Cyanotoxin management and human health risk mitigation in recreational waters

The occurrence and severity of harmful cyanobacterial or blue-green algal blooms (HABs) have increased in recent decades, posing a serious threat of illness to humans. In some countries, water contaminated with cyanotoxins that is used for drinking or haemodialysis has posed a particularly serious risk. However, it is now recognized that recreational exposure to natural toxins by skin contact, accidental swallowing of water or inhalation can also cause a wide range of acute or chronic illnesses. In this review, we focus on the importance of cyanotoxin management in recreational waters. The symptoms related with HAB poisonings, the recommended safety concentrations limit for cyanobacteria and cyanotoxins in such waters, as well as early health hazard indicators of their presence and their monitoring are all discussed. We also present in this review an overview of the methods developed in recent decades for eliminating cyanobacteria and the toxic compounds that they produce.     

Intra-laboratory evaluation of Microbial Assay for Risk Assessment (MARA) for potential application in the implementation of the Water Framework Directive (WFD)

The Microbial Assay for Risk Assessment (MARA) is an innovative system based on an array of 11 different microbial species freeze-dried in a 96-well micro-titre plate format. Developed for testing the toxicity of chemicals, mixtures and environmental samples, the assay employs species of a taxonomically diverse range. In addition to ten prokaryotic species, a eukaryote (yeast) is included in the range. The MARA's innate scope of a multi-dimensional test allows determination of toxicity based on a unique assay fingerprint or index, numerically expressed as the mean Microbial Toxic Concentration (MTC). The most significant potential of the test is in the additional inference that can be conveyed to the toxicity evaluation because of the presence of each of the constituent species. In view of the fact that conventional aquatic bioassays, like fish or cladoceran tests, are expensive and impractical, the MARA could provide a cost-effective solution for routine ecotoxicological testing. The performance of the MARA was evaluated to ascertain its capability and potential scope. Sensitivity to toxicants and different environmental samples was assessed. Evaluation included comparison with other tests: namely Microtox, invertebrate (Daphnia magna and Thamnocephalus platyurus) microbiotests, and respiration-inhibition and nitrification-inhibition tests. The most sensitive invertebrate test was found to be the T. platyurus microbiotest for three of the four metals tested. The LC(50) values for this test for Cd(ii), Cr(vi) and As(iii) were 0.2, 0.018 and 0.3 mg l(-1), respectively; and the corresponding most sensitive MARA species MTC values were 4.4, 2.8 and 17 mg l(-1), respectively.     

Impacts of the fish farms on the water column nutrient concentrations and accumulation of heavy metals in the sediments in the eastern Aegean Sea (Turkey)

Pulp and paper mill effluents may cause harmful effects to the aquatic environment due to the combined influence of physical factors, toxic compounds, and nutrient enrichment. In the present study, the effectiveness of secondary treatment in reducing the toxicity of an elemental chlorine-free bleached-kraft pulp mill effluent was evaluated. To characterize the toxicity of the effluent, before and after the implementation of secondary treatment, a battery of tests with organisms bearing different functions at the ecosystem level was used, namely Vibrio fischeri (5-min luminescence), Pseudokirchneriella subcapitata (72-h growth), Lemna minor (7-day growth), Daphnia magna (21-day reproduction and 24-h postexposure feeding), Chironomus riparius (9-day growth), and Danio rerio (28-day growth). For the effluent sample collected before the implementation of secondary treatment, P. subcapitata was the most sensitive organism followed by V. fischeri and D. magna, and no toxic effects were observed toward the other organisms. For the effluent sample collected after the implementation of secondary treatment, the effluent caused no toxic effects on any of the tested species. The present results demonstrated not only that secondary treatment efficaciously reduced effluent toxicity toward the selected test organisms but also the usefulness of a battery of tests to characterize the toxicity of pulp mill effluents.     

