Acute and chronic toxicity of copper to the euryhaline rotifer, Brachionus plicatilis ("L" strain).

This article presents data from original research, intended for the use in the development of copper (Cu) criteria for the protection of estuarine and marine organisms and their uses in the United States. Two 48-h static-acute toxicity tests-one with and one without added food-and a 96-h static multigeneration life-cycle test (P1-F2 generations) were performed concurrently using the euryhaline rotifer Brachionus plicatilis ("L" strain) to develop a Cu acute-to-chronic ratio (ACR) for this species. Tests were performed at 15 g/L salinity, at 25°C, and the exposure concentrations of dissolved Cu were verified. Supplemental chemical analyses were performed and reported for the development of a Cu-saltwater biotic ligand model (BLM). Supplemental analyses included alkalinity, calcium, chloride, dissolved organic carbon (DOC), hardness, magnesium, potassium, sodium, and temperature. The acute toxicity test measurement end points were the dissolved Cu median lethal concentration (LC50) values based on rotifer survival. The chronic measurement end points were the dissolved Cu no-observed-effect concentration (NOEC), lowest-observed-effect concentration (LOEC), EC25, EC20, and EC10 based on the intrinsic rate of rotifer population increase (r). The 48-h LC50(Fed), 48-h LC50(Unfed), 96-h NOEC, 96-h LOEC, EC25, EC20, and EC10 were 20.8, 13.4, 6.1, 10.3, 11.7, 10.9, and 8.8 µg Cu/L, respectively. The ACRs were calculated as ratios of each 48-h LC50 value [fed and unfed) and each of the 96-h chronic values (ChV; geometric mean of NOEC and LOEC)], EC10, EC20, and EC25. The ACRs ranged from 1.15 to 2.63.

The effects of salinity, pH, and dissolved organic matter on acute copper toxicity to the rotifer, Brachionus plicatilis ("L" strain).

This paper presents data from original research for use in the development of a marine biotic ligand model and, ultimately, copper criteria for the protection of estuarine and marine organisms and their uses. Ten 48-h static acute (unfed) copper toxicity tests using the euryhaline rotifer Brachionus plicatilis ("L" strain) were performed to assess the effects of salinity, pH, and dissolved organic matter (measured as dissolved organic carbon; DOC) on median lethal dissolved copper concentrations (LC50). Reconstituted and natural saltwater samples were tested at seven salinities (6, 11, 13, 15, 20, 24, and 29 g/L), over a pH range of 6.8-8.6 and a range of dissolved organic carbon of <0.5-4.1 mg C/L. Water chemistry analyses (alkalinity, calcium, chloride, DOC, hardness, magnesium, potassium, sodium, salinity, and temperature) are presented for input parameters to the biotic ligand model. In stepwise multiple regression analysis of experimental results where salinity, pH, and DOC concentrations varied, copper toxicity was significantly related only to the dissolved organic matter content (pH and salinity not statistically retained; alpha=0.05). The relationship of the 48-h dissolved copper LC50 values and dissolved organic carbon concentrations was LC50 (microg Cu/L)=27.1xDOC (mg C/L)1.25; r2=0.94.

The influence of salinity and dissolved organic carbon on the toxicity of copper to the estuarine copepod, Eurytemora affinis.

The objectives of this study were to determine the influence of salinity (2.5, 5, 15, and 25 ppt) at dissolved organic carbon (DOC) concentrations of 1.3-3.3 mg/L and DOC concentrations of 2, 4, 6, and 8 mg/L at a fixed salinity of 10 ppt on the acute toxicity (96-h LC50s) of copper to the sensitive estuarine copepod, Eurytemora affinis. For both salinity and DOC experiments, various other chemical constituents such as DOC, Ca2+, Cl(-), Mg2+, Na+, K+, SO4 (2-) , hardness, alkalinity, salinity, pH, temperature, and dissolved oxygen were measured at selected copper concentrations at test initiation and test termination. Dissolved copper, copper speciation, and organic copper complexation were measured at various test conditions during the salinity and DOC experiments. Ninety-six-hour dissolved copper LC50 values for the four salinities ranged from 58 microg/L (25 ppt) to 104 microg/L (5 ppt) with intermediate values of 71 microg/L (2.5 ppt) and 68 microg/L (15 ppt). The 58, 68, and 71 microg/L LC50 values were not significantly different. Copper LC50 values at 5 ppt were higher than at both 15 and 25 ppt. The isosmotic salinity of E. affinis is approximately 5-10 ppt, which was a likely factor for why the LC50 value increased for copper at 5 ppt. The dissolved copper 96-h LC50s for E. affinis increased from 76 to 166 microg/L as DOC increased from 2 to 8 mg/L. This result is not surprising and is consistent with reported values for other saltwater species.

