Ecological risk assessment of multimedia hazardous air pollutants: estimating exposure and effects.

Hazardous air pollutants, some of which have the potential for multimedia distribution, raise several hurdles for ecological risk assessment including: (1) the development of an adequate transport, fate and exposure model; and (2) the selection of exposure-response models that can accommodate multiple exposure routes for ecological receptors. To address the first issue, the EPA Office of Air Quality Planning and Standards has developed TRIM.FaTE, a mass-balance, fate, transport, and ecological exposure model that is a component of the Total Risk Integrated Methodology (TRIM) for air pollutants. In addition to abiotic transfers and transformations, TRIM.FaTE estimates the uptake of a chemical by terrestrial and aquatic organisms with time. Measures of exposure that TRIM.FaTE can provide include: (1) body burdens or tissue concentrations; (2) doses averaged over any time period; or (3) concentrations of chemicals in abiotic media. The model provides the user with the flexibility to choose the exposure-response thresholds or dose-response relationships that are best suited to data availability, routes of exposure, and the mechanism of toxicity of the chemical to an ecological receptor. One of the challenges of incorporating TRIM.FaTE into a risk assessment methodology lies in defining a streamlined model simulation scenario for initial screening-level risk assessments. These assessments may encompass multiple facilities that emit a variety of pollutants near diverse ecosystems. The information on ecological risk assessment methodology that is described is applicable to the EPA Residual Risk Program with emphasis on multimedia pollutants and the role of TRIM.FaTE.     

生物操纵法对调蓄水库藻类的控制

通过分析调蓄水库鱼的种群、食性及其与水库中藻类、水草和鱼种彼此间的食物链关系,有针对性地选择适当的滤食藻类和水草的鱼类,研究了生物操纵法对调蓄水库藻类的控制效果。基于食物链关系制定生物操纵方案,同时根据调蓄水库容积,计算出各鱼种的投放量。通过对高藻期藻类含量进行统计发现,采用生物操纵法代替化学药剂法控制调蓄水库原水中的藻类,可使藻类含量控制在2000×10^4个/L以下,同时每年可节约药剂费用16万元。     

Toxic and genotoxic evaluation of six antibiotics on non-target organisms

The ecotoxicity of the following six antibiotics on aquatic organisms was investigated: Erythromycin, Oxytetracyclin, Sulfamethoxazole, Ofloxacin, Lincomycin and Clarithromycin. Bioassays were performed on bacteria, algae, rotifers, microcrustaceans and fish to assess acute and chronic toxicity, while SOS Chromotest and Ames test were used to detect the genotoxic potential of the investigated drugs. For risk assessment, the environmental impact was calculated by MEC/PNEC ratio using the available data from the literature regarding their occurrence in the aquatic environment and the toxicity data obtained from the bioassays performed. The ecotoxicological results showed that acute toxicity was in the order of mg/L while, for the chronic data the antibiotics were bioactive at concentrations in the order of microg/L, mainly for the algae. Drugs investigated were one or two order of magnitude less active against rotifers and crustaceans. Ofloxacin was the only genotoxic compound and Sulfamethoxazole, Ofloxacin and Lincomycin were mutagenic. As for environmental risk, the macrolides were found to be the most harmful for the aquatic environment.     

Probabilistic ecological risk assessment of DDTs in the Bohai Bay based on a food web bioaccumulation model

The fugacity-based food web model was developed to simulate the bioaccumulation of dichloro-diphenyl-trichloroethanes (DDTs) in the aquatic ecosystem in the Bohai Bay. The internal exposure levels (IELs) of DDTs in various organism categories were calculated. Monte Carlo-based uncertainty analysis was performed to get the of IEL distributions of DDTs in organisms. Probabilistic ecological risk assessment (ERA) was performed based on IEL distributions and internal species sensitivity distributions (SSDs). The results show that fugacities and bioaccumulation factors (BAFs) generally increased with increasing trophic level in the food web. Octanol-water partition coefficient (K_ow), DDT levels in water and the lipid contents had the greatest influences on IELs in the organism bodies. The ecological risks of DDTs were relatively high. The risk order was p,p′-DDT > p,p′-DDE > p,p′-DDD. At an internal hazard quotient (HQ_int) criterion of 1/5, the risk probabilities were 0.10 (0.055-0.17), 0.079 (0.045-0.13) and 0.053 (0.028-0.092) for p,p′-DDT, p,p′-DDE and p,p′-DDD, respectively. The results from ERA based on the internal exposure approximated those based on external exposure. The food web model is a feasible method to predict the extent of bioaccumulation and IELs of hydrophobic organic pollutants in organisms as a step to evaluate their risk posed on aquatic ecosystems.     

