Acute photo-induced toxicity and toxicokinetics of single compounds and mixtures of polycyclic aromatic hydrocarbons in zebrafish

A comparative account of phototoxicity of anthracene and pyrene in the tadpoles of the anuran amphibian Fejervarya limnocharis using multiple toxicological end points

Anthracene (Anth) and pyrene (Pyr), two of the priority polycyclic aromatic hydrocarbons (PAHs), being lipophilic in nature, not only accumulate in animals, but also settle in the sediment of water bodies leading to continuous exposure for animals. Anth and Pyr when exposed to sunlight can be photoactivated and have harmful effects on aquatic organisms. A comparative analysis was carried out to assess the acute, sub-chronic, genetic and biochemical toxicity of Anth and Pyr in F. limnocharis tadpoles following short exposures to sunlight on a daily basis. In the bioaccumulation studies, it was found that both Anth and Pyr accumulated in the tadpole tissues in a concentration and time dependent manner. The LC50 values for Anth (under 15 min of daily sunlight exposure) were found to be 2.87, 2.59, 2.28, 1.80 mg/L at 24, 48, 72 and 96 h of the exposures. The corresponding LC50 values for Pyr were 1.03, 0.80, 0.62, 0.42 mg/L. Sublethal exposure of Anth and Pyr affected the survivality, time to metamorphosis as well as morphometric parameters under sunlight exposure. In the genotoxicity assessment studies, particularly the micronucleus test and comet assay, it was found that Pyr led to a higher incidence of micronucleus formation and DNA damage in comparison to Anth. The exposure to PAHs resulted in significant changes in the activity of antioxidant-mediated protective response, specifically the SOD activity, which varied between the groups treated with Anth and Pyr. On the other hand, Pyr treated group showed a higher level of GSH as compared to Anth treated groups. Moreover, the elevation in MDA level in the Anth and Pyr treated groups suggests an increase in lipid peroxidation. Future research should focus on understanding the ecotoxicological risk faced by anuran amphibia due to PAHs that frequently occur in aquatic environments and developing strategies to mitigate these risks.

Pollution characteristics, distribution, and source analysis of carbazole and polyhalogenated carbazoles in coastal areas of Bohai Bay, China

Polyhalogenated carbazoles (PHCZs) are a class of emerging environmental contaminants formed by the substitution of hydrogen on carbazole (CZ) benzene rings with halogens (Cl, Br, I) with potential dioxin-like toxicity, and they have been frequently detected in various environmental media and organisms recently. Nevertheless, co-research of CZ/PHCZs with PAHs is very limited. In addition, I-PHCZs, which are believed to be much more toxic than CZ, Cl-PHCZs and Br-PHCZs, have a few data in sediments previously. The concentration and distribution of CZ/PHCZs and PAHs were analyzed in 18 surface sediments of Bohai Bay, China. There is a significant correlation (R = 0.64, P＜0.05) between PHCZs and PAHs, and principal component analysis (PCA) also indicating that they may have a certain similarity in origin. Additionally, total CZ and PHCZs was up to 230.57 ng/g dw in the studied samples, which was approximately 1-2 orders of magnitude lower than PAHs and other common persistent organic pollutants (POPs). The compositions of the CZ/PHCZs in our study were dominated by CZ (2.74-18.28, median 2.92 ng/g dw), 3,6-dichlorocarbazole (n.d-6.78, median 0.97 ng/g dw) and 3,6-iodocarbazole (n.d-12.68, median 1.65 ng/g dw). Results of this study discovered the varying origins of CZ and PHCZs and/or a complexity of anthropogenic influences and natural sources processes, and revealed a wide distribution of CZ/PHCZs across the studied. Moreover, more attention should be paid by comparing CZ/PHCZs with other widely distributed POPs.

New Insights into the Phototoxicity of Anthracene-Based Chromophores: The Chloride Salt Effect†

