Interspecies correlations of toxicity to eight aquatic organisms: Theoretical considerations

Interspecies correlations allow the prediction of toxicity to a number of other species. However, little attention has been paid to the theoretical considerations of the interspecies relationship based on the differences of bio-uptake and toxic mechanism between species. This study examines the interspecies correlations of toxicity between species of Vibrio fischeri, river bacteria, algae, Daphnia magna, carp, Tetrahymena pyriformis, fathead minnow and guppy based on the theoretical background. The results show that there are good interspecies correlations between marine bacterium and fresh water bacteria or fish and fish. It is suggested that compounds share the same bio-uptake and toxic mechanism of action between the species. On the other hand, poor interspecies relationships were found between toxicities to algae and T. pyriformis or D. magna. It is suggested that compounds have different toxic mechanisms of action between these species. Interspecies relationships can be improved by inclusion of the octanol/water partition coefficient or the energy of the lowest unoccupied molecular orbital. They reflect the difference of bio-uptake or toxic mechanism of action between species for organic compounds. Benzoic acids show very different toxicity contributions to the three species, V. fischeri, D. magna and carp. They can be easily absorbed into the unicellular bacteria, V. fischeri. On the contrary, the skin and lipid content of multicellular organisms, such as D. magna and fish, can strongly inhibit the bio-uptake for ionizable compounds, which results in the different toxic effect between V. fischeri and D. magna or carp. Good correlation coefficients were observed between toxicities to V. fischeri and D. magna or fishes by inclusion of hydrophobic and ionization parameters. V. fischeri or D. magna can serve as a surrogate of fish toxicity for hydrophobic and ionizable compounds studied. Toxic mechanisms of action are discussed based on the theoretical background of the interspecies correlation.     

Effect of water hardness on the toxicity of a nonionic detergent to fish

Fish (trout and goldfish) were placed in treatment solutions of different water hardnesses containing ethoxylate (EO) detergents. Survival times were recorded, ¹⁴C-labelled EO was used to assess absorption. The toxicity of ethoxylates to fish acclimatised and treated in different water hardnesses, and the effect of cations on ethoxylate toxicity were also investigated, EO is slightly less toxic in hard water than in soft water. The hardness of the treatment solution has no marked influence on the amount of EO absorbed by the fish. Evidence suggests that there is little relationship between the composition of cations constituting a particular hardness and the toxicity of EO. Acclimatisation in different water hardnesses does not affect the susceptibility of fish to nonionic ethoxylate detergents.     

Acute toxicity of selected hydrazines to the common guppy

Hydrazine, unsymmetrical dimethylhydrazine (UDMH), Aerozine-50 and monomethylhydrazine were evaluated, respectively, in three or four static bioassays each using hard and soft water. Hydrazine was the most toxic compound and UDMH the least toxic to common guppies. Hydrazine was significantly more toxic in soft water than hard water, whereas UDMH was the opposite. The results of bioassays in which survival times of fish pre-exposed to these compounds were compared to those previously unexposed, along with other observations, indicate that the toxic effects of the hydrazines are cumulative. The effects of chemical differences in these compounds, of water quality characteristics and of other factors on acute toxicity are discussed.     

Acute and chronic toxicity of lead to rainbow trout salmo gairdneri, in hard and soft water

Lead was found to be highly toxic to rainbow trout in both hard water (hardness 353 mg l⁻¹ as CaCO₃) and soft water (hardness 28 mg l⁻¹. Analytical results differ greatly with methods of analysis when measuring concentrations of lead in the two types of water. This is exemplified in LC50's and maximum acceptable toxicant concentrations (MATC's) obtained when reported as dissolved lead vs total lead added in hard water. Two static bioassays in hard water gave 96-h LC50's of 1.32 and 1.47 mg l⁻¹ dissolved lead vs total lead LC50's of 542 and 471 mg l⁻¹, respectively. In a flow-through bioassay in soft water a 96-h LC50 of 1.17 mg l⁻¹, expressed as either dissolved or total lead, was obtained. From chronic bioassays, MATC's of lead for rainbow trout in hard water were between 18.2 and 31.7 μg l⁻¹ dissolved lead vs 120–360 μg l⁻¹ total lead. In soft water, where exposure to lead was initiated at the eyed egg stage of development, the MATC was between 4.1 and 7.6 μg l⁻¹. With exposure to lead beginning after hatching and swim-up of fry, the MATC was between 7.2 and 14.6 μg l⁻¹. Therefore, fish were more sensitive to the effects of lead when exposed as eggs.     