Development of a dynamic model for estimating the food web transfer of chemicals in small aquatic ecosystems

A dynamic combined fate and food web model was developed to estimate the food web transfer of chemicals in small aquatic ecosystems (i.e. ponds). A novel feature of the modeling approach is that aquatic macrophytes (submerged aquatic vegetation) were included in the fate model and were also a food item in the food web model. The paper aims to investigate whether macrophytes are effective at mitigating chemical exposure and to compare the modeling approach developed here with previous modeling approaches recommended in the European Union (EU) guideline for risk assessment of pesticides. The model was used to estimate bioaccumulation of three hypothetical chemicals of varying hydrophobicity in a pond food web comprising 11 species. Three different macrophyte biomass densities were simulated in the model experiments to determine the influence of macrophytes on fate and bioaccumulation. Macrophytes were shown to have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log K_OW > = 5. Modeled peak concentrations in biota were highest for the scenarios with the lowest macrophyte biomass density. The distribution and food web transfer of the hypothetical compound with the lowest hydrophobicity (log K_OW = 3) was not affected by the inclusion of aquatic macrophytes in the pond environment. For the three different hypothetical chemicals and at all macrophyte biomass densities, the maximum predicted concentrations in the top predator in the food web model were at least one order of magnitude lower than the values estimated using methods suggested in EU guidelines. The EU guideline thus provides a highly conservative estimate of risk. In our opinion, and subject to further model evaluation, a realistic assessment of dynamic food web transfer and risk can be obtained using the model presented here.     

Comparison of the toxicity thresholds of water pollutants to bacteria, algae, and protozoa in the cell multiplication inhibition test

Using analogous methods of the cell multiplication inhibition test, the toxicity threshold (TT) of 156 potential water pollutants was determined for model organisms of biological self-purification, i.e. bacteria of the species Pseudomonas putida, green algae of the species Scenedesmus quadricauda, and flagellate protozoa of the species Entosiphon sulcatum. From the number of 156 inorganic and organic pollutants tested, 23 exhibited a pronounced selective toxic action on bacteria of the species Pseudomonas putida, 47 on algae of the species Scenedesmus quadricauda, and 43 on flagellate protozoa of the species Entosiphon sulcatum. It is seen from the ratios found that a determination of the toxicity threshold of potential water pollutants for these three model organisms from the microbiological spectrum would provide a broader basis for assessing the damaging action of water pollutants to model organisms active in the biological self-purification of water. Ecotoxicological testing of potential water pollutants to evaluate their toxicity involving only one model organism of biological self-purification would give an incomplete and biased picture of the effects of pollutants.     

Environmental fate and toxicity of ionic liquids: A review

Ionic liquids (ILs) are organic salts with low melting point that are being considered as green replacements for industrial volatile organic compounds. The reputation of these solvents as “environmental friendly” chemicals is based primarily on their negligible vapor pressure. Nonetheless, the solubility of ILs in water and a number of literature documenting toxicity of ILs to aquatic organisms highlight a real cause for concern. The knowledge of ILs behavior in the terrestrial environment, which includes microbial degradation, sorption and desorption, is equally important since both soil and aquatic milieu are possible recipients of IL contamination. This article reviews the achievements and current status of environmental risk assessment of ILs, and hopefully provides insights into this research frontier.     