Unraveling the causes underlying polycyclic aromatic hydrocarbon phototoxicity is an essential step in understanding the harmful effects of these compounds in nature. Toward this end, we have studied the DNA interactions and photochemistry of N1-(anthracen-9-ylmethyl)ethane-1,2-diaminium dichloride in the presence and absence of NaF, KF, NaCl, KCl, NaBr, KBr, NaI, and KI (350 nm hν, pH 7.0). Exposing pUC19 plasmid to UV light in solutions containing 400 mM KCl formed significantly more direct strand breaks in DNA compared to no-salt control reactions. In contrast, NaCl increased DNA damage moderately, while the sodium(I) and potassium(I) fluoride, bromide, and iodide salts generally inhibited cleavage (I- > Br- > F-). A halide anion-induced heavy-atom effect was indicated by monitoring anthracene photodegradation and by employing the hydroxyl radical (•OH) probe hydroxyphenyl fluorescein (HPF). These studies revealed that among no-salt controls and the eight halide salts, only NaCl and KCl enabled the anthracene to photosensitize the production of high levels of DNA-damaging reactive oxygen species (ROS). Pre-irradiation of N1-(anthracen-9-ylmethyl)ethane-1,2-diaminium dichloride at 350 nm increased the amounts of chloride salt-induced •OH detected by HPF in subsequent anthracene photoactivation experiments. Taking into consideration that •OH and other highly reactive ROS are extremely short-lived, this result suggests that the pre-irradiation step might lead to the formation of oxidized anthracene photoproducts that are exceedingly redox-active. The fluorometric probes HPF and Singlet Oxygen Sensor Green revealed that KCl concentrations ranging from 150 to 400 mM and from 100 to 400 mM, respectively, enhanced N1-(anthracen-9-ylmethyl)ethane-1,2-diaminium dichloride photosensitized •OH and singlet oxygen (1O2) production over no-salt controls. Considering the relatively high levels of Na+, K+, and Cl- ions that exist in the environment and in living organisms, our findings may be relevant to the phototoxic effects exhibited by anthracenes and other polycyclic hydrocarbons in vivo.

Soil to earthworm bioaccumulation of polyhalogenated carbazoles and related compounds: Lab and field tests

Polyhalogenated carbazoles (PHCZs) are an emerging group of organic contaminants that have attracted attention because of their ubiquity, resistance to biodegradation, and toxicities. However, studies on the bioaccumulation of PHCZs in terrestrial organisms are limited. In the present study, bioaccumulation of 11 PHCZs and two related compounds, carbazole (CZ) and benzocarbazole (BZCZ), from soil to earthworms was investigated by paired soil-earthworm samples from Hangzhou, China and a laboratory bioaccumulation test. The sum of the concentrations of the 11 polyhalogenated carbazoles (Σ₁₁PHCZs), CZ and BZCZ in soils from Hangzhou were 1.78-67.27 ng/g dry weight, 1.11-57.90 ng/g dry weight, and 22.87-171.98 ng/g dry weight, respectively, while those in the earthworms were 179.49-892.90 ng/g lipid weight, 42.90-2140.42 ng/g lipid weight, and not detectable-2514.76 ng/g lipid weight, respectively. The average in situ biota-to-soil accumulation factors (BSAFs) ranged from 0.38 to 13.23, comparable to those in some reports for polychlorinated biphenyls and polybrominated diphenlethers. Site-independence of BSAFs and no correlation between log C_worm and log C_soil together support the hypothesis that distribution of PHCZs between soil and worms in Hangzhou didn't reach equilibrium. In the laboratory test, the accumulation trends of CZ, BZCZ, 3-bromocarbazole, 3,6-dichlorocarbazole, and 2,7-dibromocarbazole well fit to the first-order kinetics, with r² ranging from 0.796 to 0.997. The BSAFs under two exposure concentration groups at steady-state conditions were 38.8-56.0 and 2.1-4.4, respectively, suggesting the capacity of bioaccumulation for these compounds. Enhancement of concentrations and resident time of the chemicals in soil would reduce the BSAF values, which may be related to the change of uptake process of the compound or redistribution of compound between soil and earthworm. A comparison of the theoretical steady-state concentrations with the nonlinear regression-based concentrations indicates that increasing the exposure time beyond 28 days is beneficial for studying the bioaccumulation of PHCZs.

Occurrence, bioaccumulation and potential risk of polyhalogenated carbazoles in marine organisms from the East China Sea

As well-known emergent environmental contaminants, polyhalogenated carbazoles (PHCZs) have recently received increasing attention. In this study, we investigated the concentrations of carbazole (CZ) and PHCZs in 70 marine organisms from the East China Sea (ECS). CZ and 9-11 PHCZs were detected in organisms from the ECS, with concentrations in the range of 0.75-33 ng/g lipid weight, lw and 4.3-113 ng/g lw, respectively. Among the PHCZs, there were 3-4 major components in zooplankton, fish, shrimp, crabs, snails and shellfish, and the sum of these major components accounted for 59% to 67% of ∑PHCZs. The bioaccumulation potentials of 1,3,6,8-tetrachlorocarbazole (1368-CCZ) and 3-chlorocarbazole (3-CCZ) from water were observed. The logarithmic bioaccumulation factor (logBAF) values of the CZ and PHCZs increased significantly with increasing logK_OW values (R = 0.449-0.784, p < 0.01). The trophic magnification factor (TMF) values of the CZ, 9 PHCZs and ∑PHCZs were calculated to be 3.32, 1.87-4.06 and 2.36, respectively, indicating the potential biomagnification of the CZ and PHCZs in the zooplankton-shrimp-fish food web. The toxic equivalents (TEQs) of PHCZs in organisms from the ECS were in the range of 0.78-36 pg TEQ/g lw. Overall, for the first time, this study systematically examined the occurrence, bioaccumulation and potential risk of PHCZs in the marine food web of the East China Sea.

