Optimal conditions for three brood chronic toxicity test method using a freshwater macroinvertebrate Moina macrocopa

Di (2-ethylhexyl) phthalate effects on the growth, development, and reproduction of Moina macrocopa (Crustacea: Cladocera)

Di (2-ethylhexyl) phthalate (DEHP) is used as a plasticizer in plastics. The effects of DEHP on terrestrial vertebrates have been extensively reported but the effects of DEHP contamination on aquatic ecosystems have not been thoroughly studied. Since water bodies are one of the main mediums through which DEHP is released worldwide, the impacts of DEHP contamination should be manifested in water fleas. Therefore, maternal Moina macrocopa were exposed to 1, 10, 100, and 1000 μg/L concentrations of DEHP. Changes in growth and reproduction were evaluated. The findings demonstrated that DEHP exposure did not have a negative impact on growth or the ability to reproduce. An analysis of the ovary yolk body (YB) demonstrated that the average size and number of yolk bodies (YBs) produced by M. macrocopa exposed to 1000 μg/L DEHP were not significantly different to the average size and number of YBs produced in blank control and solvent control conditions. These outcomes support the cellular pathology data gathered by other researchers. Nevertheless, when M. macrocopa was exposed to 1000 μg/L DEHP for five days, a significant increase in YB numbers was observed with changes in YB morphology. The critical cellular pathology of YB showed morphological abnormalities, including rod-shaped YBs, and YB density was higher than in the blank and solvent controls. Even though these results suggest that antioxidative stress can be induced by DEHP exposure, growth, and reproduction were not significantly different among exposed water fleas compared to fleas in the blank and solvent controls. The result was attributed to the antioxidant response of the water flea. In conclusion, the present study enhances our understanding of previous findings from risk assessments of DEHP contamination in aquatic ecosystems.

Toxicity of triclosan, an antimicrobial agent, to a nontarget freshwater zooplankton species, Moina macrocopa

The toxicity of triclosan (TCS) on the freshwater cladoceran Moina macrocopa was investigated by acute and chronic toxicity assessments followed by genotoxicity and oxidative stress response analyses. The 48-h LC50 of TCS for ≤24-h-old M. macrocopa was determined as 539 μg L-1 . Chronic exposure to TCS at concentrations ranging from 5 to 100 μg L-1 showed a stimulatory effect at low concentrations (≤10 μg L-1 ) and an inhibitory effect at high concentrations (≥50 μg L-1 ) on growth, reproduction, and population-growth-related parameters of M. macrocopa. The genotoxicity test results indicated that TCS concentrations ranging from 50 to 100 μg L-1 can alter individuals' DNA. Analysis of the antioxidant enzymes catalase (CAT) and glutathione s-transferase (GST) demonstrated increased levels of these enzymes at high TCS concentrations. Our results indicated that TCS concentrations found in the natural environment have minimal acute toxicity to M. macrocopa. However, TCS at even low concentrations can significantly affect its growth, reproduction, and population-growth-related characteristics. The observed responses suggest a hormetic dose-response pattern and imply a potential endocrine-disrupting effect of TCS. Our molecular and biochemical findings indicated that high concentrations of TCS have the potential to induce oxidative stress that may lead to DNA alterations in M. macrocopa.

First complete mitochondrial genome from family Moinidae, Moina macrocopa (Straus, 1820) (Cladocera; Moinidae)

We sequenced and annotated the complete mitochondrial genome for the freshwater water flea Moina macrocopa (Straus, 1820). This is the first mitogenome for the family Moinidae. The complete mitogenome of M. macrocopa is 16,072 bp, with 35.8% A, 17.6% C, 12.8% G, and 33.8% T. The mitogenome comprises 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a non-coding region. Phylogenomic analysis based on 28 in-group taxa belonging to the orders Anostraca, Diplostraca, and Notostraca is congruent with published phylogenetic relationship for cladocerans, with M. macrocopa being grouped with members of the Daphniidae. This mitogenome resource will be useful for future phylogenetic studies of water fleas.

