Acute Toxicity Of Heavy Metals Research Articles

Trophic transfer and toxicity of heavy metals from dengue mosquito Aedes aegypti to predator dragonfly Tramea cophysa.

Heavy metal pollution in aquatic habitats can be detrimental to both prey and predators in a food web. To investigate the potential for bio-transfer and bioaccumulation of heavy metals between specific trophic levels, 3rd instar larvae of Aedes aegypti were exposed to mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) for three consecutive generations and fed to dragonfly (Tramea cophysa) nymphs. Exposure to Hg caused the highest mortality in A. aegypti larvae and T. cophysa nymphs. Bioaccumulation and life-history parameters of A. aegypti, including egg hatching time, larval and pupal duration, male and female life span, and fecundity, were also evaluated after metals exposure. All life-history parameters except larval duration were significantly affected by heavy metal treatments. Bioaccumulation of metals in A. aegypti larvae and adults gradually and significantly increased from 1st to 3rd generation. To the best of our knowledge, this is the first study describing the acute toxicity of heavy metals to mosquitoes. Our study shows that heavy metals cause dietary toxicity to an aquatic predator, dragonfly, via trophic transfer, which could have considerable consequences on aquatic ecosystems.

Acute heavy metal toxicity test based on bacteria-hydrogel

Toxicity test sensor for heavy metal ions is developed in this work. It founds that toxic heavy metal ions leads both bacterial enzymatic activity and viability. Moreover, the hydrogel encapsulation of bacteria was performed to achieve two purposes: (1) to enhance the viability/activity of the biological sensing agent and thus prolong the shelf life of biosensors based on bacteria; and (2) to further improve the portability of the bioassay system and simplify the bioassay operation. The developed bioassay demonstrates potentials in comprehensive toxicity test of real water samples containing multiplex heavy metal ions. This work paves the way for on-site biotoxicity test based on microorganisms and provides clues for the development of long-term validity biosensors.

Pb, Cd, and Zn soil contamination: Monitoring functional and structural impacts on the microbiome

Heavy metals (HM) contamination in soils due to anthropogenic activities is a serious environmental problem. In this study, we investigated the impact of Pb, Cd and Zn at soil pollution levels on soil organisms, with special attentions to microbiota. We monitored by Illumina MiSeq technology and bioinformatics analysis the functional and structural evolution of the HM-exposed soil microbiome after different exposure times (0–160 days). Ecotoxicological tests showed 100% acute toxicity of HMs towards the nematode Caenorhabditis elegans and a significant decrease in the metabolic activity of bacteria. Firmicutes was the most resistant phylum, which selectively displaced other bacterial phyla (Proteobacteria, Actinobacteria and Verrucomicrobia). This was likely related to its capability to form endospores under stressed environment. A bioinformatics analysis using PICRUSt showed that HM exposure had a strong effect on metabolic pathways, specifically, genetic information processing (transcription factors), metabolism (glycan biosynthesis and energy metabolism), and environmental information processing (transporters and ABC transporters), particularly after 55 days of exposure. The assessment of functional and structural development of a HM-exposed soil allowed evaluation on the cellular adaptive responses to the tested environmental stresses, and provided valuable information to assist developing effective remediation strategies of HMs polluted soils using bacteria as the remediator.

Combined effect of heavy metals and shungite on the indicator plankton species

The combined effect of salts of heavy metals and shungite on the test organisms of phyto- and zooplankton has been studied. The toxic effect of both cadmium sulfate and potassium dichromate on the culture of Scenedesmus guadricauda was inactivated in the presence of shungite (100 g/L). The efficiency of photosynthesis, the number of cells, the proportion of living cells, and the lifetime of the microalgae cell population increased after adding shungite to the medium (without toxicants). In addition, in acute experiments that lasted up to 96 h, the toxicity of potassium dichromate, copper sulfate, and cadmium sulfate on crustaceans (Daphnia magna and Ceriodaphnia affinis) was studied in the presence of shungite (0.01 g/L) and without it. This study of the effect of shungite’s presence on crustaceans showed that it protected both Daphnia magna and Ceriodaphnia affinis from the action of toxicants at the minimum concentration (0.01 g/L) of the five tested. Daphnia magna died at higher concentrations of shungite. It was shown that the acute toxicity of heavy metals for the two crustacean species decreased in the series Cu–Cd–Cr. The analysis of the obtained data showed that the shungite concentrations necessary for the inactivation of heavy metals were thousands of times higher for algae than for crustaceans. Therefore, when using the shungite as a protector against the toxic effects of various substances, a preliminary laboratory analysis of the survival of different species of hydrobionts in a specific aquatic environment is necessary.

