Leachates from solid wastes: chemical and eco(geno)toxicological differences between leachates obtained from fresh and stabilized industrial organic sludge

The chemical and ecotoxicological characteristics of fresh and stabilized industrial organic sludge leachates were compared to obtain information regarding how the stabilization process can influence the ecotoxic potential of this industrial waste, which could be used for the amendment of degraded soil. Physicochemical analysis of the sludge leachates, as well as a battery of eco(geno)toxicity tests on bacteria, algae, daphnids, and higher plants (including Vicia faba genotoxicity test) and the determination of hydrolytic enzyme activity, was performed according to standard methods. The chemical comparison of the two types of leachate showed that the samples obtained from stabilized sludge had a lower organic content and higher metal content than leachates of the fresh sludge. The eco(geno)toxicological results obtained with aquatic organisms showed that the stabilized sludge leachate was more toxic than the fresh sludge leachate, both originating from the same industrial organic sludge sample. Nevertheless, phytotoxicity tests carried out with a reference peat soil irrigated with stabilized sludge leachate showed the same toxicity as the fresh sludge leachate. In the case of the industrial solid organic sludge studied, stabilization through a biodegradation process promoted a higher metal mobility/bioavailability/eco(geno)toxicity in the stabilized sludge leachate compared to the fresh sludge leachate.     

Estimation of the environmental risk posed by landfills using chemical, microbiological and ecotoxicological testing of leachates

The leachates from 22 municipal solid waste (MSW) landfill sites in Southern Poland were characterized by evaluation of chemical, microbiological and ecotoxicological parameters. Chemical analyses were mainly focused on the identification of the priority hazardous substances according to Directive on Priority Substances, 2008/105/EC (a daughter directive of the WFD) in leachates. As showed, only five substances (Cd, Hg, hexachlorobutadiene, pentachlorobenzene and PAHs) were detected in the leachates. The compounds tested were absent or present at very low concentrations. Among them, only PAHs were found in all samples in the range from 0.057 to 77.2 μg L⁻¹. The leachates were contaminated with bacteria, including aerobic, psychrophilic and mesophilic bacteria, coliform and fecal coliforms, and spore-forming-bacteria, including Clostridium perfringens, and with filamentous fungi. From the analysis of specific microorganism groups (indicators of environmental pollution by pathogenic or opportunistic pathogenic organisms) it can be concluded that the landfill leachates showed sanitary and epidemiological hazard. In the ecotoxicological study, a battery of tests comprised of 5 bioassays, i.e. Microtox®, Spirotox, Rotoxkit F™, Thamnotoxkit F™ and Daphtoxkit F™ magna was applied. The leachate samples were classified as toxic in 13.6%, highly toxic in 54.6% and very highly toxic in 31.8%. The Spirotox test was the most sensitive bioassay used. The percentage of class weight score was very high - above 60%; these samples could definitely be considered seriously hazardous and acutely toxic to the fauna and microflora.No correlations were found between the toxicity values and chemical parameters. The toxicity of leachate samples cannot be explained by low levels of the priority pollutants. It seems that other kinds of xenobiotics present in the samples at subacute levels gave the high aggregate toxic effect.The chemical, ecotoxicological and microbiological parameters of the landfill leachates should be analyzed together to assess the environmental risk posed by landfill emissions.     

Comparative acute toxicity of leachates from plastic products made of polypropylene, polyethylene, PVC, acrylonitrile–butadiene–styrene, and epoxy to Daphnia magna

Purpose

The large global production of plastics and their presence everywhere in the society and the environment create a need for assessing chemical hazards and risks associated with plastic products. The aims of this study were to determine and compare the toxicity of leachates from plastic products made of five plastics types and to identify the class of compounds that is causing the toxicity.

Methods

Selected plastic types were those with the largest global annual production, that is, polypropylene, polyethylene, and polyvinyl chloride (PVC), or those composed of hazardous monomers (e.g., PVC, acrylonitrile?Cbutadiene?Cstyrene [ABS], and epoxy). Altogether 26 plastic products were leached in deionized water (3?days at 50°C), and the water phases were tested for acute toxicity to Daphnia magna. Initial Toxicity Identification Evaluations (C18 filtration and EDTA addition) were performed on six leachates.