A review of human and animals exposure to polycyclic aromatic hydrocarbons: Health risk and adverse effects, photo-induced toxicity and regulating effect of microplastics

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widely distributed persistent organic pollutants (POPs) in the environmental media. PAHs have been widely concerned due to their significant health risk and adverse effects to human and animals. Currently, the main sources of PAHs in the environment are the incomplete combustion of fossil fuels, as well as municipal waste incineration and agricultural non-surface source emissions. In this work, the scope of our attention includes 16 typical PAHs themselves without involving their metabolites and industrial by-products. Exposure of human and animals to PAHs can lead to a variety of adverse effects, including carcinogenicity and teratogenicity, genotoxicity, reproductive- and endocrine-disrupting effects, immunotoxicity and neurotoxicity, the type and severity of which depend on a variety of factors. On the other hand, the regulatory effect of microplastics (MPs) on the bio-toxicity and bioaccumulation capacity of PAHs has now gradually attracted attention. We critically reviewed the adsorption capacity and mechanisms of MPs on PAHs as well as the effects of MPs on PAHs toxicity, thus highlighting the importance of paying attention to the joint bio-toxicity caused by PAHs-MPs interactions. In addition, due to the extensive nature of the common exposure pathway of PAHs and ultraviolet ray, an accurate understanding of biological processes exposed to both PAHs and UV light is necessary to develop effective protective strategies. Finally, based on the above critical review, we highlighted the research gaps and pointed out the priority of further studies.

Histological, biochemical and transcriptomic analyses reveal liver damage in zebrafish (Danio rerio) exposed to phenanthrene

Phenanthrene (PHE) is a common polycyclic aromatic hydrocarbon (PAH) in aquatic environments, and this contaminant can cause adverse effects on teleostean performance. In this study, we exposed the model freshwater fish (zebrafish; Danio rerio) to 300 μg/L PHE for 15 days. Histological analysis demonstrated that liver morphology deteriorated in PHE-exposed zebrafish, and cellular damage in the liver increased. Biological analysis revealed that exposure to PHE elicited significant changes in glutathione S-transferases (GST) and superoxide dismutase (SOD) activities. 476 differentially expressed genes (DEGs) were identified in liver between control and PHE treated groups through the transcriptomic analysis. Gene Ontology enrichment analysis (GO) suggested that PHE exposure induced changes in the expression of genes associated with "lipid transporter activity", "catalytic activity", "metal ion binding", "lipid transport" and "transmembrane transport". Furthermore, the "vitamin digestion and absorption" and "fat digestion and absorption" pathways enriched in Kyoto Encyclopedia of Genes and Genomes analysis (KEGG). Additionally, five candidate biomarkers associated with the PHE response in zebrafish were identified. In conclusion, our results elucidate the physiological and molecular responses to PHE exposure in the liver of zebrafish, and provide a framework for further studies of the mechanisms underlying the toxic effects of polycyclic aromatic hydrocarbons (PAHs) on aquatic organisms.

Arctic marine fish 'biotransformation toxicity' model for ecological risk assessment

Oil and gas exploration and marine transport in the Arctic region have put the focus on the ecological risk of the possibly exposed organisms. In the present study, the impacts of sea ice, extreme light regime, various polar region-specific physiological characteristics in polar cod (Boreogadus saida) and their effects on xenobiotic distribution and metabolism are studied. A Bayesian belief network is used to model individual fish toxicity. The enzyme activity in the fish liver and other pertinent organs is used as a proxy for cellular damage and repair and is subsequently linked to toxicity in polar cod. Seasonal baseline variation in enzyme production is also taken into consideration. The model estimates the probability of exposure concentration to cause cytotoxicity and circumvents the need to use the traditionally obtained No Observed Effect Concentration (NOEC). Instead, it uses biotransformation enzyme activity as a basis to estimate the probability of individual cell damages.

Interactive Effects of Mixtures of Phototoxic PAHs

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment as components in complex mixtures derived from petroleum based products. PAHs are unique in their ability to absorb UV light, resulting in significant increases in acute toxicity. The objective of this study was to determine if mixtures of the phototoxic PAHs fluoranthene, pyrene, and anthracene conform to the additive model of toxicity. Median lethal concentrations (LC50) were calculated for mysid shrimp (Americamysis bahia) and inland silverside (Menidia beryllina) exposed to individual, binary, and ternary mixtures of the selected PAHs. Mixtures were evaluated on a toxic unit basis to account for potency differences and toxicity data was analyzed using the concentration-addition and independent-action models. Data indicated that the model of additivity is sufficient in describing the toxicity of mixtures of phototoxic PAHs; therefore predictive models should consider an additivity model for assessing the toxicity of hydrocarbon mixtures.

