Environmentally-relevant Levels Research Articles

Mercury (II) impairs nucleotide excision repair (NER) in zebrafish (Danio rerio) embryos by targeting primarily at the stage of DNA incision

Mercuric ion (Hg2+) is the most prevalent form of inorganic Hg found in polluted aquatic environment. As inhibition of DNA damage repair has been proposed as one of the mechanisms of Hg2+-induced genotoxicity in aquatic animals and mammalian cells, this study explored the susceptibility of different stages of nucleotide excision repair (NER) in zebrafish (Danio rerio) embryos to Hg2+ using UV-damaged DNA as the repair substrate. Exposure of embryos at 1h post fertilization (hpf) to HgCl2 at 0.1–2.5μM for 9h caused a concentration-dependent inhibition of NER capacity monitored by a transcription-based DNA repair assay. The extracts of embryos exposed to 2.5μM Hg2+ almost failed to up-regulate UV-suppressed marker cDNA transcription. No inhibition of ATP production was observed in all Hg2+-exposed embryos. Hg2+ exposure imposed either weak inhibitory or stimulating effects on the gene expression of NER factors, while band shift assay showed the inhibition of photolesion binding activities to about 40% of control in embryos treated with 1–2.5μM HgCl2. The damage incision stage of NER in zebrafish embryos was found to be more sensitive to Hg2+ than photolesion binding capacity due to the complete loss of damage incision activity in the extracts of embryos exposed to 1–2.5μM Hg2+. NER-related DNA incision was induced in UV-irradiated embryos based on the production of short DNA fragments matching the sizes of excision products generated by eukaryotic NER. Pre-exposure of embryos to Hg2+ at 0.1–2.5μM all suppressed DNA incision/excision in UV-irradiated embryos, reflecting a high sensitivity of DNA damage incision/excision to Hg2+. Our results showed the potential of Hg2+ at environmental relevant levels to disturb NER in zebrafish embryos by targeting primarily at the stage of DNA incision/excision.

The increased toxicity of UV-degraded nitroguanidine and IMX-101 to zebrafish larvae: Evidence implicating oxidative stress

Insensitive munitions (IMs) improve soldier safety by decreasing sympathetic detonation during training and use in theatre. IMs are being increasingly deployed, although the environmental effects of IM constituents such as nitroguanidine (NQ) and IM mixture formulations such as IMX-101 remain largely unknown. In the present study, we investigated the acute (96h) toxicity of NQ and IMX-101 to zebrafish larvae (21d post-fertilization), both in the parent materials and after the materials had been irradiated with environmentally-relevant levels of ultraviolet (UV) light. The UV-treatment increased the toxicity of NQ by 17-fold (LC50 decreased from 1323mg/L to 77.2mg/L). Similarly, UV-treatment increased the toxicity of IMX-101 by nearly two fold (LC50 decreased from 131.3 to 67.6mg/L). To gain insight into the cause(s) of the observed UV-enhanced toxicity of the IMs, comparative molecular responses to parent and UV-treated IMs were assessed using microarray-based global transcript expression assays. Both gene set enrichment analysis (GSEA) and differential transcript expression analysis coupled with pathway and annotation cluster enrichment were conducted to provide functional interpretations of expression results and hypothetical modes of toxicity. The parent NQ exposure caused significant enrichment of functions related to immune responses and proteasome-mediated protein metabolism occurring primarily at low, sublethal exposure levels (5.5 and 45.6mg/L). Enriched functions in the IMX-101 exposure were indicative of increased xenobiotic metabolism, oxidative stress mitigation, protein degradation, and anti-inflammatory responses, each of which displayed predominantly positive concentration-response relationships. UV-treated NQ had a fundamentally different transcriptomic expression profile relative to parent NQ causing positive concentration-response relationships for genes involved in oxidative-stress mitigation pathways and inhibited expression of multiple cadherins that facilitate zebrafish neurological and retinal development. Transcriptomic profiles were similar between UV-treated versus parent IMX-101 exposures. However, more significant and diverse enrichment as well as greater magnitudes of differential expression for oxidative stress responses were observed in UV-treated IMX-101 exposures. Further, transcriptomics indicated potential for cytokine signaling suppression providing potential connections between oxidative stress and anti-inflammatory responses. Given the overall results, we hypothesize that the increased toxicity of UV-irradiated NQ and the IMX-101 mixture result from breakdown products with elevated potential to elicit oxidative stress.