Exposure of mayfly Ephemera orientalis (Ephemeroptera) eggs to heavy metals and discovery of biomarkers

The objective of this study was to assess acute toxicity of heavy metals in eggs of mayfly Ephemera orientalis McLachlan, and to elucidate relationships between heavy metal toxicity and protein expression patterns determined using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI–TOF-MS). Acute toxicity analysis was conducted using five heavy metals (cadmium, chromium, copper, lead, and mercury), and the toxicity endpoint was established from the egg hatching rate during a 14-day exposure period. Median hatching toxicity (HC50) values were determined for each heavy metal, and the most toxic heavy metal was found to be mercury (0.11mg/L), followed by copper (0.32mg/L) and lead (4.39mg/L). E. orientalis eggs were highly tolerant to cadmium and chromium (>120mg/L). Proteinchip® array analysis using a strong anion exchange proteinchip (Q10) in conjunction with SELDI–TOF-MS was used to assess the protein expression patterns after exposure to heavy metals at the EHC10 (prohibiting hatching concentration to 10% eggs), except for cadmium and chromium, which were used at concentrations of 1, 10, and 100mg/L. Three novel biomarker candidate proteins, i.e., 4269, 4283, and 4623 m/z, were identified for the detection of heavy metal toxicity in aquatic ecosystems at the level of HC10 in E. orientalis eggs. SELDI-TOF MS analysis for detecting differential expression of proteins was found to be more effective than Q10 proteinchip separation in the mayfly eggs.

Acute Toxicity of Heavy Metals to Tetrahymena in an In Vitro Experiment and Envelope Damage Study

The toxicity of Cr³⁺, Cu²⁺ and Cd²⁺ to Tetrahymena growth metabolism was studied by microcalorimetry at 28°C, and the growth constant (k), peak time (T) and generation times (T(G)) were calculated. The metal ion concentrations that resulted in 50% inhibition (IC₅₀) of population growth were obtained through the dynamic parameters. The results indicated that the order of toxicity was Cd²⁺> Cr³⁺> Cu²⁺. Inductively coupled plasma-atomic emission spectrometry results suggested that the metal ions affected the permeability of the cell membrane. Observations of the Cd-exposed organisms by scanning electron microscopy revealed damage to the cell membrane in the form of an altered surface appearance. The cells suffered serious damage after sufficient acting time. Attenuated total reflection Fourier transform infrared spectra revealed that amide groups and PO₂⁻ of the phospholipid phospho-diester, both located in the hydrophobic end of the outer layer of the cell membrane, were most readily affected.

Expression profiles of heat shock protein gene families in the monogonont rotifer Brachionus koreanus — exposed to copper and cadmium

Heat shock proteins play an important role in protein homeostasis under stress conditions, and act as molecular chaperons in living organisms. Here, we investigate acute toxicity of heavy metals (Cu and Cd) and the transcriptional changes of the heat shock proteins (hsps) family genes (hsp20, hsp27, hsp70, hsp90α-1, and hsp90β) in Brachionus koreanus-exposed to heavy metals. As a result, 48-h LC50 values were 0.956 mg/L (95%-cl. 0.678–1.348) for Cu and 57.563 mg/L (95%-cl. 47.691-69.477) for Cd. The expressions of hsp90α-1 and hsp70 mRNA level at all concentrations were significantly upregulated 24 h after exposure to Cu and Cd. In particular, a significant increase in hsp27 and hsp70 mRNA level indicated higher sensitivity to Cd. This finding indicates that HSPs play protective roles under heavy metal stress in this species. In addition, the expression profiles of hsp27, hsp70, and hsp90α-1 may be useful as molecular marker for monitoring heavy metal toxicity in the aquatic environment.