Application and validation of a biotic ligand model for calculating acute toxicity of lead to Moina dubia in lakes of Hanoi, Vietnam

It is increasingly being recognized that biotic ligand models (BLMs) can successfully predict the toxicity of divalent metals toward aquatic biota applied to temperate freshwater ecosystems. However, studies on the eutrophic lakes in tropical regions toward native tropical organisms, including Moina, are relatively limited. In this study, Moina dubia, the native organism of the Hanoi eutrophic urban lakes, were used in toxicological studies of lead (Pb); 24-h EC₅₀ value of Pb was 523.19 µg/L under optimal living conditions for M. dubia in the laboratory. The constant binding of Pb²⁺ on M. dubia surface sites (log K_PbBL = 2.38) was significantly low. Other stability constants were obtained under experiments as logK_CaBL = 2.48, logK_MgBL = 2.80, logK_NaBL = 2.35, logK_KBL = 2.49, and logK_HBL = 3.026. A BLM was developed to calculate the acute toxicity (EC₅₀-24 h) of lead on M. dubia based on the condition of the urban lakes of Hanoi. Validation with toxicity data in synthetic medium showed a coefficient determination of 79.16% and a mean absolute percentage error (MAPE) of 10.2%, while the validation with the toxicity data with natural water medium from 11 Hanoi lakes showed a coefficient determination of 73.7% and a MAPE of 13.66%. The BLM worked well with water at a pH of 7.0 to 8.0, but failed with water at a pH above 8.0. Eutrophic conditions proved to have a significant effect on the toxicity of lead on local zooplankton.

Ecological Risk Assessment of Amoxicillin, Enrofloxacin, and Neomycin: Are Their Current Levels in the Freshwater Environment Safe?

Veterinary pharmaceuticals may cause unexpected adverse effects on non-target aquatic species. While these pharmaceuticals were previously identified as priority compounds in ambient water, their ecological risks are relatively unknown. In this study, a series of chronic toxicity tests were conducted for these pharmaceuticals using algae, two cladocerans, and a fish. After a 21-d exposure to amoxicillin, enrofloxacin, and neomycin, no observed effect concentration (NOEC) for the reproduction of Daphnia magna was detected at 27.2, 3.3, and 0.15 mg/L, respectively. For the survival of juvenile Oryzias latipes following the 40-d exposure, NOEC was found at 21.8, 3.2, and 0.87 mg/L, respectively. Based on the results of the chronic toxicity tests and those reported in the literature, predicted no-effect concentrations (PNECs) were determined at 0.078, 4.9, and 3.0 µg/L for amoxicillin, enrofloxacin, and neomycin, respectively. Their hazard quotients (HQs) were less than 1 at their average levels of occurrence in ambient freshwater. However, HQs based on the maximum detected levels of amoxicillin and enrofloxacin were determined at 21.2 and 6.1, respectively, suggesting potential ecological risks. As the potential ecological risks of these veterinary pharmaceuticals at heavily contaminated sites cannot be ignored, hotspot delineation and its management are required.

Reversible and irreversible transgenerational effects of metal exposure on nine generations of a tropical micro-crustacean

Micro-crustaceans are important grazers that control the algal blooms in eutrophic lakes. However, we know little about how these key species may be affected by long-term exposure to contaminants and when the transgenerational effects are reversible and irreversible. To address this, we investigated the effects of lead (Pb, 100 μg L^-1) exposure on morphology and reproduction of Moina dubia for nine consecutive generations (F1-F9) in three treatments: control, Pb, and pPb (M. dubia from Pb-exposed parents returned to the control condition). In F1-F2, Pb did not affect morphology, and reproduction of M. dubia. In all later generations, Pb-exposed M. dubia had a smaller body and shorter antennae than those in control. In F3-F6, pPb-exposed animals showed no differences in body size and antennae compared to the control, suggesting recoverable effects. In F7-F9, the body size and antennae of pPb-exposed animals did not differ compared to Pb-exposed ones, and both were smaller than the control animals, suggesting irreversible effects. Pb exposure reduced the brood size, number of broods and total neonates per female in F3-F9, yet the reproduction could recover in pPb treatment until F7. No recovery of the brood size and number of broods per female was observed in pPb-exposed animals in the F8-F9. Our study suggests that long-term exposure to metals, here Pb, may cause irreversible impairments in morphology and reproduction of tropical urban micro-crustaceans that may lower the top-down control on algal blooms and functioning of eutrophic urban lakes.

