90-days Of Exposure Research Articles

Effects of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS) on Soil Microbial Community.

The extensive application of perfluoroalkyl and polyfluoroalkyl substances (PFASs) causes their frequent detection in various environments. In this work, two typical PFASs, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are selected to investigate their effects on soil microorganisms. Microbial community structure and microbe-microbe relationships were investigated by high-throughput sequencing and co-occurrence network analysis. Under 90days of exposure, the alpha-diversity of soil microbial communities was increased with the PFOS treatment, followed by the PFOA treatment. The exposure of PFASs substantially changed the compositions of soil microbial communities, leading to the enrichment of more PFASs-tolerant bacteria, such as Proteobacteria, Burkholderiales, and Rhodocyclales. Comparative co-occurrence networks were constructed to investigate the microbe-microbe interactions under different PFASs treatments. The majority of nodes in the PFOA and PFOS networks were associated with the genus Azospirillum and Hydrogenophaga, respectively. The LEfSe analysis further identified a set of biomarkers in the soil microbial communities, such as Azospirillum, Methyloversatilis, Hydrogenophaga, Pseudoxanthomonas, and Fusibacter. The relative abundances of these biomarkers were also changed by different PFASs treatments. Functional gene prediction suggested that the microbial metabolism processes, such as nucleotide transport and metabolism, cell motility, carbohydrate transport and metabolism, energy production and conversion, and secondary metabolites biosynthesis transport and catabolism, might be inhibited under PFAS exposure, which may further affect soil ecological services.

Acoustic sound-induced stress response of Nile tilapia (Oreochromis niloticus) to long-term underwater sound transmissions of urban and shipping noises.

Human-made impacts on the acoustic environment from marine industries is becoming a more significant issue with increasing public concern of environmental consequences. Even though there are several reports with scientific evidences on harmful influences of anthropogenic underwater sounds on the aquatic ecosystem, most of the studies so far dealt with trigger effects of short term noise impacts on aquatic animals. In the present study, however, long-term experimentation was conducted with Nile tilapia (Oreochromis niloticus) in order to figure out how fish may respond to long-term exposure of underwater sounds and if the level of response may change (increase or decline) over time. A startle reflex as a sign of stress was seen immediately at the start of the playbacks of ship noise or urban sounds in this study. Peaks of elevated respiratory movements of ventilation (opercula beats and pectoral wing rates) retained high over the following 30days of sound initiation and underwent a declining trend over the following 90days of exposure. At the end of the 120-day study period, the lowered response of fish after long-term sound exposure is likely due to the increased tolerance of fish to human-generated underwater sounds of urban and shipping noises. Different than short-term noise impacts, information on long-term exposure of anthropogenic underwater sounds is important for environmental management and setting new regulations for the sustainable use of water resources in the world.

Long-term exposures to ethion and endotoxin cause lung inflammation and induce genotoxicity in mice.

Ethion, an organophosphorus pesticide, is used worldwide and has potential for toxicity and inflammation. There are very limited data on the pulmonary and genotoxic effects of ethion especially when the exposure is combined with lipopolysaccharide. Therefore, we used a mouse model to test the hypothesis that prolonged exposure to ethion alone or in conjunction with lipopolysaccharide (LPS) will cause lung inflammation and genotoxicity in a mouse model. Swiss albino (n = 30) were divided into a control (n = 10) and two treatment groups (n = 10; each group). The treatment groups were orally administered ethion (4 or 2mg/kg/animal/day; n = 10 each) dissolved in corn oil for 90days. After 90days of exposure, five animals from each of the groups were challenged with 80μg Escherichia coli lipopolysaccharide (LPS) intranasally and the remaining five animals with normal saline solution via the same route. Ethion at both dosages induced lung inflammation as indicated by increased (p < 0.05) perivascular and peribronchial accumulation of inflammatory cells along with thickening of the alveolar septal wall. Ethion at 4mg/kg altered (p < 0.05) the mRNA and protein expression of TLR-9 and IL-1β in the lungs and induced genotoxicity in blood cells as determined by single cell gel electrophoresis (Comet assay). Further, both dosages of ethion in combination with E. coli LPS caused genotoxicity and increased (p < 0.05) pulmonary expression of TLR-4, TLR-9 and IL-1β. The data taken together suggest ethion induces lung inflammation and interaction between ethion and LPS increases genotoxicity in blood cells.