Investigation of acute toxicity of heavy metals in Artemia salina acclimated to different salinity

Environment plays a vital role in the growth and metabolism of aquatic organisms. Pollutants are known to produce marked changes in the food cycle. In order to study the impact of prey on aquaculture, this study was conducted in live fish feed Artemia salina. Since changes in the culture tank due to environmental factors were mainly responsible for the decline of aquaculture, this study focused on the effect of salinity and heavy metal, including mercury (Hg), copper (Cu), and chromium (Cr), on two life stages of A. salina. Cr-exposed groups showed the highest morality at 0.052 ppm (99%) with the growth of 60%. Percentage mortality was observed to be in the order of Cr>Hg>Cu. Growth was significantly reduced. Artemia was able to accumulate Hg (9–13%), Cu (5.4–5.9%), and Cr (16.4–35%) in the body. The concentrations of heavy metals in water samples were 50–64% of Hg, 52–78% of Cu, and 62% of Cr. Metal stress induced elevated protein content, which may be due to the stress response of the organism against free radicals.

Oxidative Response and Antioxidative Mechanism in Germinating Soybean Seeds Exposed to Cadmium

Seeds of soybean (Glycine max L.) exposed to 50 mg/L (Cd50), 100 mg/L (Cd100) and 200 mg/L (Cd200) cadmium solution for 24, 48, 72 and 96 h were examined with reference to Cd accumulation, oxidative stress and antioxidative responses. Soybean seeds accumulated Cd in an exposure time-and dosage-dependent manner. FRAP (ferric reducing ability of plasma) concentration, GSH/hGSH content, and GST activity showed a pronounced exposure time-dependent response. Cd100 enhanced FRAP concentration in germinating soybean seeds as compared to Cd50 treatment after 24 h exposure. Cd200 however increased statistically GST activities after 72 and 96 h exposure. Under all Cd dosages, GSH/hGSH concentrations were depressed with increasing exposure time. Reduction of GSH/hGSH content and concomitant increase of GST activity suggested a possible participation of GSH into GSH-Cd conjugates synthesis. MDA content is a potential biomarker for monitoring Cd phytotoxicity because it responds significantly to treatment dosage, exposure time and dosage × exposure time interaction. Increase of proline content may be a response to acute heavy metal toxicity in soybean seeds.

The temperature dependence of the acute toxicity of heavy metals (cadmium, copper and mercury) to a freshwater pond snail, Lymnae aluteola L.

Responses of a freshwater pulmonate snail Lymnae aluteola L. to copper, cadmium and mercury were observed at four temperatures in the range of 15.0 oC to 30.0 oC. Acute static bioassays were carried out at 15.0 oC, 20.0 oC, 25.0 oC and 30.0 oC to determine the percent mortality and median lethal concentrations (LC50) and their 95 percent confidence limits. The acute toxicity of mercury, copper and mercury increased with the increase of temperature from 15oCto 30oC. The 96 h LC50 values and percent mortality indicate that metals at 15oCwas least toxic while at 30oC it was highly toxic.

Specific Death Symptoms and Organic Lesions of Blood Clam <i>Tegillarca granosa</i> in Acute Copper, Zinc, Lead and Cadmium Exposures

Blood clam, Tegillarca granosa, habit in near-shore muddy sediments facing increasing danger of heavy metal contamination. In order to assess the acute toxicity of heavy metals on T. granosa, short term lethal concentration (LC50) of copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) were determined, symptoms of death and organic lesions were illustrated. With relative high LC50 values obtained, T. granosa showed great heavy metal tolerance indicates adaptations to habitat environment. T. granosa died in acute Cd exposure showed specific death symptom with foot extended outside of the tightly closed shells. In this study, different metals led to different organic lesions. Dark red erosive and inflamed gills were observed for T. granosa exposed to acute Cu and Pb, respectively. Inflamed gonad and foot, and contracted mantle were observed for Cd and Zn exposure trials, respectively. The results of this study may provide knowledge to assist in heavy metal pollution bio-monitoring and quick diagnosis of massive death incidence.

