Laboratory evaluation of the toxicity of Perfluorooctane Sulfonate (PFOS) on Selenastrum capricornutum,Chlorella vulgaris,Lemna gibba,Daphnia magna,and Daphnia pulicaria

Perfluorooctane sulfonate (PFOS) is an anthropogenic compound found in trace amounts in many environmental compartments far from areas of production. This, along with the highly persistent nature of PFOS, presents a concern for possible effects in aquatic ecosystems. The objective of this study was to determine the toxicity of PFOS in representative freshwater organisms. Toxicity testing using standard laboratory protocols was performed on the green algae Selenastrum capricornutum and Chlorella vulgaris, the floating macrophyte Lemna gibba, and the invertebrates Daphnia magna and Daphnia pulicaria. No observable effect concentration (NOEC) values were generated from the most sensitive endpoints for all organisms. Autotroph inhibition of growth NOEC values were 5.3, 8.2, and 6.6 mg/L for S. capricornutum, C. vulgaris, and L. gibba, respectively. The 48-h immobility NOEC values for D. magna and D. pulicaria were 0.8 and 13.6 mg/L, respectively. In comparison to immobility, the 21-day lethality NOEC for D. magna was 5.3 mg/L. Based on effect (immobility) values, the most sensitive of all test organisms was D. magna. The most sensitive organism based on 50% inhibition of growth (IC(50)) was L. gibba, with an IC(50) value of 31.1 mg/L determined from wet weight. This is 4.3 times less than the LC(50) for D. pulicaria, which was 134 mg/L. Significant adverse effects (p < or = 0.05) were observed for all organisms in concentrations >134 mg/L. The results indicate that under laboratory conditions PFOS is acutely toxic to freshwater organisms at concentrations at or near 100 mg/L. Based on known environmental concentrations of PFOS, which occur in the low ng/L to low microg/L range, there is no apparent risk to freshwater systems. However, further work is required to investigate long-term effects in these and other freshwater organisms.     

Toxicity of perfluorooctane sulfonic acid and perfluorooctanoic acid to Chironomus tentans

Two perfluorinated surfactants, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), were evaluated for their toxicity to the aquatic midge, Chironomus tentans. Impetus for this laboratory study originated from a 10-d, in situ field assessment in which C. tentans was exposed to PFOS at concentrations ranging from 300 to 30,000 microg/L. No midges survived these exposures. Midge survival in a preliminary, acute 10-d laboratory test with nominal PFOS concentrations ranging from 0.1 to 100,000 microg/L showed similar toxicity with respect to survival (median lethal concentration [LC50], 45.2 microg/L) and growth (median effective concentration [EC50], 27.4 microg/L). A parallel test using PFOA indicated no significant impacts on survival or growth. A definitive 10-d assay with PFOS concentrations ranging from 1 to 150 microg/L produced an EC50 for growth (87.2+/-11.6 microg/L) of the same order of magnitude as that in the preliminary findings. The same was not true for survival, however, with the LC50 falling outside the range of test concentrations. To further investigate the sensitivity of C. tentans to PFOS, we conducted a chronic life-cycle test using a nominal concentration range of 1 to 100 microg/L. Three of the four endpoints measured-survival, growth, and emergence-were significantly affected, with EC50 values of 92.2+/-3.1, 93.8+/-2.6, and 94.5+/-3.2 microg/L, respectively. Reproduction was not affected by those PFOS concentrations at which females emerged. The results of the present study indicate that PFOS toxicity thresholds for C. tentans are as much as three orders of magnitude lower than those reported for other aquatic organisms but, at present, are approximately two orders of magnitude higher than those concentrations typically observed in aquatic environments.     