Quantification of 226Ra at environmental relevant levels in natural waters by ICP-MS: Optimization, validation and limitations of an extraction and preconcentration approach

Radium (Ra) at environmental relevant levels in natural waters was determined by ICP-MS after an off-line pre-concentration procedure. The latter consisted of Ra selective elution from potential interfering elements (i.e. other alkaline earth cations: Ba2+, Sr2+, Ca2+, Mg2+) on a series of two different ion exchange resins (AG50W-X8 and Sr-resin). The overall analytical method was optimized according to the instrumental performance, the volume of water sample loaded on resins, and the sample salinity. Longer acquisition time (up to 150 s) was required to ensure stable measurement of Ra by ICP-MS at ultra trace level (1.0pgL−1). For a synthetic groundwater spiked with Ra at 10.0pgL−1, the analytical procedure demonstrated efficient separation of the analyte from its potential interfering elements and a complete recovery, independent of the sample volume tested from 10 up to 100mL. For synthetic seawater spiked at a level of 10.0pgL−1 of Ra, the total load of salts on the two resins should not exceed 0.35g in order to ensure a complete separation and recovery of Ra. The method was validated on natural waters (i.e. groundwater, freshwater and seawater samples) spiked with Ra at different levels (0.0, 0.5, 1.0 and 5.0pgL−1). Absolute Ra detection limits were determined at 0.020pgL−1 (0.73mBqL−1) and 0.12pgL−1 (4.4mBqL−1) respectively for 60.0mL of freshwater sample and for 10.0mL of seawater.

Disruption of thyroxine and sex hormones by 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (DBE-DBCH) in American kestrels (Falco sparverius) and associations with reproductive and behavioral changes

1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (DBE-DBCH - formerly TBECH) is an emerging brominated flame retardant (BFR) pollutant with androgen potentiating ability and other endocrine disrupting effects in birds and fish. The objectives of this study were to determine the effects of exposure to environmentally-relevant levels of DBE-DBCH on circulating levels of thyroid and sex steroid hormones in American kestrels, and if hormonal concentrations were related to previously reported changes in reproductive success and courtship behaviors. Sixteen kestrel pairs were exposed to 0.239ng β-DBE-DBCH/g kestrel/day by diet, based on concentrations in wild bird eggs, from 4 weeks before pairing until the chicks hatched (mean 82 d), and were compared with vehicle-only-exposed control pairs (n=15). As previously reported, DBE-DBCH concentrations were not detected in tissue or eggs of these birds, nor were any potential metabolites, despite the low method limits of detection (≤0.4ng/g wet weight), suggesting it may be rapidly metabolized and/or eliminated by the kestrels. Nevertheless, exposed kestrels demonstrated changes in reproduction and behavior, indicating an effect from exposure. During early breeding, males were sampled at multiple time points at pairing and during courtship and incubation; females were blood sampled at pairing only; both sexes were sampled at the end of the season. All comparisons are made to control males or control females, and the relative differences in hormone concentrations between treatment and control birds, calculated separately for each sex, are presented for each time point. Males exposed to β-DBE-DBCH demonstrated significantly (p=0.05) lower concentrations of total thyroxine (TT4) overall, that were 11–28% lower than those of control males at the individual sampling points, yet significantly higher (p=0.03) concentrations of free thyroxine (FT4), that were 5–13% higher than those of control males at the individual sampling points; females had similar concentrations of TT4 and FT4 at the time of pairing, and T4 was similar in both sexes at the end of the breeding season. Testosterone (T) concentrations in the treatment males were significantly higher during early (85%) and mid-courtship (30%) (time*treatment p=0.001), whereas females demonstrated a reduction in T at the time of pairing (17%, p=0.05). In the treatment females, concentrations of 17β-estradiol (E2) showed a non-significant decrease (20%) and were positively correlated with T concentrations (p=0.03); E2 concentrations were below quantification limits in males. For males, some variation in T was also significantly associated with their sexual behavior (p<0.001) and FT4 concentrations (p=0.01). For females, there was no relationship between hormones measured at pairing and subsequent sexual behaviors or reproductive measures. This study demonstrates that exposure to β-DBE-DBCH at levels that are likely below those experienced by wild birds, affects the thyroid and sex steroid axes in birds and thus may be a contaminant of concern for wildlife warranting further research.

Effects of environmentally-relevant antibiotic mixtures on marine microalgal growth.