Chronic toxicity of endocrine disrupting chemicals used in plastic products in Korean resident species: Implications for aquatic ecological risk assessment

In this study, chronic toxicity of three endocrine disrupting chemicals (EDCs) used to make plastic products (i.e., bisphenol A (BPA), bis(2-ethylhexyl)phthalate (DEHP) and nonylphenol (NP)) in a Korean resident fish (Cyprinus carpio), crustacean (Moina macrocopa) and green alga (Pseudokirchneriella subcapitata) species was tested. It was found that M. macrocopa was particularly sensitive to those EDCs, especially DEHP and NP. We exposed M. macrocopa to DEHP (0.0012-0.1 mg/L) and NP (0.00037-0.03 mg/L), and as a result, both chemicals significantly delayed the first day of reproduction. The no observed effect concentrations (NOECs) of DEHP and NP for this endpoint were determined to be 0.0012 and 0.00037 mg/L, respectively, which are far lower than NOECs for any other freshwater species. Existing water quality criteria of various governmental agencies do not consider the toxicity of those EDCs on M. macrocopa, and thus, use of the existing criteria for the risk assessment of the Korean freshwater environment may underestimate the ecological risk. This study recommends using the water quality criteria derived in this study (0.95 μg/L for DEHP and 0.16 μg/L for NP) based on the chronic toxicity data on Korean resident species including M. macrocopa for the aquatic ecological risk assessment in Korea rather than adopting the existing water quality criteria.

Chronic effects of bisphenol S and bisphenol SIP on freshwater waterflea and ecological risk assessment

Bisphenol S (BPS) and 4-hydroxyphenyl 4-isoprooxyphenylsulfone (BPSIP) have been used as substitutes for bisphenol A (BPA) owing to increased regulation of BPA in plastics. In this study, long-term toxicity tests of BPS and BPSIP were performed using Daphnia magna and Moina macrocopa. The predicted no-effect concentration (PNEC) of BPA, BPS, and BPSIP were derived by the assessment factor (AF) method and the species sensitivity distribution (SSD) method. An ecological risk assessment was performed based on the measured environmental concentrations of BPA in surface water worldwide and the derived PNECs. The chronic NOEC of D. magna was 2.5 mg/L for BPS and 0.5 mg/L for BPSIP, and that of M. macrocopa was 0.03 mg/L for BPS and 0.1 mg/L for BPSIP. The PNEC_AF was generally one order of magnitude less than the PNEC_SSD, and the PNEC of BPS was 10 times lower than that of BPA. The hazard quotients of BPA and BPS exceeded 1, indicating that concentrations in ambient water conditions could pose a potential risk to aquatic organisms. Since the use of alternative compounds is increasing, further monitoring data of the water environment and chronic toxicity in various aquatic organisms appears to be necessary.

Chronic toxicity and endocrine disruption of naproxen in freshwater waterfleas and fish, and steroidogenic alteration using H295R cell assay

Naproxen is a non-steroidal anti-inflammatory drug (NSAID) and has been frequently detected in surface waters around the world. Although endocrine disruption and reproduction related effects of NSAIDs are of increasing concern, the ecotoxicity of naproxen in aquatic organisms is limited primarily to acute lethal effects. In this study, chronic toxicity of naproxen was evaluated employing two daphnids (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). The effects of naproxen on sex steroid hormones and gene transcription related to steroidogenesis were also evaluated in H295R cells. The chronic no observed effect concentrations (NOECs) of naproxen for reproduction were determined to be 10 mg L^-1 in D. magna and 0.3 mg L^-1 in M. macrocopa. At concentrations of 0.5 mg L^-1, the survival of juvenile medaka fish was significantly decreased and transcription of erβ2 gene was significantly increased. Concentration of 17β-estradiol (E2) and the ratio of E2 and testosterone were significantly increased in H295R cells at 10 mg L^-1, suggesting that naproxen could modulate sex hormone production. The current detected levels of naproxen in ambient Korean rivers are far lower than the effective levels, however potential adverse effects cannot be ignored in some highly polluted areas. Endocrine disruption effects in fish warrant further investigation particularly for their ecological implications.

