Simulated Environmental Exposure Research Articles

Prepared microplastics interaction with Artemia salina under low pH conditions representing ocean acidification; a simulated environmental exposure

Ocean acidification and microplastic pollution are two of the major ecological concerns. The distribution of large quantities of plastic debris and microplastics all across the oceans emphasises the need to determine the influence of microplastics in ocean acidification and to evaluate its concomitant toxicological effects on aquatic life forms. Studies on the combined impact of both the stressors are very limited, but much needed in the current scenario. Where most of the present-day research use purchased microplastics of defined size and morphology (microspheres, fibres, rods, etc.), the present study employs prepared “true to life microplastics” that resemble the environmental microplastic pollutants in morphology and size heterogeneity. The present study focusses on evaluating the fate and impact of oceanic microplastics on the physiology and development of Artemia salina (Brine shrimp), one among the most ecologically significant zooplankton species. Natural sea water was acidified by controlled perturbation of carbon dioxide using a valve system. The hatching rate of A. salina cysts receded significantly (p < 0.05) upon singular exposures to microplastics and low pH (7.80), whereas combined effect was insignificant. The reactive oxygen species (ROS) elevated as a result of individual exposures to microplastics and low pH. However, only in 0.5 mg mL−1 PE treatments at pH 7.80, an additive impact was reported for ROS activity (p < 0.05). The SOD activities increased significantly but it can be attributed as the individual responses towards exposure to both the stressors. A significant additive impact was not observed for SOD activity (p > 0.05). But during the development, significant morphological anomalies were observed. Changes in the appendages of nauplii and juveniles as a result of combined exposure to microplastics and low pH treatments are significant findings. Our observations suggest that coupled exposure to microplastics and low pH could induce significant oxidative stress in the marine zooplanktons and also adversely affect their normal development. Findings from the current study emphasise the need for further research to understand the coupled toxicological impacts of ocean acidification and predominant pollutants such as microplastics to other marine animals as well.

Method for rapid biofilm cultivation on microplastics and investigation of its effect on the agglomeration and removal of microplastics using organosilanes

Since microplastics were recognized as a global environmental problem in the early 2000s, research began on possible solutions such as the removal of microplastics from waters. A novel and promising approach for this purpose is microplastics agglomeration-fixation using organosilanes. In this study, it is investigated how biofilm coverage of microplastics affects this process. The biofilm was grown on the microplastics by cultivating it for one week in a packed bed column operated with biologically treated municipal wastewater enriched with glucose. The biofilm was characterized using confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and Fourier-Transform infrared spectroscopy (FT-IR). The results show a partial coverage of the microplastics with attached bacteria and extracellular polymeric substances (EPS) after 7 days of incubation. Comparing five polymer types (polyethylene, polypropylene, polyamide, polyester, and polyvinyl chloride) and three organosilanes, the biofilm coverage caused a reduced removal efficiency for all combinations tested as it changes the surface chemistry of the microplastics and therefore the interaction with the organosilanes tested in this study. Treatment of biofilm covered microplastic with ultrasound partly recovers the removal. However, the results underline the importance of simulated environmental exposure when performing experiments for microplastic removal.

Influence of CNT loading and environmental stressors on leaching of polymer-associated chemicals from epoxy and polycarbonate nanocomposites

Environmental context Carbon nanotubes are added to polymers such as polycarbonate and epoxy to form nanocomposites with enhanced material properties. Environmental factors including temperature, UV light exposure and pH have the potential to degrade these composites and increase the release of toxic polymer-associated chemicals. This study investigates how carbon nanotube loading decreases the release of known endocrine-disrupting compounds, bisphenol A and 4-tert-butylphenol, from polymer nanocomposites under simulated weathering environments. Abstract Nanoparticles such as carbon nanotubes are increasingly added to polymer matrices to improve tensile strength and electrical and thermal conductivity, and to reduce gas permeability. During use and after disposal, these plastic nanocomposites (PNCs) are degraded into microplastics by physical and chemical processes including mechanical abrasion, UV light exposure, hydrolysis and oxidation. Such polymers have the potential to enter aquatic environments and release potentially hazardous polymer-associated chemicals and transformation products. This work identifies and quantifies polymer-associated chemicals leached from polymers and nanocomposites during simulated environmental exposure. Epoxy and polycarbonate PNCs containing single-walled carbon nanotube (SWCNT) loadings ranging from 0 to 1 wt-% were exposed to water for 5 days, and the release of the chemicals bisphenol A (BPA) and 4-tert-butylphenol (TBP) was measured. The role of UV exposure, pH, temperature and natural organic matter in regulating chemical release was also investigated. Temperature, pH and UV light were found to be the most significant factors influencing release of TBP and BPA from PNCs. Additionally, increasing carbon nanotube loading in both polycarbonate and epoxy composites was found to decrease the release of these phenolic chemicals. A 0.3 % higher SWCNT loading decreased the release of BPA 45 ± 18 %, and a 1 % SWCNT loading decreased chemical release from epoxy by 48 ± 26 % for BPA and 58 ± 8 % for TBP. This information provides important data that can be used to help assess the risks posed by SWCNT polymer nanocomposites in aqueous environments, particularly as they age and are transformed.