As of 2008, approximately 48% of Americans use prescription drugs within any given 30-day period. Many pharmaceutical compounds are not fully metabolized by the human body, nor fully removed by wastewater treatment systems, before release into the environment. As a result, a vast array of pharmaceuticals has been detected in marine and freshwater organisms, sediments, and waters, with unintended effects on non-target organisms, and limited studies of environmental effects. The antibiotics sulfamethoxazole (SMX), and trimethoprim (TRI), often prescribed together to treat bacterial infections, have been detected worldwide in marine and estuarine environments at concentrations up to 765-870ng/L each. Little research has examined sub-lethal effects of antibiotic mixtures at environmentally-relevant concentrations on marine organisms. We examined the effects of mixtures of these two antibiotics on three marine microalgal species with wide geographic ranges: Isochrysis galbana, Chaetoceros neogracile, and Nannochloropsis oculata. In separate simulations using a temperature/light-controlled set-up, we measured the growth response for each species to environmentally-relevant levels of SMX and TRI. N. oculata growth was significantly reduced by mixture treatments of both drugs (p<0.05), by TRI (p<0.001), and by SMX (p<0.001), whereas only aggregated SMX levels significantly reduced growth for the other two species (p<0.005). The exposure time at which growth rates were affected varied across species, with significant reduction in growth focused in the latter half of the experimental period for C. neogracile and N. oculata (Days 15 and 6 respectively), and midway through the experimental period for I. galbana (by Day 3). This study finds that important marine primary producers respond to the presence of SMX and TRI in the water, offering an understanding of environmental consequences of anthropogenic pharmaceuticals contaminants, and specifically the suite of antibiotics, that are released into marine ecosystems at an ever-growing rate, and highlighting potential cascading effects through trophic levels.

Fetal Exposure to Low Levels of the Plasticizer DEHP Predisposes the Adult Male Adrenal Gland to Endocrine Disruption.

In utero exposure to endocrine disrupting chemicals (EDCs) may affect adult health. Di-(2-ethylhexyl) phthalate (DEHP) is an EDC widely used in the production of polyvinyl chloride products and an ubiquitous environmental contaminant. We used a rat model system to show that fetal exposure to DEHP decreased levels of major steroid hormones in adulthood and that environmentally-relevant levels of DEHP affected both gene expression and epigenomic loci that were affected by exposure to high levels. In the adrenal gland, we reported that the peroxisome proliferator-activated receptor (PPAR) and cholesterol biosynthesis pathways were sensitive targets of DEHP. We hypothesized that low levels of DEHP exposure insult the endocrine system (a "first hit") and increase its susceptibility to later exposure ("second hit") and subsequent disease. Here, we demonstrate that a second hit in the adult offspring exposed in utero to low levels of DEHP affected serum aldosterone levels. To unveil the first hit influence of early DEHP exposure, we treated in utero DEHP-exposed adult offspring with stressors that targeted the PPAR or cholesterol biosynthesis pathways. Treatment with the PPAR-gamma antagonist T0070907 reduced serum aldosterone compared to animals not exposed to DEHP in utero. Analysis of gene expression in animals that were subjected to both early and late exposure revealed deregulation of genes for the potassium channel Kcnk5 and the retinoid-X receptors (RXR) Rxra and Rxrb, indicating that these entities are linked to endocrine disruption. We propose that early exposure to environmental doses of DEHP predisposes the animal for disease later in life.

Degradation of dibutyl phthalate (DBP) by UV-254nm/H2O2 photochemical oxidation: kinetics and influence of various process parameters.

Degradation of dibuytl phthalate (DBP), a plasticizer and also a widely distributed endocrine disruptor, by UV-254nm/H2O2 advanced oxidation process (AOP) was investigated in this study. A significant DBP removal of 77.1% at an initial concentration of 1.0μM was achieved at UV fluence of 160mJ/cm2, initial H2O2 dosage of 1.0mM, and pH of 7.6±0.1. The DBP degradation exhibited a pseudo-first-order reaction kinetic pattern, with the rate constants linearly increasing with increasing H2O2 dosage while decreasing with increasing initial DBP concentration and pH value in a specific range. DBP destruction was significantly inhibited in the presence of alkalinity and natural organic matter (NOM), two known factors that should be taken a serious consideration of in the research and design of UV/H2O2-based AOPs. Presence of common inorganic anions (i.e., Cl-, SO42-, and NO3-) and metal cations (i.e., Fe3+ and Zn2+) had a slight impact on the degradation of DBP, although Cu2+ could improve the degradation efficiency even at a concentration as low as 0.01mg/L, suggesting a strong potential of applying UV/H2O2 for the removal of DBP with an environmental relevant level of copper.