Bioaccumulation and toxicity of copper as affected by interactions between humic acid and water hardness

This study evaluated the effects of water hardness and humic acid (HA) on the acute and chronic toxicity of copper to Daphnia pulex and on its accumulation by D. magna. Hardness had little effect on either the acute (3-day) or the chronic (42-day) toxicity of copper. Humic acid significantly reduced both the acute and chronic toxicity of copper when added to waters having hardnesses of 58, 115 and 230 mg l^?1 as CaCO₃. The effect, per unit of HA, on chronic toxicity was very similar for soft and medium water but less in hard water. At each of two HA concentrations, copper was chronically more toxic in hard water than in either medium or soft water. Bioaccumulation of copper varied with relative hardness and HA concentration and this was further affected by age at exposure. For 1-day-old animals, an increase in either hardness or HA- or any combination of the two, tended to decrease bioaccumulation. Results for 7-day-old animals were in general agreement except for animals exposed to copper in hard water at an intermediate HA concentration. These animals accumulated significantly more copper in the presence of HA. This agrees with the fact that this concentration of HA also increased the chronic toxicity of copper in hard water. Both of those phenomena are probably due to the displacement of Cu²⁺ from HA by competition from the increased concentrations of Ca²⁺ and Mg²⁺. The fact that HA had the opposite effect on copper accumulation by young animals in hard water could not be explained.     

A single bioavailability model can accurately predict Ni toxicity to green microalgae in soft and hard surface waters

The major research questions addressed in this study were (i) whether green microalgae living in soft water (operationally defined water hardness <10 mg CaCO₃/L) are intrinsically more sensitive to Ni than green microalgae living in hard water (operationally defined water hardness >25 mg CaCO₃/L), and (ii) whether a single bioavailability model can be used to predict the effect of water hardness on the toxicity of Ni to green microalgae in both soft and hard water. Algal growth inhibition tests were conducted with clones of 10 different species collected in soft and hard water lakes in Sweden. Soft water algae were tested in a ‘soft’ and a ‘moderately hard’ test medium (nominal water hardness = 6.25 and 16.3 mg CaCO₃/L, respectively), whereas hard water algae were tested in a ‘moderately hard’ and a ‘hard’ test medium (nominal water hardness = 16.3 and 43.4 mg CaCO₃/L, respectively). The results from the growth inhibition tests in the ‘moderately hard’ test medium revealed no significant sensitivity differences between the soft and the hard water algae used in this study. Increasing water hardness significantly reduced Ni toxicity to both soft and hard water algae. Because it has previously been demonstrated that Ca does not significantly protect the unicellular green alga Pseudokirchneriella subcapitata against Ni toxicity, it was assumed that the protective effect of water hardness can be ascribed to Mg alone. The log K_MgBL (= 5.5) was calculated to be identical for the soft and the hard water algae used in this study. A single bioavailability model can therefore be used to predict Ni toxicity to green microalgae in soft and hard surface waters as a function of water hardness.     

Microbial toxicity of metal oxide nanoparticles (CuO, NiO, ZnO, and Sb2O3) to Escherichia coli, Bacillus subtilis, and Streptococcus aureus

