The effect of food on the acute toxicity of silver nitrate to four freshwater test species and acute-to-chronic ratios

Acute silver toxicity studies were conducted with and without food for four common freshwater test species: Daphnia magna, Ceriodaphnia dubia, Pimephales promelas (fathead minnow—FHM), and Oncorhynchus mykiss (rainbow trout—RBT) in order to generate acute-to-chronic ratios (ACR). The studies were conducted similarly (i.e., static-renewal or flow-through) to chronic/early-life stage studies that were previously performed in this laboratory. The acute toxicity (EC/LC50 values) of silver without food ranged from 0.57 μg dissolved Ag/l for C.dubia to 9.15 μg dissolved Ag/l for RBT. The presence of food resulted in an increase in EC/LC50 values from 1.25× for RBT to 22.4× for C. dubia. Invertebrate food type was also shown to effect acute silver toxicity. Food did not affect EC/LC50s or ACRs as greatly in fish studies as in invertebrate studies. ACRs for both invertebrate species were <1.0 when using acute studies without food but were 1.22 and 1.33 when using acute studies with food. ACRs for FHMs ranged from 4.06 to 7.19, while RBT ACRs ranged from 28.6 to 35.8 depending on whether food was present in acute studies. The data generated from this research program should be useful in re-determining a final ACR for silver in freshwater as well as in risk assessments.     

Toxicity of Lithium to Three Freshwater Organisms and the Antagonistic Effect of Sodium

Lithium (Li) is the lightest metal and occurs primarily in stable minerals and salts. Concentrations of Li in surface water are typically <0.04mg l^–1 but can be elevated in contaminated streams. Because of the general lack of information concerning the toxicity of Li to common toxicity test organisms, we evaluated the toxicity of Li to Pimephales promelas (fathead minnow), Ceriodaphnia dubia, and a freshwater snail (Elimia clavaeformis). In the laboratory, the concentration of Li that inhibited P. promelas growth or C. dubia reproduction by 25% (IC25) was dependant upon the dilution water. In laboratory control water containing little sodium (2.8mg l^–1), the IC25s were 0.38 and 0.32mg Li l^–1 and in ambient stream water containing 17mg Na l^–1, the IC25s were 1.99 and 3.33, respectively. A Li concentration of 0.15mgl^–1 inhibited the feeding of E. clavaeformis in laboratory tests. Toxicity tests conducted to evaluate the effect of sodium on the toxicity of Li were conducted with fathead minnows and C. dubia. The presence of sodium greatly affected the toxicity of Li. Fathead minnows and Ceriodaphnia, for example, tolerated concentrations of Li as great as 6mg l^–1 when sufficient Na was present. The interaction of Li and Na on the reproduction of Ceriodaphnia was investigated in depth and can be described using an exponential model. The model predicts that C. dubia reproduction would not be affected when animals are exposed to combinations of lithium and sodium with a log ratio of mmol Na to mmol Li equal to at least 1.63. The results of this study indicate that for most natural waters, the presence of sodium is sufficient to prevent Li toxicity. However, in areas of historical disposal or heavy processing or use, an evaluation of Li from a water quality perspective would be warranted.     

Toxicity of nanoparticles of ZnO, CuO and TiO2 to yeast Saccharomyces cerevisiae

The aim of this study was to evaluate the toxic effect of nanosized ZnO, CuO and TiO₂ to Saccharomyces cerevisiae – a widely used unicellular eukaryotic model organisms in molecular and cell biology. The effect of metal oxide nanoparticles, their bulk forms and respective ionic forms were compared. The bioavailable Zn²⁺ and Cu²⁺ ions in the growth medium were quantified by recombinant microbial sensors.Nano and bulk TiO₂ were not toxic even at 20000 mg/l. Both, nano and bulk ZnO were of comparable toxicity (8-h EC₅₀ 121–134 mg ZnO/l and 24-h EC₅₀ 131–158 mg/l). The toxicity was explained by soluble Zn-ions as proved by the microbial sensor. However, nano CuO was about 60-fold more toxic than bulk CuO: 8-h EC₅₀ were 20.7 and 1297 mg CuO/l and 24-h EC₅₀ were 13.4 and 873 mg/l, respectively. The increase in toxicity of both CuO formulations at 24th hour of growth was due to the increased dissolution of copper ions from CuO over time. Comparison of EC₅₀ values of nano CuO, bulk CuO and Cu²⁺ with bioavailable copper concentrations in the growth medium showed that the solubilized Cu-ions explained only about 50% of the toxicity of both, nano and bulk CuO. To our knowledge, this is the first study that evaluates the toxicity of ZnO, CuO and TiO₂ nanoparticles to S. cerevisiae.     