Results

For eleven leachates (42%) 48-h EC50s (i.e the concentration that causes effect in 50 percent of the test organisms) were below the highest test concentration, 250 g plastic/L. All leachates from plasticized PVC (5/5) and epoxy (5/5) products were toxic (48-h EC50s ranging from 2 to 235?g plastic/L). None of the leachates from polypropylene (5/5), ABS (5/5), and rigid PVC (1/1) products showed toxicity, but one of the five tested HDPE leachates was toxic (48-h EC50 17?C24?g plastic/L). Toxicity Identification Evaluations indicated that mainly hydrophobic organics were causing the toxicity and that metals were the main cause for one leachate (metal release was also confirmed by chemical analysis).

Conclusions

Toxic chemicals leached even during the short-term leaching in water, mainly from plasticized PVC and epoxy products.     

Efficacy and toxicity of self-polishing biocide-free antifouling paints

The ban on harmful substances in antifouling paints requires the development of new antifouling strategies. Alternatives should be as effective as conventional paints but of lower toxicity. In the present study two commercially available, self-polishing antifouling paints were examined in order to get information on their antifouling properties and toxicological potential. Efficacy was shown in settlement assays with the marine barnacle species Balanus amphitrite, however, efficacy was related to toxic effects observed on target and non-target organisms. Toxicity of the paint extracts was concentration-dependent and differed according to the paint and the species investigated. Toxicity could at least partially be attributed to zinc leached from the paints. Effects of a water-soluble paint were more pronounced in larvae of B. amphitrite, Artemia salina and in the green algae Dunaliella tertiolecta. Embryos of the freshwater species Danio rerio and Vibrio fisheri were more affected by a paint based on organic solvents.     

A new simple method with high precision for determining the toxicity of antifouling paints on brine shrimp larvae (Artemia): first results

The use of antifouling paints is the only truly effective method for the protection of underwater structures from the development of fouling organisms. In the present study, the surface to volume concept constitutes the basis for the development of a new and improved method for determining the toxicity of antifouling paints on marine organisms. Particular emphasis is placed on the attainment of a standardized uniformity of coated surfaces. Failure to control the thickness of the coat of paint in previous studies of this type, has led to inaccurate evaluation of the relative toxicity of samples. Herein, an attempt is made to solve this problem using a simple technique which gives completely uniform and smooth surfaces. The effectiveness of this technique is assessed through two series of experiments using two different types of test containers: 50 ml modified syringes and 7 ml multiwells. The results of the toxicity experiments follow a normal distribution around the average value which allows to consider these values as reliable for comparison of the level of toxic effect detected with the two types of test containers. The mean lethal concentration L(S/V)(50) in the test series conducted in the multiwells (20.38 mm(2)ml(-1)) does not differ significantly from that obtained in the test series using modified syringes (20.065 mm(2)ml(-1)). It can thus be concluded from this preliminary study that the new method and the two different ways of exposing the test organisms to the antifouling paints and their leachates gave reliable and replicable results.     

Persistence of TBT and copper in excess on leisure boat hulls around the Baltic Sea