Infrared spectroscopy detects changes in an amphibian cell line induced by fungicides: Comparison of single and mixture effects

Amphibians are regarded as sensitive sentinels of environmental pollution due to their permeable skin and complex life cycle, which usually involves reproduction and development in the aquatic environment. Fungicides are widely applied agrochemicals and have been associated with developmental defects in amphibians; thus, it is important to determine chronic effects of environmentally-relevant concentrations of such contaminants in target cells. Infrared (IR) spectroscopy has been employed to signature the biological effects of environmental contaminants through extracting key features in IR spectra with chemometric methods. Herein, the Xenopus laevis (A6) cell line was exposed to low concentrations of carbendazim (a benzimidazole fungicide) or flusilazole (a triazole fungicide) either singly or as a binary mixture. Cells were then examined using attenuated total reflection Fourier-transform IR (ATR-FTIR) spectroscopy coupled with multivariate analysis. Results indicate significant changes in the IR spectra of cells induced by both agents at all concentrations following single exposures, primarily in regions associated with protein and phospholipids. Distinct differences were apparent in the IR spectra of cells exposed to carbendazim and those exposed to flusilazole, suggesting different mechanisms of action. Exposure to binary mixtures of carbendazim and flusilazole also induced significant spectral alterations, again in regions associated with phospholipids and proteins, but also in regions associated with DNA and carbohydrates. Overall these findings demonstrate that IR spectroscopy is a sensitive technique for examining the effects of environmentally-relevant levels of fungicides at the cellular level. The combination of IR spectroscopy with the A6 cell line could serve as a useful model to identify agents that might threaten amphibian health in a rapid and high throughput manner.

Progestins alter photo-transduction cascade and circadian rhythm network in eyes of zebrafish (Danio rerio)

Environmental progestins are implicated in endocrine disruption in vertebrates. Additional targets that may be affected in organisms are poorly known. Here we report that progesterone (P4) and drospirenone (DRS) interfere with the photo-transduction cascade and circadian rhythm network in the eyes of zebrafish. Breeding pairs of adult zebrafish were exposed to P4 and DRS for 21 days with different measured concentrations of 7–742 ng/L and 99-13´650 ng/L, respectively. Of totally 10 key photo-transduction cascade genes analyzed, transcriptional levels of most were significantly up-regulated, or normal down-regulation was attenuated. Similarly, for some circadian rhythm genes, dose-dependent transcriptional alterations were also observed in the totally 33 genes analyzed. Significant alterations occurred even at environmental relevant levels of 7 ng/L P4. Different patterns were observed for these transcriptional alterations, of which, the nfil3 family displayed most significant changes. Furthermore, we demonstrate the importance of sampling time for the determination and interpretation of gene expression data, and put forward recommendations for sampling strategies to avoid false interpretations. Our results suggest that photo-transduction signals and circadian rhythm are potential targets for progestins. Further studies are required to assess alterations on the protein level, on physiology and behavior, as well as on implications in mammals.

A method for the determination of fullerenes in soil and sediment matrices using ultra-high performance liquid chromatography coupled with heated electrospray quadrupole time of flight mass spectrometry

The increasing production of fullerenes likely means a release of these chemicals in the environment. Since soils and sediments are expected to act as a sink, analytical tools are needed to assess the presence of fullerenes in these matrices. In the present work, a method was developed for the determination of fullerenes at environmental relevant levels employing Ultra High Performance Liquid Chromatograph coupled with High Resolution Mass Spectrometry (UHPLC-HRMS). Chromatographic separation was achieved with a core–shell biphenyl stationary phase that provided fast analysis with complete baseline separation. Ion Booster Electro Spray Ionization (IB-ESI) resulted in higher ionization efficiency and was much less susceptible to adduct formation in comparison with standard ESI, whereas Quadrupole Time of Flight (QTOF) MS granted high resolution mass spectra used for accurate identification. The Instrumental method limits of detection (ILoD) and quantification (ILoQ) were 6 and 20fg, respectively, for C60 and 12 and 39fg, respectively, for C70. Matrix effects related to co-extractants were systematically investigated in soil and sediments extracts through standard addition method (SAM) and monitoring the signal response during the chromatographic run of these samples. Consequently, minor chromatographic modifications were necessary for the analysis of matrices with high organic carbon content. The method limit of detection (MLoD)ranged from 84pg/kg to 335pg/kg, whereas limit of quantification (MLoQ) ranged from 279pg/kg to 1.1ng/kg. Furthermore, the method was successfully applied for the analysis of functionalized fullerenes (i.e. methanofullerenes). To the best of our knowledge, this is the first analytical method for the analysis of fullerenes in soils and sediments that employ core–shell biphenyl stationary phase as well as IB-ESI-QTOF MS hyphenated with UHPLC.

