6. Intervention studies impacting English

Researchers in the U.S. have also investigated the effects of focused instruction and other interventions. Several post-intervention studies show different patterns of activation in the reading networks, evidence of the strength of experimental results in suggesting effective neurobiologically-based remedial instructional practices. Shaywitz et al. found increased LH activation of the inferior frontal gyrus (IFG) and the middle temporal gyrus only in children with the characteristics of dyslexia who participated in daily tutoring of the alphabetic principle and phonological processing and not in those children who participated in a variety of common reading interventions exclusive of explicit phonology [73]. Their longitudinal data also indicated a continuation of correct activation patterns 1 year past, suggesting the durable nature of the processing change. Similarly, Simos, Breier, Fletcher, Bergman, and Papanicolaou using MSI found that after 80 hours of

intensive phonological intervention, dyslexic children showed a dramatic increase in the activation of left temporo-parietal regions, predominately in the left posterior superior temporal gyrus (STG), the network that supports grapheme-phoneme recoding in typical developing readers. However, even after intervention, neural activity was delayed in the dyslexic children relative to the controls (837 ms on average for dyslexics and 600 ms for controls), indicating that even with intensive phonological remediation, dyslexic children are slower to achieve the same reading fluency shown by non-dyslexic children. Further, high-risk children, who were nonresponsive to the phonological remediation package that was being offered, were distinct in showing earlier onset of activity in IFG compared to the temporoparietal regions [74]. This would indicate a persistent processing anomaly that influences ineffective decoding as well as decreased processing speed.

new technology included a modified version of a computerized system for visual hemisphere-specific stimulation (VHSS), "FlashWord" [77]. After 1440 minutes (24 h) of intervention, Lorusso et al. applied only behavioral measures and found that all students with the characteristics of dyslexia, regardless of their sub-type, improved not only in accuracy and fluency as compared to non-impaired controls, but also showed gains in spelling, memory, and general processing speed. Further, the dyslexic students gained 0.33 syllables / second more in reading speed over the same period of time than their non-impaired controls [76]. These extraordinary results suggest that requiring very fast processing of the presented visual stimuli in a targeted brain hemisphere may produce a greater degree of automatisation of the

component processes. It is this automatisation of the underlying lexical and sublexical processes that Wolfe and Katzir-Cohen validate as critical influences on fluent reading of connected text in their comprehensive definition of fluency [66].

for evidence of developing automaticity in regions of interest [78].

Italian students in total time spent: 1440 minutes (or 24 hours) total.

Subsequent research using FlashWord in English with American students has built on the successes in Dutch and Italian. Koen et al. used fMRI technology to localize brain activity before and after VHSS training in students who qualified with the characteristics of developmental dyslexia. This research was designed to test the hypothesis that subtyping students with the characteristics of dyslexia based on their reading behaviors as Bakker proposed, and administering VHSS intervention based on those subtypes (FlashWord-modified and in English), would improve fluency performance across dyslexia sub-types more effectively than other currently used reading fluency programs. Secondarily, the location and level of activation differences from pre-intervention and post-intervention scans were analyzed

FlashWord, Ver. 2.2, written by Franco Fabbro and Cristina Masutto (copyright,

This fMRI experiment used a mixed design, in that the events of interest (Word Pair analysis) are randomized with perceptual controls (Letter Match analysis) to provide robust event-related activation maps and estimates of hemodynamic response. The Letter Match task demands that the child decide whether two letter strings (e.g., szpy and sxpy), printed in all black letters and shown simultaneously one above the other, match exactly. The length of the letter strings is comparable to the length of the pseudo-words used in the phonological analysis task. As this is the control task, attention to all letter positions is necessary but the assignment of speech sounds to letters is not. For the phonological analysis task, the Word Pairs were two decodable non-words printed in black, also presented visually, one above

1995–2004 by Editrice TecnoScuola) is a computer program that uses a gameformat to present words or phrases in the right or left visual hemi-field at increasingly rapid rates. According to their dyslexia sub-type, each student sees the words (or phrases) projected on either the right or left side of the computer screen, stimulating either the right or left visual field and the opposite brain hemisphere. Ocular fixation is confirmed by directing the child to watch a luminous dot oscillating up and down on the screen at an adjustable speed. A word is revealed only when the child clicks the mouse exactly when the dot is crossing the central target. This ensures visual attention to the stimulus. The child's task is to read the words as they are flashed on the screen in ever shortening durations. Reading rates of 250– 100 ms for single words are generally considered to reflect "emerging fluency" [75]. For this study, students repeated all of the lessons in their assigned program (34 for the LH program and 27 for the RH program) at their own speed, matching the

