Robert L. Spehar

Toxicity and bioaccumulation of cadmium and lead in aquatic invertebrates

Abstract Cadmium toxicity and lead toxicity to four species of insects ( Pteronarcys dorsata, Hydropsyche betteni, Brachycentrus sp. and Ephemerella sp.), one snail ( Physa integra ) and one amphipod ( Gammarus pseudolimnaeus ) were determined during 28-day exposures. The 28-day LC50 values for cadmium-exposed snails and lead-exposed amphipods were eleven and four times lower than the 7- and 4-day (96 h) values for these metals, respectively. Lowest effect concentrations obtained after 28 days for cadmium-exposed mayflies ( Ephemerella sp.) and snails and lead-exposed amphipods were similar to those affecting fish exposed over their complete life cycle in water of similar quality. Lethal threshold concentrations were not observed for species exposed to either metal, indicating that possible effects could occur at lower concentrations during longer exposure periods. Cadmium and lead concentrations in the animals tested generally increased with increasing water concentrations and were up to 30,000 and 9000 times greater than corresponding metal concentrations in the water.

Comparative toxicity of arsenic compounds and their accumulation in invertebrates and fish

The toxicity of arsenic III, arsenic V, sodium dimethyl arsenate, and disodium methyl arsenate to stoneflies, snails, amphipods, and trout, and the bioaccumulation of these compounds were studied during a 28-day flow-through test.Daphnia magna were exposed for 21 days in static tests to determine life-cycle effects. All animals were exposed to concentrations of approximately 100 and 1000μg/L (as arsenic) of each of the compounds. Arsenic III, the most toxic compound, caused a significant reduction in the survival of amphipods at 1000μg As/L after seven days. None of the compounds significantly affected the survival of other test species after 28 days or reduced young production inDaphnia after 14 days of exposure. The concentration of accumulated arsenic in stoneflies, snails,and Daphnia was as much as 131, 99, and 219 times greater than the water concentration, whereas amphipods and rainbow trout contained arsenic residues similar to the controls. Residues in stoneflies, snails, andDaphnia exposed to 1000μg As/L were higher than those in animals exposed to 100μg As/L, but appeared to reach a steady state after 14 days. Total arsenic accumulation was greatest in organisms exposed to inorganic arsenic, particularly at 100μg/L.

Chronic Effects of Cadmium and Zinc Mixtures on Flagfish (Jordanella floridae)

Abstract Flagfish were exposed to cadmium and zinc as individual metals and as mixtures (4.3-8.5 μg Cd/liter and 73.4-139 μg Zn/liter) through one complete life cycle in Lake Superior water (45 mg/liter total hardness). Cadmium and zinc did not act additively at sublethal concentrations when combined as mixtures; however, a joint action of the toxicants was indicated. Effects on survival showed that the toxicity of cadmium and zinc mixtures was little if any greater than the toxicity of zinc alone. Mechanisms of zinc toxicity in this test were similar to those in previous chronic tests of individual metals, indicating that the presence of cadmium did not influence the mode of action of zinc. Comparisons between metal residues in fish exposed to each individual metal or to the metal mixtures showed that the uptake of one metal was not influenced by the presence of the other.

Toxicity of the synthetic pyrethroids, permethrin and AC 222, 705 and their accumulation in early life stages of fathead minnows and snails

Abstract Early life stages of fathead minnows ( Pimephales promelas ) were exposed to permethrin and AC 222, 705 and snails ( Helisoma trivolvis ) were exposed to permethrin in continuous flow-through exposures for approximately 30 days. Saturated solutions of each pesticide were used to avoid the use of solvents. Survival of newly hatched larvae and early juveniles was found to be the most sensitive measure of effect on fathead minnows of both pesticides. AC 222, 705 was approximately 20 times more toxic to fathead minnows than permethrin by the end of the test period. Based on the chronic limits, as defined in these tests, the predicted chronic no-effect concentrations for fathead minnows were between 0.66 and 1.4 μ/l for permethrin and 0.03 and 0.07 μ/l for AC 222, 705. The no-effect concentration for permethrin and snails was ≥ 0.33 μ g/l. The chronic values for these compounds were approximately one-sixteenth and one-fourth of the corresponding 96-h LC 50 values, respectively, for fathead minnows in Lake Superior water. The mean bioconcentration factors (BCFs) for permethrin were 2800 for fathead minnows and 800 for snails. The mean BCF for AC 222, 705 and fathead minnows was 4000. Residue concentrations for both pesticides increased with increased water concentrations.