A handheld XRF-analyzer specially calibrated for measurements of metals on plastic boat hulls has been used on leisure boats in Denmark (DK), Finland (FI), and Germany (DE). The results on tin and copper are presented as μg metal/cm². Tin is a proxy for the occurrence of organotin compounds on the boat. Two or three sites were visited in each country and between 25 and 90 boats were measured at each site. Every boat was measured at six to eight places, and the results are presented both as mean and median values. Linear regression of mean to median values of the 377 data pairs shows high relationship with R²?=?0.9566 for tin and R² of 0.9724 for copper and thus both ways of calculation may be used. However, for regulative use, it is suggested that all individual measurements on each boat should be presented and used for decisions of removal or sealing of boat hulls. The results are compared with published data from different parts of Sweden, i.e., boats in fresh water, brackish water, and salt water. The results show that tin with mean values >?50 μg Sn/cm² is still found on 42, 24, and 23% of the boats in DK, FI, and DE, respectively. The corresponding percentages based on median values are 38, 22, and 18% for DK, FI, and DE, respectively. The variation among boats is high with a maximum mean value of 2000 μg Sn/cm². As comparison, one layer of an old TBT antifouling paint Hempels Hard racing superior, corresponds to 300 μg Sn/cm². The percentage of boats with tin >?400 μg Sn/cm² content based on mean values was 10% in DK, 5% in FI, and 1% in DE. The corresponding median values were 9, 6, and 1% for DK, FI, and DE. Copper, >?100 μg Cu/cm², was detected on all measured boats in DK and in DE and on all but 3% of the FI boats. One layer of Hempels MilleXtra corresponds to ? 4000 μg Cu/cm². The recommendation on the can is to apply two layers. The proportion of boats with higher mean copper values than 8000 μg Cu/cm² was 51, 56, and 61 for boats in DK, FI, and DE, respectively. The proportion based on median values >?8000 μg Cu/cm² was 50, 54, and 61% for DK, FI, and DE. The conclusion is that many leisure boats around the Baltic Sea still display or possess antifouling paints containing organotin compounds and that more than half of the boats have more copper than needed for one boat season according to the paint producers. Much of these known toxic compounds will probably be released into the environment and harm the biota. The calibrated XRF-method, intended for area measurements on boat hulls, is an easy and cheap way to detect boats with organotin compounds and high copper content. We recommend environmental authorities to use this method for identification of such boats and to use the results for requesting measures to minimize further leakage to the environment.

     

Application of a battery of biotests for the determination of leachate toxicity to bacteria and invertebrates from sewage sludge-amended soil

The objective of the study was to determine the leachates toxicity from sewage sludge-amended soils (sandy and loamy). Samples originated from a plot experiment realized over a period of 29 months. Two types of soil were fertilized with sewage sludges at the dose of 3 % (90 t/ha). Soil samples were taken after 0, 7, 17, and 29 months from the application of sewage sludges. Leachates were obtained according to the EN 12457–2 protocol. The following commercial tests were applied for the estimation of the toxicity: Microtox (Vibrio fischeri), Microbial assay for toxic risk assessment (ten bacteria and one yeast), Protoxkit F? (Tetrahymena thermophila), Rotoxkit F? (Brachionus calyciflorus), and Daphtoxkit F? (Daphnia magna). The test organisms displayed varied toxicity with relation to the soils amended with sewage sludges. The toxicity of the leachates depended both on the soil type and on the kind of sewage sludge applied. Notable differences were also observed in the sensitivity of the test organisms to the presence of sewage sludge in the soil. The highest sensitivity was a characteristic of B. calyciflorus, while the lowest sensitivity to the presence of the sludges was revealed by the protozoa T. thermophila. Throughout the periods of the study, constant variations of toxicity were observed for most of the test organisms. The intensity as well as the range of those variations depended both on the kind of test organism and on the kind of sludge and soil type. In most cases, an increase of the toxicity of soils amended with the sewage sludges was observed after 29 months of the experiment.     

Leaf litter leachates have the potential to increase lifespan, body size, and offspring numbers in a clone of Moina macrocopa

Leaf litter processing is one major pathway of the global organic carbon cycle. During this process, a variety of small reactive organic compounds are released and transported to the aquatic environment, and may directly impact aquatic organisms as natural xenobiotics. We hypothesize that different forest stockings produce different leachate qualities, which in turn, stress the aquatic communities and, eventually, separate sensitive from tolerant species. Particularly, leachates from coniferous trees are suspected to have strongly adverse impacts on sensitive species. We exposed individuals of a clone of the model organism, Moina macrocopa, to comparable concentrations (approximately 2 mM) of litter leachates of Norway spruce, Picea abies, Colorado blue spruce, Picea pungens, black poplar, Populus nigra, and sessile oak, Quercus petraea. The animals were fed ad libitum. The following life trait variables were recorded: growth, lifespan, and lifetime offspring. To identify, whether or not exposure to litter leachates provokes an internal oxidative stress in the exposed animals we measured the superoxide anion radical scavenging capacity via photoluminescence. Except of P. abies, exposure to the leachates reduced this antioxidant capacity by approximately 50%. Leachate exposures, except that of Quercus, increased body size and extended lifespan; furthermore, particularly the leachates of both Picea species significantly increased the offspring numbers. This unexpected behavior of exposed Moina may be based on food supplements (e.g., high carbohydrate contents) in the leachates or on yet to be identified regulatory pathways of energy allocation. Overall, our results suggest that the potentially adverse effects of litter leachates can be overruled by either bacterial-growth supporting fractions in the leachates or an internal compensation mechanism in the Moina individuals.     