Multilaboratory evaluation of 15 bioassays for (eco)toxicity screening and hazard ranking of engineered nanomaterials: FP7 project NANOVALID

Within EU FP7 project NANOVALID, the (eco)toxicity of 7 well-characterized engineered nanomaterials (NMs) was evaluated by 15 bioassays in 4 laboratories. The highest tested nominal concentration of NMs was 100?mg/l. The panel of the bioassays yielded the following toxicity order: Ag?>?ZnO?>?CuO?>?TiO_2?>_?MWCNTs?>?SiO_2?>_?Au. Ag, ZnO and CuO proved very toxic in the majority of assays, assumingly due to dissolution. The latter was supported by the parallel analysis of the toxicity of respective soluble metal salts. The most sensitive tests/species were Daphnia magna (towards Ag NMs, 24-h EC_50?=_?0.003?mg Ag/l), algae Raphidocelis subcapitata (ZnO and CuO, 72-h EC_50?=_?0.14?mg Zn/l and 0.7?mg Cu/l, respectively) and murine fibroblasts BALB/3T3 (CuO, 48-h EC_50?=_?0.7?mg Cu/l). MWCNTs showed toxicity only towards rat alveolar macrophages (EC_50?=_?15.3?mg/l) assumingly due to high aspect ratio and TiO₂ towards R. subcapitata (EC_50?=_?6.8?mg Ti/l) due to agglomeration of TiO₂ and entrapment of algal cells. Finally, we constructed a decision tree to select the bioassays for hazard ranking of NMs. For NM testing, we recommend a multitrophic suite of 4 in vitro (eco)toxicity assays: 48-h D. magna immobilization (OECD202), 72-h R. subcapitata growth inhibition (OECD201), 30-min Vibrio fischeri bioluminescence inhibition (ISO2010) and 48-h murine fibroblast BALB/3T3 neutral red uptake in vitro (OECD129) representing crustaceans, algae, bacteria and mammalian cells, respectively. Notably, our results showed that these assays, standardized for toxicity evaluation of “regular” chemicals, proved efficient also for shortlisting of hazardous NMs. Additional assays are recommended for immunotoxicity evaluation of high aspect ratio NMs (such as MWCNTs).     

Measurement of the aquatic toxicity of volatile nitrosamines.

The acute toxicity of N-nitrosodimethylamine (DMN) and N-nitrosodiethylamine (DEN) was determined for three groups of aquatic organisms: algae, invertebrates, and fish. Toxicity of DMN and DEN to algae was assessed as a repression in the growth rate of either Selenastrum capricornutum or Anabaena flos-aquae in static bioassay tests. DMN and DEN concentrations of 1-10 ppm depressed algal growth in all cases. Invertebrate toxicity was determined in 96-h static bioassay tests with Dugesia dorotocephala and Gammarus limnaeus. The data indicated that these organisms are not highly susceptible to nitrosamine toxicity. The 96-h LC50s for D. dorotocephala were 1365 and 1490 ppm for DMN and DEN, respectively. Similar studies with G. limnaeus indicated LC50s of 330 and 500 ppm for DMN and DEN, respectively. Fish toxicity was also determined in 96-h statis bioassays with the fathead minnow (Pimephales promelas). Acute toxicities were calculated as LC50s of 940 and 775 ppm for DMN and DEN, respectively. Algae were calculated as LC50s of 940 and 775 ppm for DMN and DEN, respectively. Algae were quite sensitive to relative low levels of volatile nitrosamines, but higher organisms (invertebrates and fish) were relatively insensitive.     

