Chapter 6 - Repeated-exposure systemic toxicity (subacute, subchronic, and chronic systemic toxicity)

Introduction. Biomedical implants in present time are under active research. Titanium nickelide (NiTi) is alloy widely uses for its properties. Despite the advantages of NiTi, its use is limited by the potential risks associated with abnormal tissue reaction. Therefore, significant efforts are being made to improve the biocompatibility of NiTi and reduce its toxicity.The purpose of the study is to research potential changes in hematological parameters, to assess acute, subacute and chronic toxicity that may be associated with NiTi-silver (Ag) alloys.Materials and methods. The study was conducted as part of an open, randomized, controlled experiment lasting 9 months. The object of study was samples of NiTi powder with Ag addition. NiTi powder without the addition of Ag was used as a control. The study of acute, subacute, subchronic, chronic toxicity and hematological profile in particular, were conducted.Results. When assessing the condition of laboratory animals after conducting a test to determine acute systemic toxicity, animal deaths and adverse clinical signs were not recorded in any group of animals during the entire observation period. To study the potential for subacute toxicity, a general blood test was performed, and the potential anti-inflammatory activity of the implant was noted.Conclusion. Assessment of acute, subacute, subchronic and chronic toxicity of NiTi revealed no signs of animal death or pronounced clinical symptoms indicating a general toxic effect after surgery. As a result of the dynamic assessment parameters of the blood, no changes characteristic of the toxic effect of the alloy on hematopoiesis were detected.

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.

The pollution of aquatic systems with microplastics (MPs) affects marine and freshwater fish species worldwide. However, little is known about the size‐dependent retention time of these inert particles. To approach this question, the retention time of MP particles was examined in two freshwater fish species with distinct differences in gastrointestinal morphology: rainbow trout (Oncorhynchus mykiss) with a true stomach, and stomachless common carp (Cyprinus carpio). A special diet was developed that contained environmentally relevant concentrations of MPs with sizes ranging from 20 to 1,000 µm. The two species were exposed to three different concentrations and numbers of retained particle were determined up to 72 hr after administration. The results revealed significant differences in retention time between large and small MP particles in rainbow trout, in which the T50 value (time for 50% of particles to be evacuated) ranged from 12.1 hr for 42.7 µm particles to 4.0 hr for 1,086 µm particles. In contrast, the differences observed between sizes in common carp were considerably smaller, with T50 ranging from 7.3 hr for 42.7 µm particles to 4.6 hr for 1,086 µm particles. It is therefore concluded that large particles in rainbow trout must be actively transported out of the stomach, as the evacuation times are significantly shorter than those for food. Small particles, however, are passively excreted with the chyme. In common carp, the evacuation rates of all particle sizes were in the range of that for food, suggesting a passive excretion. The results are particularly relevant in the contexts of particle transfer through the food chain, the release of toxic chemicals, and the translocation into tissues and organs. For this reason, it is essential that the particle size is given more consideration in future studies of microplastics in aquatic environments.

As recent events have shown, terrorists with national, regional and limited socio-cultural interests are capable of waging global campaigns. The predominant weapons in the near future are likely to remain conventional, but with an increasing use of chemical, biological, radiological and nuclear weapons (CBRN). Additionally, a consequence of technology is the use, storage, and transport of toxic chemicals, biological pathogens and radiological materials, which directly increase the risk of unintentional release of CBRN materials. Recognising this, a variety of organisations at all levels of government and in the public and private sectors have either initiated or increased consideration of these potentially catastrophic events in their planning process. Given the potential for very large numbers of casualties and significant disruption to economies, it is prudent to consider what measures are available to mitigate morbidity, mortality and economic disruption. Analysis of victim presentation from previous releases of toxic chemicals reveals patterns that can guide response planning efforts.

Objective Armed conflicts result in the release of toxic chemicals into the surrounding environment and civilians are commonly exposed to these toxicants. This paper reviews the evidence on civilian exposure to toxic chemicals, including but not limited to inhaled toxic substances, in post-World War II armed conflicts, and proposes a framework for the implementation of long-term surveillance programs for these populations. Materials and Methods Four databases of peer-reviewed health articles were searched for all English-language articles with a primary focus on toxic chemical exposures among civilians in armed conflicts since World War II. The review was supplemented substantially by the gray literature. Results In the 66 articles that met the inclusion criteria, the authors categorized the chemical toxicants to which civilians have been exposed in modern armed conflicts as ubiquitous (e.g. smoke, dust, and munitions components present in all conflicts) or particular agents (e.g. specific chemical agents used in a few conflicts). While most studies focused on particular agents, the vast majority of civilians are in fact exposed to ubiquitous agents both in the acute conflict phase and through persistent environmental exposures after the cessation of hostilities. Discussion/Conclusion There is a dearth of research concerning civilian exposures to toxic chemicals during armed conflicts. In line with principles of equity, justice, and accountability, robust research and surveillance programs are urgently needed to document exposures and provide ongoing assessments and any necessary treatment for these long-ignored populations, most of whom live in the Global South.