Seasonal availability and sensitivity of two field-collected mayflies for the development of a standardized toxicity test

Ecologically relevant toxicity tests may provide the best protection of sensitive aquatic fauna, but without established culturing or test methodology for such organisms, results may be unreliable and difficult to repeat. Further, field-collected organisms may not be feasible for routine testing purposes, as often required for permitted discharges. This study examined the feasibility of testing two field-collected mayflies, Isonychia bicolor and Maccaffertium spp., over a 1-year period. Seasonal comparisons of availability indicated I. bicolor and Maccaffertium spp. were most abundant during the winter months, resulting in 31 and 49 % of total organisms collected in 2009, while summer was the most difficult time to collect either species. Initial testing in January 2009 resulted in the highest no observable effect concentration (NOEC) values for survivorship (8 g NaCl for I. bicolor and 4 and 8 g NaCl/L for Maccaffertium spp.) when tested at 9°C. Subsequent tests conducted at 20–23°C resulted in 7-day NOEC values substantially lower (mean?=?1.44 and 1.59 g NaCl/L). Geometric means of exuviae indicated a dose-dependent response for I. bicolor exposed to NaCl, while no dose-dependent response was observed for Maccaffertium spp. with average number of molts varying from 4.93 in the 0.5 g NaCl/L concentration to 3.80 for control organisms followed by 2.24 (1 g NaCl/L). Averages again increased to 3.09 in the 2 g NaCl/L concentration, but declined in the highest concentrations (4–10 g NaCl/L). Based on the results of this feasibility study, field-collected mayflies appear to be too unpredictable in test responses, and therefore, such tests would be unreliable as stand-alone indicators of effluent toxicity.     

Seasonal variation of Sarpa salpa fish toxicity, as related to phytoplankton consumption, accumulation of heavy metals, lipids peroxidation level in fish tissues and toxicity upon mice

The aim of this work was to investigate for Sarpa salpa the seasonal trend in the food sources, heavy metals bioaccumulation and the oxidative stress in the organs. In addition, the toxicity was assessed by mouse bioassay of extract of the fish's organs collected in autumn, the peak of occurrence of hallucinatory syndrome. The toxicity was further studied for compounds present in epiphyte collected from the sea at the end of spring and in summer that are digested by the S. salpa in these seasons. We observed a higher lipid peroxydation in different tissues of S. salpa compared to the control fish Diplodus annularis. Furthermore, heavy metals accumulation in organs of these fish showed a significant variation between the two species (P?<?0.05). The lethal dose (LD50%) determined for crude ciguatoxin (neurotoxins) extracts of viscera, liver, brain and muscle of S. salpa were as follows: 1.217, 2.195, 14.395, 18.645 g/kg mouse, respectively. We noticed a significant correlation (P?<?0.05) between the total amount of toxic dinoflagellates and the level of TBARS in the liver, the brain and the muscle, this for all seasons and all sizes. Moreover, the cytotoxic effect observed for epiphytes extract confirms the transfer of toxins originating from toxic dinoflagellates, which live as epiphytes on P. oceanica leaves, to the fish by grazing. Our work indicates that, toxic phytoplanktons and heavy metals accumulation are responsible for the increase of oxidative stress in the organs of S. salpa. Hence, the edible part of S. salpa, especially the viscera and liver, can cause a threat to human health, and consumption should, for this reason, be dissuaded.     

Detection of hormones in surface and drinking water in Brazil by LC-ESI-MS/MS and ecotoxicological assessment with <Emphasis Type="Italic">Daphnia magna</Emphasis>

The growing use of pharmaceutical drug is mainly due to several diseases in human and in animal husbandry. As these drugs are discharged into waterways via wastewater, they cause a major impact on the environment. Many of these drugs are hormones; in which even at low concentrations can alter metabolic and physiological functions in many organisms. Hormones were found in surface water, groundwater, soil, and sediment at concentrations from nanograms to milligrams per liter of volume—quantities known to cause changes in the endocrine system of aquatic organisms. This study aimed to develop a methodology for hormone detection (estriol, estrone, 17β-estradiol, 17α-ethinylestradiol, progesterone, and testosterone) on surface and treated water samples. Sample toxicity was assessed by ecotoxicology tests using Daphnia magna. A liquid chromatograph coupled to a mass spectrometer with an electrospray ionization source (LC-ESI-MS/MS) was used for the analysis. The results showed that samples were contaminated by the hormones estriol, estrone, progesterone, 17β-estradiol, and 17α-ethinylestradiol during the sampling period, and the highest concentrations measured were 90, 28, 26, 137, and 194 ng·L^?1, respectively. This indicates the inflow of sewage containing these hormones at some points in the Piracicaba River in the State of Sao Paulo—Brazil. Results indicated little toxicity of the hormone estriol in D. magna, indicating that chronic studies with this microcrustacean are necessary.     