Accumulation of Cu and Zn from antifouling paint particles by the marine macroalga,Ulva lactuca

The marine macroalga, Ulva lactuca, has been exposed to different concentrations of antifouling paint particles (4–200 mg L^?1) in the presence of a fixed quantity of clean estuarine sediment and its photosynthetic response and accumulation of Cu and Zn monitored over a period of 2 days. An immediate (<2 h) toxic effect was elicited under all experimental conditions that was quantitatively related to the concentration of contaminated particles present. Likewise, the rate of leaching of both Cu and Zn was correlated with the concentration of paint particles added. Copper accumulation by the alga increased linearly with aqueous Cu concentration, largely through adsorption to the cell surface, but significant accumulation of Zn was not observed. Thus, in coastal environments where boat maintenance is practiced, discarded antifouling paint particles are an important source of Cu, but not Zn, to U. lactuca.     

Mammalian cell line-based bioassays for toxicological evaluation of landfill leachate treated by Pseudomonas sp. ISTDF1

Landfill leachate has become a serious environmental concern because of the presence of many hazardous compounds which even at trace levels are a threat to human health and environment. Therefore, it is important to assess the toxicity of leachate generated and discharge it conforming to the safety standards. The present work examined the efficiency of an earlier reported Pseudomonas sp. strain ISTDF1 for detoxification of leachate collected from Okhla landfill site (New Delhi, India). GC-MS analysis performed after treatment showed the removal of compounds like alpha-limonene diepoxide, brominated dioxin-2-one, Bisphenol A, nitromusk, phthalate derivative, and nitrobenzene originally found in untreated leachate. ICP-AES analysis for heavy metals also showed reduction in concentrations of Zn, Cd, Cr, Fe, Ni, and Pb bringing them within the limit of safety discharge. Methyl tetrazolium (MTT) assay for cytotoxicity, alkaline comet assay for genotoxicity, and 7-ethoxyresorufin-O-deethylase (EROD) assay for dioxin-like behavior were carried out in human hepato-carcinoma cell line HepG2 to evaluate the toxic potential of treated and untreated leachates. The bacterium reduced toxicity as shown by 2.5-fold reduction of MTT EC₅₀ value, 7-fold reduction in Olive Tail Moment, and 2.8-fold reduction in EROD induction after 240 h of bacterial treatment.     

Polymer coating of copper oxide nanoparticles increases nanoparticles uptake and toxicity in the green alga Chlamydomonas reinhardtii

Copper oxide nanoparticles (CuO NPs) are frequently used in a polymer-coated form, to be included in paints or fabrics for antimicrobial properties. Their application in antifouling paints may lead to the contamination of aquatic ecosystems. However, the toxicological risk of NPs in the environment is hard to evaluate due to a lack of knowledge on the mechanisms of NP interaction with biological systems. In this study, we investigated the effect of polymer coating on CuO NP toxicity in the green alga Chlamydomonas reinhardtii by comparing bare and polymer-coated CuO NPs prepared from the same CuO nanopowder. Both CuO NP suspensions were toxic to C. reinhardtii after 6 h treatment to concentrations of 0.005-0.04 g L⁻¹. Bare and polymer-coated CuO NPs induced a decrease of Photosystem II activity and the formation of reactive oxygen species. Polymer-coated CuO NP was found to be more toxic than the uncoated CuO NP. The higher toxicity of CS-CuO NP was mainly associated with the increased capacity of polymer-coated CuO NP to penetrate the cell compared to bare CuO NPs. These results indicates that the high toxicity of polymer-coated CuO NPs in algal cells results of intracellular interactions between NPs and the cellular system.     