Validation and update of a model used to predict copper toxicity to the marine bivalve Mytilus sp.

A model was recently published that relates the toxicity of copper to the most sensitive taxa in the U.S. Environmental Protection Agency's criteria database (Mytilus sp.) with dissolved organic carbon concentrations in saltwater. This model was developed for potential use in risk assessment and in the development of site-specific criteria (SSC) for copper in saltwater environments where Mytilus sp. is considered an appropriate indicator species. This manuscript presents the results of a field validation study of that model. Effective concentration 50% (EC(50)) values (n = 21) for seven sites were all predicted by the model within the previously established range of acceptability. Slopes and intercepts of the two data sets were not significantly different. Consequently, the data were pooled, and new equations were developed. Dissolved copper EC(50) values were highly correlated (r(2) = 0.76, n = 75, P < 0.0001) across a wide range of sample dissolved organic carbon (DOC) concentrations (0.3-12 mg C/L) and were explained by the equation EC(50) = 11.22 DOC(0.60). Two updated equations are proposed for consideration as a means of estimating site-specific final chronic criteria (FCC) and final acute criteria (FAC) for copper in marine and estuarine environments (copper FCC(DOC) = 3.59 DOC(0.60); copper FAC(DOC) = 5.61 DOC(0.60)).

Predicting copper toxicity in estuarine and marine waters using the Biotic Ligand Model.

The Biotic Ligand Model (BLM) has proven efficient in predicting the toxicity of a variety of metals to freshwater organisms. Consequently, the US EPA has proposed its use for calculating freshwater copper criteria. This study evaluates the BLM for use in estuarine and marine waters. Studies were conducted using the bivalve, Mytilus sp. and 48-h embryo-larval development chronic estimator test methods. These are the most sensitive taxa and test in the US EPA saltwater copper criteria database. Samples from five locations around the USA were tested. There is a strong relationship between measured and BLM predicted copper EC50s (log transformed data, r(2)=0.76, p<0.001, n=44). The BLM predicted within a factor +/-2 of measured EC50s in 41 of 44 cases. However, the BLM tends to predict lower EC50s when measured EC50s are approximately < or =10 microg Cu/L. This may be due to limitations of the metal-dissolved organic matter interaction model.

Acute toxicity of vanadium to the threespine stickleback, Gasterosteus aculeatus.

Vanadium is widely distributed, occurring in many types of minerals, coal, and petroleum. Anthropogenic sources of vanadium originate from the production, processing, and wastes of these materials. The aquatic toxicity of vanadium to fish species is not well characterized. This study focused on the three-spined stickleback, Gasterosteus aculeatus, a small and widely distributed euryhaline species of fish. The three-spined stickleback is used as an effluent-monitoring species in both Canada and the United States. Five 96-h static renewal acute toxicity tests were performed in moderately hard water with adult fish. The geometric mean and range of the five 96-h LC(50)s based on measured concentrations of total vanadium in the test solution were 3.17 and 2.35-4.07 mg V/L, respectively. A conservative estimation of a safe concentration of vanadium that would not affect survival of adult three-spined sticklebacks over a 96-h exposure period in moderately hard water is approximately 0.30 mg V/L. A comparison with other fish species previously tested suggests that the three-spined stickleback is intermediate in sensitivity to vanadium. Information reported from this study may be useful in effluent toxicity identification evaluations and ecological risk assessments related to vanadium.

MTBE ambient water quality criteria development: a public/private partnership.