Mercury contamination in the vicinity of a derelict chlor-alkali plant Part II: contamination of the aquatic and terrestrial food chain and potential risks to the local population

This study investigated the environmental impact and level of risk associated with mercury (Hg) contamination near a derelict chlor-alkali plant in Pavlodar, Northern Kazakhstan. Several species of fish were sampled from the highly polluted Lake Balkyldak and the nearby river Irtysh, to assess the extent of Hg bioaccumulation in the aquatic food chain and potential human health risks. A small number of bovine tissue samples, water samples, soil and plant samples from a nearby village were also investigated in order to make a preliminary assessment of potential impacts on the terrestrial food chain. Mercury levels in fish caught from Lake Balkyldak ranged from 0.16 to 2.2 mg kg(-1) and the majority of fish exceeded current human health criteria for Hg. Interspecies comparisons indicated that Hg is accumulated in the order dace>carp>tench. Site-specific bioaccumulation factors (BAF) were calculated for THg, and were estimated for MeHg. Fish from the river Irtysh and floodplain oxbow lakes contained between 0.075 and 0.159 mg kg(-1) of Hg and can be regarded as uncontaminated. Soils were found to be impacted by past atmospheric emissions of Hg. Cattle grazing in the surroundings of the factory are exposed to Hg from contaminated soils, plants and surface water, but the consumption of contaminated fish from the lake appears to be the main route of exposure for humans.     

What can be learnt from an ecotoxicity database in the framework of the REACh regulation?

Since REACh applies in all of EU, special emphasis has been put on the reduction of systematic ecotoxicity testing. In this context, it is important to extract a maximum of information from existing ecotoxicity databases in order to propose alternative methods aimed at replacing and reducing experimental testing. Consequently, we analyzed a database of new chemicals registered in France and Europe during the last twenty years reporting aquatic ecotoxicity data with respect to three trophic levels (i.e., Algae EC50 72 h, Daphnia EC50 48 h and Fish LC50 96 h). In order to ensure the relevance of the comparison between these three experimental tests, we performed a stringent data selection based on the pertinence and quality of available ecotoxicological information. At the end of this selection, less than 5% of the initial number of chemicals was retained for subsequent analysis. Such an analysis showed that fish was the least sensitive trophic level, whereas Daphnia had the highest sensitivity. Moreover, thanks to an analysis of the relative sensitivity of trophic levels, it was possible to establish that respective correction factors of 50 and 10 would be necessary if only one or two test values were available. From a physicochemical point of view, it was possible to characterize two significant correlations relating the sensitivity of the aforementioned trophic levels with the chemical structure of the retained substances. This analysis showed that algae displayed a higher sensitivity towards chemicals containing acid fragments whereas fish presented a higher sensitivity towards chemicals containing aromatic ether fragments.Overall, our work suggests that statistical analysis of historical data combined with data yielded by the REACh regulation should permit the derivation of robust safety factors, testing strategies and mathematical models. These alternative methods, in turn, could allow a replacement and reduction of ecotoxicological testing.     

Toxicity and transformation of fenamiphos and its metabolites by two micro algae Pseudokirchneriella subcapitata and Chlorococcum sp

The acute toxicity of an organophosphorous pesticide, fenamiphos and its metabolites, fenamiphos sulfoxide (FSO), fenamiphos sulfone (FSO(2)), fenamiphos phenol (FP), fenamiphos sulfoxide phenol (FSOP) and fenamiphos sulfone phenol (FSO(2)P), to the aquatic alga Pseudokirchneriella subcapitata and the terrestrial alga Chlorococcum sp. was studied. The toxicity followed the order: fenamiphos phenol>fenamiphos sulfone phenol>fenamiphos sulfoxide phenol>fenamiphos. The oxidation products of fenamiphos, FSO and FSO(2) were not toxic to the algal species up to 100 mg L(-1). Both algae were able to transform fenamiphos, FSO and FSO(2), while the phenols were found to be stable in the incubation media. Bioaccumulation of both fenamiphos and its metabolites was observed in the case of Chlorococcum sp. while only metabolites were accumulated in P. subcapitata. This study demonstrates that (i) the hydrolysis products of fenamiphos, FSOP and FSO(2)P are more toxic to both fresh water and soil algae than their parent chemicals, (ii) further fenamiphos can be transformed and bioconcentrated by these algae. Therefore, contamination of natural environments such as waterbodies with fenamiphos or its metabolites can have adverse impacts on the food chain and associated biota (especially to the primary consumers such as Daphnia) since algae are the primary producers located at the base of the food chain. Further, the finding that the fenamiphos phenols are more toxic to algae highlights the need to consider the transformation products in ecological risk assessment of fenamiphos.     