Phytoplankton toxicity of the antibiotic chlortetracycline and its UV light degradation products

Two common freshwater phytoplankton species Microcystis aeruginosa and Scenedesmus obliquus were employed as test organisms to investigate the toxic effects of chlortetracycline widely used in human medicine and veterinary as antibiotic. Toxicity assays were performed into two parts: antibiotic toxicity test and antibiotic degraded products toxicity test. In general, chlortetracycline had significantly toxic effect on population growth and chlorophyll-a accumulation of two phytoplankton. Although M. aeruginosa had ability to grow after exposed to chlortetracycline at 0.5 mg L⁻¹, its photosynthesis function was also disrupted. Compared with the data in two phytoplankton species, the chlorophyceae was more sensitive than the cyanophyceae. The adverse effect on S. obliquus was stronger than that on M. aeruginosa with increasing concentrations. In addition, for M. aeruginosa, regardless of the UV light degradation time, the treated chlortetracycline also had adverse effect on population growth and chlorophyll-a accumulated. The degraded chlortetracycline under any treatment time was more toxic for S. obliquus than chlortetracycline itself excluding under 24 h. However, the correlation between the toxicity and degradation time was not clear and toxicity enhanced in fact did not follow the increase or decrease in degradation time. Our study showed that the antibiotic chlortetracycline and its degraded products had adverse effect on freshwater phytoplankton, the former has not been reported before and the latter has been overlooked in other research in the past.     

Cell cycle stage specific application of municipal landfill leachates to assess the genotoxicity in root meristem cells of barley (Hordeum vulgare)

Municipal solid wastes (MSW) are unavoidable sources of environmental pollution. Improper disposal of municipal waste results in the leaching of toxic metals and organic chemicals, which can contaminate the surface and ground water leading to serious health hazard. In this study, the toxic effects of the leachate prepared from municipal solid waste samples were examined in root meristem cells of barley (Hordeum vulgare L.) at various stages of cell cycle, i.e., G₁, S, and G₂. Seeds of barley were exposed to 2.5, 5, and 10 % of leachates in soil and aqueous media in 48 h at different cell cycle stages. The physicochemical data of the present study revealed that municipal solid waste leachate contains high amount of heavy metals, which significantly affected growth and physiological activities of barley. Significant inhibition in hypocotyl length, germination, and mitotic index were observed at all concentration of leachate treatment. Induction of chromosomal aberrations (CA’s) and micronuclei (MN) formation were also observed with different concentrations of leachate treatment at 7, 17, and 27 h of presoaking durations, which falls in G₁, S, and G₂ phase of the cell cycle, respectively. Also, exposure of leachate at S phase of the cell cycle had significant effects in barley through chromosomal aberration and micronuclei formation.     

Acute toxicity of leachates of tire wear material to Daphnia magna--variability and toxic components

Large amounts of tire rubber are deposited along the roads due to tread wear. Several compounds may leach from the rubber and cause toxicity to aquatic organisms. To investigate the toxic effects of tire wear material from different tires, rubber was abraded from the treads of twenty-five tires. Leachates were prepared by allowing the rubber to equilibrate with dilution water at 44 degrees C for 72 h. Then the rubber was filtered from the leachates, and test organisms (Daphnia magna) were added. Forty-eight hour EC50s ranged from 0.5 to >10.0 g l(-1). The toxicity identification evaluation (TIE) indicated that non-polar organic compounds caused most of the toxicity. UV exposure of the filtered tire leachates caused no significant increase in toxicity. However, when tested as unfiltered leachates (the rubber was not filtered from the leachates before addition of D. magna) photo-enhanced toxicity was considerable for some tires, which means that test procedures are important when testing tire leachates for aquatic (photo) toxicity. The acute toxicity of tire wear for Daphnia magna was found to be <40 times a predicted environmental concentration based on reports on the concentration of a tire component found in environmental samples, which emphasizes the need for a more extensive risk assessment of tire wear for the environment.     