Transgenerational Effects of Toxicants: An Extension of the Daphnia 21-day Chronic Assay?

The assessment of transgenerational effects should be incorporated in standard chronic toxicity protocols for the sake of a realistic extrapolation of contaminant effects to the population level. We propose a simple add-on to the standard 21-day chronic Daphnia magna assay, allowing the assessment of the reproductive performance of the offspring (F₁ generation) born from the first clutch of the parental (F₀) generation. The extended generational assay was performed simultaneously with the standard reproduction assay. With this design, we evaluated the lethal, reproductive, and transgenerational effects of four widespread and extensively used substances: a biocide/anti-fouling (copper sulphate), an industrial oxidizing agent (potassium dichromate), a pharmaceutical (paracetamol), and a quaternary ammonium compound (benzalkonium chloride). Benzalkonium chloride was the most toxic in terms of lethality, whereas paracetamol, copper sulphate, and potassium dichromate caused deleterious effects in the reproductive performance of exposed D. magna. Adverse effects in the fitness of the daughter (F₁) generation were observed in the case of maternal exposure to paracetamol and copper sulphate, although they were not very pronounced. These findings highlight the usefulness of our approach and reinforce the view-shared by other authors-of the need for a generalised formal assessment of the transgenerational effects of pollutants.

Toxicity of nickel to tropical freshwater and sediment biota: A critical literature review and gap analysis

More than two-thirds of the world's nickel (Ni) lateritic deposits are in tropical regions, and just less than half are within South East Asia and Melanesia (SEAM). With increasing Ni mining and processing in SEAM, environmental risk assessment tools are required to ensure sustainable development. Currently, there are no tropical-specific water or sediment quality guideline values for Ni, and the appropriateness of applying guideline values derived for temperate systems (e.g., Europe) to tropical ecosystems is unknown. Databases of Ni toxicity and toxicity tests for tropical freshwater and sediment species were compiled. Nickel toxicity data were ranked, using a quality assessment, identifying data to potentially use to derive tropical-specific Ni guideline values. There were no data for Ni toxicity in tropical freshwater sediments. For tropical freshwaters, of 163 Ni toxicity values for 40 different species, high-quality chronic data, based on measured Ni concentrations, were found for just 4 species (1 microalga, 2 macrophytes, and 1 cnidarian), all of which were relevant to SEAM. These data were insufficient to calculate tropical-specific guideline values for long-term aquatic ecosystem protection in tropical regions. For derivation of high-reliability tropical- or SEAM-specific water and sediment quality guideline values, additional research effort is required. Using gap analysis, we recommend how research gaps could be filled. Environ Toxicol Chem 2018;37:293-317. © 2017 SETAC.

Gamma irradiation of resting eggs of Moina macrocopa affects individual and population performance of hatchlings

We investigated the effects of γ-radiation on the survival of resting eggs of the cladoceran Moina macrocopa, on the parameters of the life cycle of neonates hatched from the irradiated eggs and on the performance of the population initiated from irradiated eggs. The study showed that γ-radiation in a range of doses from the background level to 100 Gy had no effect on survival of irradiated eggs. The absorbed dose of 200 Gy was lethal to resting eggs of M. macrocopa. The number of clutches and net reproductive rate (R₀) of hatchlings from eggs exposed to radiation were the strongly affected parameters in experiments with individual females. The number of clutches per female was drastically reduced for females hatched from egg exposed to 80-100 Gy. The most sensitive parameter was the R₀. The estimated ED₅₀ for the R₀ (effective dose that induces 50% R₀ reduction) was 50 Gy. Population performance was also affected by the irradiation of the resting stage of animals that initiated population. Populations that was initiated from hatchlings from resting eggs exposed to 100 Gy was of smaller size and with fewer juvenile and parthenogenetic females in comparison with control populations. Thus, we determined the dose-response relationship for the effect of gamma radiation on survival of resting eggs and individual and population responses of hatchlings from irradiated resting eggs. We conclude that for highly polluted areas contamination of bottom sediments with radioactive materials could affect zooplankton communities through adverse chronic effects on resting eggs, which will be transmitted to hatchlings at individual or population levels.