Over the last two decades, the usage of electronic equipment in human life has been increasing dramatically and the life span of electronic products is short. E-waste is growing in the world, because they do not biodegrade easily, and most of them are not reused or recycled. In this chapter, the authors have explained the best practices and innovative approaches in e-waste collection and recycling, aiming to address environmental concerns, conserve resources, and promote sustainable waste management. The main problem is the release of toxic chemicals like lead, chromium, manganese, and polybrominated diphenyl ethers (PBDEs) from e-waste leads to many environmental and health issues as most recycling facilities are located in low-income areas. In those mainly women and children often participate in e-waste recycling as a form of income and are frequently exposed to hazardous pollutants. Some of the health effects include impaired learning and memory functions; altered thyroid, estrogen, and hormone systems; and neurotoxicity.

Photocatalysis enables room temperature synthesis of hydrogen peroxide (H2O2) without any byproducts as well as offering advantages such as low cost, and no release of toxic chemicals [1]. Thus, photocatalysis is an appealing approach for the environmentally friendly synthesis of H2O2. Two-dimensional (2D) layered transition metal chalcogenide (TMC) photocatalysts are good at light harvesting due to their high specific surface area and exhibit excellent optoelectronic properties which make them suitable for environmental remediation and energy production [2]. Metal sulfides have a narrower band gap, which improves their light absorption ability in the visible spectrum. However, they often suffer from low quantum yield and high charge recombination rate. Carbonaceous materials have been proven as very effective co-catalysts with semiconductors at increasing their photoactivity and decreasing recombination rate [3]. The present study focusses on indium sulfide (In2S3) and its composites with carbon nano tubes (CNTs) and carbon quantum dots (CQDs) for H2O2 generation via two-electron oxygen reduction reaction. In2S3, In2S3-CNT and In2S3-CQD are synthesized via hydrothermal method. Structural and optical properties characterized using several techniques such as XRD, Raman, UV-Vis-DRS, PL spectra, SEM, TEM etc. show high crystallinity of In2S3 lattice, good dispersion of carbons on In2S3 lattice, improved light absorption and decrease in recombination rate in In2S3 carbon composites. Photoelectric properties are studied using chronoamperometry, EIS, cyclic voltammetry etc. The In2S3 carbon composites show good stability and lower charge transfer resistance and higher active surface area than pure In2S3. The carbon composite materials show a significantly higher performance than the pure In2S3. In2S3-CQD achieves H2O2 production rate of 634 µM h-1, which is ~ 17 times higher than that of pure In2S3. These composites also show good performance for water treatment with In2S3-CQD removing 93% chromium(VI) and 94% rhodamine B (RhB) from contaminated water upon 2h of irradiation. The mechanism of removal of the impurities is also discussed. In2S3-CQD has shown good results owing to their good light absorption, high specific surface area, and CQDs being able to act as electron reservoir. Keywords : Photocatalysis, Hydrogen peroxide photosynthesis, Advanced Oxidation processes, Wastewater Treatment.

Sustainable chemicals and materials management deals with both the risks and the opportunities of chemicals and products. It is not only focused on hazards and risks of chemicals for human health and the environment but also includes the management of material flows from extraction of raw materials up to waste. It becomes apparent meanwhile that the ever-growing material streams endanger the Earth system. According to a recent publication of Persson et al., the planetary boundaries for chemicals and plastics have already been exceeded. Therefore, sustainable chemicals and materials management must become a third pillar of international sustainability policy. For climate change and biodiversity, binding international agreements already exist. Accordingly, a global chemicals and materials framework convention integrating the current fragmented and non-binding approaches is needed. The impacts of chemicals and materials are closely related to climate change. About one third of greenhouse gas (GHG) emissions are linked to the production of chemicals, materials and products and the growing global transport of goods. Most of it is assigned to the energy demand of production and transport. GHG emissions must be reduced by an expansion of the circular economy, i.e., the use of secondary instead of primary raw materials. The chemical industry is obliged to change its feedstock since chemicals based on mineral oil and natural gas are not sustainable. Climate change in turn has consequences for the fate and effects of substances in the environment. Rising temperature implies higher vapor pressure and may enhance the release of toxicants into the atmosphere. Organisms that are already stressed may react more sensitively when exposed to toxic chemicals. The increasing frequency of extreme weather events may re-mobilize contaminants in river sediments. Increasing chemical and material load also threatens biodiversity, e.g., by the release of toxic chemicals into air, water and soil up to high amounts of waste. Fertilizers and pesticides are damaging the biocoenoses in agrarian landscapes. In order to overcome these fatal developments, sustainable management of chemicals and materials is urgently needed. This includes safe and sustainable chemicals, sustainable chemical production and sustainable materials flow management. All these three sustainability strategies are crucial and complement each other: efficiency, consistency and sufficiency. This obligates drastic changes not only of the quantities of material streams but also of the qualities of chemicals and materials in use. A significant reduction in production volumes is necessary, aiming not only to return to a safe operating space with respect to the planetary boundary for chemicals, plastics and waste but also in order to achieve goals regarding climate and biodiversity.