Evaluation of genotoxicity after acute and chronic exposure to 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) in rodents using machine learning algorithms.

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most widely used herbicides in the world, but its mutagenic and carcinogenic potential is still controversial. We simulated environmental exposure to 2,4-D, with the objective of evaluating the genotoxic effect of acute and chronic exposure to 2,4-D in rodents. We also evaluated the performance of machine learning algorithms in detecting differences in exposure groups through recognition performed from genotoxic characteristics. In the acute phase, 88 Swiss mice were used, distributed in five groups and exposed to nebulizations at different time intervals (24, 48, 72 and 192 hr). In the chronic phase, 88 Wistar rats were used, distributed in two groups (inhaled and oral) and exposed for six months. Femoral bone marrow cells were collected for a micronucleus test and comet assay. Data were evaluated by pattern recognition algorithms. In acute exposure, medium and high concentrations induced DNA damage in the comet assay, but these concentrations did not increase micronucleated cells. In the chronic exposure, there was an increase in micronuclei and DNA damage in the comet assay in all exposed groups regardless of the exposure route. The data showed a robust pattern of distinction between exposed and nonexposed groups to 2,4-D. Our data showed that both acute inhalation exposure and chronic oral and inhalation exposure to 2,4-D can cause genotoxic effects regardless of concentration. Machine learning showed a clear distinction between the control groups and those exposed to 2,4-D, and the effects of exposure are not concentration-dependent.

Environmentally realistic exposure to weathered North Sea oil: Sublethal effects in Atlantic cod (Gadus morhua) and turbot (Scophthalmus maximus)

ABSTRACTWith increasing oil and gas activities and transport in the Arctic, there is a need to understand how operational or accidental releases of substances affect marine organisms from a pristine environment. The aim of the current study was to describe and compare the responses of two marine fish species, Atlantic cod (Gadus morhua) and turbot (Scophthalmus maximus), following exposure to three levels (low, medium, high) of the water-soluble fraction of a North Sea crude oil for 16 days. The exposure system simulated environmental exposure by allowing clean seawater to percolate through gravel covered in weathered oil before being introduced to aquaria. Both polycyclic aromatic hydrocarbon (PAH) metabolite bile concentrations and cytochrome P4501A (CYP1A) levels and activity increased markedly in comparison with controls in both species, but there were no significant differences between the three exposures. Turbot possessed 4–5-fold higher concentrations of two PAH bile metabolites compared to Atlantic cod by day 8. In contrast, hepatic CYP1A activity in cod was consistently 2–6-fold higher than in turbot with increasing differences over the experimental period. Baseline DNA strand breaks in lymphocytes and kidney cells were low in both species, but was elevated for all treatments by day two. There were no marked indications of the treatments affecting immune functions in either species. This investigation demonstrated that there may be significant differences in responses between species receiving identical exposures and that DNA strand breaks in lymphocytes and kidney cells are sensitive to confinement stress. Data also indicate that some species, such as turbot, may adapt to treatments within days and weeks.

Imidacloprid induces morphological and molecular damages on testis of lizard (Podarcis sicula)

The insecticide imidacloprid was evaluated under laboratory conditions in the adult male Italian wall lizards (Podarcis sicula) to assess its potential toxicity. By an acute oral test, LD50 was 503.76mg/kg. Changes in spermatogenesis, plasma sex hormone levels and androgen and oestrogen receptor mRNAs were analysed by subchronic test and simulated environmental exposure. 15-days subchronic test, in which lizards were orally dosed on alternate days at 0, 10, 50, 100mg/kg bw, showed a dose-dependent changes of testicular architecture and an increase of apoptotic processes. In a 30-days simulated environmental exposure spermatogenesis was arrested at secondary spermatocyte level and only few primary spermatocytes were TUNEL-positive. In all experimental groups imidacloprid was able to decrease both the level of sex hormones and the steroid receptor mRNAs. The results demonstrate that imidacloprid affects reproduction function of male lizards therefore precautions must be taken to minimize the harmful effects of this compound.