Sensitivity of early life stages of white sturgeon, rainbow trout, and fathead minnow to copper

Populations of white sturgeon (WS; Acipenser transmontanus) are in decline in several parts of the United States and Canada, attributed primarily to poor recruitment caused by degradation of habitats, including pollution with contaminants such as metals. Little is known about sensitivity of WS to contaminants or metals such as copper (Cu). Here, acute (96 h) mortalities of WS early life stages due to exposure to Cu under laboratory conditions are reported. Two standard test species, rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas), were exposed in parallel to determine relative sensitivity among species. Swim-up larvae [15 days post-hatch (dph)] and early juveniles (40?C45 dph) of WS were more sensitive to Cu (LC₅₀ = 10 and 9?C17 ??g/L, respectively) than were yolksac larvae (8 dph; LC₅₀ = 22 ??g/L) and the later juvenile life stage (100 dph; LC₅₀ = 54 ??g/L). WS were more sensitive to Cu than rainbow trout and fathead minnow at all comparable life stages tested. Yolksac larvae of rainbow trout and fathead minnow were 1.8 and 4.6 times, respectively, more tolerant than WS, while swim-up and juvenile life stages of rainbow trout were between 1.4- and 2.4-times more tolerant than WS. When plotted in a species sensitivity distribution with other fishes, the mean acute toxicity value for early life stage WS was ranked between the 1st and 2nd centile. The WS life stage of greatest Cu sensitivity coincides with the beginning of active feeding and close association with sediment, possibly increasing risk. WS early life stages are sensitive to aqueous copper exposure and site-specific water quality guidelines and criteria should be evaluated closely to ensure adequate protection.     

An ecotoxicological characterization of nanocrystalline cellulose (NCC)

Abstract

The pulp and paper industry in Canada is developing technology for the production and use of nanocrystalline cellulose (NCC). A key component of the developmental work is an assessment of potential environmental risks. Towards this goal, NCC samples as well as carboxyl methyl cellulose (CMC), a surrogate of the parent cellulosic material, were subjected to an ecotoxicological evaluation. This involved toxicity tests with rainbow trout hepatocytes and nine aquatic species. The hepatocytes were most sensitive (EC20s between 10 and 200 mg/l) to NCC, although neither NCC nor CMC caused genotoxicity. In tests with the nine species, NCC affected the reproduction of the fathead minnow at (IC25) 0.29 g/l, but no other effects on endpoints such as survival and growth occurred in the other species at concentrations below 1 g/l, which was comparable to CMC. Based on this ecotoxicological characterization, NCC was found to have low toxicity potential and environmental risk.     

The influence of modes of action and physicochemical properties of chemicals on the correlation between in vitro and acute fish toxicity data

New EU legislation is providing an impetus for research aimed at replacing acute fish toxicity testing with in vitro alternatives. In line with such research, the objective of this study was to determine what factors influence the correlation between in vitro and fish toxicity data. Basal cytotoxicity (IC₅₀) and acute toxicity data from fathead minnow (LC₅₀) of 82 industrial organic chemicals were obtained from the Halle Registry of Cytotoxicity and the US EPA Fathead Minnow Database. A good correlation between IC₅₀ with LC₅₀ data was found (r 0.84). Yet, IC₅₀ data were less sensitive than LC₅₀ data by an order of magnitude. Using multiple regression analysis, the octanol–water partition coefficient (K_OW) and the Henry’s Law Constant (H) were found to significantly explain the low absolute sensitivity. The mode of action (MOA) of the chemical was found to significantly explain the general variation in the log IC₅₀/log LC₅₀ regression line. These results support the notion that (a) the bioavailability of hydrophobic (high K_OW) and volatile (high H) chemicals is significantly lower in in vitro assays than in the fish bioassay and (b) multiple cell types and endpoints should be included to mimic the modes of action possible in the whole organism.     

Photocatalytic and phototoxic properties of TiO2-based nanofilaments: ESR and AFM assays

Abstract

There is uncertainty in understanding of the relationship between physico-chemical parameters of nanosized titanium dioxide (nano-TiO₂) and its toxicity when brought into contact with living cells. This study provides a multidisciplinary experimental insight into the toxicity and phototoxicity of the custom-made TiO₂-based nanowires (TiO₂-NWs). We employed electron spin resonance (ESR) to detect reactive oxygen species (ROS) generated in aqueous suspensions of TiO₂-NWs and combined these results with atomic force microscopy (AFM) to trace the onset of toxic effects towards human melanoma cells. The cells were treated with low concentrations (～2.5 μg/ml) of TiO₂-NWs and Degussa P25. High-resolution AFM surface topography and cell elasticity measurements revealed toxic effects both in cells incubated with TiO₂-NWs in the dark and exposed to the photo-oxidative stress under UVA radiation. In contrast to ROS generation efficacy in the absence of cells in vitro, no direct correlation was found between the physical parameters of nano-TiO₂ and cell toxicity.     