Reproductive and developmental toxicity and bioconcentration of perfluorooctanesulfonate in a partial life-cycle test with the fathead minnow (Pimephales promelas)

Perfluorooctanesulfonate (PFOS) is a widespread environmental contaminant emanating from the production and/or metabolism of fluorinated chemicals with a variety of applications. The goal of this work was to assess the toxicity and bioconcentration of PFOS in the fathead minnow (Pimephales promelas). Sexually mature fish were exposed via the water for 21 d to 0 (control), 0.03, 0.1, 0.3, or 1 mg PFOS/L, and effects on reproductive capacity and endocrinology were assessed. To determine possible developmental effects, a subset of embryos from parental exposures at each test concentration were held for an additional 24 d in the same PFOS treatments. A concentration of I mg PFOS/L was lethal to adults within two weeks. The 21-d 50% effect concentration (95% confidence interval) for effects on fecundity of the fish was 0.23 (0.19-0.25) mg PFOS/L. Exposure to PFOS caused various histopathological alterations, most prominently in ovaries of adult females. Adult males exposed to 0.3 mg PFOS/L for 21 d exhibited decreased aromatase activity and elevated concentrations of plasma 11-ketotestosterone and testosterone. No significant adverse effects on survival or growth were observed in developing fathead minnows held for 24 d at PFOS concentrations up to 0.3 mg/L. Adult fathead minnows readily accumulated PFOS from the water. The largest concentrations of PFOS were in blood, followed by liver and then gonad; for all tissues, females accumulated higher concentrations than males. Water and tissue concentrations of PFOS associated with effects in this study exceeded those reported for samples collected from the field by two to three orders of magnitude, suggesting that the current risk of PFOS on aspects of fish reproduction and development assessed in this study would be small.     

Combined Effects of PFOS and PFOA on Zebrafish (Danio rerio) Embryos

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are two kinds of emerging contaminants most studied in recent years. However, there is limited information about their combined toxicity to aquatic organisms. In the present study, the single and combined toxicity of PFOA and PFOS to zebrafish (Danio rerio) embryos were investigated. PFOS was more toxic than PFOA for the single toxicity. In four mixtures, PFOS and PFOA showed complex interactive effects that changed from additive to synergistic effect, then to antagonistic effect, and at last turnover to synergic effect again, with increased molar ratios of PFOS. Neither the concentration-addition model nor the independent-action model could predict the combined effects when strong interactive effects existed. Although the interactive effects of PFOS and PFOA affected their combined toxicity, the trend of mixture toxicity still showed an increase with increasing molar ratios of PFOS in the mixture.     

Bioavailability models for predicting acute and chronic toxicity of zinc to algae, daphnids, and fish in natural surface waters

Bioavailability models predicting acute and/or chronic zinc toxicity to a green alga (Pseudokirchneriella subcapitata), a crustacean (Daphnia magna), and a fish (Oncorhynchus mykiss) were evaluated in a series of experiments with spiked natural surface waters. The eight selected freshwater samples had varying levels of bioavailability modifying parameters: pH (5.7-8.4), dissolved organic carbon (DOC, 2.48-22.9 mg/L), Ca (1.5-80 mg/L), Mg (0.79-18 mg/L), and Na (3.8-120 mg/L). In those waters, chronic zinc toxicity (expressed as 10% effective concentrations [EC10]) varied up to 20-fold for the alga (72-h EC10 from 27.3 to 563 microg Zn/L), and approximately sixfold for the crustacean (21-d EC10 from 59.2 to 387 microg Zn/L), and fivefold for the fish (30-d LC10, lethal concentration for 10% of the organisms, from 185 to 902 microg Zn/L). For P. subcapitata a refined bioavailability model was developed by linking an empirical equation, which predicts toxicity expressed as free Zn2+ activity as a function of pH, to the geochemical speciation model WHAM/Model V. This model and previously developed acute and/or chronic biotic ligand models for D. magna and 0. mykiss generally predicted most effect concentrations by an error of less than a factor of two. In waters with pH > 8, however, chronic toxicity to D. magna was underestimated by a factor 3 to 4. Based on the results of this validation exercise and earlier research, we determined applicability ranges for pH (6-8) and Ca (5-160 mg/L) in which all three developed models are valid. Within these ranges, all three models may be considered useful tools for taking into account bioavailability in regulatory assessments of zinc.     

