Toxicity assessment of contaminated soils from an antitank firing range

Explosives are released into the environment at production and processing facilities, as well as through field use. These compounds may be toxic at relatively low concentrations to a number of ecological receptors. A toxicity assessment was carried out on soils from an explosive-contaminated site at a Canadian Forces Area Training Center. Toxicity studies on soil organisms using endpoints such as microbial processes (potential nitrification activity, dehydrogenase activity, substrate-induced respiration, basal respiration), plant seedling and growth (Lactuca sativa and Hordeum vulgare), and earthworm (Eisenia andrei) growth and reproduction were carried out. Results showed that 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane (HMX) was the principal polynitro-organic compound measured in soils. Soils from the contaminated site decreased microbial processes and earthworm reproduction; whereas plant growth was not significantly reduced. Toxicity to aquatic organisms and genotoxicity were also assessed on soil elutriates using Microtox (Vibrio fischeri), growth inhibition of algae (Selenastrum capricornutum), and SOS Chromotest (Escherichia coli). Results indicated that soil elutriates were generally not toxic to bacteria (Microtox) and algae. However, genotoxicity was found in a number of soil elutriate samples. Thus, the explosive-contaminated soils from the antitank firing range may represent a hazard for the soil organisms. Nevertheless, the global toxicity might have partially resulted from HMX as well as from other (not identified) contaminants such as heavy metals.     

Location-specific ecotoxicological risk assessment of metal-polluted soils

When chemical analysis indicates metal pollution, a second-tier method is needed to evaluate whether toxic effects occur at the polluted sites. A method based on pollution-induced community tolerance (PICT) was developed using samples taken from locations polluted with sewage more than 20 years ago. Microorganisms extracted from soil samples were exposed to a concentration range of zinc, nickel, copper, chromium (III), or chromium (VI) salts in a buffer suspension. The remaining activity of the intoxicated microorganisms was determined by color formation with 31 different organic substrates in microtiter plates. Microorganisms from moderately Zn-polluted sites (>45 mg/kg) showed an increased tolerance for zinc. Nickel tolerance was observed at 51 mg Ni/kg soil, chromium (VI) tolerance at 923 mg Cr/kg. In most cases, tolerance also was observed at higher concentrations. High concentrations of 1,494 mg Cu/kg or 3,935 mg Cr/kg did not show PICT, indicating a limited bioavailability of Cu and Cr at these sites. The benefits of our method are its greater sensitivity compared to other tests used at these sites, and its specificity for those metals that exceed allowable levels.     

Ecological risk assessment of endocrine disruptors

The European Centre for Ecotoxicology and Toxicology of Chemicals proposes a tiered approach for the ecological risk assessment of endocrine disruptors, integrating exposure and hazard (effects) characterization. Exposure assessment for endocrine disruptors should direct specific tests for wildlife species, placing hazard data into a risk assessment context. Supplementing the suite of mammalian screens now under Organization for Economic Cooperation and Development (OECD) validation, high priority should be given to developing a fish screening assay for detecting endocrine activity in oviparous species. Taking into account both exposure characterization and alerts from endocrine screening, higher tier tests are also a priority for defining adverse effects. We propose that in vivo mammalian and fish assays provide a comprehensive screening battery for diverse hormonal functions (including androgen, estrogen, and thyroid hormone), whereas Amphibia should be considered at higher tiers if there are exposure concerns. Higher tier endocrine-disruptor testing should include fish development and fish reproduction tests, whereas a full life-cycle test could be subsequently used to refine aquatic risk assessments when necessary. For avian risk assessment, the new OECD Japanese quail reproduction test guideline provides a valuable basis for developing a test to detecting endocrine-mediated reproductive effects; this species could be used, where necessary, for an avian life-cycle test. For aquatic and terrestrial invertebrates, data from existing developmental and reproductive tests remain of high value for ecological risk assessment. High priority should be given to research into comparative endocrine physiology of invertebrates to support data extrapolation to this diverse fauna.     