Quantitative assessment of aerosolized cyanobacterial toxins at two New Zealand lakes

The cyanobacterial toxins, nodularin and microcystin, are highly efficient inhibitors of cellular protein phosphatases. Toxicity primarily evolves following ingestion of cyanobacterial material or toxins and results in liver and renal pathology. Ingestion is the main route of exposure in the World Health Organizations current risk assessment of nodularin and microcystins. Nasally applied microcystin appears to have a 10-fold higher availability and toxicity than orally ingested toxins, suggesting that aerosolized toxins could represent a major risk for human populations close to lakes with cyanobacterial blooms. In this study, nodularin and microcystin levels in aerosols were assessed using high and low volume air samplers for 4, 12 and 24 h periods at lakes Forsyth and Rotorua (South Island, New Zealand). These lakes were experiencing blooms of Nodularia spumigena and Microcystis sp., respectively. Using the high volume samplers up to 16.2 pg m(-3) of nodularin and 1.8 pg m(-3) of microcystins were detected in the air. Aerosolized nodularin and microcystins do not appear to represent an acute or chronic hazard to humans. The latter was concluded based on calculations using average human air intakes, the highest nodularin or microcystin concentrations measured in the air in this study, and assuming inhalatory toxicities comparable to toxicological data obtained following intraperitoneal applications in mice. However, as the toxin concentrations in the air were calculated over extended sampling periods, peak values may be underestimated. Aerosolized toxins should be considered when developing risk assessments particularly for lakeside populations and recreational users where inhalation of cyanotoxins may be a secondary exposure source to a primary oral exposure.     

Integrated approach for the quality assessment of freshwater resources in a vineyard area (South Portugal)

An integrated chemical and biological approach for the quality assessment of freshwater resources in a vineyard area of the ??Alentejo?? region (South Portugal) is presented. This includes analysis to 11 pesticide compounds and whole toxicity testing on algae and crustaceans. Simazine, terbuthylazine, terbutryn, desethylatrazine and chlorpyrifos were the most frequently detected pesticides in water collected from wells and drainage channels. Mixtures of up to three compounds in different qualitative combinations were also found. The quality standards for individual pesticides (0.1 ??g L^???1) and pesticides-total (0.5 ??g L^???1) were exceeded in some samples. However, their maximum concentrations were lower than the WHO guidelines, the USEPA health advisory values and the environmental quality standards for priority substances applicable to surface water. In five samples, the herbicides terbuthylazine and terbutryn and the insecticide chlorpyrifos did not pass the toxicity exposure ratio (TER) trigger values specified for aquatic organisms (algae, Daphnia and fish). Maximum toxic effects on Daphnia magna (100%) and Pseudokirchneriella subcapitata (82.56%) were determined in groundwater samples, while in surface water, no toxicity was observed. Concerning effects on Heterocypris incongruens in sediment samples collected at the drainage channels, mortality and growth inhibition values were below 38%. Pro-active management of the use of pesticides is recommended for implementing at the farm and catchment level to reduce inputs into ground- and surface water.     