7. VHSS intervention in English

The Neurobiological Development of Reading Fluency DOI: http://dx.doi.org/10.5772/intechopen.82806

101

However, it is the work of Dutch and Italian researchers that provided the foundation for a fluency intervention that appears to address the processing anomalies that are prevalent in American dyslexics. Employing the commonly accepted differences in the hemispheric contributions in learning to read, Bakker and Vinke identified Dutch children with dyslexia as L-dyslexics or P-dyslexics based on oral reading error analysis, the distribution of brain responses, and other behavioral measures [75]. They proposed that L-dyslexics are insensitive to the perceptual features of text because they predominately developed left hemisphere strategies from the very onset of learning to read. Behaviorally, L-dyslexics exhibit a hurried and inaccurate style of reading with many word substitution errors. Conversely, P-dyslexics are overly sensitive to perceptual features of the text because they began the learning-to-read process in the right hemisphere, but never advanced from there. These P-dyslexics read slowly with a fragmented style. Bakker and Vinke hypothesized that since L-type dyslexics had trouble using right hemispheric strategies during reading, they might profit from specific stimulation of the right hemisphere and the opposite for P-dyslexics: they had not naturally shifted to left hemisphere processing and so would benefit from specific stimulation of the left hemisphere [75].

As a general rule, specific stimulation of a hemisphere (HSS) can be achieved by the lateral presentation of a stimulus (reading material) in the left visual field or to the fingers of the left hand in L-dyslexics, and in the right visual field or to the fingers of the right hand in P-dyslexics. Bakker and Vinke actually treated the children with a wooden tactile training box, in which the child would place their target arm through a hole in the side and manipulate plastic letters in grooves out of sight. L-type children were given regularly-formed concrete words to configure and trace with their left hand, to stimulate the right hemisphere. P-type children were given difficult-to-visualize abstract words to configure and trace with their right hand, to stimulate the left hemisphere. The results indicated that P-dyslexics showed a decrease in sound/symbol errors on both word and text reading, while L-dyslexics decreased substantive errors only on text reading [75]. In spite of several limitations in their methodology and intervention, the positive effects of even motor stimulation to the less activated hemisphere on reading performance are encouraging. Further, these findings imply that the dyslexia sub-typing procedures appear to be valid techniques for matching reading interventions to brain processing systems.

Based on the potency of these theoretical and neurobiological foundations, Lorusso, Facoetti, Paganoni, Pezzani, and Molteni achieved much stronger results in a study of Italian impaired readers employing computer technology. These researchers implemented the sub-typing of dyslexic students used by Bakker and Vinke, and added M- type dyslexia: a mixed type demonstrating both slow and inaccurate reading, indicating impaired processing in both hemispheres [76]. Their The Neurobiological Development of Reading Fluency DOI: http://dx.doi.org/10.5772/intechopen.82806

intensive phonological intervention, dyslexic children showed a dramatic increase in the activation of left temporo-parietal regions, predominately in the left posterior superior temporal gyrus (STG), the network that supports grapheme-phoneme recoding in typical developing readers. However, even after intervention, neural activity was delayed in the dyslexic children relative to the controls (837 ms on average for dyslexics and 600 ms for controls), indicating that even with intensive phonological remediation, dyslexic children are slower to achieve the same reading fluency shown by non-dyslexic children. Further, high-risk children, who were nonresponsive to the phonological remediation package that was being offered, were distinct in showing earlier onset of activity in IFG compared to the temporoparietal regions [74]. This would indicate a persistent processing anomaly that

Neurodevelopment and Neurodevelopmental Disorder

influences ineffective decoding as well as decreased processing speed.

hemisphere [75].

processing systems.