A new method for evaluating biological safety of environmental water with algae, daphnia and fish toxicity ranks

In this study, an innovative approach to evaluate biological safety of environmental water with toxicity ranks was proposed. Widely used species, algae (Selenustrum capricornutum), daphnia (Daphnia magna) and fish (Oryzias latipes larvae) belonging to three trophic levels in aquatic ecosystem, were selected and combined as a test set to measure the bio-toxicity of water sample. Maximum exposure concentrations for algae, daphnia and fish test were respectively designed as 10-, 50- and 50-fold of river water based on a simplification of conventional toxicity extrapolation method EU Directive EEC/93/67. A novel assessment index "safety score" of 1, 2, 3 and 4 with 1 being the safest was established for normalizing the toxicity effects. Safety score was determined according to the highest exposure concentration where adverse ecotoxicological effects could not be observed, and a triangle figure was designed to visually describe the safety scores of three toxicity tests. Finally, in order to conveniently evaluate the biological safety of environmental water, an integrated assessment index "bio-safety rank" (BSR) was established and determined according to the safety scores of the three tests, and with the index BSR, water sample could be ranked as A, B, C or D with A being the safest. It was shown that the proposed new method was effective for screening and evaluating the biological safety of river water in case studies.     

A proper choice of route significantly reduces air pollution exposure--a study on bicycle and bus trips in urban streets

A proper selection of route through the urban area may significantly reduce the air pollution exposure. This is the main conclusion from the presented study. Air pollution exposure is determined for two selected cohorts along the route going from home to working place, and back from working place to home. Exposure is determined with a street pollution model for three scenarios: bicycling along the shortest possible route, bicycling along the low exposure route along less trafficked streets, and finally taking the shortest trip using public transport. Furthermore, calculations are performed for the cases the trip takes place inside as well as outside the traffic rush hours. The results show that the accumulated air pollution exposure for the low exposure route is between 10% and 30% lower for the primary pollutants (NO(x) and CO). However, the difference is insignificant and in some cases even negative for the secondary pollutants (NO(2) and PM(10)/PM(2.5)). Considering only the contribution from traffic in the travelled streets, the accumulated air pollution exposure is between 54% and 67% lower for the low exposure route. The bus is generally following highly trafficked streets, and the accumulated exposure along the bus route is therefore between 79% and 115% higher than the high exposure bicycle route (the short bicycle route). Travelling outside the rush hour time periods reduces the accumulated exposure between 10% and 30% for the primary pollutants, and between 5% and 20% for the secondary pollutants. The study indicates that a web based route planner for selecting the low exposure route through the city might be a good service for the public. In addition the public may be advised to travel outside rush hour time periods.     

Survival tests with Chironomus riparius exposed to spiked sediments can profit from DEBtox model

DEBtox model is a biologically based model used to analyse aquatic toxicity data (The analysis of aquatic toxicity data, VU University Press, Amsterdam, The Netherlands, 1996, 149pp.). To date, it has not been used to analyse sediment survival tests, mainly because this would require daily counting of survivors, which is difficult for benthic organisms. In the present study, we adapted survival toxicity tests with the midge Chironomus riparius to permit survival data analysis with DEBtox. To validate the adaptation proposed, we exposed organisms to two chemicals, copper and methiocarb. We exposed larvae of second, third and fourth instar to different concentrations of the tested compounds and two different diets to assess the influence of diet and instar on DEBtox parameter estimates. Daily counting of organisms did not affect survival and did not lead to much more effort when compared to usual tests. Moreover, the analysis profited much from use of the DEBtox model. It was possible, with only survival data to estimate and validate the kinetics of the compounds, to predict survival during the recovery of exposed organisms and to assess the influence of food availability on toxicity. Food availability did not influence methiocarb toxicity, but copper was more toxic to food-limited organisms when a threshold concentration was exceeded. Comparison of parameters estimate also helped in understanding the differences in toxicity responses between instars. For the two compounds we studied, the difference was entirely explained by differences in threshold values.     