In this study, the microbial toxicities of metal oxide nanoparticles were evaluated for Escherichia coli, Bacillus subtilis, and Streptococcus aureus in laboratory experiments. The nanoparticles tested were CuO, NiO, ZnO, and Sb₂O₃. The metal oxide nanoparticles were dispersed thoroughly in a culture medium, and the microorganisms were cultivated on Luria-Bertani agar plates containing different concentrations of metal oxide nanoparticles. The bacteria were counted in terms of colony forming units (CFU). The CFU was reduced in a culture medium containing metal oxide NP, and the dose-response relationship was characterized. CuO nanoparticles were found to be the most toxic among the tested nanoparticles, followed by ZnO (except S. aureus), NiO, and Sb₂O₃ nanoparticles. We determined that the intrinsic toxic properties of heavy metals are also associated with the toxicity of metal oxide nanoparticles. Ion toxicity was also evaluated to determine the effects of metal ions dissolved from metal oxide NPs, and the toxicity induced from the dissolved ions was determined to be negligible herein. To the best of our knowledge, this is the first study of the toxicity of NiO and Sb₂O₃ NPs on microorganisms. We also discuss the implications of our findings regarding the effects of the intrinsic toxic properties of heavy metals, and concluded that the apparent toxicities of metal oxide NPs can largely be understood as a matter of particle toxicity.     

Evaluation of laboratory derived toxic effect concentrations of a mixture of metals by testing fresh water plankton communities in enclosures

The extrapolation of single-species laboratory studies to natural communities is one of the problems encountered when carrying out risk assessment of chemicals in the environment. This is especially applicable to extrapolation problems where mixtures of chemicals are involved. To investigate whether the laboratory-derived mixture toxicity approach is valid under field conditions, a mesocosm experiment was set up in which a laboratory strain of Daphnia magna was added to a natural, fresh water plankton community and exposed to three levels of a metal mixture. The mixtures, composed of arsenic, cadmium, chromium, copper, mercury, lead, nickel and zinc, were characterized by the sum of toxic units of dissolved metal concentrations (ΣTU_dis), on the basis of EC₅₀ values obtained in a laboratory study (Enserink et al., 1991). Only a small part of the metals (about one quarter) was present in dissolved form, the remainder was bound to particulate matter. The ΣTU_dis remained constant throughout the experiment. On the basis of the population development (integrated density), an EC₅₀ of 0.83 ΣTU_dis was calculated for D. magna. All other dominant cladoceran species were more sensitive than D. magna, with EC₅₀ values of 0.53 ΣTU_dis for Ceriodaphnia spp. and 0.60 ΣTU_dis for D. cucullata respectively. Copepods were less sensitive (0.98 ΣTU_dis) and rotifers were about as sensitive as cladocerans. Significant bioconcentration factors could be calculated for arsenic, nickel, lead and mercury. Toxic effects on zooplankton resulted in elevated phytoplankton biomass due to reduced grazing. Only rotifer species were able to benefit from extra food availability, but could not prevent phytoplankton blooms from forming. It is concluded that, although the relative importance of the individual metals and the physico-chemical conditions in the natural plankton community differs from laboratory test conditions, the toxic effects on D. magna are about comparable, and that some dominant naturally present cladoceran species are more sensitive than D. magna.     

Age- and size-specific patterns of heavy metals in the organs of freshwater fish Abramis brama L. populating a low-contaminated site

Concentrations of cadmium, copper, mercury, lead and zinc were determined by atomic absorption spectrophotometry in the muscle, gill and liver of bream Abramis brama L. to study the relationship between the heavy metal load of fish and their age and size, and the seasonal variation of pollutant loads. Fish were collected from the Western basin of Lake Balaton (Hungary) in October 1999 and May 2000. The average metal concentrations of different organs varied in the following ranges: Cd 0.42-2.10; Cu 1.77-56.2; Hg 0.01-0.19; Pb 0.44-3.24; Zn 10.9-82.5 microg g(-1) dry weight. The highest Cd, Cu, Pb and Zn concentrations were detected in the gill or liver of fish, whereas the highest Hg concentrations were measured in the muscle. In the liver of bream for cadmium, copper and mercury the Pearson correlation analysis revealed positive associations related to age and size (length, net weight), as well as for the mercury load of all three investigated organs. In the muscle and gill the copper, lead and zinc concentrations, similarly to the lead and zinc concentrations of the liver, the associations related to age and size were negative. The correlations between the heavy metal concentrations of organs and the individual condition factors of fish samples proved to have opposite trends compared to those related to the age and size of fish. The seasonal variations in the heavy metal load of bream could be attributed rather to the seasonal change in the condition factor of fish than to variations in the pollutant load of the site.     