Toxicity of propargylic alcohols on green alga--Pseudokirchneriella subcapitata

The present study evaluates the toxicity of 34 propargylic alcohols, including primary, primary homo-, secondary, and tertiary alcohols, based on their effects on phytoplankton. A closed-system algal toxicity test was applied because the closed-system technique presents more realistic concentration-response relationships for the above compounds than the conventional batch tests. The green alga, Pseudokirchneriella subcapitata, was the test organism and final yield and growth rate were chosen as the test endpoints. Among all the propargylic alcohols tested, 1-pentyn-3-ol is the most toxic compound with its EC50 equal to 0.50 mg L(-1), which can be classified as a "R50" compound (very toxic to aquatic organisms, EC50/LC50 < 1 mg L(-1)), following the current practice for classification of chemicals in the European Union (EU). There are several other compounds including 2-decyn-1-ol, 3-decyn-1-ol, 1-hexyn-3-ol, 3-butyn-2-ol, and 3-hexyne-2,5-diol, which deserve more attention for their possible adverse impact on the aquatic environment, because these alcohols can be classified as "R51" compounds (toxic to aquatic organisms, EC50/LC50 between 1 and 10 mg L(-1)). Compared to the base-line toxicity relationship (narcosis QSAR) derived previously, tertiary propargylic alcohols can be identified as nonpolar narcotic chemicals, while secondary alcohols and primary alcohols with low molecular weight generally exhibit obvious excess toxicity in relation to the base-line toxicity. Finally, quantitative structure-activity relationships were established for deriving a preliminary estimation of the toxicity of other propargylic alcohols.     

Acute aquatic toxicity of western juniper (Juniperus occidentalis) foliage and Port Orford cedar (Chamaecyparis lawsoniana) heartwood oils

Recently, interest has developed for using essential oils from Western juniper (Juniperus occidentalis) foliage and Port Orford cedar (Chamaecyparis lawsoniana) heartwood in commercial products such as pest repellents and cosmetics. In order to gauge the relative toxicological risk that these oils pose to freshwater and marine organisms, the acute aquatic toxicity of these oils was evaluated using OPPTS guidelines to the cladoceran Daphnia magna, the rainbow trout Oncorhynchus mykiss and the green alga Selenastrum capricornutum. For western juniper foliage oil, no toxicity was exhibited toward D. magna or O. mykiss, even at 5.0 mg/L (the highest concentration tested and limit of solubility). For toxicity to S. capricornutum using algal cell density, the 72 and 96 h EC₅₀ value was 1.7 mg/L and the no observable effect concentration (NOEC) was 0.63 mg/L. For Port Orford cedar heartwood oil, no toxicity was exhibited toward O. mykiss or S. capricornutum, even at 5.0 mg/L (the highest concentration tested and limit of solubility). The 48-h D. magna EC₅₀ value was 1.9 mg/L; the NOEC values for algal cell density were 1.25 mg/L (72 h) and 0.63 mg/L (96 h). In summary, this study shows that western juniper foliage and Port Orford cedar heartwood oils demonstrate little to no risk to aquatic organisms.     

Management of toxic cyanobacteria for drinking water production of Ain Zada Dam

Blooms of toxic cyanobacteria in Algerian reservoirs represent a potential health problem, mainly from drinking water that supplies the local population of Ain Zada (Bordj Bou Arreridj). The objective of this study is to monitor, detect, and identify the existence of cyanobacteria and microcystins during blooming times. Samples were taken in 2013 from eight stations. The results show that three potentially toxic cyanobacterial genera with the species Planktothrix agardhii were dominant. Cyanobacterial biomass, phycocyanin (PC) concentrations, and microcystin (MC) concentrations were high in the surface layer and at 14 m depth; these values were also high in the treated water. On 11 May 2013, MC concentrations were 6.3 μg/L in MC-LR equivalent in the drinking water. This study shows for the first time the presence of cyanotoxins in raw and treated waters, highlighting that regular monitoring of cyanobacteria and cyanotoxins must be undertaken to avoid potential health problems.     

Toxicity Identification Evaluation (Phase I) of water and sediment samples from a tropical reservoir contaminated with industrial and domestic effluents

The Funil Reservoir (Rio de Janeiro State, Brazil) is an environment degraded by constant discharge of nutrients and pollution coming from the most industrialized region of the country. As a consequence of eutrophication, there are continuous cyanobacteria blooms, which cause acute and chronic toxicity to zooplankton. In this context, Phase I of Toxicity Identification Evaluation (TIE) was performed on Daphnia similis using water and interstitial water from the reservoir, with the aim of identifying classes of compounds responsible for toxicity. The results indicated that water toxicity was due to cyanobacteria resulting from blooms in the reservoir and surfactants. Metals, especially copper, contributed to sediment toxicity. This research is the first attempt to describe the nature of toxicity in this reservoir using this method.     