Properties of hybrid cementitious composite with metakaolin, nanosilica and epoxy

The compressive strength and durability potentials of hybrid cementitious composites (HCC) that contain metakaolin (MK), produced in the laboratory using raw kaolin, nanosilica and epoxy resin was the main focus of this research study. The HCC specimens contain 10% metakaolin (MK), 1% colloidal nanosilica (CNS) and 1% epoxy resins and the specimens were examined for early ages of 7, 28, and 90days of exposure in both water and seawater. The durability properties investigated in this research study comprise of water absorption, intrinsic air permeability, chloride penetration and porosity. All tests were conducted to assess the influence of MK, CNS and epoxy on the compressive strength and the durability properties of the HCC specimens. The result showed that HCC specimens with 10% MK, 1% CNS was durable relative to all the properties. Nevertheless, the addition of both natural fibers (coconut and oil palm fruit bunch fibers) and synthetic fiber (bar chip fiber) has a slight negative impact on the durability properties of HCC specimens. Conclusively, the results showed that the menace of water, liquid and gas transportation by water absorption, capillary suction, porosity, chloride penetration, and intrinsic air permeability of HCC were lesser than that of control specimen.

Effects of Deltamethrin on striatum and hippocampus mitochondrial integrity and the protective role of Quercetin in rats.

The present work is to evaluate the neurotoxicity induced by pyrethroid insecticide "Deltamethrin" at 0.32mg/kg/day in two main regions of the Wistar rat brain (hippocampus and striatum) and the protective effects of Quercetin at 10mg/kg/day on this toxicity after 90days of exposure. The assay of brain parameters showed that Deltamethrin caused a significant increase of mitochondrial metabolite level (proteins, lipids, and carbohydrates) and enzyme activity (glutathione S-transferase and superoxide dismutase); a decreased amount of mitochondrial glutathione level and catalase and glutathione peroxidase activities; and an increase of malondialdehyde (MDA) acid levels of the two regions. Furthermore, mitochondrial functional testing in the brains of treated rats exhibited a significant increase in permeability followed by a mitochondrial swelling. Instead, a statistically significant decrease in mitochondrial respiration (O2 consumption) was recorded in the striatum and hippocampus. Our study showed that the pesticide caused a significant increase of the cytochrome c amount correlated with activation of neuronal apoptosis mechanisms by the significant increase of caspase-3 of hippocampus and striatum. In particular, the results of behavioral tests (open field, classic maze tests of sucrose, and Morris water maze) have significant changes, namely bad behavior of the treated rats, affecting the level of anxiety, learning, and memory, and general motor activity has mainly been shown in treated rats. In addition, the histological cuts clearly confirm cerebral necrosis in the hippocampus and the striatum caused by the pesticide. They allow us to consider the necrotic areas, black spots, reduction, and denaturation of these brain regions in the treated rats. On the other hand, we have studied the protective effects against the neurotoxicity of Deltamethrin (DLM). In this context, after the gavage of Quercetin at the dose of 10mg/kg/day, we have noticed an improvement in the entire parameters: mitochondrial enzyme, metabolic, histological, and behavioral parameters. This confirmed the improvement of preventive and curative effect of Quercetin against free radicals induced by the DLM.

Collapsibility potential of gypseous soil stabilized with fly ash geopolymer; characterization and assessment

This study focused on effects of intrinsic sulfate in gypseous soil on its collapsibility potential when stabilized with fly ash geopolymer binder. Accordingly, compression and collapsibility tests were performed on the binder and the stabilized soil, respectively. XRD, TGA, and SEM/EDX tests were also conducted to trace changes due to geopolymerization and sulfate attack before and after exposure at different ages of up to 90days. The results showed the formation of geopolymer gel (A-S-H) with higher strength and more sulfate resistance than Portland cement paste in binder. Furthermore, incorporation of KOH (12M) activated fly ash in gypseous soil recorded the lowest collapsible potential and coefficient of permeability at 90days of exposure.

Evaluation of the transfer and the accumulation of microcystins in tomato (Solanum lycopersicum cultivar MicroTom) tissues using a cyanobacterial extract containing microcystins and the radiolabeled microcystin-LR (14C-MC-LR)