Refining the risk assessment of metal-contaminated soils

Determining the bioavailability of toxic metals (Pb, As, and Cd) in a diverse range of soils, allows scientifically derived data to dictate site-specific remedies to reduce the risk for sensitive human populations. Based on a series of dosing trials in a juvenile swine model, site-specific estimates of relative bioavailability of Pb in soil ranged from 3 % to 86 % compared to soluble lead acetate. Another experiment using a pregnant swine model revealed: 1) Pb accumulation in fetal tissues was 50 % or more of maternal and; 2) pregnant females accumulated 2-to-4 times more lead in tissues than unbred females. Relative bioavailability results for arsenic- and cadmium-contaminated soils further support the view that soil metals are not always as well absorbed as soluble forms, therefore use of default toxicity factors for assessing human health risk may overestimate the hazard.     

生态危险度评定及其应用

生态危险度评定与环境毒理学的联系十分紧密，是当今环境科学的众多学科中发展最为迅速的一个新兴分支学科。本文综合美国环保署（ＥＰＡ）、加拿大环保局和欧州共同体的生态危险度评定指导原则和有关文献，结合作者在这方面的亲身经验，概括地介绍了生态危险度评定的主要内容和基本过程，以及生态危险度评定的实际应用。     

Assessing the toxicity of contaminated soils using the nematode Caenorhabditis elegans as test organism

In this study, nine uncontaminated reference soils and 22 contaminated soils with different physico-chemical properties and contamination patterns were tested with a standardized toxicity test, using the nematode, Caenorhabditis elegans, as test organism. Fertility, growth and reproduction of C. elegans in the soils were compared with the exposure in standard soil Lufa St.2.2. C. elegans showed 100% fertility and a very low variability of growth in the reference soils. Although, reproduction varied considerably between the various reference soils, validity criteria (>30 offspring per test organism) were met in all reference soils. Moreover, Lufa St. 2.2 turned out to be a suitable and representative control soil. In order to clearly classify the effects of the polluted soils on C. elegans, toxicity thresholds were derived for nematode fertility (20% inhibition), growth (10% inhibition) and reproduction (40% inhibition) on the basis of the test inherent variability (MDD=minimal detectable difference), as well as their variability between the uncontaminated reference soils (MTI=maximal tolerable inhibition). The contaminated soils showed clear toxic effects on the nematodes, whereas the toxicity was better correlated to organic than to heavy metal contamination in bulk soil. Interestingly, the results of the nematode toxicity test were not well correlated with those of tests with oligochaetes, collembolans and plants, performed with the same soils, showing that the results are not redundant. The toxicity test using C. elegans turned out to be suitable for testing the toxicity of field collected soils and might by a valuable addition to soil test batteries.     

Light as a confounding factor for toxicity assessment of complex contaminated sediments

Polycyclic aromatic hydrocarbons (PAHs) are contaminants often found in sediments. Their relevant contribution to toxic effects induced by environmental samples has been demonstrated using effect-directed analysis (EDA). Toxicity of PAHs previously has been reported to depend on light conditions. The aim of this study was to analyze the influence of simulated sunlight, in comparison to standard algal growth light, on the toxicity of samples, in which PAHs were identified as major toxicants using EDA. Additionally, toxicity of identified toxicants and mixtures of these compounds were assessed. It can be shown that the samples, the PAH compounds, and the created mixtures exhibit photoenhanced toxicity. The combined effects of the mixtures can be predicted using the model of concentration addition. This is surprising because different modes of action have been reported to contribute to phototoxicity of the identified toxicants. For the confirmation step in EDA, the toxicity assessment under simulated sunlight reveals that less of the samples' toxicity can be explained by the identified compounds, compared to the assessment conducted under standard growth light. Finally, the relevance of light conditions in the toxicity assessment is demonstrated for eight out of 13 transect samples of sediment extracts from river Elbe, Germany.     

Leaching tests: useful tools for the risk assessment of contaminated sediments

In recent years, the importance of trace metal mobile fractions rather than total contents in environmental matrices is increasing in risk assessment evaluation of contaminated sites. In this study different leaching/extraction tests, aimed at the measurements of mobile fractions of trace metals and standardized at European Committee for Standardization (CEN) for the characterization of waste, have been compared with those adopted by the Italian legislation for soils. All these procedures have been applied on Venice Lagoon sediments, in order to extend the appliance of these methods to sediments and to verify the consistency of the results when different leaching tests are applied on the same sample. The results show that these tests can be applied successfully to sediments and confirm that leaching/extraction methods based on the main parameters controlling the remobilisation of trace metals are useful tools for risk-assessment, because they can allow a "transparent" interpretation in the light of key environmental variables (such as pH and DOC) controlling metal mobility. Further the use of geochemical models in support to leaching allows the assessment of trace metals mobility in the long-term.     