Toxicity of tire wear particle leachate to the marine macroalga, Ulva lactuca

Tire wear particles filed from the treads of end-of-life vehicle tires have been added to sea water to examine the release of Zn and the toxicity of the resulting leachate and dilutions thereof to the marine macroalga, Ulva lactuca. Zinc release appeared to be diffusion-controlled, with a conditional rate constant of 5.4 μg[L(h)^1/2]⁻¹, and about 1.6% of total Zn was released after 120 h incubation. Exposure to increasing concentrations of leachate resulted in a non-linear reduction in the efficiency of photochemical energy conversion of U. lactuca and, with the exception of the undiluted leachate, increasing accumulation of Zn. Phototoxicity was significantly lower on exposure to equivalent concentrations of Zn added as Zn(NO₃)₂, suggesting that organic components of leachate are largely responsible for the overall toxicity to the alga. Given the ubiquity and abundance of TWP in urban coastal sediments, the generation, biogeochemistry and toxicity of tire leachate in the marine setting merit further attention.     

Risk assessment of biocides in roof paint

BACKGROUND, AIM AND SCOPE: Many surface coatings, including roof paints, contain biocides. It is generally not known to what extent roof paint biocides leach from the paint, and consequently, what concentration the biocide may attain in a rainwater collection system. To this end the leaching of specific biocides from a variety of German roof paints was investigated and the resulting concentrations in collected rain water were estimated. MATERIALS AND METHODS: A laboratory simulation was used to determine the time dependant leaching rate of the biocide from the paint into synthetic rainwater. The concentrations of biocide in the leachate were quantified using HPLC. The course of the leachate concentrations over time was fitted using a simple mathematical model. This was then used to estimate concentrations of biocides in a typical household rainwater collection system over time. RESULTS: Surprisingly, the biocides found in the paints did not always concur with the declared biocides. Concerning the modelling of runoff concentrations, it was found that--under the model assumptions--the rain intensity and cumulative raining time after application are the dominant factors influencing the concentration of the biocide. At the highest modelled rain intensity of 40 mm/hour it only takes about 2 hours to reach peak concentrations lower than 0.1 mg/L, at 0.3 mm/hour it takes about 10 hours to reach peak concentrations of 1.3, 0.9, 5.2 and 1.1 mg/L for terbutryn from Emalux paint, terbutryn from Südwest paint, carbendazim from Emalux paint, and carbendazim from MIPA paint, respectively. DISCUSSION: The results confirm that biocides leached from roof paint will be present in roof runoff. The highest estimated peak concentrations are close to the water solubility of the respective biocides. This indicates that the model assumption of a concentration independent leaching rate will tendentially lead to an overestimation of the leached concentrations under these circumstances. However, under most circumstances such as higher rain intensities, and longer time after peak concentrations have been reached, the runoff concentrations are far from the solubility limit, and therefore it is proposed that the model assumptions are tenable. CONCLUSIONS: The leaching of biocides from roof paints can be roughly assessed using a relatively simple approach. The declaration of biocidal ingredients in roof paints should be improved and information on their biocide leaching behaviour should be made available. Furthermore, the estimations should be evaluated by a field study. RECOMMENDATIONS AND PERSPECTIVES: The leaching study indicated that the concentrations of selected biocides can reach significant levels, especially after low intensity rainfall. Taking into account the inherent biological activity of the substances under scrutiny, it can already be concluded that it is not advisable to use runoff water from roofs freshly painted with biocide containing roof paints. These results have been complemented by a literature search of biological effects of the investigated biocides, ecotoxicological tests with several species and a risk analysis for organisms exposed to runoff water. This will be presented in Part 2 of this contribution.     

Short term recovery of periphyton photosynthesis after pulse exposition to the photosystem II inhibitors atrazine and isoproturon

Aquatic organisms are exposed to fluctuating concentrations of herbicides which contaminate rivers following their use for agricultural or domestic purposes. The development of sensitive bioanalytical tests enabling us not only to detect the effects of those pollutants but to take into account this pattern of exposure should improve the ecological relevance of river toxicity assessment. In this respect, the use of chlorophyll fluorescence measurements is a convenient way to probe the effect of photosystem II (PSII) inhibitors on primary producers. This study was devoted to validate the combined use of two fluorescence parameters, the effective and the optimal quantum yields of PSII photochemistry (Φ_PSII and F_v/F_m), as reliable biomarkers of initial isoproturon (IPU) or atrazine (ATZ) toxicity to natural periphyton in a pulse exposition scenario. Φ_PSII and F_v/F_m were regularly estimated during a 7 h-exposure to each pollutant (0-100 μM) and also later after being transferred in herbicide-free water (up to 36 h). Our results showed that IPU was more toxic than ATZ, but with effects reversible within 12 h. Moreover, these two similarly acting herbicides (i.e. same target site) presented contrasted short term recovery patterns, regarding the previous exposure duration.     

