the estrogenic compound 17b-estradiol. The ecotoxicological risk significantly decreased after the application of digested sludge or compost to the soils.
Figure 2 PhAC concentration in treated wastewater and surface water (Fent, K., Weston, A.A., Caminada, D., 2006. Ecotoxicology of human pharmaceuticals. Aquat. Toxicol. 76, 122–159.).
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Pharmaceuticals Effects in the Environment
A survey of 72 pharmaceuticals in US biosolids found two (ciprofloxacin, diphenhydramine) in all samples (n ¼ 84) and eight in at least 80 of the biosolid samples analyzed. However, 15 pharmaceuticals were not found in any sample, and 29 were present in fewer than three samples. Maximum concentrations of tetracycline (range: 0.04–5.3; mean: 1.3 mg kg1 dw) and ciprofloxacin (range: 0.08–41.0; mean: 10.5 mg kg1 dw).
Ecotoxicological Effects Nonsteroidal Antiinflammatory Drugs (NSAIDs) Nonsteroidal antiinflammatory drugs (NSAIDs) are weak acids that act by reversible or irreversible inhibition of one or both isoforms of the cyclooxygenase enzymes COX-1 and COX-2, which are involved in the synthesis of different prostaglandins from arachidonic acid. Diclofenac is the compound that has the highest acute toxicity within the class of NSAIDs. For all tests performed on this compound, the effect concentrations were <100 mg l1. Ibuprofen also presents chronic toxicity. Female Japanese medaka (Oryzias latipes) exposed to different concentrations of the drug over 6 weeks, showed a sharp rise in liver weight together with enhanced egg production, yet with a reduction in the number of weekly spawning events. The water flea Daphnia magna population growth rate was significantly reduced at concentrations ranging from 0 to 80 mg l1. Reproduction was affected at all concentrations and completely inhibited at the highest pharmaceutical level. Regarding aquatic photosynthetic organisms, specific effects have been noticed. A 5-day exposure to concentrations in the 1–1000 mg l1 range stimulated the growth of the cyanobacterium Synechocystis sp., whereas inhibiting that of the duckweed plant Lemna minor after 7 days. Acute toxicity tests performed on the rotifer Brachionus calyciflorus, the water flea Ceriodaphnia dubia, and the fairy shrimp Thamnocephalus platyurus showed that naproxen had EC50 values within the range 1–100 mg l1, with photolysis products being significantly more toxic. Highly chronic toxic properties were noticed with algae. Paracetamol (or acetaminophen) is a weak inhibitor of the cyclooxygenase enzyme, whose side effects are mainly associated with the formation of hepatotoxic metabolites, such as N-acetyl-p-benzoquinone imine when the levels of liver glutathione are low. Tests were carried out on algae, water fleas, fish embryos, luminescent bacteria, and ciliates. The most sensitive species was shown to be D. magna, for which EC50 values reported from 30 to 50 mg l1.
Blood Lipid-Lowering Agents Statins and fibrates are basically the two types of antilipidemic drugs. Both are used to decrease the concentration of cholesterol (statins and fibrates) and triglycerides (fibrates) in the blood plasma. Statins act by inhibiting the 3-hydroxymethylglutaryl coenzyme A reductase, an enzyme involved in feedback control of cholesterol synthesis. In response, the number of LDL
lipoprotein receptors at hepatocyte surfaces increases, thus lowering the circulating LDL cholesterol. Acute toxicity of lipid-lowering agents is not extensively reported. Several authors found LC50 values of 1.18 and 10 mg l1 in larval and adult grass shrimp (Palaemonetes pugio), respectively, after an exposure of 96 h to simvastatin. Simvastatin exhibited an EC50 of 22.8 mg l1 after 96 h for the marine phytoplankton Dunaliella tertiolecta. Atorvastatin can affect the development of the duckweed. Lemna gibba showed an lowest observed effect concentration of 300 mg l1 for parameters such as wet mass, frond number, chlorophyll-a, and carotenoid content for a time of exposure of 7 days. Fibrates act by activating specific transcription factors belonging to the nuclear hormone receptor superfamily known as peroxisome proliferator activated receptors (PPARs) (Staels et al., 1998). There are three types of PPARs related to different cellular events. PPAR-a and PPAR-b play key roles in catabolism and storage of fatty acids, whereas PPAR-g plays an important role in cellular differentiation. According to Quinn et al. (2008), gemfibrozil could be classified as toxic (EC50 1–10 mg l1) and bezafibrate as harmful for nontarget organisms (EC50 10–100 mg l1). Toxic properties of gemfibrozil were also investigated on the inhibition of the bacterium Vibrio fischeri luminescence, growth inhibition of the alga Chlorella vulgaris, and immobilization of the D. magna. Both the bacteria and the water flea were sensitive to gemfibrozil, with the latter being the most sensitive, having an EC50 of 30 mg l1 after 72 h.