A docking-based receptor library of antibiotics and its novel application in predicting chronic mixture toxicity for environmental risk assessment

As organisms are typically exposed to chemical mixtures over long periods of time, chronic mixture toxicity is the best way to perform an environmental risk assessment (ERA). However, it is difficult to obtain the chronic mixture toxicity data due to the high expense and the complexity of the data acquisition method. Therefore, an approach was proposed in this study to predict chronic mixture toxicity. The acute (15 min exposure) and chronic (24 h exposure) toxicity of eight antibiotics and trimethoprim to Vibrio fischeri were determined in both single and binary mixtures. The results indicated that the risk quotients (RQs) of antibiotics should be based on the chronic mixture toxicity. To predict the chronic mixture toxicity, a docking-based receptor library of antibiotics and the receptor-library-based quantitative structure–activity relationship (QSAR) model were developed. Application of the developed QSAR model to the ERA of antibiotic mixtures demonstrated that there was a close affinity between RQs based on the observed chronic toxicity and the corresponding RQs based on the predicted data. The average coefficients of variations were 46.26 and 34.93 % and the determination coefficients (R ²) were 0.999 and 0.998 for the low concentration group and the high concentration group, respectively. This result convinced us that the receptor library would be a promising tool for predicting the chronic mixture toxicity of antibiotics and that it can be further applied in ERA.     

Artemia salina as test organism for assessment of acute toxicity of leachate water from landfills

Artemia salina has, for the first time, been used as test organism for acute toxicity of leachate water from three landfills (the municipal landfills at Kristianstad, Sweden and Siauliai, Lithuania, and an industrial landfill at Stena fragmenting AB, Halmstad, as well as for leachate from Kristianstad treated in different ways in a pilot plan). Artemia can tolerate the high concentrations of chloride ions found in such waters. Large differences in toxicities were found, the leachate from Siauliai being the most toxic one. To increase the selectivity in the measurements, a fractionation was done by using ion exchange to separate ammonium/ammonia and metal ions from the leachate, and activated carbon adsorbents for organic pollutants. The influence of some metals and phenol compounds on the toxicity was investigated separately. It was found that most of the toxicity emanated from the ammonium/ammonia components in the leachate. However, there was also a significant contribution from organic pollutants, other than phenol compounds, since separate experiments had in this latter case indicated negligible impact. The concentrations of metals were at a level, shown by separate experiments, where only small contribution to the toxicity could be expected.     

Gene-TEQ--a standardized comparative assessment of effects in the comet assay using genotoxicity equivalents

Existing methods for the comparison of genotoxic effects in the comet assay bear considerable disadvantages such as the problem to link information about concentration dependence and severity of effects. Moreover, given the lack of standardized protocols and the use of various standards, it may be extremely difficult to compare different studies. In order to provide a method for standardized comparative assessment of genotoxic effects, the concept of genotoxicity equivalents (Gene-TEQ) was developed. As potential reference compounds for genotoxic effects, three directly acting (N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methyl-methanesulfonate, and N-methyl-N-nitrosourea) and three indirectly acting (cyclophosphamide, dimethylnitrosamine, and 4-nitroquinoline-oxide) genotoxic substances were compared with respect to their cytotoxic (neutral red) and genotoxic (comet assay) concentration-response profiles in the permanent fish cell line RTL-W1. For further comparison, two sediment extracts from the upper Danube River were investigated as environmental samples. Based on the results of cytotoxicity and genotoxicity testing, MNNG was selected as the reference compound. At several exposure levels and durations, genotoxic effects of both the other pure substances and the environmental samples were calculated as percentages of the maximum MNNG effect and related to the absolute MNNG effect (EC values). Thus, genotoxicity equivalent factors (Gene-TEQs) relative to MNNG could be calculated. Gene-TEQs can easily be applied to pure substances, mixtures and field samples to provide information about their toxicity relative to the reference compound. Furthermore, the Gene-TEQ concept allows a direct comparison of environmental samples from different laboratories.     