Hepatoprotection of quercetin against oxidative stress by induction of metallothionein expression through activating MAPK and PI3K pathways and enhancing Nrf2 DNA-binding activity

Flavonoids are natural phenolic substances widely found in fruit, vegetables, grains, and wine. Most of these compounds exert health-promoting effects seem to attribute to their antioxidant activity. Metallothioneins (MT) has been suggested to protect against acute heavy metal toxicity in the liver, and the proteins of MT can be induced by various stimuli including antioxidant. Measuring the induction of MT genes may provide an efficient approach to understand the chemopreventive mechanisms of flavonoids. The antioxidant activity of eight flavonoids was determined by TEAC and ORAC assays and their effects on MT protein were also measured. HepG2 cells were employed to explore the mechanisms underlying flavonoid-induced MT induction. Statistical analysis revealed a positive correlation between the antioxidant activity of flavonoids and MT expression. Quercetin-induced MT expression may function by activating the phosphorylation of JNK, p38 and PI3K/Akt as well as by enhancing Nrf2 DNA-binding activity. Moreover, quercetin exhibited a potential protective effect on t-BHP-caused injury in hepatocytes through the induction of MT. These results suggest that quercetin is a natural antioxidant in the diet and the consumption of foods that are rich in quercetin could be beneficial for the prevention of environmental oxidant-induced liver damage.

Acute Toxicity of Heavy Metals and Insecticides to a Fresh Water Shrimp Palaemon paucidens

Acute Toxicity of Heavy Metals and Insecticides to a Fresh Water Shrimp Palaemon paucidens

Fridericia peregrinabunda (Enchytraeidae) as a new test species for soil toxicity assessment

The present study proposes Fridericia peregrinabunda (Michaelsen, 1913) as a new test species for assessment of soil ecotoxicity. Fridericia is the richest genus in the Enchytraeidae family (Oligochaeta: Annelida: Clitellata: Enchytraeidae), and widely distributed. The acute toxicity of cadmium (Cd) and antimony (Sb) on the survival of F. peregrinabunda were investigated in laboratory experiments. Adult survival of F. peregrinabunda in metal spiked soil was reduced. Cadmium was more toxic to F. peregrinabunda than Sb. In the artificial soil toxicity tests, the LC50 values for F. peregrinabunda exposed to Cd and Sb for 48 h were 37, and 446 mg kg −1, respectively. The NOEC values for Cd and Sb were 20 and 100 mg kg −1 up to 48 h exposure, respectively. This is the first report on the ecotoxicological assay of contaminated soils using the enchytraeids F. peregrinabunda as a test species. It can be concluded that F. peregrinabunda is a suitable test species to measure the acute toxicity of heavy metals, and this species is more sensitive to Cd and Sb than earthworm. The filter paper contact test and 2 day-artificial soil toxicity test appear to be rapid and cost-effective protocols for the potworm assay.