How terrestrial snails can be used in risk assessment of soils

Among soil invertebrates, terrestrial snails are herbivorous and detritivorous organisms exposed to polluted soils by both digestive and cutaneous routes. Using laboratory-reared snails (Helix aspersa aspersa), we describe how the effects of contaminants on survival and growth of snails can be evaluated in laboratory bioassays. A national ring test was performed to assess the effect of Cd added to the soil or to the food. The ecotoxicity of sewage sludge also was evaluated. The present results demonstrate that toxicity depends on both the pollutants and the exposure route. Cadmium was sixfold more toxic for snails exposed via food contamination (median effective concentration [EC50], 68-139 microg/g) than via soil contamination (EC50, 534-877 microg/g), whereas the opposite occurred with the sewage sludge (EC50, 55% of sludge in the food and 10% of waste in the soil). A logistic relationship linked growth inhibition and internal Cd concentrations, which can reach 2,000 microg/g in the viscera of snails exposed to 626 microg/g in the food. No clear trend was found between Cu, Zn, Pb, Cr, and Ni concentrations in the sludge and in snail tissues. These data enabled the development of an international standard, which should enhance the use of terrestrial gastropods for both fundamental research and routine risk assessment in the terrestrial environment.     

Analysis of arsenic bioavailability in contaminated soils

The bioavailable arsenic (As) content of contaminated soils was determined by joint analyses of acid-soluble, total water-soluble, and biovailable As by using a luminescent bacterial sensor, Escherichia coli MC1061(pTOO31). According to the results of this study, a significant positive correlation was found between the concentration of total water-soluble As and the bioavailability of As. However, the bioavailability of As in soil varied between sampling sites and was not equal when compared to the concentration of total water-soluble As; bioavailable As was 3 to 77% of total water-soluble As in soil. Our experiments also showed that aging and sequestration of As occurs in contaminated soils and As compounds thus become progressively less bioavailable with time. As a consequence, the bioavailability and toxicity of As should be considered when evaluating the ecological risks of contaminated soils.     

水环境中有机紫外防晒剂的生态风险评价

目的评价水环境中有机紫外防晒剂残留的生态风险。方法查阅2001—2014年文献获取有机紫外防晒剂的环境浓度及其对水生生物的毒性数据,采用评价因子法推导预测无效应浓度(PNEC)值,随后利用风险商(RQ)法评价各有机紫外防晒剂的生态风险。结果二苯酮-3(BP-3)对藻类的最大RQ10,对鱼类也存在高风险(最大RQ1);对甲氧基肉桂酸异辛酯(EHMC)对藻类、大型蚤、虾类和鱼类的最大RQ均大于1;3-(4-甲基苯亚甲基)-樟脑(4-MBC)对藻类和虾类表现出高风险;而辛基二甲基对氨基苯甲酸(OD-PABA)仅对藻类存在高风险;二苯酮-4(BP-4)的生态风险较低(RQ0.1)。结论有机紫外防晒剂BP-3、EHMC、4-MBC和OD-PABA在实测环境浓度水平对水生生态系统存在潜在风险。     

Industrial solvents and liver toxicity: risk assessment,risk factors and mechanisms

Organic solvents utilized in various industrial processes may be associated with hepatotoxicity. The hepatotoxicity of some of the solvents was recognized as early as 1887, 1889 and 1904. Factors contributing to the hepatotoxicity of solvents include 1) species differences, 2) liver blood flow, 3) protein binding, 4) point of binding intracellularly, 5) genetic factors, 6) different cellular enzymatic degradation, 7) age, 8) nutritional condition, 9) interaction with alcohol, and 10) interaction with medications of use and abuse. The hepatotoxicity of solvents in general and of carbon tetrachloride, trichloroethylene, tetrachloroethylene, toluene, and 1,1,1-trichloroethene are discussed. Experimental animal data, human data, and in vitro studies are explored. Suggested mechanisms of direct toxicity, indirect toxicity and autoimmune mechanisms are elaborated. The most important message from this review is that laboratory testing that is commonly used by clinicians to detect liver toxicity may not be sensitive enough to detect early liver hepatotoxicity from industrial solvents and new methodologies are being encouraged and utilized in the early recognition and diagnosis of hepatotoxicity for solvents. The final clinical assessment of hepatotoxicity and industrial solvents must take into account synergism with medications, drugs of use and abuse, alcohol, age, and nutrition. Early recognition and reporting will be helpful in further understanding the incidence, cofactors and possible mechanisms.     