Some phenolic compounds of extracts obtained from Origanum species growing in Turkey

Caffeic acid, rosmarinic acid, rutin, apigenin 7-O-glucoside, apigenin, and acesetin were the main phenolic compounds of Origanum onites extracts in all applications. While acesetin contents ranged from 133.59 mg/100 g (U1) to 437.25 mg/100 g (S3), rosmarinic acid changed between 215.94 mg/100 g (U4) and 1120.56 mg/100 g (S2) in Origanum vulgare L. subsp. hirtum (Link) Ietsw. Both rosmarinic acid and acesetin were not found in U5 application. Only caffeic acid (19.39 mg/100 g) was found in U5 application. Rosmarinic acid contents of O. onites extract changed between 158.62 mg/100 g (U5) and 799.87 mg/100 g (S2). Generally, dominant phenolic compound of Origanum extracts was rosmarinic acid compared with other extracts. In addition, methanol:water:acetic acid mixture (S2) (95:4.5:0.5) was found as the best application. Phenolic contents of extracts obtained with U series mixtures were found low.     

Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in the harbour of Naples (Southern Italy): time and spatial distribution patterns

Seventeen parent polycyclic aromatic hydrocarbons (PAHs) and 38 congeners of polychlorinated biphenyls were measured at five different sediment depths (between the surface and ~300 cm below the seafloor) at 160 sites in Naples harbour. Total PAH (??PAH) and PCB (??PCB) concentrations ranged between 0.012?C21.73^???nd 0.001?C0.222 mg kg^???1, respectively. For PAHs, an evident and progressive decrease in concentration with depth documents the effects of a more intense anthropic impact of this group of pollutants in the recent period. A selected number of PAH isomer pairs (phenanthrene/anthracene, fluoranthene/pyrene and benzo(a)anthracene/crysene) were used to distinguish between contaminants of pyrolitic and petrogenic origin. More than 90% of PAHs present at the different depths of the studied sediments indicate pyrolitic industrial origins. On the other hand, relatively high concentrations of three- and four-ring PAHs suggest a limited contribution of vehicular emissions to the contamination of sediments. An unexpected and systematic increase of ??PCB concentration, exceeding values approved by international regulations, was found in the studied sediments, testifying to the uncontrolled discharge to the studied area from industrial and commercial activity on nearby land. Ecotoxicological risk levels calculated for PAHs suggests a relatively elevated level of toxicity in surface sediments decreasing with depth and very low toxicity values associated to PCB toxicity.     

An interlaboratory comparison of sediment elutriate preparation and toxicity test methods

Elutriate bioassays are among numerous methods that exist for assessing the potential toxicity of sediments in aquatic systems. In this study, interlaboratory results were compared from 96-h Ceriodaphnia dubia and Pimephales promelas static-renewal acute toxicity tests conducted independently by two laboratories using elutriate samples prepared from the same sediment. The goal of the study was to determine if the results from the elutriate tests were comparable between two U.S. Environmental Protection Agency (USEPA) laboratories when different elutriate preparation procedures were employed by each lab. Complete agreement in site characterization was attained in 22 of the 25 samples for both bioassays amongst each lab. Of the 25 samples analyzed, 10 were found to be toxic to at least one of the species tested by either laboratory. The C. dubia elutriate tests conducted by the National Exposure Research Laboratory (NERL) indicated that 7 of the 25 sediment samples were toxic, while 8 sediment samples were characterized as such in testing conducted by USEPA Region 6 (Region 6). The P. promelas elutriate tests conducted by NERL determined 8 samples as toxic, while Region 6 tests displayed toxicity in 5 of the samples. McNemar's test of symmetry for C. dubia (S?=?0.33, p?=?0.5637) and P. promelas (S?=?3.0, p?=?0.0833) tests indicated no significant differences in designating a site toxic between NERL and Region 6 laboratories. Likewise, Cohen's kappa test revealed significant agreement between NERL and Region 6 C. dubia (K?=?0.7148, p?<?0.01) and P. promelas (K?=?0.6939, p?<?0.01) elutriate tests. The authors conclude that differences in interlaboratory elutriate preparation procedures have no bearing on the ability of either the C. dubia or P. promelas bioassay testing methods to detect toxicity while yielding similar results.     