Heavy metal exposure in patients suffering from electromagnetic hypersensitivity

Background

Risks from electromagnetic devices are of considerable concern. Electrohypersensitive (EHS) persons attribute a variety of rather unspecific symptoms to the exposure to electromagnetic fields. The pathophysiology of EHS is unknown and therapy remains a challenge.

Objectives

Heavy metal load has been discussed as a potential factor in the symptomatology of EHS patients. The main objective of the study was to test the hypothesis of a link between EHS and heavy metal exposure.

Methods

We measured lead, mercury and cadmium concentrations in the blood of 132 patients (n = 42 males and n = 90 females) and 101 controls (n = 34 males and n = 67 females).

Results

Our results show that heavy metal load is of no concern in most cases of EHS but might play a role in exceptional cases.

Conclusions

The data do not support the general advice to heavy metal detoxification in EHS.     

The influence of heavy metals on a mixed bacterial population of sewage origin in the chemostat

A reproducible mixed continuous bacterial population has been cultured in the chemostat at a low dilution rate. Four species originally isolated from activated sludge were used to provide an inoculum. The influence of cadmium, chromium, copper and lead as shock doses has been examined at concentrations of 50 mg l⁻¹ and the response of the population was found to vary for each metal. The most toxic metal was copper followed by cadmium, lead and chromium. Continuous doses of chromium and lead have been studied, the latter over a range of concentrations. It appears that concentrations of lead as low as 5 mg l⁻¹ cause modifications in the individual population sizes. Some of the species studied were found to be more resistant to heavy metal toxicity than others.     

Effect of water hardness on the toxicity of an anionic detergent to fish

The toxicity to fish of anionic detergents in solution varies considerably according to the hardness of the water in which the fish are treated. Trout and goldfish are more susceptible to sodium lauryl sulphate (SLS) in hard water than soft, and the rate of absorption of detergent is greater in hard water. It has been shown that the concentration of bivalent cations has a direct effect on the toxicity of SLS. Acclimatization experiments have shown that the toxicity of SLS depends not only on the hardness of the water in which the fish are treated, but also on the hardness of the water in which the fish have previously been acclimatized. The mechanism whereby water hardness affects detergent toxicity is discussed.     

Treatment of stormwater using a detention pond and constructed filters

A stormwater treatment plant, consisting of a detention pond, a constructed filter system and a constructed wetland, has been investigated according to stormwater quality improvement, sediment and heavy metals accumulation and potential toxicity of the stormwater and sediment. The reduction of metal content in the detention pond was on average 26?–?84%. No acute toxicity in the stormwater was detected although heavy metal levels often exceeded guideline values during storm events. Pore water samples of the collected sediments were not toxic but the whole sediment was toxic when assessed with the Microtox^® Solid-phase test. The constructed filter system became clogged due to cementation of the filter substrate.     

A laboratory model for evaluating the behavior of heavy metals in an aquatic environment

A dynamic biological system capable of simultaneously distinguishing between bioaccumulation and biomagnification through successive trophic levels in an aquatic ecosystem is described. The organisms used in the system were algae, predominantly Scenedesmus sp., Daphnia magna, fresh water mussels (Ligumia sp. and Margaritifera sp.) and the fathead minnow, Pimephales promelas.Thiosulfate complexed mercury and silver were each studied at two concentrations. The water and organisms were analyzed for the metals periodically during the 10-week tests. Both mercury and silver can be bioaccumulated by fish. The concentration factors for mercury are greater than for silver. Further, mercury is biomagnified by fish whereas silver is not. Fresh water mussels were found to be poor indicator species for metal contamination.     