A public/private partnership was established in 1997, under the administrative oversight of the American Petroleum Institute (API), to develop aquatic toxicity data sufficient to calculate ambient water quality criteria for methyl tertiary-butyl ether (MTBE), a gasoline oxygenate. The MTBE Water Quality Criteria Work Group consisted of representatives from private companies, trade associations, and USEPA. Funding was provided by the private entities, while aquatic biological/toxicological expertise was provided by industry and USEPA scientists. This public/private partnership constituted a nonadversarial, cost-effective, and efficient process for generating the toxicity data necessary for deriving freshwater and marine ambient water quality criteria. Existing aquatic toxicity data were evaluated for acceptability, consistent with USEPA guidance, and nineteen freshwater and marine tests were conducted by commercial laboratories as part of this effort to satisfy the federal criteria database requirements. Definitive test data were developed and reported under the oversight of industry study monitors and Good Laboratory Practice standards auditors, and with USEPA scientists participating in advisory and critical review roles. Calculated, preliminary freshwater criteria for acute (Criterion Maximum Concentration) and chronic (Criterion Continuous Concentration) exposure effect protection are 151 and 51 mg MTBE/L, respectively. Calculated, preliminary marine criteria for acute and chronic exposure effect protection are 53 and 18 mg MTBE/L, respectively. These criteria values may be used for surface water quality management purposes, and they indicate that ambient MTBE concentrations documented in U. S. surface waters to date do not constitute a risk to aquatic organisms.

Development of a freshwater aquatic toxicity database for ambient water quality criteria for methyl tertiary-butyl ether.

The detection of methyl tertiary-butyl ether (MTBE) in groundwater and surface water in recent years has drawn attention to its potential effects in aquatic ecosystems. To address concerns regarding MTBE environmental effects and to establish safe concentrations in surface waters, a collaborative effort was initiated in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with United States Environmental Protection Agency (U.S. EPA) requirements. Acute toxicity data for six species, chronic toxicity data for a fish and an invertebrate, and plant toxicity data were developed in order to complete the freshwater database. The toxicity tests followed U.S. EPA and American Society for Testing and Materials (ASTM, Philadelphia, PA, USA) procedures and were conducted in accordance with U.S. EPA Good Laboratory Practice guidelines. Based on measured exposure concentrations, acute toxicity endpoints ranged from 472 to 1742 mg MTBE/L, while chronic endpoints (IC25) were 57 to 308 mg MTBE/L. Aquatic invertebrates were generally more sensitive than fish to MTBE in both acute and chronic exposures. Acute-to-chronic ratios for fathead minnows and Daphnia magna were 3.4 and 11.3, respectively. The measured acute and chronic toxicity were within a 10-fold factor of toxicity predicted from quantitative structure-activity relationships for baseline toxicity or nonpolar narcosis typical of ether compounds. The data developed in this study were consistent with existing data and showed that MTBE has low acute and chronic toxicity to freshwater organisms. Reported environmental concentrations of MTBE are several orders of magnitude lower than concentrations observed to cause effects in freshwater organisms.

Host cell reactivation of irradiated adenovirus in UV-sensitive Chinese hamster ovary cell mutants.

In this study we have utilized the ability of rodent cells to replicate viral DNA following semi-permissive infection by human adenovirus (Ad) to examine the host cell reactivation (HCR) of radiation-damaged Ad in several UV-sensitive Chinese hamster ovary (CHO) cell mutants. A significant reduction in HCR of viral DNA synthesis for UV-irradiated Ad was detected in a series of UV-sensitive mutants from complementation groups 1-6 derived from parental CHO-AA8 cells. HCR for UV-irradiated Ad in these CHO mutants varied from 18.8 to 48.0% of that in parental AA8 cells. However, a significant reduction in HCR of viral DNA synthesis for UV-irradiated Ad could not be detected in series of UV-sensitive PV mutants from complementation groups 1, 5, 9 and 10 derived from parental CHO-K1 cells, which harbour relatively small DNA repair deficiencies. We also report a reduced HCR for gamma-irradiated Ad in UV-sensitive CHO cell mutants from groups 1 and 4 derived from parental CHO-AA8 cells. This HCR technique for DNA synthesis of Ad can be employed to measure the DNA repair capacity of both human and rodent cells and extended to examine the repair of DNA damaged by a variety of different physical and chemical agents.