Estimating degree of degradation of spilled oils based on relative abundance of aromatic compounds observed by paper spray ionization mass spectrometry

Paper spray ionization mass spectrometry (PSI-MS) was applied for the first time to study temporal change of photo-oxidized and weathered oils subjected to degradation. PSI is chosen in this study because it is an optimal ionization technique for the analysis of degraded oils with limited sample quantity and prone to salt and particulate contamination. With PSI-MS, quantitative analysis of oils can be successfully performed with as little as 2 μg of oil sample. In addition, oil solutions containing up to 0.05% sodium chloride were successfully analyzed with PSI-MS. In the PSI-MS spectra of photo-degraded oils, the relative abundance of compounds having double equivalence value (DBE) ≥ 5 increased but those with DBE < 5 decreased in number. The summed abundance ratio of compounds having DBE < 5 and DBE ≥ 5 showed a negative exponential correlation with the duration of UV exposure in laboratory experiments. The same trend was observed from spilled oils obtained from the environment. Therefore, this ratio serves as an effective means to estimate the degree of weathering in spilled oils.

Influence of variable ultraviolet radiation and oil exposure duration on survival of red drum (Sciaenops ocellatus) larvae

The toxicity of some polycyclic aromatic hydrocarbons (PAHs) increases with ultraviolet (UV) radiation. The intensity of UV radiation varies within aquatic ecosystems, potentially providing reprieves during which tissue repair may occur. Transient/short-term PAH exposure prior to UV exposure may initiate metabolism/clearance, potentially affecting outcomes. Larval Sciaenops ocellatus were exposed to oil and UV radiation, using either variable photoperiods or pre-UV oil exposure durations. Shorter PAH exposures exhibited greater toxicity, as did exposure to shorter photoperiods. Environ Toxicol Chem 2018;37:2372-2379. © 2018 SETAC.

Phototoxic effects of PAH and UVA exposure on molecular responses and developmental success in coral larvae

Exposure to polycyclic aromatic carbons (PAHs) poses a growing risk to coral reefs due to increasing shipping and petroleum extraction in tropical waters. Damaging effects of specific PAHs can be further enhanced by the presence of ultraviolet radiation, known as phototoxicity. We tested phototoxic effects of the PAHs anthracene and phenanthrene on larvae of the scleractinian coral Acropora tenuis in the presence and absence of UVA (320-400 nm). Activity of superoxide dismutase (SOD) enzyme was reduced by anthracene while phenanthrene and UVA exposure did not have any effect. Gene expression of MnSod remained constant across all treatments. The genes Catalase, Hsp70 and Hsp90 showed increased expression levels in larvae exposed to anthracene, but not phenanthrene. Gene expression of p53 was upregulated in the presence of UVA, but downregulated when exposed to PAHs. The influence on stress-related biochemical pathways and gene expresson in A. tenuis larvae was considerably greater for anthracene than phenanthrene, and UVA-induced phototoxicity was only evident for anthracene. The combined effects of UVA and PAH exposure on larval survival and metamorphosis paralleled the sub-lethal stress responses, clearly highlighting the interaction of UVA on anthracene toxicity and ultimately the coral's development.

The effect of sewage sludge fertilization on the concentration of PAHs in urban soils

This paper analyses sources of sixteen PAHs - polycyclic aromatic hydrocarbons in urbanized areas by using selected diagnostic ratios. Simultaneously, an attempt was made to determine how sewage sludge changes PAHs content in urbanized areas soils. In the experiment three lawns along the main roads in Bialystok with different traffic intensity, three doses of sewage sludge and two years of study were considered. There was no effect of fertilization with sewage sludge on the sum of 16 PAHs in urban soil samples, nevertheless, the sum of 16 PAHs was reduced from 2.6 in 2011 to 2.3 mg/kg in 2012. Among 16 tested PAHs compounds, benzo[a]pyrene was the most dominant compound in samples collected in both years - about 15% of all PAHs. The results suggest that application of sludge into the soil did not influence the concentration of 2-3-ring, 4-ring and 5-6-ring PAHs. For the objects fertilized with a dose 150.0 Mg/ha, of sludge the total sum of potentially carcinogenic PAHs in the urban soil lowered by approximately 68% in comparison with the control plots. PAHs contamination of the urban soil samples resulted from the influence of coal, petroleum and biomass combustion. Moreover, PAHs can enter soil via at mospheric deposition.