Antibiotics The major concern is associated with the development of resistance mechanisms by bacteria that can subsequently compromise public health by means of treatment effectiveness. According to Jones et al. (2002), antibiotics could be classified as extremely toxic to microorganisms (EC50 <0.1 mg l1) and very toxic to algae (EC50 0.1–1 mg l1). Chronic toxicity tests performed on algae have shown high sensitivity to antibacterial agents as deduced from growth inhibition measurements. Antibiotics used in livestock production are excreted in the urine and feces of animals and often appear in manure. They can cause problems in terrestrial ecosystems, such as adverse effects on nitrifying bacteria or growth inhibition of crop plants and weeds. The presence of antibiotics in WWTP influents may also impair treatment processes that use bacteria and cause toxic effects in the downstream aquatic and/or terrestrial ecosystems at different trophic levels. Bacterial cultures from sewage bioreactors receiving waters from a WWTP were tested for resistance against six antibiotics, showing that all were resistant to at least two of the antibiotics, whereas bacteria isolated from receiving waters were only resistant to erythromycin and ampicillin.
Sex Hormones Sex hormones are extremely active biological compounds producing intense therapeutic effects even at very low doses. They can exist as either natural or synthetic substances, mimicking the effects of endogenous estrogens as endocrine-disrupting
Pharmaceuticals Effects in the Environment
compounds (EDCs) through binding to specific receptors common to nontarget organisms (invertebrates, fish, reptiles, birds, and mammals). In fish, estrogens are involved in several physiological functions, including (1) vitellogenin synthesis, (2) vitelline envelope (eggshell) protein production, (3) gonadal differentiation, (4) development of secondary sexual characteristics, (5) gonadotropin secretion, (6) synthesis of estrogen receptors, (7) pheromonal communication, (8) bone formation, and (9) calcium homeostasis. The enhanced production of the vitellogenin found in the blood of male and juvenile fish provides a useful biomarker of aquatic contamination by compounds with estrogenic activity. Ethinylestradiol (EE2) is a synthetic estrogen found in oral contraceptive pills with marked estrogenic effects in fish. The life cycle exposure of fathead minnows to EE2 concentrations <1 ng l1 gave an increased female population and for EE2 concentrations >3.5 ng l1, fish became completely feminized. Similar findings for zebrafish males were registered. Amphibians and reptiles exposed to environmental estrogens showed sex reversal as well as significant changes in secondary sex characteristics.
Antiepileptics These drugs act in the central nervous system (CNS) by reducing the overall neuronal activity. This is achieved either by blocking voltage-dependent sodium channels (carbamazepine) or enhancement of the inhibitory effects of the g-aminobutyric acid (GABA) neurotransmitter (benzodiazepines). Diazepam and carbamazepine are considered potentially harmful to aquatic organisms because most of the acute toxicity data are <100 mg l1. Carbamazepine is lethal to zebrafish at 43 mg l1 and sublethal changes occurred in Daphnia sp. at 92 mg l1. It is important to know that carbamazepine can absorb to sediments, in this way threatening aquatic organisms that feed on organic matter.
b-Blockers b-blockers act by competitive inhibition of b-adrenergic receptors, a class of receptors critical for normal functioning in the sympathetic branch of the vertebrate autonomic nervous system. Within the most commonly used b-blockers propranolol is a nonspecific antagonist, blocking both b1 and b2 receptors, whereas metoprolol and atenolol present b1 receptor specificity. Fish possess b receptors in the heart, liver, and reproductive system; therefore, prolonged exposure to these drugs may cause negative effects. The acute toxicity of propranolol was assessed on the invertebrates Hyalella azteca, D. magna, and C. dubia, obtaining LC50 values of 29.8, 1.6, and 0.8 mg l1, respectively, after a 48h exposure. Acute exposure to nadolol did not affect the survival of the invertebrates. Regarding metoprolol, D. magna and C. dubia exhibited LC50 values of 63.9 and 8.8 mg l1, respectively. Several authors have described significant reduction in heart rate, fecundity, and biomass of D. magna, with LOEC values of
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55, 110, and 440 mg l1, respectively, after chronic exposure to propranolol (9 days), whereas chronic exposure to metoprolol showed higher values. Chronic toxicity tests performed in algae also evidenced their sensitivity to b-blockers, with no observed effect concentration values <1 mg l1.
Antidepressants Serotonin is an important neurotransmitter in hormonal and neuronal mechanisms participating in different regulatory and endocrine functions. Altered levels may cause changes in appetite, the immune system, reproduction, and other behavioral functions. It is also important to lower vertebrates and invertebrates, although associated with different physiological mechanisms from those observed for mammals. In therapeutics, the selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine, paroxetine, and sertraline are the most widely used synthetic antidepressants. Fluoxetine is apparently the most acute toxic human pharmaceutical reported so far, with acute toxicity ranging from an EC50 (48 h, alga) value of 0.024 mg l1 to LC50 (48 h) value of 2 mg l1. Fluoxetine seems to affect phytoplankton more strongly than other aquatic organisms. Fluoxetine, fluvoxamine, paroxetine, citalopram, and sertraline showed negative effects on C. dubia reproduction by reducing the number of neonates or brood per female after 7–8 days of exposure. For the most active compound, sertraline, the LOEC was 45 mg l1 and the NOEC was 9 mg l1.