Effect of chronic exposure to two components of Tritan copolyester on Daphnia magna, Moina macrocopa, and Oryzias latipes, and potential mechanisms of endocrine disruption using H295R cells

Tritan copolyester is a novel plastic form from Eastman Company utilizing three main monomers, 1,4-cyclohexanedimethanol (CHDM), dimethyl terephthalate (DMT), and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. Despite Tritan has been widely applied for plastic bottles, the effects of long-term exposure to these compounds have seldom been investigated. We investigated chronic effects and endocrine disruption potential of CHDM and terephthalic acid (TPA), main mammalian metabolite formed from DMT, using crustacean Daphnia magna and Moina macrocopa, and freshwater fish (Oryzias latipes). The effects on sex hormone balance and the associated mechanisms were also investigated by use of H295R cells. In chronic toxicity test, D. magna showed significant decrease in reproduction (number of young per female) after exposure to 10 mg/L TPA. In early life stage exposure using O. latipes, significant decrease of juvenile survival and weight were observed in fish exposed to 10 mg/L and ≥1 mg/L CHDM, respectively. Expressions of vtg2 mRNA in fish exposed to CHDM and those of cyp19b, star, cyp17, and cyp19a mRNAs in fish exposed to TPA were significantly up-regulated. The results of H295R cell assay also showed that both chemicals at high concentrations could alter sex hormone production in steroidogenic pathway. The effective concentrations of the tested compounds were several orders of magnitude greater than the concentrations can be detected in ambient waters. Further in vivo and in vitro studies will be needed to investigate the effect of co-polymer on endocrine disruption.

Ecotoxicological assessment of cimetidine and determination of its potential for endocrine disruption using three test organisms: Daphnia magna, Moina macrocopa, and Danio rerio

Cimetidine is a histamine H2-receptor antagonist used for treatment of gastrointestinal disorders. It is often detected in aquatic environments, but its ecotoxicological effects have not been well studied. Thus, ecotoxicity of cimetidine was evaluated using Daphnia magna and Moina macrocopa, and zebrafish (Danio rerio), and a predicted no effect concentration (PNEC) was derived. In D. magna, 48 h immobilization EC50 was determined at 394.9 mg L(-1). However, reproduction damages in D. magna were not found even at the maximum exposure level (30 mg L(-1)). For M. macrocopa, 48 h EC50 was found at 175.8 mg L(-1) and the 7 d reproduction no observed effect concentration (NOEC) was 1.1 mg L(-1). For D. rerio, 40 d growth NOEC was determined at 100 mg L(-1), the highest experimental concentration. The PNEC of cimetidine was estimated at 0.1 mg L(-1) based on M. macrocopa 7d reproduction NOEC. In 14 d adult zebrafish exposure, endocrine disruption potentials of cimetidine were observed. In male, decrease in plasma 17β-estradiol and testosterone levels, up-regulation of gonadal cyp17, and down-regulation of hepatic erα were observed at 300 mg L(-1). In female, increase in plasma E2 level and down-regulation of hepatic cyp1a were noted at 3 mg L(-1). Endocrine disruption effects were also observed in early life stage exposure. Up-regulation of erβ at 17d, and cyp19a and vtg at 40 d post fertilization were detected at 100 mg L(-1), and co-occurrence of ovary and putative testis was observed at as low as 1.1 mg L(-1). The results indicate that there is little evidence for cimetidine to cause direct ecological impact at the current ambient levels in the aquatic environment. However potential consequences of endocrine disruption following long-term exposure in aquatic environment deserves further investigation.