Chemical Exposure and Effects in Freshwater Aquatic Species

To protect aquatic ecosystems from stresses induced by toxic chemicals, risk models must be developed, calibrated and verified for feral populations. Although risk models require good estimates of chemical exposure (dose) and quantitative measures of effects (response), few models, if any, have been appropriately calibrated for linking dose and response in situ. It is this lack of knowledge that limits the development of strong cause-effect relationships for aquatic species. Exposure models, using quantitative biomonitoring techniques, have been developed independently from bioassay and/or biomarker systems that are used to quantify stress. The present research integrated these two approaches by comprehensively calibrating the brown bullhead (Ameiurus nebulosus) as an appropriate bioindicator of toxicological stress in aquatic ecosystems. This was achieved by integrating quantitative biomonitoring techniques with a novel, sensitive assay for genotoxicity of polynuclear aromatic hydrocarbons (PAHs). At four sites along the river, chemical exposures and the incidence of dermal papillomas and neoplastic lesions in liver tissue were quantified, along with the measurement of PAH metabolites in bile, quantification of DNA damage in erythrocytes using the alkaline single cell gel electrophoresis (Comet assay), and the quantification of changes in apoptotic processes in dermal and liver tissues of exposed fish. Field studies on metabolite formation and apoptosis were compared to laboratory investigations in order to quantify the link between PAH metabolites and genotoxicity. Bullheads were exposed to Detroit River bottom sediment and environmentally-relevant levels of a major genotoxic PAH, benzo[a]pyrene (B[a]P), and dose-response models of metabolite formation were developed in order to determine the mass of PAH chemicals that are converted to DNA active metabolites. Genotoxicity was assessed in these laboratory populations using the comet assay on erythrocytes and liver cells. We assessed the link between DNA damage and the down-regulation of apoptosis, which is characterized as one of the key initial steps of tumorogenesis. This title belongs to WERF Research Report Series ISBN: 9781843397540 (Print) ISBN: 9781780403922 (eBook)

Effects of incorporating differently-treated rice straw on phytoavailability of methylmercury in soil.

Differently-treated crops straw is being widely used to fertilize soil, while the potential impacts of straw amendment on the biogeochemistry and phytoavailability of mercury in contaminated soils are largely unknown. In the present study, differently-treated rice straw (dry straw, composted straw, straw biochar, and straw ash) was incorporated into mercury-contaminated soil at an environment relevant level (1/100, w/w), and mercury speciation, methylmercury (MeHg) phytoavailability (using ammonium thiosulfate extraction method, validated elsewhere) and bioaccumulation (in Indian mustard Brassica junceas) were quantified. Our results indicated that incorporating straw biochar or composted straw into soil would decrease phytoavailable MeHg levels, possibly due to the strong binding of MeHg with particulate organic matter in amended straw ('MeHg immobilization effect'). Consequently, MeHg accumulation in aboveground tissue of Indian mustard harvested from straw biochar-amended soil decreased by 20% compared to the control. Differently, incorporation of dry straw resulted in elevated MeHg levels in soil ('Mercury methylation effect'). Decomposition of amended dry straw in soil would evidently increase DOC levels (averagely 40%-195% higher than the control), which may subsequently mobilize MeHg in the soil ('MeHg mobilization effect'). Accordingly, incorporation of dry straw led to increased phytoavailable MeHg levels in the soil and doubled MeHg accumulation in Indian mustard. Our results provided the first evidence that incorporating differently-treated rice straw into soil could have diverse effects on mercury biogeochemistry and phytoavailability, which should be taken into account in risk assessment or soil remediation.

Incomplete lung recovery following sub-acute inhalation of combustion-derived ultrafine particles in mice.