Combined effects of algal (Chlorella vulgaris) density and ammonia concentration on the population dynamics of Ceriodaphnia dubia and Moina macrocopa (Cladocera)

Ammonia is a natural variable in ponds and lakes. Although an important source of nitrogen for microalgae, at high concentrations ammonia can affect the density and diversity of cladocerans. Using the cladocerans Ceriodaphnia dubia, and Moina macrocopa, the effect of nominal concentrations of ammonium chloride under acute and chronic exposures at different levels of algal food was tested. Regardless of food level, C. dubia was more sensitive than M. macrocopa to ammonia. In the absence of food, the median lethal concentration of ammonia (LC(50) 24 h) for C. dubia was (112 mg L(-1)) less than half that of M. macrocopa (232 mg L(-1)). When algal food (0.5 x 10(6) and 1.5 x 10(6) cells ml(-1) of Chlorella) was used, the LC(50) values were much higher for both cladoceran species. Based on the population growth studies, it was found that in controls of M. macrocopa an increase in the availability of Chlorella from 0.5 to 1.5 x 10(6) cells mL(-1) led to an increase in the maximum density from 4.7 +/- 0.2 to 16.4 +/- 1.2 ind.mL(-1), while in C. dubia the peak population density decreased from 7.9 +/- 0.6 to 5.0 +/- l.0 ind.mL(-1). An increase in ammonia concentration (10 to 40 mg L(-1) for C. dubia and 20 to 120 mg L(-1) for M. macrocopa) resulted in a corresponding decrease in peak population densities of the tested cladocerans. The rate of population increase (r) values for M. macrocopa in the controls ranged from 0.21 +/- 0.001 and 0.25 +/- 0.02 at 0.5 and 1.5 x 10(6) cells mL(-1) of Chlorella, respectively. The corresponding values of C. dubia in controls were 0.21 +/- 0.004 and 0.18 +/- 0.01. At 0.5 x 10(6) cells mL(-1) of algal food, the r values became negative under 40 and 120 mg L(-1) of ammonia for C. dubia and M. macrocopa, respectively. The role of algal food in ammonia toxicity to cladocerans was discussed. (c) 2002 Elsevier Science (USA).     

Biochemical Responses and Accumulation Properties of Long-Chain Perfluorinated Compounds (PFOS/PFDA/PFOA) in Juvenile Chickens (<Emphasis Type="Italic">Gallus gallus</Emphasis>)

One-day-old male chickens were exposed via oral gavage to mixtures of perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and perfluorodecanoate (PFDA) at either a low dose (0.1 mg/kg body weight [b.w.]) or a high dose (1.0 mg/kg b.w.), or a saline/ethanol vehicle control, three times a week for 3 weeks. After 3 weeks of exposure, half of the chicks were sacrificed and the other half were allowed to depurate for a further 3 weeks. No dose-dependent statistically significant differences in body/organ weights were observed among treatment and control groups after 3 weeks of exposure or after three 3 of depuration. Neither 15 histological nor 14 measured plasma biochemical parameters were significantly different in chicks from the exposed groups and vehicle controls. PFOS, PFDA, and PFOA concentrations in blood/liver/kidney samples were measured throughout the exposure and depuration periods at different time intervals. PFOS and PFDA accumulated at much higher concentrations than PFOA during the experimental periods. Interestingly, PFOS and PFDA accumulation patterns in the blood were similar during the exposure and depuration periods. The half-lives for each PFC at the 0.1 and 1.0 mg/kg doses were, respectively, approximately 15 and 17 days for PFOS, 11 and 16 days for PFDA, and 3.9 and 3.9 days for PFOA. PFDA accumulation in organs was greater than or similar to that of PFOS: the liver was the main target during exposure and the blood was the main reservoir during depuration. These results indicate that exposure to a 1.0-mg mixture of PFOS/PFDA/PFOA/kg b.w. has no adverse effect on juvenile chickens.     

Response of the zooplankton community and environmental fate of perfluorooctane sulfonic acid in aquatic microcosms

Little is known regarding perfluorooctane sulfonic acid (PFOS) toxicity to freshwater organisms. This field evaluation aims to assess the toxicological risk associated with exposure to PFOS across levels of biological organization. The analysis of variance study was conducted in replicate (n = 3) 12,000 L outdoor microcosms. Multivariate techniques were used to assess the response of zooplankton community structure and dynamics, as well as a floating macrophyte, Lemna gibba. The zooplankton community was significantly affected (p < 0.05) by the treatment regime given by the Monte Carlo permutations for all sampling times. A community-level no-observable-effect concentration ([NOEC]community) of 3.0 mg/L was determined for the 35-day study, however, longer term studies are recommended. The most sensitive taxonomic groups, Cladocera and Copepoda, were virtually eliminated in 30 mg/L treatments after 7 d. The 42-d 50% inhibition concentration (IC50) for L. gibba frond number was 19.1 mg/L and the NOEC was 0.2 mg/L. Furthermore, we investigated the persistence of PFOS over 285 d in microcosms under natural conditions. Perfluorooctane sulfonic acid concentration showed no drastic reduction in any treatment microcosm over the entire study period, confirming that this compound undergoes little degradation in aquatic systems. Presently, there appears to be little hazard to these freshwater organisms at reported environmental concentrations.     