Using field data and weight of evidence to develop water quality criteria

ABSTRACT In the United States, ambient aquatic life water quality criteria are derived using guidelines developed in 1985 that include a clear and consistent methodology using data from standard toxicity tests. The methodology from these guidelines has been successful, but a broader methodology is needed because some effects of pollutants do not lend themselves to conventional toxicity testing. Criterion assessment is proposed as that methodology. In criterion assessment, a specific environmental goal is translated into a measurable benchmark of effect that is used together with a modeled exposure–response relationship to estimate a range of exposures that will achieve the specific goal. The model of the exposure–response relationships and the benchmark effect are developed from field data and laboratory data using multiple analytical methods. Then the model is solved for the effect, thereby estimating the criterion, an upper threshold for acceptable exposures. The resulting candidate criteria are synthesized to select criteria and other benchmark values, such as remedial goals. The criterion assessment process is illustrated using the US Environmental Protection Agency Framework for Developing for Suspended and Bedded Sediments Water Quality Criteria, which recommends developing alternative candidate criterion values and then evaluating them to select a final criterion. Candidate criteria may be derived from models of field observations, field manipulations, laboratory tests, or empirical and theoretical models. Final selection of a criterion uses a weight-of-evidence comparison that engenders confidence because causal associations are confirmed on the basis of different assumptions, independent data sets, and varied statistical methods, thereby compensating for the concerns raised by individual studies and methods. Thus, it becomes possible to specify criteria for agents with biological or physical modes of action, as well as those with chemical modes of action, to best achieve environmental goals.

Comparative toxicity and bioconcentration of nonylphenol in freshwater organisms

Degradation of alkylphenol ethoxylates to more persistent alkylphenols such as nonylphenol occurs in wastewater treatment plants where nonylphenol is released to aquatic systems. In this study, acute and chronic tests were conducted to determine the toxicity and bioconcentration of nonylphenol to freshwater organisms for use in deriving national water quality criteria. Acute median effect concentrations (EC50s) based on loss of equilibrium, immobility, and lethality for species representing several taxonomic groups ranged from 21 to 596 microg/L. The EC50s were up to a factor of 2 less than median lethal concentrations (LC50s) and decreased with time over the test periods of 24 to 96 h. In chronic tests, early life stages of rainbow trout were 14 times more sensitive to nonylphenol than in acute tests and approximately 20 times more sensitive than Daphnia magna exposed over their complete life cycle. Comparisons of chronic test endpoints showed that 20% effect concentrations (EC20s), determined by regression testing, and chronic values, determined by hypothesis testing, were similar for both the rainbow trout and Daphnia magna. The lowest mean tissue-effect concentrations of nonylphenol appeared to be greater for the fathead minnow than bluegill, and ranged from approximately 130 to 160 microg/g after 96-h exposure and from approximately 20 to 90 microg/g after 28-d exposure. Mean lipid normalized bioconcentration factors (BCFs) associated with no-effect concentrations were approximately 180 and 50 for the fathead minnow and bluegill, respectively. The present test results suggest that long-term exposures to nonylphenol at concentrations found in some surface waters could adversely impact sensitive components of freshwater communities.

Estimation of Effect Thresholds for the Development of Water Quality Criteria

Biological and ecological effect thresholds can be used for determining safe levels of nontraditional Stressors. The U.S. EPA Framework for Developing Suspended and Bedded Sediments (SABS) Water Quality Criteria (WQC) [36] uses a risk assessment approach to estimate effect thresholds for unacceptable levels of SABS in water bodies. Sources of SABS include: 1. Erosion from agricultural, construction, forestry practices, and stream banks 2. Resuspension of deposited sediment 3. Direct discharge from municipal, industrial, and agricultural sources Excessive levels of SABS can destroy habitat for plants and animals, reduce the quality of drinking water, impair the quality and safety of recreational waters, increase the costs associated with irrigation and navigation, and decrease aesthetics. The SABS Framework is intended as a guide to the development of water quality criteria (WQC) and restoration targets. The SABS Framework uses an eco-epidemiological perspective to incorporate information from field observations with data from controlled laboratory experiments. The combined information is used to develop relationships that estimate the levels of SABS that will impair aquatic life or pollute sources intended for drinking water. The SABS Framework uses several statistical procedures to compare the estimated effects levels derived from field and laboratory data. Protective levels and restoration goals are recommended based on scientific precedent, logical argument, and statistical resolution. The risk estimates that result from using this approach are readily applicable for use in future emergency situations.