Mixture Effects Pharmaceuticals do not occur alone in the environment, but as a mixture of different active substances, their metabolites, and transformation products. Ecotoxicological data show that mixtures might have different effects than single compounds, but in general knowledge about the toxicity of the mixture of active substances is still sparse. The simultaneous presence of several pharmaceuticals in the environment might result in a greater toxicity to nontarget organisms than that predicted for individual active substances. An approximation to assess the combined risk of PhACs detected along a basin, based on an additive model that calculates the maximum risk index (RI) for each sampling date and sampling site can be performed as follows: # " 23 X Tox j; k OMECj; k i 0:1 Max RIj; k ¼ i¼1
where i ¼ selected PhAC, j ¼ sampling site, k ¼ sampling date, Toxj,k ¼ acute toxicity for a PhAC, and MEC ¼ measured environmental concentrations. The figure obtained with this approach represents the maximum value that a single PhAC or a combination of PhACs should have for indicating that the measured concentrations do not exceed the acceptable level of long-term risk. The acute/chronic toxicity ratio for a variety of organisms and chemicals was typically on the order of about 10, but much higher values are expected for pharmaceuticals. Thus, the Max RI represents an indicator of potential environmental risk: the lower the value, the higher the potential risk.
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Pharmaceuticals Effects in the Environment
Comparison of Environmental Concentrations and Ecotoxicological Effect Concentrations The potential risk of a substance to the environment is often characterized by comparing the predicted environmental concentration (PEC) with the predicted no effect concentration (PNEC). Because of the lack of experimental ecotoxicity data (particularly chronic) estimation of PNEC, and therefore hazard and risk assessment, is difficult or even impossible to perform. Differences between LOEC and NOEC with maximum concentrations found in WWTP effluent are about one or two orders of magnitude. However, some compounds such as diclofenac, propranolol, or fluoxetine have LOEC values close to WWTP effluent concentration, showing that the safety margin is very small. In any case, more experimental data on chronic toxicity and on the potential bioaccumulation is needed to assess the real environmental risk. Pharmaceuticals are biologically active substances, either with biocidal or physiological activity. Consequently, large inter-endpoint and interspecies sensitivities should be expected. The use of standard approaches, for example, standardized toxicity test with fixed endpoints and species should be considered carefully. The relevance of the species and endpoints should be considered on a case-by-case on the basis of the pharmacokinetics and pharmacodynamics of the specific chemical and drug family.
See also: ‘Toxic’ and ‘Nontoxic’: Confirming Critical Terminology Concepts and Context for Clear Communication; Cumulative (Combined Exposures) Risk Assessment; Ecotoxicology; Aquatic Ecotoxicology; Ecotoxicology, Aquatic Invertebrates; Environmental Exposure Assessment; Environmental Fate and Behavior; Environmental Risk Assessment, Aquatic; Environmental Risk Assessment, Terrestrial; Pollution, Soil; Pollution, Water; Terrestrial Microcosms and Multispecies Soil Systems; The European Medicines Agency (EMA); Toxicity Testing, Aquatic.
Further Reading Cunningham, V.L., Buzby, M., Huthcinson, T., Mastrocco, F., Parke, N., Roden, N., 2006. Effects of human pharmaceuticals on aquatic life: next steps. Environ. Sci. Technol. 40, 3456–3462.
Fent, K., Weston, A.A., Caminada, D., 2006. Ecotoxicology of human pharmaceuticals. Aquat. Toxicol. 76, 122–159. Fernández, C., Alonso, C., Babín, M.M., Pro, J., Carbonell, G., Tarazona, J.V., 2004. Ecotoxicological assessment of Doxycycline in aged pig manure using multispecies soil systems (MS,3). Sci. Total Environ. 323, 63–69. Fernández, C., Gónzalez-Doncel, M., Pro, J., Carbonel, G., Tarazona, J.V., 2010. Occurrence of pharmaceutically active compounds in surface waters of the Henares-Jarama-Tajo river system (Madrid, Spain) and a potential risk characterization. Sci. Total Environ. 408, 543–551. Halling-Sorensen, B., Nors, S., Nielsen, P.F., Lanzky, F., Ingerslev, H.C., Holten, H.C., Jorgensen, S.E., 1998. Occurrence, fate and effects of pharmaceutical substances in the environment – a review. Chemosphere 36, 357–393. Jones, O.A.H., Voulvoulis, N., Lester, J.N., 2002. Aquatic environmental assessment of the top 25 English prescription pharmaceuticals. Water Res. 36, 5013–5022. Kümmerer, Klauss (Ed.), 2004. Pharmaceuticals in the Environment: Sources, Fate, Effects and Risks. Springer-Verlag, Berlin, Heiddelberg, New York. ISBN 3-54021342-2. Quinn, B., Gagne, F., Blaise, C., 2008. An investigation into the acute and chronic toxicity of eleven pharmaceuticals (and their solvents) found in wastewater effluent on the cnidarian, Hydra attenuata. Sci. Total Environ. 