Modeling the concentration-response function of the herbicide dinoseb on Daphnia magna (survival time, reproduction) and Pseudokirchneriella subcapitata (growth rate)

Models describing dose-response relationships are becoming increasingly popular in ecotoxicology. They allow simple and thorough evaluations of toxicity test results, including inter- and extrapolations to concentrations or exposure times other than those tested. Simple parametric regression models are of particular interest because their parameters may be attributed mechanistic meanings and they can be applied without sophisticated mathematical and computational support. We recently proposed a four-parameter logistic regression model to fit the survival data of Daphnia magna under dinoseb stress. The model parameters are the maximum survival time, the minimum time required for an individual to die, effect concentration, EC(50), and a curve shape parameter. This model has now been applied to compare the lethality and reproduction toxicity of D. magna and the growth inhibition of Pseudokirchneriella subcapitata under dinoseb stress. It can be fitted adequately to all the measured data and the parameters can be attributed biological meanings in any of the three endpoints. A comparison of the modeled concentration-response functions of all three endpoints for dinoseb toxicity shows that the range of ECs with respect to both D. magna and algae is steep (a decrease of between 0.1 and 0.6 mg/L). The survival and reproduction of D. magna exhibit similar characteristic concentration-response functions and toxicities. The statistical no-effect concentration (SNEC) is 0.14 (survival) and 0.11 (reproduction)mg/L, respectively. On the other hand, algae seem to be less sensitive to dinoseb than D. magna (SNEC: 0.48 mg/L). However, further investigations of individual algae may lead to a more suitable comparison. We speculate that the four parameters of the model function can be related to specific properties of chemicals and organisms. Characterization of these properties would allow simple and appropriate estimation of the toxic effects of these chemicals.     

Laboratory Evaluation of the Toxicity of Perfluorooctane Sulfonate (PFOS) on Selenastrum capricornutum , Chlorella vulgaris , Lemna gibba , Daphnia magna , and Daphnia pulicaria

Perfluorooctane sulfonate (PFOS) is an anthropogenic compound found in trace amounts in many environmental compartments far from areas of production. This, along with the highly persistent nature of PFOS, presents a concern for possible effects in aquatic ecosystems. The objective of this study was to determine the toxicity of PFOS in representative freshwater organisms. Toxicity testing using standard laboratory protocols was performed on the green algae Selenastrum capricornutum and Chlorella vulgaris, the floating macrophyte Lemna gibba, and the invertebrates Daphnia magna and Daphnia pulicaria. No observable effect concentration (NOEC) values were generated from the most sensitive endpoints for all organisms. Autotroph inhibition of growth NOEC values were 5.3, 8.2, and 6.6 mg/L for S. capricornutum, C. vulgaris, and L. gibba, respectively. The 48-h immobility NOEC values for D. magna and D. pulicaria were 0.8 and 13.6 mg/L, respectively. In comparison to immobility, the 21-day lethality NOEC for D. magna was 5.3 mg/L. Based on effect (immobility) values, the most sensitive of all test organisms was D. magna. The most sensitive organism based on 50% inhibition of growth (IC₅₀) was L. gibba, with an IC₅₀ value of 31.1 mg/L determined from wet weight. This is 4.3 times less than the LC₅₀ for D. pulicaria, which was 134 mg/L. Significant adverse effects (p ≤ 0.05) were observed for all organisms in concentrations >134 mg/L. The results indicate that under laboratory conditions PFOS is acutely toxic to freshwater organisms at concentrations at or near 100 mg/L. Based on known environmental concentrations of PFOS, which occur in the low ng/L to low μg/L range, there is no apparent risk to freshwater systems. However, further work is required to investigate long-term effects in these and other freshwater organisms. Received: 2 May 2002/Accepted: 29 July 2002     