The response of hydrophobic organics and potential toxicity in streams to urbanization of watersheds in six metropolitan areas of the United States

Semipermeable membrane devices (SPMDs) were deployed in streams along a gradient of urban land-use intensity in and around six metropolitan areas: Atlanta, Georgia; Raleigh-Durham, North Carolina; and Denver-Fort Collins, Colorado, in 2003; and Dallas-Fort Worth, Texas; Milwaukee-Green Bay, Wisconsin; and Portland, Oregon, in 2004 to examine relations between percent urban land cover in watersheds and the occurrence, concentrations, and potential toxicity of hydrophobic compounds. Of the 142 endpoints measured in SPMD dialysates, 30 were significantly (alpha = 0.05) related to the percent of urban land cover in the watersheds in at least one metropolitan area. These 30 endpoints included the aggregated measures of the total number of compounds detected and relative toxicity (Microtox(R) and P450RGS assays), in addition to the concentrations of 27 individual hydrophobic compounds. The number of compounds detected, P450RGS assay values, and the concentrations of pyrogenic polycyclic aromatic hydrocarbons (PAHs) were significantly related to percent urban land cover in all six metropolitan areas. Pentachloroanisole, the most frequently detected compound, was significantly related to urban land cover in all metropolitan areas except Dallas-Fort Worth. Petrogenic PAHs and dibenzofurans were positively related to percent urban land cover in Atlanta, Raleigh-Durham, Denver, and Milwaukee-Green Bay. Results for other endpoints were much more variable. The number of endpoints significantly related to urban land cover ranged from 6 in Portland to 21 Raleigh-Durham. Based on differences in the number and suite of endpoints related to urban intensity, these results provide evidence of differences in factors governing source strength, transport, and/or fate of hydrophobic compounds in the six metropolitan areas studied. The most consistent and significant results were that bioavailable, aryl hydrocarbon receptor agonists increase in streams as basins become urbanized. Potential toxicity mediated by this metabolic pathway is indicated as an important factor in the response of aquatic biota to urbanization.     

Spatial variation of potentially toxic elements in different grain size fractions of marine sediments from Gulf of Mannar, India

Marine sediments of the Gulf of Mannar (GoM), India are contaminated by potential toxic elements (PTEs) due to anthropogenic activities posing a risk to the existing fragile coral ecosystem and human health. The current study aimed to assess the distribution of PTEs (arsenic—As; cobalt—Co; copper—Cu, molybdenum—Mo; lead—Pb; and zinc—Zn) in marine sediments of different grain size fractions, viz., medium sand (710 μm), fine sand (250 μm), and clay (<63 μm) among the different coastal regions of Pamban, Palk Bay, and Rameswaram coasts of GoM, using grain size as one of the key factor controlling their concentrations. The concentrations of PTEs were measured in the different size fractions of sediment using inductively coupled plasma mass spectrophotometer. The order of accumulation of all PTEs in the three fractions was ranked as Zn > Cu > Pb > As > Co > Mo and in the three locations as Rameswaram > Palk Bay > Pamban. The concentration of PTEs in Palk Bay and Rameswaram coast was significantly different (P?<?0.05), when compared to Pamban coast. Measured geoaccumulation index (I _geo) and contamination factor (CF) indicated significant enrichment of Co and Pb from Rameswaram coast when compared to other two coasts. Although the concentration of Co was low but the measured I _geo and CF values indicated significant enrichment of this PTE in Rameswaram coast. The increased input of PTEs in the coastal regions of GoM signifies the need to monitor the coast regularly using suitable monitoring tools such as sediments to prevent further damage to the marine ecosystem.