Ecological effects testing under the Toxic Substances Control Act: Acrylamide

Analysis of acrylamide aquatic toxicity data submitted under section 4 of the Toxic Substances Control Act revealed that for acute toxicity studies with bluegill, fathead minnow, and rainbow trout, concentrations of acrylamide necessary to produce 50% mortality decreased by 50-70% as a function of increasing exposure from 1 to 4 days. Analysis of acute toxicity data for Mysidopsis bahia suggested that increases in mortality with increased exposure to acrylamide might also be observed in saltwater organisms. Ratios of acute (4-day) LC₅₀ values to chronic (28-day) maximum acceptable toxic concentrations for this saltwater invertebrate were 26 for parent and offspring survival, 115 for female dry weights, and 975 for male dry weights. These ratios illustrate that long-term acrylamide exposure to sensitive life stages of M. bahia produced adverse effects on reproduction and growth at acrylamide concentrations significantly lower than those suggested by acute LC₅₀ or EC₅₀ values.     

The toxicity of acetylenic alcohols to the fathead minnow, Pimephales promelas: narcosis and proelectrophile activation

1. The 96-h LC50 values for 16 acetylenic alcohols in the fathead minnow (Pimephales promelas) were determined using continuous-flow diluters. The measured LC50 values for seven tertiary propargylic alcohols agreed closely with the QSAR predictions based upon data for other organic non-electrolytes acting by a narcosis mechanism. 2. Four primary and four secondary propargylic alcohols were 7 to 4600 times more toxic than the respective narcotic toxicity estimated by QSAR. Metabolic activation to electrophilic alpha,beta-unsaturated propargylic aldehydes or ketones is proposed to account for the increased toxicity. 3. 3-Butyn-1-ol and 4-pentyn-2-ol, primary and secondary homopropargylic alcohols, were 320 and 160, respectively, times more toxic than predicted. In this case an activation step involving biotransformation to an allenic electrophile intermediate was proposed.     

Acute Toxicity, Uptake and Histopathology of Aqueous Methyl Mercury to Fathead Minnow Embryos

Early life stages of fishes have been shown to be especially susceptible to the toxic effects of heavy metal pollution. In this study, fathead minnow (Pimephales promelas) embryos were exposed in the laboratory to a graded series of aqueous methyl mercury concentrations under continuous-flow conditions. A number of toxicological endpoints were examined including; acute toxicity, bioaccumulation, protein production, impact on mitosis, gross and histopathology. Acute toxicity, reported as LC50 values of methyl mercury, ranged from 221 μg/l (95% C.I. 246–196 μg/l) for 24-h tests to 39 μg/l (95% C.I. 54–24 μg/l) for 96-h exposures. Fathead minnow embryos were shown to rapidly take up mercury from the surrounding water. Mercury levels in embryos reached levels of 2.80 μg/g wet weight after 96 h exposure to 40 μg/l methyl mercury. An initial elevation of total protein in embryo was observed in embryos exposed to 25 μg/l methyl mercury during the first 12 h of development. At later stages, significantly lower levels of protein/μg embryo were observed. Methyl mercury had no effect on mitotic stages (p=0.05) in early, cleaving blastula-stage embryos. Live embryos and serial sections were utilized to characterize changes in embryo morphology and histopathology.     

The Toxicity of Acetylenic Alcohols to the Fathead Minnow,Pimephales Promelas: Narcosis and Proelectrophile Activation

1. The 96-h LC₅₀ values for 16 acetylenic alcohols in the fathead minnow (Pimephales promelas) were determined using continuous-flow diluters. The measured LC₅₀ values for seven tertiary propargylic alcohols agreed closely with the QSAR predictions based upon data for other organic non-electrolytes acting by a narcosis mechanism.