Ecological food web analysis for chemical risk assessment

Food web analysis can be a critical component of ecological risk assessment, yet it has received relatively little attention among risk assessors. Food web data are currently used in modeling bioaccumulation of toxic chemicals and, to a limited extent, in the determination of the ecological significance of risks. Achieving more realism in ecological risk assessments requires new analysis tools and models that incorporate accurate information on key receptors in a food web paradigm. Application of food web analysis in risk assessments demands consideration of: 1) different kinds of food webs; 2) definition of trophic guilds; 3) variation in food webs with habitat, space, and time; and 4) issues for basic sampling design and collection of dietary data. The different kinds of food webs include connectance webs, materials flow webs, and functional (or interaction) webs. These three kinds of webs play different roles throughout various phases of an ecological risk assessment, but risk assessors have failed to distinguish among web types. When modeling food webs, choices must be made regarding the level of complexity for the web, assignment of species to trophic guilds, selection of representative species for guilds, use of average diets, the characterization of variation among individuals or guild members within a web, and the spatial and temporal scales/dynamics of webs. Integrating exposure and effects data in ecological models for risk assessment of toxic chemicals relies on coupling food web analysis with bioaccumulation models (e.g., Gobas-type models for fish and their food webs), wildlife exposure models, dose-response models, and population dynamics models.     

Biomarker response in the earthworm Lumbricus terrestris exposed to chemical pollutants

Earthworms are important organisms for the soil ecosystem. They are sensitive to toxic chemicals and represent useful bioindicator organisms for soil biomonitoring. Recently the use of biomarkers in earthworms has been increasingly investigated for soil monitoring and assessment purpose. The aim of the preset paper was to analyze the pollutant-induced response of a suite of cellular and biochemical biomarkers in the earthworm Lumbricus terrestris exposed to copper sulphate or methiocarb in OECD soil at the maximal concentrations recommended in agriculture. These responses were compared to lifecycle parameters such as survival, growth and reproduction.Granulocyte morphometric alteration, lysosomal membrane stability, metallothionein concentration, and acetylcholinesterase activity were considered. In either copper sulphate or methiocarb exposure conditions the mean percentage variation of the pollutant-induced molecular and cellular biomarkers was consistent with the whole organism end-point responses. In particular pollutant-induced granulocyte enlargement, detected in either copper sulphate or methiocarb exposed organisms, showed to be a potential general biomarker that may be directly linked to organism health. Compared to the other biological responses to pollutants, it showed high sensitivity to pollutant exposure suggesting its possible applications as a sensitive, simple, and quick general biomarker for monitoring and assessment applications.     

A strategy for assessing the effects of xenobiotics on fish reproduction

Environmental pollutants, such as industrial and agricultural chemicals, heavy metals, drugs and products with hormonal activity may disrupt reproduction of aquatic wildlife such as fish. Such xenobiotics may cause disruption of the reproductive endocrine system, or they may directly affect gamete development and viability as a result either of their cytotoxicity or by altering the hormonal environment during gamete development. The various possible sites of action are reviewed, and it is suggested that tests for toxicity should isolate the specific component of the reproductive system that is most sensitive to such disruption and that this may be at levels well below that which causes mortality or visible signs of stress. Fish are proposed as the most suitable aquatic organism for such tests.     