389, 306–314. Santos, L., Araujo, A.N., Fachini, A., Pena, A., Delerue-Matos, C., Montenegro, M.C.B.S.M., 2010. Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment. J. Hazard. Mat. 175, 45–95. Staels, B., Dallongeville, J., Auwerx, J., Schoonjans, K., Leitersdorf, E., Fruchart, J.-C., 1998. Mechanism of action of fibrates on lipid and lipoprotein metabolism. Circulation 98, 2088–2093. Tarazona, J.V., Buzby, M.E., Hartmann, A., Housenger, J.E., Olejniczak, K., Sager, N., Servos, M.R., Tolson, N.D., 2005. Scientific basis for aquatic environmental impact assessment of human pharmaceuticals, pp. 269–302. In: Williams, R. (Ed.), Science for Assessing the Impacts of Human Pharmaceuticals on Aquatic Ecosystems. SETAC Press, Pensacola, FL, 368 pp. US EPA, 2009. Targeted National Sewage Sludge Survey Statistical Analysis Report. EPA-822-R-08-018. United States Environmental Protection Agency Office of Water, Washington, DC. Williams, R.T. (Ed.), 2005. Human Pharmaceuticals: Assessing the Impacts on Aquatic Ecosystems. SETAC Press, Pensacola, FL. ISBN 1-880611-82-1. Zuccato, E., Castiglioni, S., Fanelli, R., Reitano, G., Bagnati, R., Chiabrando, C., Pomati, F., Rossetti, C., Clamari, D., 2006. Pharmaceuticals in the environment in Italy: causes, occurrence, effects and control. Environ. Sci. Pollut. Res. Int. 13 (1), 15–21.
Relevant Websites Pharmaceuticals and Personal Care Products as Pollutants (PPCPs). US Environmental Protection Agency. www.epa.gov/ppcp/ Cemagref, 2007. Environmental database for pharmaceuticals: http://pharmaecobase. lyon.cemagref.fr/. GHS, 2007. Globally Harmonized System for the classification and labelling of chemicals: http://www.unece.org/trans/danger/publi/ghs/ghs_welcome_e.html. NOAA, 2006. United States National Oceanic and Atmospheric Administration (NOAA), Pharmaceuticals in the environment: http://www.chbr.noaa.gov/peiar/. Roche, 2007. Pharmaceuticals sustainability database: http://www.roche.com/home/ sustainability/
Introduction The presence of pharmaceutically active compounds (PhACs) in the environment can pose significant human and wildlife health threats. Pharmaceuticals were initially identified in the mid1970s associated with wastewater treatment plant (WWTP) effluents in the United States. During the 1980s, there has been only little interest in this type of contamination. It has not been until this last decade that social concern has been aroused for a potential risk to ecosystems. The increased concern on the ecological effects of PhACs was initiated largely as a result of a growing number of technical papers reporting detectable levels of pharmaceuticals in WWTP effluents, surface waters, drinking waters, and sediments. For instance, >100 pharmaceuticals and personal care products have been detected in effluents of WWTPs in several countries of the European Union. The current awareness of emergent pollutants is the result of new advances in analytical techniques capable of revealing the presence of these substances at very low levels. Presumably, they have been in the environment, undetected, since their use began. These compounds and their metabolites continuously enter the aquatic environment largely through effluents from WWTPs because of incomplete elimination or sporadic direct wastewater discharge. Even low concentrations of these substances may lead to unwanted effects in aquatic systems. Although pharmaceuticals are designed as bioactive molecules to treat diseases, they can affect nontarget organisms, with harmful effects reported at environmentally relevant concentrations. Concern is such that several reviews recently published have dealt with the exposure of humans or biota to pharmaceuticals. The environmental concerns about these compounds are linked to two main factors: (1) the bioactive property of pharmaceuticals and (2) their capacity to be routinely present in aquatic environments. This situation has resulted in their characterization as ‘pseudo’ persistent compounds. The scientific community is in broad agreement on the possibility that adverse effects not only for human health but also for aquatic organisms may arise from the presence of pharmaceuticals. Several almost negligible effects have been shown to occur from continuous exposure during the life cycle of aquatic vertebrates and invertebrates to subtherapeutic drug concentrations. These effects slowly accumulate and manifest themselves as a final irreversible condition that is frequently only noticed several generations later, affecting the sustainability of aquatic organism populations.