2. Four primary and four secondary propargylic alcohols were 7 to 4600 times more toxic than the respective narcotic toxicity estimated by QSAR. Metabolic activation to electrophilic α,β-unsaturated propargylic aldehydes or ketones is proposed to account for the increased toxicity.

3. 3-Butyn-1-o1 and 4-pentyn-2-ol, primary and secondary homopropargylic alcohols, were 320 and 160, respectively, times more toxic than predicted. In this case an activation step involving biotransformation to an allenic electrophile intermediate was proposed.     

Haemato-immunological studies in ZnO and TiO2 nanoparticles exposed euryhaline fish,Oreochromis mossambicus

The present study was aimed to analyze the effect of ZnO and TiO₂ nanoparticles (NPs) on Haemato-immunological parameters in adult Tilapia, Oreochromis mossambicus. The nanoparticles size found as 47 nm and 30 nm for ZnO and TiO₂ respectively. The acute toxicity (96 h) of ZnO (LC50: 100–110 ppm) and TiO₂ (LC50: 80–90 ppm) NPs were identified by using probit analysis. RBC, Hb and HCT levels decreased in nanoparticles exposed groups resulted in decreased oxygen carrying capacity of RBC and other erythrocyte indices (MCH, MCV, MCHC). Increased WBC, neutrophils & monocytes and decreased lymphocyte levels were observed as increased concentration of the nanoparticles. The results were found as statistically significant (p < 0.05). In conclusion, the present study depicts that ZnO NPs exhibits more toxicity than TiO₂ NPs. Nanoparticles presence even in low concentration (ppm) cause damage to the connective tissues of fish, so the existing permissible levels of these nanoparticles in water are need to be revised.     

Acute aquatic toxicity of tire and road wear particles to alga,daphnid, and fish

Previous studies have indicated that tire tread particles are toxic to aquatic species, but few studies have evaluated the toxicity of such particles using sediment, the likely reservoir of tire wear particles in the environment. In this study, the acute toxicity of tire and road wear particles (TRWP) was assessed in Pseudokirchneriella subcapita, Daphnia magna, and Pimephales promelas using a sediment elutriate (100, 500, 1000 or 10000 mg/l TRWP). Under standard test temperature conditions, no concentration response was observed and EC/LC₅₀ values were greater than 10,000 mg/l. Additional tests using D. magna were performed both with and without sediment in elutriates collected under heated conditions designed to promote the release of chemicals from the rubber matrix to understand what environmental factors may influence the toxicity of TRWP. Toxicity was only observed for elutriates generated from TRWP leached under high-temperature conditions and the lowest EC/LC₅₀ value was 5,000 mg/l. In an effort to identify potential toxic chemical constituent(s) in the heated leachates, toxicity identification evaluation (TIE) studies and chemical analysis of the leachate were conducted. The TIE coupled with chemical analysis (liquid chromatography/mass spectrometry/mass spectrometry [LC/MS/MS] and inductively coupled plasma/mass spectrometry [ICP/MS]) of the leachate identified zinc and aniline as candidate toxicants. However, based on the high EC/LC₅₀ values and the limited conditions under which toxicity was observed, TRWP should be considered a low risk to aquatic ecosystems under acute exposure scenarios.     

Oxidative stress studies of six TiO2 and two CeO2 nanomaterials: Immuno-spin trapping results with DNA

Abstract

Six TiO₂ and two CeO₂ nanomaterials with dry sizes ranging from 6–410 nm were tested for their ability to cause DNA centered free radicals in vitro in the concentration range of 10–3,000 ug/ml. All eight of the nanomaterials significantly increased the adduction of the spin trap agent 5,5-dimethyl-1-pyroline N-oxide (DMPO) to DNA as measured by the experimental technique of immuno-spin trapping. The eight nanomaterials differed considerably in their potency, slope, and active concentration. The largest increase in DNA nitrone adducts was caused by a TiO₂ nanomaterial (25 nm, anatase) from Alfa Aesar. Some nanomaterials that increased the amount of DNA nitrone adducts at the lowest exposure concentrations (100 ug/ml) were Degussa TiO₂ (31 nm), Alfa Aesar TiO₂ (25 nm, anatase) and Nanoamor CeO₂ (8 nm, cerianite). At exposure concentrations of 10 or 30 ug/ml, no nanomaterials showed significant in vitro formation of DNA nitrone adducts.     