Ecotoxicity of naproxen and its phototransformation products

The occurrence of pharmaceuticals in the environment is of great concern and only few data are available about the adverse effects of such molecules and their derivatives on non-target aquatic organisms. This study was designed to assess the toxic potential of Naproxen, a nonsteroidal anti-inflammatory, Naproxen Na, its freely water soluble sodium salt and their photoproducts in the aquatic environment. Bioassays were performed on algae, rotifers and microcrustaceans to assess acute and chronic toxicity. Furthermore, possible genotoxic effects of photoderivatives were investigated using SOS chromotest and Ames fluctuation test. The results showed that photoproducts were more toxic than the parent compounds both for acute and chronic values, while genotoxic and mutagenic effects were not found. These findings suggested the opportunity to consider derivatives in ecotoxicology assessment of drugs.     

Modelling long-term ecotoxicological effects on an algal population under dynamic nutrient stress

We study the effects of toxicants on the functioning of phototrophic unicellular organism (an algae) in a simple aquatic microcosm by applying a parameter-sparse model. The model allows us to study the interaction between ecological and toxicological effects. Nutrient stress and toxicant stress, together or alone, can cause extinction of the algal population. The modelled algae consume dissolved inorganic nitrogen (DIN) under surplus light and use it for growth and maintenance. Dead algal biomass is mineralized by bacterial activity, leading to nutrient recycling. The ecological model is coupled with a toxicity-module that describes the dependency of the algal growth and death rate on the toxicant concentration. Model parameter fitting is performed on experimental data from Liebig, M., Schmidt, G., Bontje, D., Kooi, B.W., Streck, G., Traunspurger, W., Knacker, T. [2008. Direct and indirect effects of pollutants on algae and algivorous ciliates in an aquatic indoor microcosm. Aquatic Toxicology 88, 102-110]. These experiments were especially designed to include nutrient limitation, nutrient recycling and long-term exposure to toxicants. The flagellate species Cryptomonas sp. was exposed to the herbicide prometryn and insecticide methyl parathion in semi-closed Erlenmeyers. Given the total limiting amount of nitrogen in the system, the estimated toxicant concentration at which a long-term steady population of algae goes extinct will be derived. We intend to use the results of this study to investigate the effects of ecological (environmental) and toxicological stresses on more realistic ecosystem structure and functioning.     

The combined toxic effects of nonpolar narcotic chemicals to Pseudokirchneriella subcapitata

This paper presents the toxicity data of 10 nonpolar narcotic chemicals on Pseudokirchneriella subcapitata (green algae) assessed by a new algal toxicity testing technique conducted under air-tight environment. Based on DO production, median effective concentration (EC50) varies from 1.73 mg/L (1-octanol) to 8,040 mg/L (2-propanol). The endpoint of algal growth rate reveals similar sensitivity as that from DO production. Compared to literature data, Pseudokirchneriella subcapitata and Nitrosomonas are apparently more sensitive to nonpolar narcotics than other organisms such as minnow, daphnia, and Tetrahymena pyriformis. Furthermore, good correlations between toxic effects observed from Pseudokirchneriella subcapitata and other aquatic organisms were found. Hence, algal toxicity test can be considered as a surrogate test for estimating the toxicity of nonpolar chemicals to fathead minnow, Microtox, activated sludge, Daphina magna, and Tetrahymena pyriformis. The combined effects of 13 binary mixtures of nonpolar chemicals were investigated using both additive-index method and isobologram analysis. Overall speaking, the joint actions between these chemicals are strictly additive. Model analyses indicate that these compounds act on identical reaction sites or receptors, which verify that these chemicals are of the same toxicity mechanism (narcosis).     

Carbamazepine in water: persistence in the environment,ozonation treatment and preliminary assessment on algal toxicity

The presence of carbamazepine (CBZ), an antiepilectic drug, has been reported in sewage treatment plant (STP) effluents as a result of its low biodegradability. In the present work, the persistence of CBZ in aquatic environment with respect to abiotic transformation processes along with its toxicity and capability of accumulating in single aquatic organisms (algae) are evaluated. The possibility of removing CBZ from STP effluents is studied by characterizing its ozonation process through the assessment of kinetics and the distribution of oxidation products.