Toxicity of aqueous C70-gallic acid suspension in Daphnia magna

The present study assessed the toxic effects of stable aqueous colloidal suspensions of gallic-acid-stabilized C(70) fullerene on Daphnia magna. The suspensions were stabilized through noncovalent surface modification with gallic acid. In addition to whole-organism responses, changes in antioxidative processes in D. magna were quantified. Acute toxicity was observed with 96LC50 for C(70) -gallic acid of 0.4?±?0.1?mg/L?C(70) . Daphnia magna fecundity was significantly reduced in 21-d bioassays at C(70) -gallic aqcid concentrations below quantifiable limits. Antioxidant enzyme activities of glutathione peroxidase and superoxide dismutase as well as lipid peroxidation suggested that exposed organisms experienced oxidative stress. Microscopic techniques used to determine cellular toxicity via apoptosis proved unsuccessful.     

Occurrences and ecological risks of roxithromycin, trimethoprim, and chloramphenicol in the Han River, Korea

We evaluated the occurrence of three antibiotics (roxithromycin, trimethoprim, and chloramphenicol) in surface water and effluents from several sewage treatment plants (STPs) on the Han River, Korea. In addition, standard acute toxicity tests were conducted using the microbe Vibrio fischeri, freshwater macroinvertebrates Daphnia magna and Moina macrocopa, and fish (Oryzias latipes) for these antibiotics. Antibiotics were more frequently detected at higher amounts in effluent samples and in samples collected during the low-flow season. For trimethoprim and chloramphenicol, the levels observed in surface water during low flow were, on average, 108 and 31 ng/L, respectively. These levels were comparable to those measured in the municipal effluents (average, 80 and 37 ng/L, respectively), suggesting the presence of other sources upstream (e.g., livestock wastes). For roxithromycin, surface water levels were approximately an order of magnitude lower than effluent levels. Adverse effects of roxithromycin, trimethoprim, and chloramphenicol were observed at mg/L levels in standard acute aquatic ecotoxicity tests. Based on hazard quotients calculated for the three antibiotics, minimal risks to aquatic systems are suggested. To further increase scientific understanding about the potential impacts of these pharmaceuticals in the environment, however, chronic ecotoxicology studies, with more subtle but ecologically meaningful end points or in combination with other mechanistically related contaminants, may be beneficial.     

焦性没食子酸对3种不同水生生物的毒性作用

目的研究焦性没食子酸对水生生物的毒性作用。方法以蛋白核小球藻(Chlorella pyrenoidosaChick)、斜生栅藻(Scenedesmus obliquus)和多刺裸腹溞(Moina macrocopa)作为受试对象,探讨不同浓度的焦性没食子酸(pyrogallol)的急性毒性效应。结果随焦性没食子酸浓度的增加藻细胞密度和溞数量明显下降,呈现剂量-效应关系;焦性没食子酸对蛋白核小球藻和斜生栅藻半抑制效应浓度(EC50)分别为19.7mg/L和19.8mg/L,对多刺裸腹溞24h和48h半抑制效应浓度分别为18.25mg/L和13.96mg/L。结论焦性没食子酸对蛋白核小球藻、斜生栅藻和多刺裸腹溞均属于中毒。     

沈阳和重庆人群血清中全氟辛烷磺酸和全氟辛酸的污染水平比较研究

目的阐明沈阳和重庆两地一般人群血清中全氟辛烷磺酸(PFOS)和全氟辛酸(PFOA)污染水平,比较两地人群血清中PFOS和PFOA分布特征。方法采集沈阳和重庆地区无职业性PFOS和PFOA暴露人群血清,采用高压液相色谱-质谱仪联机系统测定血清中PFOS和PFOA含量。结果沈阳地区一般人群血清中PFOS和PFOA浓度中位数分别为22·40μg/L和4·32μg/L,重庆地区分别为7·40μg/L和1·00μg/L。沈阳地区人群血清中PFOS、PFOA浓度明显高于重庆地区(P<0·01)。两地区女性人群血清中PFOS和PFOA浓度均高于男性水平,沈阳地区人群血清中PFOS浓度男、女性别间差异显著(P<0·05)。重庆地区女性人群血清中PFOS、PFOA浓度与年龄呈正相关关系(rPFOS=0·298,rPFOA=0·271),50岁以上女性人群的相关程度大于13岁以下和13~50岁年龄组。结论沈阳和重庆两地人群血清中PFOS和PFOA污染水平具有显著的地区性差异和分布特征,血清中PFOS和PFOA水平与年龄存在相关性。     