Sources of PhACs Environmental Contamination The main pathway for environmental contamination of medicines is via the metabolic excretion (nonmetabolized
844
parent drug, parent–drug conjugates, and bioactive metabolites) in urine and faces, although other anthropogenic mechanisms should be assumed: a) Disposal of unused/outdated medication to sewage systems b) Release of treated/untreated hospital wastes to domestic sewage systems c) Release to private septic/leach fields: treated effluent from domestic sewage treatment plants discharged to surface waters d) Transfer of sewage solids (‘biosolids’) to land as amendments/fertilizers e) Direct release to open waters via washing, bathing, or swimming f) Discharge of regulated/controlled industrial manufacturing waste streams g) Direct release from aquaculture facilities (fish farming)
Environmental Fate In general, a wide-dispersive environmental release should be assumed. After human or animal treatment, most drugs are excreted partly nonmetabolized. Some, such as X-ray contrast media, are excreted as a parent drug. PhACs as well as disinfectants are used in medicine, which enter municipal sewage and WWTPs. Pharmaceuticals not readily degraded in WWTPs are being discharged in treated effluents, resulting in the contamination of surface waters, groundwater, and drinking water. In addition, the conjugated metabolites can be hydrolyzed, releasing the parent drug or Phase I metabolites. When sewage sludge is applied to agricultural fields, contamination of soil, runoff into surface water, and drainage may occur. In addition, veterinary drugs may enter aquatic systems via manure application to fields and subsequent runoff. Drugs used in animal husbandry as well as aquaculture are also discharged into the environment. Finally, PhACs reach groundwater via soil after manure or sewage sludge application as fertilizers (see Figure 1).
Environmental Concentrations Since 1976, when Garrison et al. reported the occurrence of clofibric acid, in the range 0.2–2 mg l1, in treated wastewater in the United States, pharmaceuticals have been detected in many countries around the world. In the last decade, specialized literature has supplied a lot of data on PhAC concentration in surface and groundwater, WWTP influents and effluents, soils, sediments, biosolids, biota, and so on. Environmental concentrations of pharmaceuticals have been mainly reported in WWTP effluents and surface water. WWTP effluent concentrations range from ng l1 to mg l1. In surface water, the level of contamination
Encyclopedia of Toxicology, Volume 3
http://dx.doi.org/10.1016/B978-0-12-386454-3.00571-6
Pharmaceuticals Effects in the Environment
PhACs for human use
Excretion (hospital effluents)
Excretion (WWTPs effluents)
Municipal effluents
845
PhACs for veterinary use
Disposal of unused/outdated medication Domestic sewage
Excretion
Manure
Agro industrial effluents WWTPs
Sewage sludges
Surface water
Aquaculture
Figure 1
Landfields
Soil
Groundwater
Drinking water Pharmaceutical Industry
Sources, distribution, and sinks of PhACs in the environment.
is in the range of ng l1. Data have been compiled up to 2006 and are reviewed by Fent et al., as shown in Figure 2. After reaching WWTPs, PhACs are degradated and partitioned in effluent and sewage sludge. Mean concentration levels of the PhACs ranged between 20 and 4000 mg kg1 dw, 15 and 1000 mg kg1 dw, 3 and 600 mg kg1 dw, and 10 and
1000 mg kg1 dw in primary, secondary, digested sludge, and compost, respectively. The highest ecotoxicological risk, in digested sludge and compost, was caused by the estrogenic compound 17b-estradiol. The ecotoxicological risk significantly decreased after the application of digested sludge or compost to the soils.
Figure 2 PhAC concentration in treated wastewater and surface water (Fent, K., Weston, A.A., Caminada, D., 2006. Ecotoxicology of human pharmaceuticals. Aquat. Toxicol. 76, 122–159.).
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Pharmaceuticals Effects in the Environment
A survey of 72 pharmaceuticals in US biosolids found two (ciprofloxacin, diphenhydramine) in all samples (n ¼ 84) and eight in at least 80 of the biosolid samples analyzed. However, 15 pharmaceuticals were not found in any sample, and 29 were present in fewer than three samples. Maximum concentrations of tetracycline (range: 0.04–5.3; mean: 1.3 mg kg1 dw) and ciprofloxacin (range: 0.08–41.0; mean: 10.5 mg kg1 dw).
Ecotoxicological Effects Nonsteroidal Antiinflammatory Drugs (NSAIDs) Nonsteroidal antiinflammatory drugs (NSAIDs) are weak acids that act by reversible or irreversible inhibition of one or both isoforms of the cyclooxygenase enzymes COX-1 and COX-2, which are involved in the synthesis of different prostaglandins from arachidonic acid. Diclofenac is the compound that has the highest acute toxicity within the class of NSAIDs. For all tests performed on this compound, the effect concentrations were <100 mg l1. Ibuprofen also presents chronic toxicity. Female Japanese medaka (Oryzias latipes) exposed to different concentrations of the drug over 6 weeks, showed a sharp rise in liver weight together with enhanced egg production, yet with a reduction in the number of weekly spawning events. The water flea Daphnia magna population growth rate was significantly reduced at concentrations ranging from 0 to 80 mg l1. Reproduction was affected at all concentrations and completely inhibited at the highest pharmaceutical level. Regarding aquatic photosynthetic organisms, specific effects have been noticed. A 5-day exposure to concentrations in the 1–1000 mg l1 range stimulated the growth of the cyanobacterium Synechocystis sp., whereas inhibiting that of the duckweed plant Lemna minor after 7 days. Acute toxicity tests performed on the rotifer Brachionus calyciflorus, the water flea Ceriodaphnia dubia, and the fairy shrimp Thamnocephalus platyurus showed that naproxen had EC50 values within the range 1–100 mg l1, with photolysis products being significantly more toxic. Highly chronic toxic properties were noticed with algae. Paracetamol (or acetaminophen) is a weak inhibitor of the cyclooxygenase enzyme, whose side effects are mainly associated with the formation of hepatotoxic metabolites, such as N-acetyl-p-benzoquinone imine when the levels of liver glutathione are low. Tests were carried out on algae, water fleas, fish embryos, luminescent bacteria, and ciliates. The most sensitive species was shown to be D. magna, for which EC50 values reported from 30 to 50 mg l1.