100

However, it is the work of Dutch and Italian researchers that provided the foundation for a fluency intervention that appears to address the processing anomalies that are prevalent in American dyslexics. Employing the commonly accepted differences in the hemispheric contributions in learning to read, Bakker and Vinke identified Dutch children with dyslexia as L-dyslexics or P-dyslexics based on oral reading error analysis, the distribution of brain responses, and other behavioral measures [75]. They proposed that L-dyslexics are insensitive to the perceptual features of text because they predominately developed left hemisphere strategies from the very onset of learning to read. Behaviorally, L-dyslexics exhibit a hurried and inaccurate style of reading with many word substitution errors. Conversely, P-dyslexics are overly sensitive to perceptual features of the text because they began the learning-to-read process in the right hemisphere, but never advanced from there. These P-dyslexics read slowly with a fragmented style. Bakker and Vinke hypothesized that since L-type dyslexics had trouble using right hemispheric strategies during reading, they might profit from specific stimulation of the right hemisphere and the opposite for P-dyslexics: they had not naturally shifted to left hemisphere processing and so would benefit from specific stimulation of the left

As a general rule, specific stimulation of a hemisphere (HSS) can be achieved by the lateral presentation of a stimulus (reading material) in the left visual field or to the fingers of the left hand in L-dyslexics, and in the right visual field or to the fingers of the right hand in P-dyslexics. Bakker and Vinke actually treated the children with a wooden tactile training box, in which the child would place their target arm through a hole in the side and manipulate plastic letters in grooves out of sight. L-type children were given regularly-formed concrete words to configure and trace with their left hand, to stimulate the right hemisphere. P-type children were given difficult-to-visualize abstract words to configure and trace with their right hand, to stimulate the left hemisphere. The results indicated that P-dyslexics showed a decrease in sound/symbol errors on both word and text reading, while L-dyslexics decreased substantive errors only on text reading [75]. In spite of several limitations in their methodology and intervention, the positive effects of even motor stimulation to the less activated hemisphere on reading performance are encouraging. Further, these findings imply that the dyslexia sub-typing procedures

appear to be valid techniques for matching reading interventions to brain

Based on the potency of these theoretical and neurobiological foundations, Lorusso, Facoetti, Paganoni, Pezzani, and Molteni achieved much stronger results in a study of Italian impaired readers employing computer technology. These researchers implemented the sub-typing of dyslexic students used by Bakker and Vinke, and added M- type dyslexia: a mixed type demonstrating both slow and inaccurate reading, indicating impaired processing in both hemispheres [76]. Their new technology included a modified version of a computerized system for visual hemisphere-specific stimulation (VHSS), "FlashWord" [77]. After 1440 minutes (24 h) of intervention, Lorusso et al. applied only behavioral measures and found that all students with the characteristics of dyslexia, regardless of their sub-type, improved not only in accuracy and fluency as compared to non-impaired controls, but also showed gains in spelling, memory, and general processing speed. Further, the dyslexic students gained 0.33 syllables / second more in reading speed over the same period of time than their non-impaired controls [76]. These extraordinary results suggest that requiring very fast processing of the presented visual stimuli in a targeted brain hemisphere may produce a greater degree of automatisation of the component processes. It is this automatisation of the underlying lexical and sublexical processes that Wolfe and Katzir-Cohen validate as critical influences on fluent reading of connected text in their comprehensive definition of fluency [66].


**4.1** *Citrus* **fruits and (COVID-19)**

The potential significance of diet in the mitigation of coronavirus infection 2019 (COVID-19) has been undervalued so far among the different options. Foods contain usually compounds that may have a health benefit, and some of these chemicals may have antiviral properties and may be useful in altering the immune function and source of antioxidants from the oxidative stress generated by infection [37]. *Citrus* fruits are high in flavanones, vitamin C, and anthocyanins the most abundant of which are naringin and hesperidin, both of which have antioxidant and antiinflammatory qualities [38–40]. Fibers, such as pectin, which is more abundant in the solid section, aid in the regulation of intestinal activities and the prevention of LDL cholesterol absorption. *Citrus* may also be effective in reducing the risk and cure of viral diseases [37].

**Figure 2.**

*Health benefits of* Citrus *and its constituent [27, 33–36].*

#### Citrus*: An Overview of Food Uses and Health Benefits DOI: http://dx.doi.org/10.5772/intechopen.106420*

The revelation that hesperidin possesses a chemical-physical structure that allows it to attach to critical proteins involved in the SARS-CoV-2 virus's activity has piqued scientists' curiosity. At least six investigations returned similar outcomes [41–45].