Photoenhanced Toxicity of Weathered Crude Oil in Sediment and Water to Larval Zebrafish

Solar radiation exposure can increase the toxicity of bioaccumulated oil compounds in a diversity of aquatic species. We investigated the photoenhanced toxicity of weathered South Louisiana crude oil in sediment and water accommodated fractions (WAF) to larval zebrafish. Larvae were first exposed for 24 h to one of six treatments: no oil (sediment or water), 7.5 g oil/kg sediment, oil-only WAF, oil WAF plus the dispersant Corexit 9500A, or dispersant alone. Larvae were then exposed to high or low levels of sunlight in control water for 3 or 3.5 h. Hydrocarbon concentrations were measured in exposure media, including alkanes, polycyclic aromatic compounds and total petroleum hydrocarbons. Significant phototoxicity was observed in larvae exposed to oiled sediment, oil-only WAF, and oil plus dispersant WAF. The results indicated that petroleum from the northern Gulf of Mexico can be phototoxic to larval fish exposed to oil in either the water column or sediment.

Solvent bar micro-extraction (SBME) based determination of PAHs in seawater samples

Measuring the impact of PAHs in seawater samples is often difficult due to the low concentrations in which they appear and the complexity of the sample matrix. Traditional methods for sample preparation such as liquid-liquid extraction and solid phase extraction require the use of excessive amounts of solvents and reagents, and sample handling. In this work, hollow fiber liquid phase micro-extraction (HFLPME), in the configuration of solvent bar micro-extraction (SBME), was proposed as an environmentally friendly and more effective tool, for the extraction of the 16 priority PAHs from seawater samples. Extraction was conducted using hexane as a solvent. Enrichment factors from 45 to 163 were obtained after 60min at a stirring rate of 500rpm in the sample. Moreover, a negative linear relationship was observed between the enrichment factor and the molecular weight of the PAHs. Under optimized conditions, the limits of detection were in the range from 0.21 to 0.82ngL^-1, the method showed a linear response up to 500μgL^-1, and the average relative standard deviation for seawater samples spiked with 5ngL^-1 was 11.6%. After calibration, the SBME was applied to extract PAHs in seawater samples from the Bay of Cadiz (SW Spain), showing an average recovery of 99%. In conclusion, the SBME is an environmentally friendly, one-step alternative for sample preparation in the determination of PAHs in seawater samples.

Evaluation of the phototoxicity of unsubstituted and alkylated polycyclic aromatic hydrocarbons to mysid shrimp (Americamysis bahia): Validation of predictive models

Crude oils are composed of an assortment of hydrocarbons, some of which are polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons are of particular interest due to their narcotic and potential phototoxic effects. Several studies have examined the phototoxicity of individual PAHs and fresh and weathered crude oils, and several models have been developed to predict PAH toxicity. Fingerprint analyses of oils have shown that PAHs in crude oils are predominantly alkylated. However, current models for estimating PAH phototoxicity assume toxic equivalence between unsubstituted (i.e., parent) and alkyl-substituted compounds. This approach may be incorrect if substantial differences in toxic potency exist between unsubstituted and substituted PAHs. The objective of the present study was to examine the narcotic and photo-enhanced toxicity of commercially available unsubstituted and alkylated PAHs to mysid shrimp (Americamysis bahia). Data were used to validate predictive models of phototoxicity based on the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap approach and to develop relative effect potencies. Results demonstrated that photo-enhanced toxicity increased with increasing methylation and that phototoxic PAH potencies vary significantly among unsubstituted compounds. Overall, predictive models based on the HOMO-LUMO gap were relatively accurate in predicting phototoxicity for unsubstituted PAHs but are limited to qualitative assessments. Environ Toxicol Chem 2017;36:2043-2049. © 2017 SETAC.

Photoenhanced Toxicity of Petroleum to Aquatic Invertebrates and Fish

Photoenhanced toxicity is a distinct mechanism of petroleum toxicity that is mediated by the interaction of solar radiation with specific polycyclic aromatic compounds in oil. Phototoxicity is observed as a twofold to greater than 1000-fold increase in chemical toxicity to aquatic organisms that also have been exposed to light sources containing sufficient quantity and quality of ultraviolet radiation (UV). When tested under natural sunlight or laboratory sources of UV, fresh, and weathered middle distillates, crudes and heavy oils can exhibit photoenhanced toxicity. These same products do not exhibit phototoxicity in standard test protocols because of low UV irradiance in laboratory lighting. Fresh, estuarine, and marine waters have been shown to have sufficient solar radiation exposure to elicit photoenhanced toxicity, and a diversity of aquatic invertebrate and fish species can exhibit photoenhanced toxicity when exposed to combinations of oil and UV. Risks of photoenhanced toxicity will be greatest to early life stages of aquatic organisms that are translucent to UV and that inhabit the photic zone of the water column and intertidal areas exposed to oil.