Blood Lipid-Lowering Agents Statins and fibrates are basically the two types of antilipidemic drugs. Both are used to decrease the concentration of cholesterol (statins and fibrates) and triglycerides (fibrates) in the blood plasma. Statins act by inhibiting the 3-hydroxymethylglutaryl coenzyme A reductase, an enzyme involved in feedback control of cholesterol synthesis. In response, the number of LDL
lipoprotein receptors at hepatocyte surfaces increases, thus lowering the circulating LDL cholesterol. Acute toxicity of lipid-lowering agents is not extensively reported. Several authors found LC50 values of 1.18 and 10 mg l1 in larval and adult grass shrimp (Palaemonetes pugio), respectively, after an exposure of 96 h to simvastatin. Simvastatin exhibited an EC50 of 22.8 mg l1 after 96 h for the marine phytoplankton Dunaliella tertiolecta. Atorvastatin can affect the development of the duckweed. Lemna gibba showed an lowest observed effect concentration of 300 mg l1 for parameters such as wet mass, frond number, chlorophyll-a, and carotenoid content for a time of exposure of 7 days. Fibrates act by activating specific transcription factors belonging to the nuclear hormone receptor superfamily known as peroxisome proliferator activated receptors (PPARs) (Staels et al., 1998). There are three types of PPARs related to different cellular events. PPAR-a and PPAR-b play key roles in catabolism and storage of fatty acids, whereas PPAR-g plays an important role in cellular differentiation. According to Quinn et al. (2008), gemfibrozil could be classified as toxic (EC50 1–10 mg l1) and bezafibrate as harmful for nontarget organisms (EC50 10–100 mg l1). Toxic properties of gemfibrozil were also investigated on the inhibition of the bacterium Vibrio fischeri luminescence, growth inhibition of the alga Chlorella vulgaris, and immobilization of the D. magna. Both the bacteria and the water flea were sensitive to gemfibrozil, with the latter being the most sensitive, having an EC50 of 30 mg l1 after 72 h.
Antibiotics The major concern is associated with the development of resistance mechanisms by bacteria that can subsequently compromise public health by means of treatment effectiveness. According to Jones et al. (2002), antibiotics could be classified as extremely toxic to microorganisms (EC50 <0.1 mg l1) and very toxic to algae (EC50 0.1–1 mg l1). Chronic toxicity tests performed on algae have shown high sensitivity to antibacterial agents as deduced from growth inhibition measurements. Antibiotics used in livestock production are excreted in the urine and feces of animals and often appear in manure. They can cause problems in terrestrial ecosystems, such as adverse effects on nitrifying bacteria or growth inhibition of crop plants and weeds. The presence of antibiotics in WWTP influents may also impair treatment processes that use bacteria and cause toxic effects in the downstream aquatic and/or terrestrial ecosystems at different trophic levels. Bacterial cultures from sewage bioreactors receiving waters from a WWTP were tested for resistance against six antibiotics, showing that all were resistant to at least two of the antibiotics, whereas bacteria isolated from receiving waters were only resistant to erythromycin and ampicillin.
Sex Hormones Sex hormones are extremely active biological compounds producing intense therapeutic effects even at very low doses. They can exist as either natural or synthetic substances, mimicking the effects of endogenous estrogens as endocrine-disrupting
Pharmaceuticals Effects in the Environment
compounds (EDCs) through binding to specific receptors common to nontarget organisms (invertebrates, fish, reptiles, birds, and mammals). In fish, estrogens are involved in several physiological functions, including (1) vitellogenin synthesis, (2) vitelline envelope (eggshell) protein production, (3) gonadal differentiation, (4) development of secondary sexual characteristics, (5) gonadotropin secretion, (6) synthesis of estrogen receptors, (7) pheromonal communication, (8) bone formation, and (9) calcium homeostasis. The enhanced production of the vitellogenin found in the blood of male and juvenile fish provides a useful biomarker of aquatic contamination by compounds with estrogenic activity. Ethinylestradiol (EE2) is a synthetic estrogen found in oral contraceptive pills with marked estrogenic effects in fish. The life cycle exposure of fathead minnows to EE2 concentrations <1 ng l1 gave an increased female population and for EE2 concentrations >3.5 ng l1, fish became completely feminized. Similar findings for zebrafish males were registered. Amphibians and reptiles exposed to environmental estrogens showed sex reversal as well as significant changes in secondary sex characteristics.