Microcystins are the most common cyanotoxins and may be expected wherever blooms of cyanobacteria occur in surface waters. Their persistence both in the irrigation water and in the soil can lead to their transfer and bioaccumulation into agricultural plants. The aim of this work was to investigate microcystin accumulation in Solanum lycopersicum cultivar MicroTom. The plant was exposed to either Microcystis aeruginosa crude extracts containing up to 100μgeq.MC-LRL−1 in a soil–plant system for 90days or pure radiolabeled 14C-MC-LR in a hydroponic condition for 48h. Toxin bioaccumulation in the soil and different plant tissues was assessed both by the PP2A inhibition assay and by liquid chromatography-mass spectrometry (LC/MS/MS). After 90days of exposure, microcystins persisted in the soil and their free extractable concentrations accumulated were very low varying between 1.6 and 3.9μgeq.MC-LRkg−1 DW. Free MC-LR was detected only in roots and leaves with concentrations varying between 4.5 and 8.1μgkg−1 DW and between 0.29 and 0.55μgkg−1 DW, respectively. By using radioactivity (14C-MC-LR), the results have reported a growing accumulation of toxins within the organs roots>leaves>stems and allowed them to confirm the absence of MC-LR in fruits after 48h of exposure. The bioconcentration factor (BCF) was 13.6 in roots, 4.5 in leaves, and 1.4 in stems. On the other hand, the results highlight the presence of two radioactive fractions in different plant tissues. The non-extractable fraction of radioactivity, corresponding to the covalently bound MC-LR, was higher than that of the extractable fraction only in roots and leaves reaching 56% and 71% of the total accumulated toxin, respectively. Therefore, results raise that monitoring programs must monitor the presence of MCs in the irrigation water to avoid the transfer and accumulation of these toxins in crops.

The fate of a nitrobenzene-degrading bacterium in pharmaceutical wastewater treatment sludge

This paper describes the fate of a nitrobenzene-degrading bacterium, Klebsiella oxytoca NBA-1, which was isolated from a pharmaceutical wastewater treatment facility. The 90-day survivability of strain NBA-1 after exposure to sludge under anaerobic and aerobic conditions was investigated. The bacterium was inoculated into sludge amended with glucose and p-chloronitrobenzene (p-CNB) to compare the bacterial community variations between the modified sludge and nitrobenzene amendment. The results showed that glucose had no obvious effect on nitrobenzene biodegradation in the co-metabolism process, regardless of the presence/absence of oxygen. When p-CNB was added under anaerobic conditions, the biodegradation rate of nitrobenzene remained unchanged although p-CNB inhibited the production of aniline. The diversity of the microbial community increased and NBA-1 continued to be one of the dominant strains. Under aerobic conditions, the degradation rate of both nitrobenzene and p-CNB was only 20% of that under anaerobic conditions. p-CNB had a toxic effect on the microorganisms in the sludge so that most of the DGGE (denaturing gradient gel electrophoresis) bands, including that of NBA-1, began to disappear under aerobic conditions after 90days of exposure. These data show that the bacterial community was stable under anaerobic conditions and the microorganisms, including NBA-1, were more resistant to the adverse environment.

Durability of alkali activated cement produced from kaolinitic clay

Alkali activated products were synthesized by activation of kaolinitic clay from Hiswa area, Jordan with a sodium hydroxide solution. These specimens were subjected to long-term durability tests under different environmental and chemical conditions. The geopolymer specimens undergo very low drying shrinkage. The specimens perform well under ambient, de-ionized water, wet–dry cycles, sea water, and sodium sulfate conditions. The newly developed material from Hiswa clay shows a stable strength under all these conditions. The specimens are however attacked by acid solutions and lose about 9.7% of their mass after 90days of exposure. The alkali–silica reaction has highly affected the geopolymer specimens as indicated by cracking, expansion and loss of mechanical strength.

Toxicity of Phenanthrene in Freshwater Sediments to the Rooted Submersed Macrophyte, Vallisneria spiralis

A study was conducted to determine the response of the rooted submersed macrophyte, Vallisneria spiralis to phenanthrene in freshwater sediments with initial phenanthrene concentrations from 0 to 80mgkg(-1) dry sediment. The sensitivity of various morphological endpoints was evaluated after 90days of exposure. The most sensitive toxicity test endpoints were those that reflected root growth. Toxicological sensitivity of the endpoints changed with the effect level selected. The toxicity threshold from a plot of the EC(10) values was 1-2 orders of magnitude lower than those calculated for the threshold from plots of the EC(25) or EC(50) values. In addition, stimulatory responses (hormesis) on root growth were observed at subtoxic concentrations of phenanthrene, and a hormetic model should thus be incorporated for ecological risk assessment.