Chelation Therapy Trials Halted

THE FEDERAL GOVERNMENT AND INvestigators have called off or suspended enrollment for 2 clinical trials testing chelation therapy as a treatment for autism or coronary artery disease. Critics charged that the studies had little scientific merit and exposed participants to unacceptable safety risks. The US Food and Drug Administration has approved chelating agents, which bind and remove heavy metals from the body, for treating acute toxicity of heavy metals. But, according to the National Center for Complimentary and Alternative Medicine (NCCAM), off-label uses of chelating agents contribute to an estimated 800 000 physician visits annually. Advocates argue that the approach is beneficial forautismandcoronaryartery disease, despite the absence of evidence fromrigorousclinicaltrials.Withthegoal ofclarifyingwhetherchelationoffersbenefitsbeyonditsindicationsforacuteheavy metal toxicity, the National Institutes of Health(NIH)decidedto fund2randomized controlled trials: the Trial to Assess Chelation Therapy (TACT), to evaluate the approach’s safety and efficacy in reducingtheriskofcoronaryarterydisease, and the Mercury Chelation to Treat Autism study. However, on September 17, the National InstituteofMentalHealth(NIMH) announcedthecancellationoftheautism study.Aweeklater, investigatorsrunning TACT,sponsoredbytheNCCAMandthe NationalHeart,Lung,andBloodInstitute, suspendedenrollmentasallegationsofimproper consent forms were evaluated. However, the5-yeartrialwouldcontinue with those already enrolled. The mercury chelation study was intended to test a theory—embraced by someantivaccineactivistsbutrejectedby mostscientists—thatavaccinepreservative containing mercury (no longer in use) can cause autism, and that removing mercury from the body would improve social reciprocity and language skills inchildrenwithautism.Inthetrial, 120 children with autism spectrum disorderanddetectable(butnottoxic)blood levels of mercury or lead were to receive a chelating agent (succimer) or placebo.

Aquatic Toxicity of Leachates Generated from Electronic Devices

Heavy metal leaching of electronic waste has been documented in recent literature. Heavy metal aquatic toxicity in the toxicity characteristic (TC) leachates produced from 56 electronic devices were tested using the aquatic toxicity assays such as Ceriodaphnia dubia 48-hr acute toxicity assay, the Selenatastrum capricornutum chronic algal growth inhibition assay (test used only for circuit-board leachates), and the MetPLATE acute heavy metal toxicity tests. The electronic devices tested, include 9 circuit boards (printed wire boards), 2 videocassette recorders, 4 remote controls, 1 cathode ray tube, 15 cellular phones, 1 calculator, 5 smoke detectors and their PC board components, 3 printers, 4 laptop computers, and 7 personal computer central processing units (CPUs). The toxicity tests showed toxicity in 51 of the 56 Toxicity Characteristic Leaching Procedure leachates of electronic devices assayed.

Effect of Binary Mixtures of Three Heavy Metals on Larvae of Chironomus calligraphus

Toxic effects of binary mixtures of three heavy metals: Cd2+ and Hg2+ (constant); Pb2+ and Hg2+ (constant); Hg2+ and Cd2+ (constant); Pb2+ and Cd2+ (constant); Cd2+ and Pb2+ (constant); and finally Hg2+ and Pb2+(constant) on larvae of Chironomus calligraphus (Goeldi, 1905) (Diptera: Chironomidae) after 48 h exposure were evaluated. The acute toxicity of heavy metals in pairs of mixtures, showed synergistic interactions (Toxic Unit = (TU) < 1) for Pb2+ and Hg2+(constant) (TU = 0.44); Cd2+ and Pb2+ (constant) (TU = 0.61); Pb2+ and Cd2+(constant) (TU = 0.63); and Hg2+ and Cd2+ (constant) (TU = 0.77), and antagonistic interactions (TU > 1) for Cd2+ and Hg2+ (constant) (TU = 1.23) and Hg2+ and Pb2+ (constant) (TU = 4.15). Obtained results showed that C. calligraphus is a suitable ecotoxicological tool to evaluate mixtures of heavy metals.

Acute toxicity of heavy metals towards freshwater ciliated protists

The acute toxicity of five heavy metals to four species of freshwater ciliates ( Colpidium colpoda, Dexiotricha granulosa, Euplotes aediculatus, and Halteria grandinella) was examined in laboratory tests. After exposing the ciliates to soluble compound of cadmium, copper, chromium, lead, and nickel at several selected concentrations, the mortality rate was registered and the LC 50 values (with 95% confidence intervals) were calculated. Large differences appeared in sensitivities of the four species to the metals. H. grandinella showed the highest sensitivity for cadmium (0.07 mg l −1, LC 50) and lead (0.12 mg l −1, LC 50), whilst E. aediculatus showed the highest sensitivity for nickel (0.03 mg l −1, LC 50). The comparison with data obtained with other species indicate that Halteria grandinella and Euplotes aediculatus are excellent and convenient bioindicator for evaluating the toxicity of waters and wastewaters polluted by heavy metals. The short time (24 h) and simplicity of the test procedure enable this test to be used in laboratory studies.