Antiepileptics These drugs act in the central nervous system (CNS) by reducing the overall neuronal activity. This is achieved either by blocking voltage-dependent sodium channels (carbamazepine) or enhancement of the inhibitory effects of the g-aminobutyric acid (GABA) neurotransmitter (benzodiazepines). Diazepam and carbamazepine are considered potentially harmful to aquatic organisms because most of the acute toxicity data are <100 mg l1. Carbamazepine is lethal to zebrafish at 43 mg l1 and sublethal changes occurred in Daphnia sp. at 92 mg l1. It is important to know that carbamazepine can absorb to sediments, in this way threatening aquatic organisms that feed on organic matter.
b-Blockers b-blockers act by competitive inhibition of b-adrenergic receptors, a class of receptors critical for normal functioning in the sympathetic branch of the vertebrate autonomic nervous system. Within the most commonly used b-blockers propranolol is a nonspecific antagonist, blocking both b1 and b2 receptors, whereas metoprolol and atenolol present b1 receptor specificity. Fish possess b receptors in the heart, liver, and reproductive system; therefore, prolonged exposure to these drugs may cause negative effects. The acute toxicity of propranolol was assessed on the invertebrates Hyalella azteca, D. magna, and C. dubia, obtaining LC50 values of 29.8, 1.6, and 0.8 mg l1, respectively, after a 48h exposure. Acute exposure to nadolol did not affect the survival of the invertebrates. Regarding metoprolol, D. magna and C. dubia exhibited LC50 values of 63.9 and 8.8 mg l1, respectively. Several authors have described significant reduction in heart rate, fecundity, and biomass of D. magna, with LOEC values of
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55, 110, and 440 mg l1, respectively, after chronic exposure to propranolol (9 days), whereas chronic exposure to metoprolol showed higher values. Chronic toxicity tests performed in algae also evidenced their sensitivity to b-blockers, with no observed effect concentration values <1 mg l1.
Antidepressants Serotonin is an important neurotransmitter in hormonal and neuronal mechanisms participating in different regulatory and endocrine functions. Altered levels may cause changes in appetite, the immune system, reproduction, and other behavioral functions. It is also important to lower vertebrates and invertebrates, although associated with different physiological mechanisms from those observed for mammals. In therapeutics, the selective serotonin reuptake inhibitors (SSRIs) fluoxetine, fluvoxamine, paroxetine, and sertraline are the most widely used synthetic antidepressants. Fluoxetine is apparently the most acute toxic human pharmaceutical reported so far, with acute toxicity ranging from an EC50 (48 h, alga) value of 0.024 mg l1 to LC50 (48 h) value of 2 mg l1. Fluoxetine seems to affect phytoplankton more strongly than other aquatic organisms. Fluoxetine, fluvoxamine, paroxetine, citalopram, and sertraline showed negative effects on C. dubia reproduction by reducing the number of neonates or brood per female after 7–8 days of exposure. For the most active compound, sertraline, the LOEC was 45 mg l1 and the NOEC was 9 mg l1.
Mixture Effects Pharmaceuticals do not occur alone in the environment, but as a mixture of different active substances, their metabolites, and transformation products. Ecotoxicological data show that mixtures might have different effects than single compounds, but in general knowledge about the toxicity of the mixture of active substances is still sparse. The simultaneous presence of several pharmaceuticals in the environment might result in a greater toxicity to nontarget organisms than that predicted for individual active substances. An approximation to assess the combined risk of PhACs detected along a basin, based on an additive model that calculates the maximum risk index (RI) for each sampling date and sampling site can be performed as follows: # " 23 X Tox j; k OMECj; k i 0:1 Max RIj; k ¼ i¼1
where i ¼ selected PhAC, j ¼ sampling site, k ¼ sampling date, Toxj,k ¼ acute toxicity for a PhAC, and MEC ¼ measured environmental concentrations. The figure obtained with this approach represents the maximum value that a single PhAC or a combination of PhACs should have for indicating that the measured concentrations do not exceed the acceptable level of long-term risk. The acute/chronic toxicity ratio for a variety of organisms and chemicals was typically on the order of about 10, but much higher values are expected for pharmaceuticals. Thus, the Max RI represents an indicator of potential environmental risk: the lower the value, the higher the potential risk.
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Pharmaceuticals Effects in the Environment
Comparison of Environmental Concentrations and Ecotoxicological Effect Concentrations The potential risk of a substance to the environment is often characterized by comparing the predicted environmental concentration (PEC) with the predicted no effect concentration (PNEC). Because of the lack of experimental ecotoxicity data (particularly chronic) estimation of PNEC, and therefore hazard and risk assessment, is difficult or even impossible to perform. Differences between LOEC and NOEC with maximum concentrations found in WWTP effluent are about one or two orders of magnitude. However, some compounds such as diclofenac, propranolol, or fluoxetine have LOEC values close to WWTP effluent concentration, showing that the safety margin is very small. In any case, more experimental data on chronic toxicity and on the potential bioaccumulation is needed to assess the real environmental risk. Pharmaceuticals are biologically active substances, either with biocidal or physiological activity. Consequently, large inter-endpoint and interspecies sensitivities should be expected. The use of standard approaches, for example, standardized toxicity test with fixed endpoints and species should be considered carefully. The relevance of the species and endpoints should be considered on a case-by-case on the basis of the pharmacokinetics and pharmacodynamics of the specific chemical and drug family.