Effect of ammonia toxicity on the competition among three species of cladocerans (Crustacea: Cladocera)

Among the natural abiotic variables affecting the species density and composition of cladocerans, ammonia is important. Using population growth data as tool, we studied the competitive outcome of three cladoceran species (Ceriodaphnia dubia, Daphnia pulex, and Moina macrocopa) grown alone and together at three different concentrations (0, 25, and 100 mg L(-1)) of ammonia at one density (1 x 10(6)cells ml(-1)) of the microalga Chlorella vulgaris. Regardless of the presence or absence of competing species, C. dubia showed little population growth at 100 mg L(-1) of ammonia. At 25 mg L(-1) of ammonia, the population density of C. dubia increased but the value was much lower than that in control. D. pulex was able to grow at the ammonia concentration of 25 mg L(-1), comparable to controls. However, at 100 mg L(-1) of ammonia, the population declined and more rapidly when competed with other cladocerans. M. macrocopa showed decreased population density with increasing ammonia concentration in the medium. This trend was accelerated by the presence of competing cladocerans. M. macrocopa was benefited by the presence of D. pulex at 0 and 25 mg L(-1) of ammonia in the medium. The peak population density of C. dubia varied from 0.5 to 9 ind.ml(-1), whereas for D. pulex and M. macrocopa, these values varied from 1 to 3 ind.ml(-1) and 7 to 18 ind.ml(-1), respectively, depending on the ammonia concentration and the presence of competing species. The rates of population increase per day of C. dubia, D. pulex, and M. macrocopa ranged from -0.12+/-0.001 to 0.30+/-0.01, 0.04+/-0.001 to 0.22+/-0.002, and 0.201+/-0.028 to 0.235+/-0.019, respectively, depending on the ammonia concentration and the presence of competitors. Our study showed that while competition within the chosen cladoceran species caused suppression of one or two competing species, the presence of ammonia expedited this process based on the relative sensitivities of the tested zooplankton.     

Ecological impact and environmental fate of perfluorooctane sulfonate on the zooplankton community in indoor microcosms

There is presently a substantial amount of information being gathered concerning the environmental risk associated with the perfluorooctane sulfonate (PFOS) compound. The U.S. Environmental Protection Agency (U.S. EPA) is requiring that more research be completed before making definitive decisions concerning the regulatory issues covered in the significant new use rule (18/10-2000) under the Toxic Substance Control Act. However, there are no risk assessment requirements under seminatural conditions in microcosms. The PFOS can enter, and has been found in, the aquatic environment through different pathways, including spills associated with use of fire-fighting foams containing PFOS, leaching from washing Scotchgard-treated clothes with the wastewater, leaching from various coatings, discharges as residual waste from fluorochemical production, or volatilization and transportation atmospherically. The biota is the sink of PFOS rather than the sediment or soil. The aim of this article is to determine a 35-d community no-observable-effect concentration (NOECcommunity) for freshwater zooplankton and the fate of PFOS during the course of study. The PFOS persisted in the water phase with only slight reductions over the study; only the decrease from 33.9 mg/L at day 1 to 29.8 mg/L at day 35 was significant. A 90 to 100% reduction (p < 0.01) of the total zooplankton population was found after one week of exposure to 30 mg PFOS/L and a similar reduction after two weeks at 10 mg PFOS/L. The Daphnia magna 21-d NOECsurvival of 12 mg/L has previously been found in a standard laboratory bioassay by 3M. The rank order of susceptibility for the test community was Copepoda > Cladocera > Rotifera, assuming all adverse direct effects.     

Impacts of two perfluorinated compounds (PFOS and PFOA) on human hepatoma cells: cytotoxicity but no genotoxicity?