Wu and collaborators [41] for binding to SARS-CoV-2 proteins, evaluated 1066 natural compounds with the ability of antiviral effects, along with 78 antiviral medicines that have previously been described. The best option for bonding to the "spike" was hesperidin. At the point when the ACE2 — RBD complex is superimposed over the hesperidin — RBD complex, there is critical hesperidin contact with the ACE2 interface, showing that hesperidin may alter ACE2's interaction with RBD. Another thorough molecular docking investigation of the hesperidin-Mpro interaction was published recently [44]. The lowest binding energy (showing the most affinity) was revealed to be rutin (9.55 kcal/mol), followed by hesperidin (9.02 kcal/mol), emetine (9.07 kcal/mol), ritonavir (9.52 kcal/mol), and indinavir (8.84 kcal/mol) in a screening of 33 natural and already known antiviral compounds. THR45, THR25, THR24, CYS145, HIS4, and SER46 are among the amino acids to which hesperidin forms hydrogen bonds. Joshi et al. research provided more evidence [45], who discovered hesperidin as one of the numerous natural compounds that adhere to the primary protease of the SARS-CoV-2 virus. In addition, the viral receptor angiotensin-converting enzyme-2 is involved (ACE-2).

As a powerful antioxidant against superoxide and hydroxyl radicals, hesperidin plays an important role in antioxidant defense mechanisms [46], and hesperetin, a derivative of it, prevents LPS-stimulated microglial cells from producing nitric oxide [47]. Another research found that *Citrus* flavanones, such as naringenin and hesperidin, reversed age-related decreases in superoxide dismutase, catalase, and glutathione reductase in the livers of elderly rats [48]. Coronaviruses are one type of virus that causes the common cold, a condition for which there is no treatment or vaccination. Given the fact that SARS-CoV is a coronavirus, as well as the low cost and high security of fresh foods with high doses of vitamin C, it has been proposed that boosting regular consumption of these foods may be advantageous during the COVID-19 pandemic [49–51]. **Figure 3** shows hesperidin and L-ascorbic acid reduces the cell pattern of the SARS COVID-2 (SARS-CoV-2) infection, as well as the regions of infection, started cell, and fundamental illness (set apart with an "X") [37].

As well as aiding the development of collagen in connective tissue, L-ascorbic acid has antioxidant capacity, and when combined with other minerals, enzymes, and vitamins, can lessen the effects of free radicals. Human vascular smooth muscle cells are considered to be protected by vitamin C from apoptosis by preventing LDL oxidation [52]. *Citrus* fruits may have a substantial impact on COVID-19 therapy, through pathways other than viral replication suppression and antioxidant activity [37]. The numerous biological effects of vitamin C and hesperidin are two core aspects of *Citrus* fruits that appear to be excellent choices for counteracting SARS-CoV-2 cell infiltration and modulating the disease's systemic immuno-pathological stages. The more epidemiological, preclinical, and clinical study is required to verify the concept that a diet rich in *Citrus* fruits or comparable compounds may help COVID-19 prevention efforts [37].

#### **4.2 Antioxidant activity**

The primary source of reactive oxygen species (ROS) is oxygen, in living organisms through a variety of metabolic routes, such as hydroxyl radicals, hydrogen

**Figure 3.** *Hesperidin and vitamin C impact on infected cell cycle [37].*

peroxide, and superoxide anion, while antioxidant systems may combat them to maintain equilibrium [53]. However, contemporary lifestyle variables may increase the number of reactive oxygen species, which play an important role in the development of different diseases, such as inflammation, heart disease, arthritis, aging, and cancer, and produce oxidative stress. *Citrus* extracts, including *Citrus* bergamia juice extracts, karna peel extracts, and *Citrus limetta* peel extracts, have been demonstrated to have antioxidant activity [33, 34]. *Citrus* fruits are said to be high in antioxidants because they contain phenolic compounds with poly-hydroxyl groups, such as flavonoids, phenolic acids, and their derivatives [54]. The following are the major antioxidant mechanisms:


*Article* **An Overview on Solid Waste Generation and Management: Current Status in Chile**