An approach to environmental risk assessment using avian toxicity tests

Toxicity tests results are often condensed into a single endpoint (LC50) to facilitate their use in environmental management. The single number cannot distinguish between two tests with equal LC50s but dissimilar slopes at LC50 and it cannot describe the response at low and high dose levels. Some chemicals produce a flat response at low dose levels, others produce a steep response. The management of different chemicals requires different strategies and a more comprehensive approach to analysis of test data than use of a single endpoint. An alternative analysis of test data using Weibull survivor function produces information on the overall form of the dose-response curve and enables calculation of toxicity, the slope, and errors at arbitrary protection levels, including the conventional 50% level.     

An assessment and quantitative uncertainty analysis of the health risks to workers exposed to chromium contaminated soils

Millions of tons of chromite-ore processing residue have been used as fill in various locations in Northern New Jersey and elsewhere in the United States. The primary toxicants in the residue are trivalent chromium [Cr(III)] and hexavalent chromium [Cr(VI)]. The hazard posed by Cr(III) is negligible due to its low acute and chronic toxicity. In contrast, Cr(VI) is considered a inhalation human carcinogen at high concentrations. Approximately 40 commercial and industrial properties in Northern New Jersey have been identified as containing chromite ore processing residue in the soil. One site, a partially-paved trucking terminal, was evaluated in this assessment. The arithmetic mean and geometric mean concentrations of total chromium in soil were 977 and 359 mg/kg, respectively. The data were log-normal distributed. The arithmetic mean and geometric mean concentrations of Cr(VI) in surface soil were 37.6 and 3.1 mg/kg, respectively. The data could not be fit to a standard distribution, likely due to the large number of samples with concentrations below the method detection limit (65%). Dose was calculated for each exposure route using a Monte Carlo statistical simulation. Probability distributions of most exposure parameters were incorporated into the analyses to predict the range and probability of uptake for persons in the exposed population. The exposure parameter distributions included in this assessment are: the concentrations of Cr(VI) and total chromium in air and soil, fraction of the year when suspension of airborne soil particulates is likely to occur due to weather conditions, fraction of Cr(VI) in air which is respirable (less than 10 microns), soil loading rate on skin, occupational tenure, and body weight. The techniques used in this assessment are applicable for evaluating the human health risks posed by most industrial sites having contaminated soil. The estimated average daily dose (ADD) via ingestion and dermal absorption for the individual exposed at the 95th percentile was about 48,000- and 91-fold below the U.S. EPA reference dose (RfD) for Cr(III) and Cr(VI), respectively. Since inhalation of Cr(VI) contaminated dust (but not ingestion or dermal contact) poses a cancer hazard, the lifetime average daily doses (LADDs) associated with exposure at the 50th and 95th percentile were calculated to be 9.8 x 10(-8) and 1.3 x 10(-6), respectively. Based on this analysis, industrial sites having soil concentrations of Cr(VI) below 230 ppm do not pose a significant noncarcinogenic or carcinogenic health hazard following acute or chronic exposure. These risks would be even smaller if the sites were paved.     

Substrate-mediated toxicity of deltamethrin residues to beneficial invertebrates: Estimation of toxicity factors to aid risk assessment