BackgroundParticulate matter (PM) is one of the six criteria pollutant classes for which National Ambient Air Quality Standards have been set by the United States Environmental Protection Agency. Exposures to PM have been correlated with increased cardio-pulmonary morbidity and mortality. Butadiene soot (BDS), generated from the incomplete combustion of 1,3-butadiene (BD), is both a model PM mixture and a real-life example of a petrochemical product of incomplete combustion. There are numerous events, including wildfires, accidents at refineries and tank car explosions that result in sub-acute exposure to high levels of airborne particles, with the people exposed facing serious health problems. These real-life events highlight the need to investigate the health effects induced by short-term exposure to elevated levels of PM, as well as to assess whether, and if so, how well these adverse effects are resolved over time. In the present study, we investigated the extent of recovery of mouse lungs 10 days after inhalation exposures to environmentally-relevant levels of BDS aerosols had ended.MethodsFemale BALB/c mice exposed to either HEPA-filtered air or to BDS (5 mg/m3 in HEPA filtered air, 4 h/day, 21 consecutive days) were sacrificed immediately, or 10 days after the final BDS exposure. Bronchoalveolar lavage fluid (BALF) was collected for cytology and cytokine analysis. Lung proteins and RNA were extracted for protein and gene expression analysis. Lung histopathology evaluation also was performed.ResultsSub-acute exposures of mice to hydrocarbon-rich ultrafine particles induced: (1) BALF neutrophil elevation; (2) lung mucosal inflammation, and (3) increased BALF IL-1β concentration; with all three outcomes returning to baseline levels 10 days post-exposure. In contrast, (4) lung connective tissue inflammation persisted 10 days post-exposure; (5) we detected time-dependent up-regulation of biotransformation and oxidative stress genes, with incomplete return to baseline levels; and (6) we observed persistent particle alveolar load following 10 days of recovery.ConclusionThese data show that 10 days after a 21-day exposure to 5 mg/m3 of BDS has ended, incomplete lung recovery promotes a pro-biotransformation, pro-oxidant, and pro-inflammatory milieu, which may be a starting point for potential long-term cardio-pulmonary effects.

Effect of butyl paraben on the development and microbial composition of periphyton.

Parabens are extensively used as preservatives and bactericides in personal care and other consumer products, and are commonly found in wastewater and surface water as contaminants. However, few data are currently available on the ecotoxicity of parabens. Periphyton biofilm, a widely distributed microbial aggregate of ecological importance in aquatic environment, is frequently used for water quality monitoring, ecological restoration, and toxicity assessment. In this work, the effects of butyl paraben on the development and microbial composition of periphyton biofilm was studied in a laboratory experiment for 32 days using flow through channels. No effect was observed at the environmental relevant concentration level (0.5 μg L(-1)) during the experiment. At the highest tested concentration level (5000 μg L(-1)), following effects were noted: (1) inhibition on algae growth at the end of the experiment as indicated by the chlorophyll a and total biovolume; (2) inhibition of photosynthetic efficiency on day 24 as suggested by the maximal Photosystem II quantum yield (Fv/Fm); (3) decrease of the algal diversity on day 24 and 32 as reflected by the Pielou and Shannon-Weiner indices. Bacteria were less sensitive than algae in the periphyton biofilm, which showed no difference at all tested concentration levels as illustrated by the Biolog EcoPlates™ analysis. Therefore, we conclude that environmental residues of butyl paraben have a very low risk to periphyton in aquatic ecosystems.

Exposure to environmentally-relevant levels of ozone negatively influence pollen and fruit development

A combination of in vitro and in vivo studies on tomato (Lycopersicon esculentum Mill. cv. Triton) revealed that environmentally-relevant levels of ozone (O3) pollution adversely affected pollen germination, germ tube growth and pollen-stigma interactions – pollen originating from plants raised in charcoal-Purafil® filtered air (CFA) exhibited reduced germ tube development on the stigma of plants exposed to environmentally-relevant levels of O3. The O3-induced decline in in vivo pollen viability was reflected in increased numbers of non-fertilized and fertilized non-viable ovules in immature fruit. Negative effects of O3 on fertilization occurred regardless of the timing of exposure, with reductions in ovule viability evident in O3 × CFA and CFA × O3 crossed plants. This suggests O3-induced reductions in fertilization were associated with reduced pollen viability and/or ovule development. Fruit born on trusses independently exposed to 100 nmol mol−1 O3 (10 h d−1) from flowering exhibited a decline in seed number and this was reflected in a marked decline in the weight and size of individual fruit – a clear demonstration of the direct consequence of the effects of the pollutant on reproductive processes. Ozone exposure also resulted in shifts in the starch and ascorbic acid (Vitamin C) content of fruit that were consistent with accelerated ripening. The findings of this study draw attention to the need for greater consideration of, and possibly the adoption of weightings for the direct impacts of O3, and potentially other gaseous pollutants, on reproductive biology during ‘risk assessment’ exercises.