Toxicity of effluents from gasoline stations oil-water separators to early life stages of zebrafish Danio rerio

Used petroleum hydrocarbons and gasoline stations runoff are significant sources of polycyclic aromatic hydrocarbons (PAHs) to aquatic ecosystems. Samples of the final effluent of oil-water-separators were collected at gasoline stations in the metropolitan region of Recife, Brazil, before release to sewage or rainwater systems. Effluent soluble fractions (ESF) were prepared and bioassays were performed according to the Fish Embryo Toxicity Test. The test involved exposing zebrafish Danio rerio embryos to dilutions of the ESFs for 96 h, with daily examination of lethality and sublethal morphological effects integrated through the General Morphology Score (GMS), based on the achievement of developmental hallmarks. Frequencies of abnormalities were recorded after exposures. ESF LC50-96h (lethal concentration to 50% of exposed embryos) in the most toxic effluent achieved 8.9% (v/v), equivalent to 11 μg phenanthrene equivalents L^-1. GMS scores indicated significantly delayed embryo-larval development at ESF dilutions of 10% and 20% from effluents of all gas stations. Major abnormalities detected after the 96 h exposure included the presence of a yolk sac not fully absorbed coupled with the lack of an inflated swim bladder, lack of both pectoral fins, and the failure to develop a protruding mouth. Effective equivalent PAH concentrations that induce a 50% frequency of larvae without an inflated swim bladder (EC50) were 4.9 μg phenanthrene L^-1, 21.8 μg naphthalene L^-1, and 34.1 μg chrysene L^-1. This study shows that PAHs in ESFs from gas stations oil water separators are toxic to zebrafish, contributing to the toxicity of urban storm waters.

Co-exposure to sunlight enhances the toxicity of naturally weathered Deepwater Horizon oil to early lifestage red drum (Sciaenops ocellatus) and speckled seatrout (Cynoscion nebulosus)

The 2010 Deepwater Horizon oil spill resulted in the accidental release of millions of barrels of crude oil into the Gulf of Mexico. Photo-induced toxicity following co-exposure to ultraviolet (UV) radiation is 1 mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Red drum and speckled seatrout are both important fishery resources in the Gulf of Mexico. They spawn near-shore and produce positively buoyant embryos that hatch into larvae in approximately 24 h. The goal of the present study was to determine whether exposure to UV as natural sunlight enhances the toxicity of crude oil to early lifestage red drum and speckled seatrout. Larval fish were exposed to several dilutions of high-energy water-accommodated fractions (HEWAFs) from 2 different oils collected in the field under chain of custody during the 2010 spill and 3 gradations of natural sunlight in a factorial design. Co-exposure to natural sunlight and oil significantly reduced larval survival compared with exposure to oil alone. Although both species were sensitive at PAH concentrations reported during the Deepwater Horizon spill, speckled seatrout demonstrated a greater sensitivity to photo-induced toxicity than red drum. These data demonstrate that even advanced weathering of slicks does not ameliorate the potential for photo-induced toxicity of oil to these species. Environ Toxicol Chem 2017;36:780-785. © 2016 SETAC.

Review of the photo-induced toxicity of environmental contaminants

Solar radiation is a vital component of ecosystem function. However, sunlight can also interact with certain xenobiotic compounds in a phenomenon known as photo-induced, photo-enhanced, photo-activated, or photo-toxicity. This phenomenon broadly refers to an interaction between a chemical and sunlight resulting in increased toxicity. Because most aquatic ecosystems receive some amount of sunlight, co-exposure to xenobiotic chemicals and solar radiation is likely to occur in the environment, and photo-induced toxicity may be an important factor impacting aquatic ecosystems. However, photo-induced toxicity is not likely to be relevant in all aquatic systems or exposure scenarios due to variation in important ecological factors as well as physiological adaptations of the species that reside there. Here, we provide an updated review of the state of the science of photo-induced toxicity in aquatic ecosystems.

Chronic toxicity of selected polycyclic aromatic hydrocarbons to algae and crustaceans using passive dosing

Because of the large number of possible aromatic hydrocarbon structures, predictive toxicity models are needed to support substance hazard and risk assessments. Calibration and evaluation of such models requires toxicity data with well-defined exposures. The present study has applied a passive dosing method to generate reliable chronic effects data for 8 polycyclic aromatic hydrocarbons (PAHs) on the green algae Pseudokirchneriella subcapitata and the crustacean Ceriodaphnia dubia. The observed toxicity of these substances on algal growth rate and neonate production were then compared with available literature toxicity data for these species, as well as target lipid model and chemical activity-based model predictions. The use of passive dosing provided well-controlled exposures that yielded more consistent data sets than attained by past literature studies. Results from the present study, which were designed to exclude the complicating influence of ultraviolet light, were found to be well described by both target lipid model and chemical activity effect models. The present study also found that the lack of chronic effects for high molecular weight PAHs was consistent with the limited chemical activity that could be achieved for these compounds in the aqueous test media. Findings from this analysis highlight that variability in past literature toxicity data for PAHs may be complicated by both poorly controlled exposures and photochemical processes that can modulate both exposure and toxicity. Environ Toxicol Chem 2016;35:2948-2957. © 2016 SETAC.