A study of metal concentrations and metallothionein binding capacity in liver, kidney and brain tissues of three Arctic seal species

Arctic seals are known to accumulate relatively high concentrations of potential toxic heavy metals in their vital organs, such as livers and kidneys, as well as in their central nervous system. We therefore decided to determine whether mercury, copper, cadmium and zinc levels in liver, kidney and brain tissues of three Arctic seal species were associated with the intracellular metal-binding protein metallothionein (MT) as a sign of toxic exposure. Samples from four ringed (Phoca hispida), five harp (P.groenlandica) and five hooded (Cystophora cristata) seals taken during field trips to Central West Greenland (Godhavn) and the Barents Sea in the spring of 1999 were used for the present study. In all three seal species concentrations of mercury, zinc and copper were highest in the liver, except for cadmium which was highest in the kidneys. Metal concentrations increased significantly in the order: ringed seal < harp seal < hooded seal for both kidney and liver tissues. MT concentrations were highest in the kidneys and the concentrations increased in the order: ringed seal < hooded seal < harp seal. MT metal-binding capacity was highest in the kidneys for all three species and increased in the same order: ringed seals (2-10%) < hooded seals (8-15%) < harp seals (27-63%). We therefore suggest that there are species-specific differences in the sub-cellular handling of heavy metals which indicate differences in sensitivity and health implications. However, a larger sample size is needed in order to test the relationship between metal concentrations and MT up-regulation in order to decide which metals are the most important and to elucidate whether the MT binding capacity is sufficient to protect tissues (i.e. kidney) from metal toxicosis. MT with its binding capacity could be a useful marker for environmental exposure to metals and their potential toxicity in the Arctic.     

Whole blood mercury and selenium concentrations in a selected Austrian population: does gender matter?

Background

Data on mercury exposure of the Austrian population were inadequate. This study was performed to determine the causal factors underlying mercury exposure and selenium concentrations, and to estimate the gender-related health impacts.

Methodology

Venous blood samples of 78 women and 81 men were drawn at the Austrian Red Cross, Vienna. Mercury contents in acid-digested whole blood samples were measured after amalgam enrichment by CV-AAS, and selenium by AAS (heated quartz-cell) after hydrid formation.

Results

The average total mercury blood content of Austrians was low (2.38 ± 1.55 μgL^− 1; N = 152). Mercury and selenium concentrations were not different between the genders (P > 0.05) but we observed discrepancies regarding the causal factors. Mercury levels in men were influenced not only by fish consumption but also by age, education level, and amalgam fillings, whereas in women, only the diet (fish/seafood, red wine consumption) determined blood mercury (P < 0.05). Moreover, only the males indicated a depressive effect of dental amalgam on hematocrit (P < 0.05). Regarding selenium, age and alcohol consumption led to lower concentrations in men, whereas a high-level education had the opposite effect; no determinant was found for women. For the whole study group, a significant effect of chronic disease on selenium levels could be detected (P < 0.05). 18% of women and 13% of men showed marginal selenium deficiency (blood selenium < 65 μgL^− 1). Selenium and mercury concentrations were not correlated.

Conclusions

Our results indicate the need to evaluate and integrate gender-related findings in metal toxicology and trace element research, because different causal factors require different preventive measures to reduce mercury exposure and the risk of low selenium concentrations. Future research is needed on the gender- and age-related differences in fish/seafood consumption habits, the modifications of mercury toxicokinetics through sex hormones, the selenium supply in Austria, and the clinical relevance of a low selenium status.     

The influence of nitrilotriacetic acid on heavy metal transfer in the activated sludge process-I. at constant loading

Removal of metals in the sewage treatment process is closely related to the chemical forms in which the metals exist. One critical factor controlling the forms of the metals in sewage is the chemical matrix of the sewage; as a consequence of their chelating capacity detergent builders are important in modifying the sewage matrix. Laboratory simulations of the activated sludge process have been studied to estimate the impact of the detergent builder nitrilotriacetic acid on the removal of heavy metals from sewage in this treatment process.The acclimation period for the biodegradation of nitrilotriacetic acid in a hard water synthetic sewage was found to vary from 16 to 31 days. In a soft water synthetic sewage, biodegradation was not observed even after 60 days. Hydrolysis of condensed phosphates in both hard and soft water synthetic sewages occurred within 3 h. Even when substantially biodegraded in hard water synthetic sewage, nitrilotriacetic acid appeared to be adversely affected by the absorption of cadmium, copper and zinc by the biological solids. The greatest absorption of heavy metals to the biological solids occurred when condensed phosphates were present. In soft water synthetic sewage metal absorption was minimal in the presence of nitrilotriacetic acid. In the presence of condensed phosphates absorption was considerably higher but not comparable with that achieved in hard water synthetic sewage.     