Laboratory bioassays were carried out to determine the toxicity of residues of the synthetic pyrethroid insecticide, deltamethrin ((S)--cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropanecarboxylate) to a range of beneficial invertebrates exposed to treated wheat foliage, sandy loam soil, and glass surfaces. The test invertebrates represented a range of predators and a parasitoid that inhabit the foliage and grounds layers of temperate cereal crops, i.e., Pterostichus melanarius (Illiger), Nebria brevicollis (F.), Demetrias atricapillus (L.) and Bembidion obtusum (Serville) (Coleoptera: Carabidae), Tachyporus hypnorum (F.) (Coleoptera: Staphylinidae), Coccinella septempunctata (L.) (Coleoptera: Coccinellidae) adults (A) and larvae (L), Episyrphus balteatus (Degeer) (Diptera: Syrphidae), and Aphidius rhopalosiphi (De Stefani-Perez) (Hymenoptera: Braconidae). In 2 h flag leaf exposure bioassays, the LD₅₀ values varied from 0.4 g ai/ha to >50 g ai/ha. The susceptibility ranking, from most to least susceptible, was C. septempunctata (L) > T. hypnorum > C. septempunctata (A) > E. balteatus > A. rhopalosiphi > D. atricapillus. On soil, the LD₅₀ values were 52.8 g ai/ha for T. hypnorum and 97.8 g ai/ha for C. septempunctata (A) after 2 h exposure. This period of exposure was, however, found to be of insufficient duration to separate the susceptibilities of the other test species adequately, and therefore 72 h exposure bioassays were also carried out. The 72 h LD₅₀ values varied between 4.2 g ai/ha and 267 g ai/ha. The susceptibility ranking, from most to least susceptible, was T. hypnorum > B. obtusum > C. septempunctata (A) > P. melanarius > N. brevicollis > D. atricapillus. In 2 h glass bioassays the LD₅₀ range was 1.2 g ai/ha to >37 g ai/ha and the susceptibility ranking was T. hypnorum > C. septempunctata (A) > N. brevicollis, and D. atricapillus. Residual toxicities in the different 2 h exposure bioassays were compared for T. hypnorum and C. septempunctata (A) by iterating sequences of lethal dose ratios between LD₁₀ and LD₉₀ from the dose-response statistics for each respective pair of substrates. The mean ratios were termed toxicity factors (Tf). Tf values comparing glass and flag leaf assays, were 0.98 and 1.23, respectively for T. hypnorum and C. septempunctata (A), indicating that the toxicity of fresh deltamethrin residues to both species was similar on these surfaces. Tf values comparing either glass or flag leaf and soil were however in the range of 50–60 for T. hypnorum and C. septempunctata (A), indicating much lower effects on soil. Estimates of the bioavailable half-life on leaf and soil, obtained from in situ bioassays, indicated that effects in the field may vary two- to threefold as a result of differences in the duration of toxicity on these substrates. Overall, T. hypnorum could be at more than 150 times greater risk on leaf compared to soil surfaces. The potential for extrapolating laboratory toxicity data to the field is discussed.     

Cancer risk assessment for arsenic exposure through oyster consumption

Risk is assessed on the basis of assumptions, but this practice might not be well received by the general public. To avoid miscommunication, the assumptions should be stated clearly in reporting the results. Recently, a report on an assessment of the cancer risk associated with consumption of oysters caused a panic among consumers in Taiwan and produced significant effects on related industries. A group of researchers measured the arsenic content in oysters in the Taiwan area and conducted a cancer risk assessment accordingly. The results, published in a research article in an international journal, included a lifetime cancer risk estimate of 5.10/10(-4) as calculated based on the assumption that a person consumes oysters with the highest arsenic level (19.3 mg/g dry weight) at the highest rate (139 g/day) for 30 years. A national newspaper in Taiwan translated part of the article and published results that focused on the finding that this estimate was more than 500 times higher than what would be considered acceptable by the U.S. Environmental Protection Agency. As a result, most consumers stopped purchasing oysters, and the related industries suffered substantial losses. The newspaper's omission of the key assumptions in the risk assessment and the extreme assumptions made in the risk assessment led to this tragedy. This event demonstrated the importance of careful communication of risk assessment results.     

Human toxicity potentials for life-cycle assessment and toxics release inventory risk screening

The human toxicity potential (HTP), a calculated index that reflects the potential harm of a unit of chemical released into the environment, is based on both the inherent toxicity of a compound and its potential dose. It is used to weight emissions inventoried as part of a life-cycle assessment (LCA) or in the toxics release inventory (TRI) and to aggregate emissions in terms of a reference compound. Total emissions can be evaluated in terms of benzene equivalence (carcinogens) and toluene equivalents (noncarcinogens). The potential dose is calculated using a generic fate and exposure model, CalTOX, which determines the distribution of a chemical in a model environment and accounts for a number of exposure routes, including inhalation, ingestion of produce, fish, and meat, and dermal contact with water and soil. Toxicity is represented by the cancer potency q1* for carcinogens and the safe dose (RfD, RfC) for noncarcinogens. This article presents cancer and noncancer HTP values for air and surface-water emissions of 330 compounds. This list covers 258 chemicals listed in U.S. Environmental Protection Agency TRI, or 79 weight-% of the TRI releases to air reported in 1997.