Quantitative determination of ultra-trace carbazoles in sediments in the coastal environment

Carbazole and some of its derivatives may possess dioxin-like toxicity and could be persistent in the environment, but information on their distribution and environmental fate is limited. This study developed and validated an ultra-trace targeted-analysis method for the determination of carbazole, 1,2-benzocarbazole, and 13 halogenated carbazoles in sediments from the river, coast, and North Sea. An 8-g sediment sample was extracted using accelerated solvent extraction combined with in-cell cleanup and analyzed using gas chromatography-tandem mass spectrometry. The method was sensitive and reliable with method detection limits ranging from 4.54 to 52.9 pg/g, and most of the quantification biases and relative standard deviations were <20 and <15%, respectively. Carbazole and 1,2-benzocarbazole were the predominant substances in the sediments (median 565 and 369 pg/g, respectively) followed by 3,6-dichlorocarbazole (median 196 pg/g). The detection frequencies of carbazole, benzo-, 3-chloro-, and 3,6-dichlorocarbazole were >75%, while those of 3,6-dibromo-, 1-bromo-3,6-dichloro-, and 1,8-dibromo-3,6-dichlorocarbazole were approximately 50%. Brominated carbazoles occurred more frequently in marine than river-influenced sediments, which could indicate halogenation after discharge into the river. This is the first study regarding these substances in coastal environments without apparent contamination history. The ubiquity and bioaccumulative potential of these substances needs to be considered.

Contaminant-induced oxidative stress in fish: a mechanistic approach

The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described.

Immuno-PCR in cancer and non-cancer related diseases: a review

Polymerase chain reaction-amplified immunoassay (immuno-PCR, iPCR) is a method that combines the specificity of an immunological detection method and the sensitivity of a nucleic acid amplification method. In this way, immuno-PCR uses a minimum amount of sample, and allows the detection of rare diseases and those diseases in very early stage (i.e. infectious diseases, degenerative disorders, or neoplastic diseases). The present review was aimed to describe this new methodology and applications to the early detection of cancer and non-cancer related diseases, and discuss about the possibility to detect diverse biomarkers of oncology disorders, such as breast, gastric, colorectal and nasopharynx cancer, and other factors related to the growth of the neoplastic disease.

Ultraviolet Radiation Enhances the Toxicity of Deepwater Horizon Oil to Mahi-mahi (Coryphaena hippurus) Embryos

The 2010 Deepwater Horizon oil spill resulted in the accidental release of millions barrels of crude oil into the Gulf of Mexico. Photoinduced toxicity following coexposure to ultraviolet (UV) radiation is one mechanism by which polycyclic aromatic hydrocarbons (PAHs) from oil spills may exert toxicity. Mahi-mahi (Coryphaena hippurus), an important fishery resource, have positively buoyant, transparent eggs. These characteristics may result in mahi-mahi embryos being at particular risk from photoinduced toxicity. The goal of this study was to determine whether exposure to ultraviolet radiation as natural sunlight enhances the toxicity of crude oil to embryonic mahi-mahi. Mahi-mahi embryos were exposed to several dilutions of water accommodated fractions (WAF) from slick oil collected during the 2010 spill and gradations of natural sunlight in a fully factorial design. Here, we report that coexposure to natural sunlight and WAF significantly reduced percent hatch in mahi-mahi embryos. Effect concentrations of PAH in WAF were within the range of surface PAH concentrations reported in the Gulf of Mexico during the Deepwater Horizon spill. These data suggest that laboratory toxicity tests that do not include UV may underestimate the toxicity of oil spills to early lifestage fish species.

Severe Coal Tar Sealcoat Runoff Toxicity to Fish Is Prevented by Bioretention Filtration

Coal tar sealcoats applied to asphalt surfaces in North America, east of the Continental Divide, are enriched in petroleum-derived compounds, including polycyclic aromatic hydrocarbons (PAHs). The release of PAHs and other chemicals from sealcoat has the potential to contaminate nearby water bodies, reducing the resiliency of aquatic communities. Despite this, relatively little is known about the aquatic toxicology of sealcoat-derived contaminants. We assessed the impacts of stormwater runoff from sealcoated asphalt on juvenile coho salmon (Oncorhynchus kisutch) and embryo-larval zebrafish (Danio rerio). We furthermore evaluated the effectiveness of bioretention as a green stormwater method to remove PAHs and reduce lethal and sublethal toxicity in both species. We applied a coal tar sealcoat to conventional asphalt and collected runoff from simulated rainfall events up to 7 months postapplication. Whereas sealcoat runoff was more acutely lethal to salmon, a spectrum of cardiovascular abnormalities was consistently evident in early life stage zebrafish. Soil bioretention effectively reduced PAH concentrations by an order of magnitude, prevented mortality in juvenile salmon, and significantly reduced cardiotoxicity in zebrafish. Our findings show that inexpensive bioretention methods can markedly improve stormwater quality and protect fish health.