Phytoprotective influence of bacteria on growth and cadmium accumulation in the aquatic plant Lemna minor

Certain plants are known to accumulate heavy metals, and can be used in remediation of polluted soil or water. Plant-associated bacteria, especially those that are metal tolerant, may enhance the total amount of metal accumulated by the plant, but this process is still unclear. In this study, we investigated metal enhancement vs. exclusion by plants, and the phytoprotective role plant-associated bacteria might provide to plants exposed to heavy metal. We isolated cadmium-tolerant bacteria from the roots of the aquatic plant Lemna minor grown in heavy metal-polluted waters, and tested these isolates for tolerance to cadmium. The efficiency of plants to accumulate heavy metal from their surrounding environment was then tested by comparing L. minor plants grown with added metal tolerant bacteria to plants grown axenically to determine, whether bacteria associated with these plants increase metal accumulation in the plant.Unexpectedly, cadmium tolerance was not seen in all bacterial isolates that had been exposed to cadmium. Axenic plants accumulated slightly more cadmium than plants inoculated with bacterial isolates. Certain isolates promoted root growth, but overall, addition of bacterial strains did not enhance plant cadmium uptake, and in some cases, inhibited cadmium accumulation by plants. This suggests that bacteria serve a phytoprotective role in their relationship with Lemna minor, preventing toxic cadmium from entering plants.     

Influence of prefreezing on heavy metal concentrations in Bluegill sunfish

Concern for possible changes in tissue metal concentrations due to freezing of fish specimens prior to analysis prompted this investigation. Bluegill sunfish (Lepomis macrochirus) were collected from a Virginia stream and prepared for analysis of zinc, cadmium and lead concentrations either fresh or after 1, 7, and 70 days of freezing. Intact specimens as well as bone and liver tissue were then analyzed. Zinc concentrations displayed a statistically significant (P < 0.05) negative trend with duration of freezing in whole-body, liver and bone samples. Lead and cadmium concentrations showed no consistent pattern which could be related to length of the freezing period in any of the tissues analyzed. However, median concentrations of zinc, cadmium and lead were 10–30% lower in prefrozen sunfish (aggregated over freezing periods) than in sunfish which were analyzed fresh in seven of the eight tissue-metal combinations examined. These results indicate that freezing of sunfish prior to sample preparation can depress metal concentrations in both tissues and whole fish. Programs to monitor heavy metal contamination in sunfish and other fishes may incur bias unless specimens are prepared for analysis fresh or all samples experience equivalent freezing regimes.     

Blood total mercury and fish consumption in the Korean general population in KNHANES III, 2005

Objectives

The obejective of this study was to assess the association between the blood total mercury concentration and fish consumption in the Korean general adult population using a representative sample.

Methods

We studied the blood mercury concentration in a representative sample of 1,749 Koreans who were included in the Third Korean National Health and Nutritional Examination Survey (KNHANES III) performed in 2005, and compared it with the frequency of fish consumption collected during the nutrition survey of KNHANES III.

Results

The geometric means of the blood mercury levels in female subjects (n = 890), male subjects (n = 859), and all participants (n = 1,749) representing adult Koreans aged ≥ 20 years were 3.70 μg/L [95% confidence interval (CI), 3.46-3.94 μg/L], 4.70 μg/L (95% CI, 4.38-5.02 μg/L), and 4.15 μg/L (95% CI, 3.93-4.38 μg/L), respectively. The geometric mean of the blood mercury level was significantly higher in the high-fish-consumption group (4.38 μg/L; more than once a week) than in the low-consumption group (3.71 μg/L: less than once a week), but the intergroup difference of 18% was less than that in Western countries. Among the nine listed individual types of fish and shellfish, there was a general trend for the blood mercury level to increase with the consumption frequency of squid, clam, salted seafood, and mackerel. The proportion of Korean women aged 20-49 years having blood mercury levels of at least 5.8 μg/L was 27.7% (150/542) in our study.

Conclusions

The blood mercury level in a representative sample of the Korean adult population was found to be associated with fish consumption in both men and women. However, a high consumption of fish increased the blood mercury level by only 18%.