Potential role of engineered nanoparticles as contaminant carriers in aquatic ecosystems: Estimating sorption processes of the cyanobacterial toxin microcystin-LR by TiO2 nanoparticles

Abstract In the present study, the adsorption of a cyanobacterial toxin, microcystin-LR (MC-LR), onto titanium dioxide nanoparticles (TiO 2 -NPs) was investigated in aqueous solution. TiO 2 -NPs with different crystalline phases (anatase, rutile, anatase-rutile mixture) and MC-LR in an environmental relevant concentration for German water bodies were used to make results more applicable to environmental conditions. To investigate the adsorption mechanism as well as to determine the rate-limiting step of adsorption, analysis of the adsorption kinetic was performed and common kinetic models were applied to the experimental data. Additionally, the influence of nano-TiO 2 dosage (0.01–10 mg/L) and particle size on adsorption capacity was examined, the latter by comparing the adsorption data of TiO 2 -NPs to a bulk sized counterpart. The analysis of the adsorption kinetic indicates a complex adsorption mechanism and the involvement of pseudo-second-order chemisorption in the adsorption process. While only anatase TiO 2 showed a variation of MC-LR adsorption at different adsorbent concentrations, the particle size of the adsorbents appears to be the most influencing factor on toxin adsorption. All TiO 2 -NPs exhibited higher adsorption capacities compared to the bulk TiO 2 counterpart, which was statistically significant for the environmental relevant concentration levels of TiO 2 -NPs. The obtained results emphasise the potential of TiO 2 -NPs to act as carriers for environmental contaminants such as the cyanobacterial toxin MC-LR, and thus to influence its fate in aquatic ecoystems.

Relative developmental toxicities of pentachloroanisole and pentachlorophenol in a zebrafish model (Danio rerio)

Pentachloroanisole (PCA) and pentachlorophenol (PCP) are chlorinated aromatic compounds that have been found in the environment and in human populations. The objective of this study is to characterize the effects of PCA in comparison to those of PCP on development at environmental relevant levels using a fish model. Zebrafish embryos were exposed to 0.1, 1, 10, 100, 500, 1000μg/L PCA and PCP respectively for 96h. Malformation observation, LC50 testing for survival rate at 96 hours post fertilization (hpf) and EC50 testing for hatching rate at 72 hpf indicated that the developmental toxicity of PCP was about 15 times higher than that of PCA. PCP exposure at 10μg/L resulted in elevated 3, 3′, 5-triiodothyronine (T3) levels and decreased thyroxine (T4) levels, whereas PCA had no effects on T3 or T4 levels. PCP and PCA exposure at 1 and 10μg/L showed possible hyperthyroid effects similar to that of T3, due to increased relative mRNA expression of synapsin I (SYN), iodothyronine deiodinase type III (Dio3), thyroid hormone receptor alpha a (THRαa) and thyroid hormone receptor beta (THRβ), and decreased expression of iodothyronine deiodinase type II (Dio2). The results indicate that both PCA and PCP exposure can cause morphological deformities, possibly affect the timing and coordination of development in the central nervous system, and alter thyroid hormone levels by disrupting thyroid hormone regulating pathways. However, the developmental toxicity of PCA is at least ten times lower than that of PCP. Our results on the relative developmental toxicities of PCA and PCP and the possible underlying mechanisms will be useful to support interpretation of envrionmental concentrations and body burden levels observed in human populations.

Prenatal exposure to manganese at environment relevant level and neonatal neurobehavioral development

BackgroundEffects of prenatal Manganese (Mn) exposure at an environmental relevant level on neonatal neurodevelopment remains unclear. ObjectivesIn the multi-center study, we assessed the impact of low level prenatal Mn exposure on neonatal behavioral neurological assessments (NBNA), and explore a threshold umbilical cord blood Mn on neonatal neurological development. MethodsWe investigated 933 mother-newborn pairs in Shanghai, China, from 2008 through 2009. Umbilical cord serum concentrations of Mn were measured and NBNA tests were conducted. The NBNA contains five clusters: behavior, active tone, passive tone, primary reflexes and general assessment with a maximal total score of 40. The score<37 is defined as low. ResultsThe median serum Mn concentration was 4.0μg/L. Of the 933 infants, 44 (4.7%) had low NBNA. After adjusting for potential confounders, a high level of Mn (≥75th percentile ) was associated with a lower NBNA score (adjusted ß=−1.1, 95% CI: −1.4–0.7, p<0.01) and a higher risk of low NBNA (adjusted OR=9.4, 95% CI: 3.4–25.7, p<0.01). A nonlinear relationship was observed between cord serum Mn and NBNA after adjusting for potential confounders. NBNA score decreased with increasing Mn levels after 5.0μg/L(LgMn≥0.7). The cord serum Mn≥5.0μg/L had adverse effects on behavior, active tone and general reactions of clusters (p<0.001). ConclusionsHigh prenatal Mn exposure even at an environmental relevant level, is associated with poor fetal neurobehavioral development in a nonlinear pattern. A threshold cord serum Mn of 5.0μg/L existed for lower neonatal behavioral neurological assessments.