Effects of Water Hardness and Metal Concentration on a Freshwater Tubifex Tubifex Muller

The present investigation was designed to determine the effectsof water hardness and heavy metals concentrations on a freshwaterTubifex tubifex. Very few data concerning the effect of water hardness on the acute toxicity of heavy metals are available on T. tubifex, which has been proposed as a testorganism for ecotoxicological studies. The effect of water hardness on the toxicity of heavy metals is discussed. The acutetoxicity of selected heavy metals to a freshwater T. tubifex Muller was determined in very soft, soft, hard and veryhard (12, 45, 170 and 300 mg CaCO3 L-1 total hardness,respectively) water. Percentage mortality of T. tubifex as influenced by heavy metals was studied in water of variable hardness. Water hardness had a significant effect on heavy metalstoxicity. The concentrations of metals necessary to immobilize 50% of the test animals at 24, 48, 72, 96 hr were significantlydifferent in soft and hard water. The 96 hr EC50 valuesfor T. tubifex were higher in hard and very hard watercompared with soft and very soft water. Median effectiveconcentrations (EC50) and their 95% confidence limits weredetermined for cadmium, cobalt, chromium, copper, iron, lead, manganese, mercury, nickel, and zinc during exposure for 24, 48,72 and 96 hr in four different water hardness. Hardness has a muchsmaller effect upon the acute toxicity of mercury than the otherheavy metals tested. The results indicate that Cu, Cd, Hg and Zninduced autotomy of the caudal region and mucus production. It isconcluded that water hardness parameters should be considered inestablishing appropriate water quality criteria and standards forthe protection of aquatic fauna and flora, and ultimately human health.

Acute toxicity of heavy metals to acetate‐utilizing mixed cultures of sulfate‐reducing bacteria: EC100 and EC50

Acid mine drainage from abandoned mines and acid mine pit lakes is an important environmental concern and usually contains appreciable concentrations of heavy metals. Because sulfate-reducing bacteria (SRB) are involved in the treatment of acid mine drainage, knowledge of acute metal toxicity levels for SRB is essential for the proper functioning of the treatment system for acid mine drainage. Quantification of heavy metal toxicity to mixed cultures of SRB is complicated by the confounding effects of metal hydroxide and sulfide precipitation, biosorption, and complexation with the constituents of the reaction matrix. The objective of this paper was to demonstrate that measurements of dissolved metal concentrations could be used to determine the toxicity parameters for mixed cultures of sulfate-reducing bacteria. The effective concentration, 100% (EC100), the lowest initial dissolved metal concentrations at which no sulfate reduction is observed, and the effective concentration, 50% (EC50), the initial dissolved metal concentrations resulting in a 50% decrease in sulfate reduction, for copper and zinc were determined in the present study by means of nondestructive, rapid physical and chemical analytical techniques. The reaction medium used in the experiments was designed specifically (in terms of pH and chemical composition) to provide the nutrients necessary for the sulfidogenic activity of the SRB and to preclude chemical precipitation of the metals under investigation. The toxicity-mitigating effects of biosorption of dissolved metals were also quantified. Anaerobic Hungate tubes were set up (at least in triplicate) and monitored for sulfate-reduction activity. The onset of SRB activity was detected by the blackening of the reaction mixture because of formation of insoluble ferrous sulfide. The EC100 values were found to be 12 mg/L for copper and 20 mg/L for zinc. The dissolved metal concentration measurements were effective as the indicators of the effect of the heavy metals at concentrations below EC100. The 7-d EC50 values obtained from the difference between the dissolved metal concentrations for the control tubes (tubes not containing copper or zinc) and tubes containing metals were found to be 10.5 mg/L for copper and 16.5 mg/L for zinc. Measurements of the turbidity and pH, bacterial population estimations by means of a most-probable number technique, and metal recovery in the sulfide precipitate were found to have only a limited applicability in these determinations.