Subchronic inhalation toxicity of gold nanoparticles

BackgroundGold nanoparticles are widely used in consumer products, including cosmetics, food packaging, beverages, toothpaste, automobiles, and lubricants. With this increase in consumer products containing gold nanoparticles, the potential for worker exposure to gold nanoparticles will also increase. Only a few studies have produced data on the in vivo toxicology of gold nanoparticles, meaning that the absorption, distribution, metabolism, and excretion (ADME) of gold nanoparticles remain unclear.ResultsThe toxicity of gold nanoparticles was studied in Sprague Dawley rats by inhalation. Seven-week-old rats, weighing approximately 200 g (males) and 145 g (females), were divided into 4 groups (10 rats in each group): fresh-air control, low-dose (2.36 × 104 particle/cm3, 0.04 μg/m3), middle-dose (2.36 × 105 particle/cm3, 0.38 μg/m3), and high-dose (1.85 × 106 particle/cm3, 20.02 μg/m3). The animals were exposed to gold nanoparticles (average diameter 4-5 nm) for 6 hours/day, 5 days/week, for 90-days in a whole-body inhalation chamber. In addition to mortality and clinical observations, body weight, food consumption, and lung function were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for hematology and clinical chemistry tests, and organ weights were measured. Cellular differential counts and cytotoxicity measurements, such as albumin, lactate dehydrogenase (LDH), and total protein were also monitored in a cellular bronchoalveolar lavage (BAL) fluid. Among lung function test measurements, tidal volume and minute volume showed a tendency to decrease comparing control and dose groups during the 90-days of exposure. Although no statistically significant differences were found in cellular differential counts, histopathologic examination showed minimal alveoli, an inflammatory infiltrate with a mixed cell type, and increased macrophages in the high-dose rats. Tissue distribution of gold nanoparticles showed a dose-dependent accumulation of gold in only lungs and kidneys with a gender-related difference in gold nanoparticles content in kidneys.ConclusionsLungs were the only organ in which there were dose-related changes in both male and female rats. Changes observed in lung histopathology and function in high-dose animals indicate that the highest concentration (20 μg/m3) is a LOAEL and the middle concentration (0.38 μg/m3) is a NOAEL for this study.

Toxicological considerations on the use of propylene glycol as a humectant in cigarettes

Propylene glycol (PG) is a humectant commonly used in cigarettes. Previous toxicological examinations of the effects on the addition of PG to tobacco used mixtures with several other flavoring agents. In the present work, toxicological comparisons were made of experimental cigarettes containing no added PG against otherwise similar cigarettes with three different amounts of PG added to the tobacco. The main toxicological comparison was a sub-chronic inhalation study with mainstream smoke in Sprague–Dawley rats (exposures of 150 mg/m 3 of total particulate matter, 6 h exposure per day, for 90 consecutive days). The target PG concentrations in the tobacco of the four cigarette types were 0, 4, 7 and 10%. Additional studies with mainstream smoke were bacterial mutagenicity (5 Salmonella strains, both with and without metabolic activation, particulate phase only), cytotoxicity of both particulate and gas/vapor phases (using the neutral red uptake assay), and analytical chemistry (41 analytes). The graded inclusion of PG into experimental cigarettes resulted in increases in the smoke concentrations of propylene oxide, at very low concentrations. Broadly similar responses were seen across the four cigarette types, and the responses were similar to those previously described in the scientific literature. The addition of PG to experimental cigarettes reduced concentrations of some smoke components (e.g. nicotine), but had minimal effects on the biological responses. Most of the changes produced in the 90-days of exposure were resolved in a 42-day post-inhalation period.

Behavioral effects of chronic exposure to 0.5 mW/cm2 of 2,450-MHz microwaves.

Adult male, Long-Evans rats were exposed 7 h a day for 90 days to continuous wave (CW) 2,450-MHz microwaves at an average power density of 0.5 mW/cm2. Exposures were in a monopole-above-ground radiation chamber with rats in Plexiglas cages. The resulting specific absorption rate (SAR) was 0.14 W/kg (+/- 0.01 SEM). Additional rats served as sham-exposed and home-caged controls. All were evaluated daily for body mass and food and water intakes. Once each 30 days, throughout baseline and exposure phases of the experiment, rats in the sham- and microwave-exposed groups were tested for their sensitivity to footshock. After 90-days of exposure, the rats were evaluated an open field, an active avoidance task and an operant task for food reinforcement. Performance of sham- and microwave-irradiated rats was reliably different on only one measure, the lever-pressing task. The general conclusion reached was that exposure to CW 2,450-MHz microwave radiation at 0.5 mW/cm2 was below the threshold for behavioral effects over a wide range of variables, but did have an effect on a time-related operant task, although the direction of the effect was unpredictable.