Individual- and population-level toxicity of the insecticide,spirotetramat and the agricultural adjuvant,Destiny to the Cladoceran, <Emphasis Type="Italic">Ceriodaphnia dubia</Emphasis>

The effects of the tetramic acid insecticide, spirotetramat and the agricultural adjuvant, Destiny, were evaluated on the Cladoceran, Ceriodaphnia dubia. These compounds were evaluated separately and as a mixture because they can be applied together for control of certain crop pests and therefore have the potential to enter surface water as a binary mixture. Acute mortality estimates (48 h) were developed followed by chronic exposure (8 days) studies where several population parameters were recorded. Acute LC50 and 95% CL for spirotetramat and Destiny were estimated to be 23.8 (14.5–35.4) and 26.71 (20.8–34.0) mg/l, respectively. Thus, spirotetramat and Destiny were equitoxic to C. dubia at LC50. For the chronic population study, C. dubia populations were exposed to a range of concentrations for spirotetramat and Destiny singly and as a mixture. Each chemical alone reduced the number of founding individuals, offspring/female, final population size, and population growth rate in a concentration-dependent manner. However, exposure to the mixture caused significantly greater reductions in these parameters than either compound alone. These results indicate that agricultural adjuvants and pesticides may cause more damage to aquatic organisms as a mixture than either product alone. Therefore, future evaluations of pesticide effects should consider the effects of adjuvants as a mixture with pesticides when these products are recommended to be applied together for pest control.     

Assessment of the potential toxicity of a linear alkylbenzene sulfonate (LAS) to freshwater animal life by means of cladoceran bioassays

The acute and chronic toxic effects of LAS on the cladocerans Daphnia similis, Ceriodaphnia dubia and Ceriodaphnia silvestrii were tested. Both types of toxicity bioassays and the methods of culture and stock maintenance of the test organisms conformed to the recommendations of ABNT (Brazilian Society of Technical Standards), which closely follow the standard methods of USEPA. The results obtained for EC₅₀ (48 h) were: 14.17 mg L⁻¹ for D. similis, 11.84 mg L⁻¹ for C. dubia and 13.52 mg L⁻¹ for C. silvestrii. In the chronic toxicity tests performed on C. dubia and C. silvestrii, there was a significant decrease in the fecundity of the exposed animals; the value of NOEC for C. dubia and C. silvestrii were 1.00 mg L⁻¹ and 2.50 mg L⁻¹, respectively. Cladoceran bioassays provided evidence that LAS concentration as low as 1.00 mg L⁻¹ can damage invertebrate animal life in freshwaters, concentrations that can be found in many eutrophic rivers and reservoirs.     

QSAR modelling of the ERL-D fathead minnow acute toxicity database

1. Regression analysis has been applied to examine the structure-activity relationships regarding the acute fish toxicity (96 h LC50 fathead minnow) of organic chemicals. The log P dependent baseline toxicity model has been confirmed for a data set composed of 618 compounds from 24 chemical classes associated with a putative common mode of action. 2. Covariance analysis of the discrete by class regression functions resulted in the combination of chemicals to subsets associated with their mode of action. Separate models were derived for nonpolar (Class I) and polar (Class II and III) compounds. Chemicals which are more toxic than estimated from the baseline model are identified.     

Aquatic toxicity of acrylates and methacrylates: Quantitative structure-activity relationships based on Kow and LC50

Recent EPA scrutiny of acrylate and methacrylate monomers has resulted in restrictive consent orders and Significant New Use Rules under the Toxic Substances Control Act, based on structure-activity relationships using mouse skin painting studies. The concern is centered on human health issues regarding worker and consumer exposure. Environmental issues, such as aquatic toxicity, are still of concern. Understanding the relationships and environmental risks to aquatic organisms may improve the understanding of the potential risks to human health. This study evaluates the quantitative structure-activity relationships from measured log K_ow's and log LC₅₀'s for Pimephales promelas (fathead minnow) and Carassius auratus (goldfish). Scientific support of the current regulations is also addressed. Two monomer classes were designated: acrylates and methacrylates. Spearman rank correlation and linear regression were run. Based on this study, an ecotoxicological difference exists between acrylates and methacrylates. Regulatory activities and scientific study should reflect this difference.