Perfluorinated compounds (PFCs) and particularly two of them, perfluoroctanoate (PFOA) and perfluorooctanesulfonate (PFOS), have been widely produced and used since 1950. They both persist in the environment and accumulate in wildlife and humans. The toxicity of PFOS and PFOA has been studied extensively in rodents with several adverse effects mainly a hepatocarcinogenic potential. Carcinogenic effects are not highlighted in humans' studies. In this study, we investigated the cytotoxic and genotoxic effects of PFOA and PFOS using human HepG2 cells after 1 or 24h of exposure. The cytotoxic and genotoxic potential was evaluated by MTT assay, single cell gel electrophoresis (SCGE) assay and micronucleus assay respectively. We measured the intracellular generation of reactive oxygen species (ROS) using dichlorofluorescein diacetate to identify a potential mechanism of toxicity. We observed a cytotoxic effect of PFOA and PFOS after 24h of exposure starting from a concentration of 200 μM (MTT: -14.6%) and 300 μM (MTT: -51.2%) respectively. We did not observe an increase of DNA damage with the comet assay or micronucleus with the micronucleus assay after exposure to the two PFCs. After 24h of exposure, both PFOA and PFOS highlight a decrease of ROS generation (-5.9% to -23%). We did not find an effect after an hour of exposure. Our findings show that PFOA and PFOS exert a cytotoxic effect on the human cells line HepG2 but nor PFOA or PFOS could induce an increase of DNA damage (DNA strand breaks and micronucleus) or reactive oxygen species at the range concentration tested. Our results do not support that oxidative stress and DNA damage are relevant for potential adverse effects of PFOA and PFOS. These results tend to support epidemiological studies that do not show evidence of carcinogenicity.     

Toxicity of fluoroquinolone antibiotics to aquatic organisms

Toxicity tests were performed with seven fluoroquinolone antibiotics, ciprofloxacin, lomefloxacin, ofloxacin, levofloxacin, clinafloxacin, enrofloxacin, and flumequine, on five aquatic organisms. Overall toxicity values ranged from 7.9 to 23,000 microg/L. The cyanobacterium Microcystis aeruginosa was the most sensitive organism (5-d growth and reproduction, effective concentrations [EC50s] ranging from 7.9 to 1,960 microg/L and a median of 49 microg/L), followed by duckweed (Lemna minor, 7-d reproduction, EC50 values ranged from 53 to 2,470 microg/L with a median of 106 microg/L) and the green alga Pseudokirchneriella subcapitata (3-d growth and reproduction, EC50 values ranged from 1,100 to 22,700 microg/L with a median 7,400 microg/L). Results from tests with the crustacean Daphnia magna (48-h survival) and fathead minnow (Pimephales promelas, 7-d early life stage survival and growth) showed limited toxicity with no-observed-effect concentrations at or near 10 mg/L. Fish dry weights obtained in the ciprofloxacin, levofloxacin, and ofloxacin treatments (10 mg/L) were significantly higher than in control fish. The hazard of adverse effects occurring to the tested organisms in the environment was quantified by using hazard quotients. An estimated environmental concentration of 1 microg/L was chosen based on measured environmental concentrations previously reported in surface water; at this level, only M. aeruginosa may be at risk in surface water. However, the selective toxicity of these compounds may have implications for aquatic community structure.     

Effects of perfluorooctane sulfonate and perfluorooctanoic acid on the zooplanktonic community

This comparative survey summarizes six individual studies on the ecological effects of two common perfluorinated surfactants, PFOS and PFOA, on zooplankton. We compare the test designs and quantify the relative sensitivity and statistical power (1-beta > or = 0.8). The survey compares 30-L indoor microcosm to 12,000-L outdoor microcosm experiments, with 225-mL single species laboratory tests as reference. By this we elucidate the extrapolation of ecological effects in space and complexity. Generally, zooplankton had lower tolerance toward PFOS than toward PFOA. With increasing concentrations the zooplankton community became simplified toward more robust rotifer species, which, as an indirect effect, increased their abundance due to a shift in competition and predation. The statistical power of the designs exhibits inverse proportionality between complexity and realism, indoor microcosm>outdoor microcosm. Surprisingly, the 30-L study had a lower LOEC value for Daphnia magna than the laboratory chronic test, indicating that D. magna and D. pulicaria were not the most sensitive species and that laboratory tests are not always conservative relative to microcosm experiments. Food scarcity due to phytotoxicity was not the reason for the difference.