Effects of Arsenic and Cadmium on the Post Larvae of Giant Freshwater Prawn (Macrobrachium rosenbergii) a Preliminary Study

Arsenic (As) and Cadmium (Cd) are two of the heavy metals that gained public and nationalattention of the Sri Lankan community. Globally, As and Cd are reported as two of the mosttoxic heavy metals that cause physiological and biochemical alterations and mortality inexposed organisms. Cadmium levels in the range of 0.001 to 0.138 mg l-1 have been reportedin both ground and surface water sources of Sri Lanka. Few studies in the country havedocumented levels of arsenic in natural water bodies. Furthermore, studies assessing thepotential toxicity of these two metals to species that are of importance to Sri Lanka, arescarce. The aim of this preliminary study was to investigate the effects of environmentallyrelevant levels of As and Cd on the commercially exploited fresh water prawnMacrobrachium rosenbergii, using its post larvae, which are initially released into reservoirsin Sri Lanka. Post larvae were collected from a culture facility in Pambala, Chilaw and weremaintained in glass beakers. They were acclimatized before use for 96 hr acute toxicity trials,where they were exposed to a series of concentrations of either As (from 0.001 to 0.08 mg l-1)and Cd (from 0.001 to 0.05 mg l-1). Constant experimental conditions were maintained inboth the control and treatment, each conducted in triplicate.The results show that the heavy metals at the tested concentrations induced significantlyhigher levels of mortality (p&lt;0.05). For instance, the lowest test level of As (0.001 mg l-1)induced a twofold higher level of mortality (50%) than the control (20 %), whilst that withthe lowest level of Cd was also similarly high (46.7 %). A strong and positive dose dependenttrend (R2 = 0.87; p&lt;0.05) was, however, evident only for Cd. Comparing the toxicity of theheavy metals in terms of inducing mortality, Cd appears to be potentially more toxic than As.A level of 0.05 mg l-1 of Cd induced 99 % mortality in the post larvae, whilst a higher level ofAs (0.08 mg l-1) induced only around 56 % mortality. It is interesting that both heavy metalsdid not cause marked alterations in growth with no significant differences being evidentbetween the body sizes of the control and treated larvae after exposure. It should however benoted that there was a greater deviation in body sizes in treated larvae than in those of thecontrol, indicating that there may be differential sensitivity among the individual larvae. Theresults of this study are important since heavy metal pollution may threaten the incomegenerating capacity of Sri Lanka’s inland reservoir fishery.

Environmental exposure to arsenic may reduce human semen quality: associations derived from a Chinese cross-sectional study

BackgroundRecent observations in in vitro and in vivo models suggest that arsenic (As) is an endocrine disruptor at environmentally-relevant levels. When exposed to As, male rats and mice show steroidogenic dysfunction that can lead to infertility. However, the possible effects of As on human male semen quality remain obscure.MethodsWe monitored the profile of As species in the urine of a reproductive-age human cohort and assessed its association with semen quality. Men (n = 96) were recruited in an infertility clinic from July 2009 to August 2010 in the Affiliated Hospital of Chongqing Institute for Population and Family Planning. Five urinary As species were analyzed by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Clinical information on the semen volume, sperm concentration and motility was employed to catalogue and evaluate semen quality according to WHO guidelines. As species concentrations in addition to other continuous variables were dichotomized by the medians and modelled as categorical variables in order to explore using the binary logistic regression possible associations between As exposure and semen quality.ResultsUrinary concentrations (geometric mean ± SD, μg g-1 creatinine) of different As species were 7.49 (±24.8) for AsB, 20.9 (±13.7) for DMA, 2.77 (±3.33) for MMA, and 4.03 (±3.67) for Asi (AsiIII and AsiV). DMA concentrations above the median were significantly associated with below-reference sperm concentrations (P =0.02) after adjusting for age, body mass index (BMI), abstinence, smoking and drinking habits. In addition, smoking was positively associated with MMA.ConclusionReduced parameters in human semen quality are positively associated with As exposure in a reproductive-age Chinese cohort.