Combined effects of the cyanobacterial toxin microcystin-LR and environmental factors on life-history traits of indigenous cladoceran Moina macrocopa

Environmental factors are important in that they might interact with toxicants and could affect the concentration-response relationship of the toxicants in the water environment. Microcystins (MCs) produced by algal blooming are natural toxins that exert severe impacts on aquatic organisms. Despite the possibility of interaction effects between environmental factors and MCs, very few studies have been carried out to date. In the present study, the authors evaluated the effect of 3 environmental factors on chronic toxicity of MC-leucine-arginine (MC-LR; 0 µg/L, 0.8 µg/L, 4 µg/L, 20 µg/L, 100 µg/L, 500 µg/L) to the freshwater invertebrate Moina macrocopa. Three environmental factors were determined to reflect the reasonable worst conditions of the water body in South Korea: high water temperature (25 °C), the highest concentration of nutrients (ammonia-nitrogen [NH3 -N] = 3.8 mg/L; nitrate-nitrogen [NO3 -N] = 8.5 mg/L) during the occurrence of algal bloom, and 2 pH conditions of 7.0 and 9.0, which satisfy the test acceptance criteria for the Daphnia test. Among the various environmental factors being tested, high water temperature and NO3 -N elevated chronic toxicity of MC-LR, whereas NH3 -N reduced toxicity. Water pH did not influence chronic toxicity of MC-LR to M. macrocopa. This observation suggests that those environmental factors are responsible for changing the trend of MC-LR toxicity.

Non-monotonic concentration-response relationship of TiO(2) nanoparticles in freshwater cladocerans under environmentally relevant UV-A light

The effects of UV-A on the toxicity of TiO2 nano-particles (NPs) were evaluated using Moina macrocopa and Daphnia magna under environmentally relevant level of UV-A. The waterfleas were exposed to TiO2 NPs with different sizes of ~298nm, ~132nm, or ~72nm for up to 48h, with or without UV-A light. Whole body reactive oxygen species and transcription of antioxidant enzyme genes were measured, as well as the survival of the waterflea. In the presence of UV-A, the survival rates of M. macrocopa significantly decreased in concentration dependent way until ~1mg/L TiO2 NPs, but the survivals were reversed at greater concentrations. This peculiar non-monotonic trend of concentration-response relationship might be explained by changes of particle size under different light conditions. TiO2 NPs within a certain size range could be trapped in the filter apparatus and exert toxicity, and the NPs of greater size were subject to either precipitation or ingestion leading to no or little toxicity. Observed TiO2 toxicity was associated with oxidative stress in the filter apparatus. The results of this study showed that the size change due to UV-A irradiation should be considered in evaluation of ecological risks of TiO2 NP.

In vitro and in vivo toxicities of sediment and surface water in an area near a major steel industry of Korea: endocrine disruption, reproduction, or survival effects combined with instrumental analysis

The influence of industrial and/or municipal contaminant inputs on the aquatic environment of Pohang, Korea was investigated, with a focus on bioassay combined with instrumental analysis. Pohang is the most heavily populated city in Gyeongsangbuk-do province of Korea, with more than half a million residents, and also hosts the nation's biggest steel manufacturer and related industries. Sediment (n=15) and surface water samples (n=17) were collected from Hyeongsan River which runs across the Pohang city, in two separate events, i.e., June 2010 and February 2011. Sediment samples were first Soxhlet-extracted (raw extract) and were measured for estrogenicity using H295R cell line, and also analyzed for alkylphenols (APs), bisphenol A (BPA), PAHs, and PCBs. For sediment samples which exhibited greatest effects in the cell line, further fractionation was performed into non-polar, mid-polar, and polar portions. In surface water samples, heavy metals were also analyzed. Among 15 sediment samples, station S2 near the steel industry complex and station M3 near the municipal area showed the greatest sex hormone changes, and these changes were generally explained by the fractions which contained APs and BPA. Principal component analysis (PCA) however suggests that chemicals that were not analyzed in the present study would better explain endocrine disruption capacity of sediments. In water samples, adverse effects on hatchability and growth of Japanese medaka fish, and on Daphnia reproduction were noted following exposure to six water samples collected from stations near industrial and municipal areas. Several heavy metals and nonylphenol (NP) concentrations exceeded surface water quality guidelines, suggesting adverse effects of contamination inputs from both industrial and municipal activities. Observed estrogenicities in stations such as S2 and M3 warrant further investigations on longer term ecosystem impacts near industrial and municipal areas. The levels of major organic chemicals in sediments are quite comparable to those reported in ~10 years ago, emphasizing a need for source control.