Exposure to runoff from coal-tar-sealed pavement induces genotoxicity and impairment of DNA repair capacity in the RTL-W1 fish liver cell line

Coal-tar-based (CTB) sealcoat, frequently applied to parking lots and driveways in North America, contains elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) and related compounds. The RTL-W1 fish liver cell line was used to investigate two endpoints (genotoxicity and DNA-repair-capacity impairment) associated with exposure to runoff from asphalt pavement with CTB sealcoat or with an asphalt-based sealcoat hypothesized to contain about 7% CTB sealcoat (AS-blend). Genotoxic potential was assessed by the Formamido pyrimidine glycosylase (Fpg)-modified comet assay for 1:10 and 1:100 dilutions of runoff samples collected from 5 h to 36 d following sealcoat application. DNA-repair capacity was assessed by the base excision repair comet assay for 1:10 dilution of samples collected 26 h and 36 d following application. Both assays were run with and without co-exposure to ultraviolet-A radiation (UVA). With co-exposure to UVA, genotoxic effects were significant for both dilutions of CTB runoff for three of four sample times, and for some samples of AS-blend runoff. Base excision repair was significantly impaired for CTB runoff both with and without UVA exposure, and for AS-blend runoff only in the absence of UVA. This study is the first to investigate the effects of exposure to the complex mixture of chemicals in coal tar on DNA repair capacity. The results indicate that co-exposure to runoff from CT-sealcoated pavement and UVA as much as a month after sealcoat application has the potential to cause genotoxicity and impair DNA repair capacity.

Acute toxicity of runoff from sealcoated pavement to Ceriodaphnia dubia and Pimephales promelas

Runoff from coal-tar-based (CT) sealcoated pavement is a source of polycyclic aromatic hydrocarbons (PAHs) and N-heterocycles to surface waters. We investigated acute toxicity of simulated runoff collected from 5 h to 111 days after application of CT sealcoat and from 4 h to 36 days after application of asphalt-based sealcoat containing about 7% CT sealcoat (AS/CT-blend). Ceriodaphnia dubia (cladocerans) and Pimephales promelas (fathead minnows) were exposed in the laboratory to undiluted and 1:10 diluted runoff for 48 h, then transferred to control water and exposed to 4 h of ultraviolet radiation (UVR). Mortality following exposure to undiluted runoff from unsealed asphalt pavement and UVR was ≤10% in all treatments. Test organisms exposed to undiluted CT runoff samples collected during the 3 days (C. dubia) or 36 days (P. promelas) following sealcoat application experienced 100% mortality prior to UVR exposure; with UVR exposure, mortality was 100% for runoff collected across the entire sampling period. Phototoxic-equivalent PAH concentrations and mortality demonstrated an exposure-response relation. The results indicate that runoff remains acutely toxic for weeks to months after CT sealcoat application.

Real-time immuno-PCR for ultrasensitive detection of pyrene and other homologous PAHs

Polycyclic aromatic hydrocarbons (PAHs) are significant environmental pollutant that can lead to cancer and endocrine system disrupting. Here we developed a real-time immuno-PCR (RT-IPCR) assay based on a biotinylated reporter DNA system for ultrasensitive detection of pyrene (PYR) and homologous PAHs in water. The PAHs in sample compete with PYR-OVA coated on PCR plate to bind with monoclonal antibody (McAb). The biotinylated goat anti-mouse IgG (Bio-IgG) can be captured by the McAb bound with PYR-OVA. Then streptavidin is bound with biotin on Bio-IgG. Finally biotinylated reporter DNA is captured by the streptavidin and quantified by real-time PCR using FastStart universal SYBR Green Master (ROX) kit. The linear range of the assay was from 500 fmol L(-1) to 5 nmol L(-)) with a detection limit of 450 fmol L(-1). The average recoveries of PYR and homologous PAHs from lake water, tap water and commercial mineral water were 96.8%, 101.4% and 99.6% respectively, indicating that water samples had little interfere with the assay. The results demonstrated that the developed RT-IPCR might be a potential method for ultrasensitive detection of PYR and homologous PAHs in drinking and environment water sample.