Improved durability of electrochromic switchable mirror with surface coating in environment

Electrochromic switchable mirrors can be reversibly changed between a reflective state and a transparent state by applying a voltage. In our previous work, the properties of the device were significantly affected by environmental factors such as temperature and relative humidity. In that work, the effects on the device properties were investigated through an accelerated degradation test in a thermostat/humidistat bath at a constant temperature of 40 °C and a relative humidity of 80%. The switching speed between the reflective state and transparent state increased as the duration of the simulated environmental exposure increased. The device stored for 7 days under the simulated environmental conditions showed a around 45-fold slower switching speed than that of the as-prepared device. In this work, a high-durability surface coating material constructed from a cyclo olefin polymer sheet and ultraviolet resin was developed to protect the device from environmental degradation. The device with surface coating kept under the simulated environmental conditions for 7 days showed almost the same switching speed as the as-prepared device with the surface coating.

Environmental Durability of Fabric-Reinforced Shape-Memory Polymer Composites

This study is a baseline assessment of the environmental durability of current state-of-the-art, fabric-reinforced shape-memory (SM) materials being considered for morphing applications. Tensile dog-bone-shaped specimens are cut along three different directions, namely, along (0°), perpendicular (90°), and oblique (45°) to the planar orientation of the fabric. The elastomeric response and shape memory properties before and after simulated environmental exposure to moisture, lubrication oil, and UV radiation are measured. Weight loss of the as-received and conditioned specimens is monitored and the dog-bone-shaped specimens are subjected to recovery following fixation. Parameters being investigated include modulus in the glassy and rubbery state, stored strain, shape fixity, recovery stress, and unconstrained shape recovery. There is a twofold decrease in the composite stiffness as the material is cycled between room and elevated (above the glass transition) temperature. At room temperature, the 0-degree specimen has the maximum stiffness (5.8 GPa), failure strength (94 MPa), and failure strain (5.4%), while above the Tg, the 90-degree specimen has the least stiffness (∼18 MPa) and largest strain to failure (&gt;200%). Thus, the composite exhibits large deformation in its rubbery state. Parameters which are strongly affected by the damage developed during the first SM cycle include rubbery and glassy (or unloading) moduli values measured during the second SM cycle, while smaller changes are observed in shape fixity and recovery properties.

Environmental-Like Exposure to Low Levels of Estrogen Affects Sexual Behavior and Physiology of Female Rats

Xenoestrogens are endocrine-disrupting chemicals that mimic the action of endogenous estrogen hormones. Effects of xenoestrogen on aquatic wildlife are well documented, whereas the experimental evidence for impairment of reproductive behavior and physiology in mammals after exposure to xenoestrogens has been debated. The strongest arguments against such studies have been that the route, time course, and intensity of exposure did not simulate environmental exposure and that the chemicals tested have additional nonestrogenic toxic effects, hindering generalization of actual xenoestrogenic effects. Here we show that environmental-like exposure to the pure estrogen 17alpha-ethinylestradiol during development alters reproductive behavior and physiology in adult female Sprague-Dawley rats. We simulated environmental exposure by giving low doses (0.4 and 0.004 microg/kg.d) of 17alpha-ethinylestradiol orally to pregnant females from conception to weaning of the pups, which continued to receive the treatment until puberty. We studied the sexual behavior, estrous cycle, and estradiol plasma levels of intact female rats when they reached 3 months of age. Exposure to the higher dose strongly affected female sexual behavior and physiology, with suppression of lordosis and the estrous cycle and enhanced aggression toward males. The lower dose disrupted appetitive components of sexual behavior that influence the rate of copulation. Estradiol plasma levels were not affected by the treatment. Our study revealed that exposure to low oral doses of a pure estrogen during development alters female sexual behavior and physiology. These results suggest potential risks of reproductive failure from xenoestrogen exposure in realistic ecological conditions.

Toxicology of 85Kr: chronic exposure studies.

Male and female Wistar rats were exposed chronically to graded doses of 85Kr to determine long-term biological effects of simulated environmental exposure. Rats were exposed in 4 groups, including room air-exposed controls and 3 groups exposed to 85Kr concentrations equivalent to 10(2), 10(3) and 10(4) times the maximum permissible concentration (MPC) for the general population (3 X 10(-7) microCi/ml). Exposures continued 24 hr/day, 7 days/week for 808 days, until only approximately 10% of the original 400 rats were alive. No effect of 85Kr exposure was observed on weight gain or tumor incidence, including leukemias. The results support the adequacy of established 85Kr exposure limits for the general population in light of the absence of evidence of build-up in tissues after chronic exposure and the lack of exposure-related biological effects in rats after near-lifespan exposure to concentrations equivalent to 10,000 times the MPC.