The exploitation of bio-electrochemical system and microplastics removal: Possibilities and perspectives

Events leading up to the release of toxic chemicals in the processing plants are one of the main hazards of chemical industries that can endanger employees and also people in neighborhood. In this study, DOW's Chemical Exposure Index (CEI) is used to determine hazard distances of possible toxic chemical releases in one of the South Pars gas refineries. To do this, 318 considerable release scenarios were identified and by process parameters and CEI equations, airborne quantity, chemical exposure index and hazard distances were calculated. In the worst case of a toxic chemical release, hazard distance of the studied refinery is 10000 meters. The Sludge Catcher unit is the most dangerous unit in terms of toxic chemical release. In addition to the advantages of the CEI observed in this study also some limitations were observed including sensitivity to process parameters, no consideration of the material inventory and the concentration in the CEI calculations

Subject of research: prophylactic iodine-containing drug developed for iodine deficiency prevention on the basis of the Amur Region’s natural zeolites. Test objective: assessment of acute and chronic toxicity using laboratory rats as experimental animals; assessment of sub-chronic toxicity using newborn calves as experimental animals. Method of study of acute toxicity: initial dose-1.0 g / kg of body weight, which was increased up to 2,0 g/kg in two days. Later on the dose was doubled to determine average lethal dose (LD50). Chronic toxicity was determined by feeding three groups of laboratory rats with the drug doses 1.0, 2.0 and 3.0 g / kg of body weight for 60 days. To determine sub-chronic toxicity, the newborn calves were fed with drug dose of 2.0 g / kg for 30 days. It was found that prophylactic iodinecontaining drug, developed on the basis of the Amur Region’s natural zeolites, had neither acute and chronic toxicity for laboratory rats, nor sub-chronic toxicity for calves. Prophylactic drug being fed to rats increases the body weight of rats of experimental groups. Introduction of iodine-containing drug to the diet of newborn calves for the prevention of iodine deficiency for 30 days is accompanied by improved immunobiochemical parameters of animals.

Phytochemical identification, acute and subchronic oral toxicity assessments of hydroalcoholic extract of Acroptilon repens in BALB/c mice: A toxicological and mechanistic study

This toxicity test was conducted to determine if the effluent causes death (acute toxicity) or reduction in the reproduction of the test organisms (chronic toxicity) during a seven day period. A series of dilutions of the effluent are set to determine how much the effluent must be diluted before toxic effects are no longer noted. Acute toxicity is checked by statistically analyzing whether significantly more organisms die in the effluent dilutions than in the control treatment, and, if significantly more die, how much the effluent must be diluted so as to kill only 50% of the test organisms (the LC50). Chronic toxicity is checked by statistically analyzing whether significantly fewer young are produced by test organisms exposed to the effluent dilutions. Results indicate the lowest effluent concentration which shows a toxic effect (the LOEC) and the highest effluent concentration which does not demonstrate an effect (NOEC).

Aims: Coula edulis Baill., (Olacaceae) is a non-lignified forest product not well known and widely used in sub-Saharan Africa as a phytomedicine or food additive. However, the toxicity of this plant remains unknown. This study aimed to assess the safety of the ethanolic extract of C. edulis stem bark (CEE). Study Design: Pharmacological study. Place and Duration of Study: Laboratory of Nutrition and Nutritional Biochemistry, Department of Biochemistry, University of Yaounde 1 (Cameroon), between June 2018 and July 2022. Methodology: Studies on the assessment of acute and subchronic toxicity were carried out by guidelines 423 of the Organization for Economic Co-operation and Development (OECD). Subacute toxicity of the sample was assessed over 28 days using repeated doses by OECD Guideline 407. Results: No cases of death and clinical signs of toxicity were observed in the treated rats, suggesting that the LD50 of C. edulis ethanolic extract is greater than 2000 mg/kg bw. Regarding the subacute toxicity study, the administration of CEE also did not result in any changes in the course of body weight. Only a significant decrease in the relative weight of the ovaries in females at the highest dose of 600 mg/kg was observed. In males and females, CEE did not affect lipid profile markers or transaminase levels (AST, ALT). In addition, a small but non-significant (p> 0.05) increase in creatinine was observed without kidney dysfunction. In males, CEE induced an increase in mean corpuscular volume number at 600 mg/kg, while at the same time, mean corpuscular hemoglobin concentration decreased at the 300 mg/kg dose. In females, a significant increase in the number of monocytes, red blood cells, and hemoglobin level were observed. No difference in the levels of urea, glucose, and lipid markers was observed nor histological changes in the organs studied. Conclusion: As would be expected, exposure to CEE did not cause significant toxic effects in treated rats. Therefore, this plant extract can be safely recommended for therapeutic use.

not merely the absence of disease or infirmity.