Toxicity of two types of silver nanoparticles to aquatic crustaceans Daphnia magna and Thamnocephalus platyurus

Although silver nanoparticles (NPs) are increasingly used in various consumer products and produced in industrial scale, information on harmful effects of nanosilver to environmentally relevant organisms is still scarce. This paper studies the adverse effects of silver NPs to two aquatic crustaceans, Daphnia magna and Thamnocephalus platyurus. For that, silver NPs were synthesized where Ag is covalently attached to poly(vinylpyrrolidone) (PVP). In parallel, the toxicity of collargol (protein-coated nanosilver) and AgNO₃ was analyzed. Both types of silver NPs were highly toxic to both crustaceans: the EC50 values in artificial freshwater were 15–17 ppb for D. magna and 20–27 ppb for T. platyurus. The natural water (five different waters with dissolved organic carbon from 5 to 35 mg C/L were studied) mitigated the toxic effect of studied silver compounds up to 8-fold compared with artificial freshwater. The toxicity of silver NPs in all test media was up to 10-fold lower than that of soluble silver salt, AgNO₃. The pattern of the toxic response of both crustacean species to the silver compounds was almost similar in artificial freshwater and in natural waters. The chronic 21-day toxicity of silver NPs to D. magna in natural water was at the part-per-billion level, and adult mortality was more sensitive toxicity test endpoint than the reproduction (the number of offspring per adult).     

Inputs of antifouling paint-derived dichlorodiphenyltrichloroethanes (DDTs) to a typical mariculture zone (South China): potential impact on aquafarming environment

Existing evidence indicated that dichlorodiphenyltrichloroethane (DDT)-containing antifouling paints were an important source of DDT residues to mariculture zones. However, the magnitude of the impact on aquafarming environment has remained largely unknown. In the present study, the concentrations of DDT and its metabolites (designated as DDXs) were determined in harbor sediment and antifouling paint samples collected from a typical mariculture zone in South China. Compositional and concentration correlation analyses implicated the DDT-containing antifouling paints for fishing boat maintenance as an important source of DDT in the mariculture zone. The annual emission of DDXs to the study region was estimated at 0.58 tons/yr. Furthermore, a comparison of the expected DDT loadings in pelagic fish and field measurements indicated that fish feed especially trash fish was a major source of DDTs in the fish body. Nevertheless, the use of DDT-containing antifouling paints should be limited to prevent further deterioration in aquafarming environment.     

Effects of the neurotoxic thionophosphate pesticide chlorpyrifos on differentiating alternative models

Studies by researchers worldwide have revealed that, even in industrialised nations, people, infants and the aged in particular, are even more exposed to neurotoxic drugs as a consequence of the increased quantity of pesticide residues in food. This phenomenon, as underlined by The Worldwatch Institute (2006), is linked to the exponential increase in the use of these toxic compounds over the last 40 years, up from 0.49 kg per hectare in 1961 to 2 kg in 2004, with the result that these substances are found in the daily diet.Many studies have demonstrated how the assumption of pesticides in the neonatal period and early infancy can alter the development and function of the nervous, immune, endocrine and reproductive apparatuses. Moreover, the unequivocal relationship between brain tumours, infant leukemia and pesticides are well recognised.On the basis of the above information, the effects of the neurotoxic thionophosphate pesticide chlorpyrifos (CPF) have been tested, considering biomarkers of toxicity and toxicity endpoint, on the biological models Dictyostelium discoideum, Paracentrotus lividus, and NTera2 Cells, as they are compatible with the 3Rs strategy (Reduction, Replacement, and Refinement in animal experiments). Our results have revealed that developing organisms are particularly sensitive to the toxic effects of CPF.