Toxicity and endocrine disruption in zebrafish (Danio rerio) and two freshwater invertebrates (Daphnia magna and Moina macrocopa) after chronic exposure to mefenamic acid

Pharmaceuticals have been frequently detected in the aquatic environment. Their potential effects on the endocrine system in wildlife are of special concern because these alterations could lead to impaired reproduction. We evaluated ecotoxicities associated with long-term exposure to mefenamic acid (MFA) and potential endocrine disruption. For this purpose, acute and chronic toxicities of MFA on several aquatic organisms, including two cladocerans, Daphnia magna and Moina macrocopa, and a teleost, Danio rerio were evaluated. The 48 h acute median effective concentration (EC50) of D. magna and M. macrocopa was 17.16 mg/L and 2.93 mg/L, respectively. In chronic toxicity test, D. magna and M. macrocopa showed significant changes in reproduction (number of young per adult) after the exposure to 1.0 mg/L and 0.25 mg/L MFA, respectively. In early life stage exposure using D. rerio, significant decrease of larval survival was observed at 1 mg/L. Changes in vitellogenin (VTG) protein concentrations in 32 day post fertilization fish and vtgI mRNA expression in adult male fish suggest endocrine disruption potentials of MFA. Among the genes of hypothalamus-pituitary-gonad axis, transcriptions of gnrh, gnrhr, cyp19a, and cyp19b increased, supporting estrogenic potential of MFA. Along with histological changes in ovaries, the results of this study provide evidences of endocrine disruption capacity of MFA. However, the effective concentrations are orders of magnitude greater than those occurring in the ambient aquatic environment.

Risk assessment of chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin in aquatic environment: are the current environmental concentrations safe?

To understand potential risks of major pharmaceutical residues in waters, we evaluated ecotoxicities of five major veterinary pharmaceuticals, i.e., chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin, which have been frequently detected in freshwater environment worldwide. We conducted acute and chronic toxicity tests using two freshwater invertebrates (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). In general, D. magna exhibited greater sensitivity than M. macrocopa, and chronic reproduction was the most sensitive endpoints for both organisms. The population growth rate was adversely influenced by exposure to chlortetracycline, sulfamethazine, or sulfathiazole in water fleas, but reduction in population size was not expected. In O. latipes, the tested pharmaceuticals affected several reproduction related endpoints including time to hatch and growth. Based on the toxicity values from the present study and literature, algae appeared to be the most sensitive organism, followed by Daphnia and fish. Hazard quotients derived from measured environmental concentrations (MECs) and predicted no effect concentrations (PNECs) for erythromycin and oxytetracycline exceeded unity, suggesting that potential ecological effects at highly contaminated sites cannot be ruled out. Long-term consequences of veterinary pharmaceutical contamination in the environment deserve further investigation.

Effect of chronic exposure to acetaminophen and lincomycin on Japanese medaka (Oryzias latipes) and freshwater cladocerans Daphnia magna and Moina macrocopa, and potential mechanisms of endocrine disruption

Chronic toxicity of acetaminophen and lincomycin were evaluated using freshwater organisms including two crustaceans (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). H295R, a human adrenal cell was also used to understand the effects on steroidogenesis. In 21 d D. magna exposure, survival NOEC was found at 5.72 mg L(-1) and no reproduction related effects were noted at this level of exposure to acetaminophen, while 21 d survival or growth effects were not observed even at the highest exposure levels (153 mg L(-1)) for lincomycin. In the chronic fish toxicity test, significant reduction in juvenile survival was observed at 30 d post-hatch (dph) at 95 mg L(-1) of acetaminophen, and 0.42 mg L(-1) of lincomycin. After the exposure to both pharmaceuticals, vitellogenin levels tended to increase in male fish at 90 dph. In the eggs which were prenatally exposed to 9.5 mg L(-1) of acetaminophen, reduced hatchability was observed. The results of H295R cell assay showed that both pharmaceuticals could alter steroidogenic pathway and increase estrogenicity. Endocrine disruption potentials and their ecological implication may deserve further studies. Our observations suggest however that ecological risks of both pharmaceuticals are negligible at the concentrations currently found in the environment.