See also: ‘Toxic’ and ‘Nontoxic’: Confirming Critical Terminology Concepts and Context for Clear Communication; Cumulative (Combined Exposures) Risk Assessment; Ecotoxicology; Aquatic Ecotoxicology; Ecotoxicology, Aquatic Invertebrates; Environmental Exposure Assessment; Environmental Fate and Behavior; Environmental Risk Assessment, Aquatic; Environmental Risk Assessment, Terrestrial; Pollution, Soil; Pollution, Water; Terrestrial Microcosms and Multispecies Soil Systems; The European Medicines Agency (EMA); Toxicity Testing, Aquatic.
Further Reading Cunningham, V.L., Buzby, M., Huthcinson, T., Mastrocco, F., Parke, N., Roden, N., 2006. Effects of human pharmaceuticals on aquatic life: next steps. Environ. Sci. Technol. 40, 3456–3462.
Fent, K., Weston, A.A., Caminada, D., 2006. Ecotoxicology of human pharmaceuticals. Aquat. Toxicol. 76, 122–159. Fernández, C., Alonso, C., Babín, M.M., Pro, J., Carbonell, G., Tarazona, J.V., 2004. Ecotoxicological assessment of Doxycycline in aged pig manure using multispecies soil systems (MS,3). Sci. Total Environ. 323, 63–69. Fernández, C., Gónzalez-Doncel, M., Pro, J., Carbonel, G., Tarazona, J.V., 2010. Occurrence of pharmaceutically active compounds in surface waters of the Henares-Jarama-Tajo river system (Madrid, Spain) and a potential risk characterization. Sci. Total Environ. 408, 543–551. Halling-Sorensen, B., Nors, S., Nielsen, P.F., Lanzky, F., Ingerslev, H.C., Holten, H.C., Jorgensen, S.E., 1998. Occurrence, fate and effects of pharmaceutical substances in the environment – a review. Chemosphere 36, 357–393. Jones, O.A.H., Voulvoulis, N., Lester, J.N., 2002. Aquatic environmental assessment of the top 25 English prescription pharmaceuticals. Water Res. 36, 5013–5022. Kümmerer, Klauss (Ed.), 2004. Pharmaceuticals in the Environment: Sources, Fate, Effects and Risks. Springer-Verlag, Berlin, Heiddelberg, New York. ISBN 3-54021342-2. Quinn, B., Gagne, F., Blaise, C., 2008. An investigation into the acute and chronic toxicity of eleven pharmaceuticals (and their solvents) found in wastewater effluent on the cnidarian, Hydra attenuata. Sci. Total Environ. 389, 306–314. Santos, L., Araujo, A.N., Fachini, A., Pena, A., Delerue-Matos, C., Montenegro, M.C.B.S.M., 2010. Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment. J. Hazard. Mat. 175, 45–95. Staels, B., Dallongeville, J., Auwerx, J., Schoonjans, K., Leitersdorf, E., Fruchart, J.-C., 1998. Mechanism of action of fibrates on lipid and lipoprotein metabolism. Circulation 98, 2088–2093. Tarazona, J.V., Buzby, M.E., Hartmann, A., Housenger, J.E., Olejniczak, K., Sager, N., Servos, M.R., Tolson, N.D., 2005. Scientific basis for aquatic environmental impact assessment of human pharmaceuticals, pp. 269–302. In: Williams, R. (Ed.), Science for Assessing the Impacts of Human Pharmaceuticals on Aquatic Ecosystems. SETAC Press, Pensacola, FL, 368 pp. US EPA, 2009. Targeted National Sewage Sludge Survey Statistical Analysis Report. EPA-822-R-08-018. United States Environmental Protection Agency Office of Water, Washington, DC. Williams, R.T. (Ed.), 2005. Human Pharmaceuticals: Assessing the Impacts on Aquatic Ecosystems. SETAC Press, Pensacola, FL. ISBN 1-880611-82-1. Zuccato, E., Castiglioni, S., Fanelli, R., Reitano, G., Bagnati, R., Chiabrando, C., Pomati, F., Rossetti, C., Clamari, D., 2006. Pharmaceuticals in the environment in Italy: causes, occurrence, effects and control. Environ. Sci. Pollut. Res. Int. 13 (1), 15–21.
Relevant Websites Pharmaceuticals and Personal Care Products as Pollutants (PPCPs). US Environmental Protection Agency. www.epa.gov/ppcp/ Cemagref, 2007. Environmental database for pharmaceuticals: http://pharmaecobase. lyon.cemagref.fr/. GHS, 2007. Globally Harmonized System for the classification and labelling of chemicals: http://www.unece.org/trans/danger/publi/ghs/ghs_welcome_e.html. NOAA, 2006. United States National Oceanic and Atmospheric Administration (NOAA), Pharmaceuticals in the environment: http://www.chbr.noaa.gov/peiar/. Roche, 2007. Pharmaceuticals sustainability database: http://www.roche.com/home/ sustainability/