**Romina Cayumil 1, Rita Khanna 2,\*, Yuri Konyukhov 3, Igor Burmistrov 4, Jumat Beisembekovich Kargin 5 and Partha Sarathy Mukherjee 6**

	- 6 Institute of Minerals and Materials Technology (Ret.), Council of Scientific and Industrial Research, Bhubaneshwar 751013, India<EMAIL_ADDRESS>	- **\*** Correspondence<EMAIL_ADDRESS>Tel.: +61-0434155956

**Abstract:** The widespread generation of, ever increasing volumes of and the sustainable management of solid wastes are global issues of great concern. Due to wide variations in composition and associated complexities, significant efforts are required for their collection, processing and environmentally safe disposal in a cost effective manner. An overview of solid wastes is presented in this article with a specific focus on municipal solid wastes and industrial waste from the iron/steelmaking and aluminium industries. Key waste issues such as its sources, compositions, volumes, the factors affecting waste generation and waste processing are first discussed, followed by a further discussion regarding recycling, resource recovery, disposal and the associated environmental impacts. In a special case study, waste generation and management in Chile is presented in greater detail. Detailed information is provided on government initiatives and legislation for integrated solid waste management and its movement towards a circular economy. Measures include regulations on waste management framework which concerns the transboundary movements of hazardous wastes, persistent organic pollutants, the closure of mining activities and installations and restrictions on plastics disposal. With Chile being world's largest producer of copper, significant efforts for mining waste management, its infrastructure and procedures are being put in place to reduce the environmental impact of the mining sector and its associated waste generation.

**Keywords:** solid wastes; MSW; industrial wastes; iron/steel sector; aluminium sector; copper mining

## **1. Introduction**

Solid waste management is a global issue affecting individuals, communities and governments in most countries. Poor and inadequate waste management decisions can affect daily health, cleanliness and productivity, thereby affecting economic development at all levels of society. Some of the issues include the contamination of oceans, flooding, clogged drains, respiratory diseases, airborne particulates, waste consumption by animals and air and land pollution. The growing level of prosperity, rapid urbanization and population growth has led to increases in the per capita generation of waste. In addition, waste management is often administered by local authorities with limited capacity for management, operational monitoring and financial resources. It has been estimated that every year, over a billion tonnes of waste are produced globally. This number continues to rise for most nations with data reported in 2018 at: East Asia and the Pacific (468 MT); Europe

**Citation:** Cayumil, R.; Khanna, R.; Konyukhov, Y.; Burmistrov, I.; Kargin, J.B.; Mukherjee, P.S. An Overview on Solid Waste Generation and Management: Current Status in Chile. *Sustainability* **2021**, *13*, 11644. https:// doi.org/10.3390/su132111644

Academic Editor: Vincenzo Torretta

Received: 14 September 2021 Accepted: 12 October 2021 Published: 21 October 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

and Central Asia (392 MT); South Asia (334 MT); North America (289 MT); Latin America (231 MT); Sub-Saharan Africa (174 MT) and Middle east and North Africa (129 MT) [1,2]. Unless urgent action is taken on several waste management fronts, global waste generation rates may increase to 20 billion tonnes/year by 2050.

Due to the wide variation in waste composition and characteristics, different types of solid wastes can be classified as: Municipal Solid Waste (MSW), Industrial Waste (IW), Agricultural Waste (AW), Construction and Demolition Waste (C&DW), Hazardous Waste, Medical Waste and Electronic Waste (e-waste). The world-bank has reported that highincome countries, with a population of 16% of globe inhabitants, produce approximately 34% of the planet's waste [3]. Table 1 summarizes the amount of different wastes generated per capita per day worldwide. The largest quantities of wastes were found to be industrial types of waste (12.73 kg), followed by agricultural waste (3.35 kg). Further, there was an estimated 1.68 kg of C&D waste, 0.74 kg of MSW produced globally, followed by 0.32 kg of hazardous waste, 0.25 kg of medical waste, and 0.02 kg of e-waste [4].

**Table 1.** Global generation of various wastes.

Through a focus on solid waste generation and management, this article is organized as follows: an overview of different types of wastes is presented in Section 2 along with detailed statistics on two major solid wastes, namely, municipal solid waste and industrial waste from key metal processing industries. The complexities associated with these wastes including their composition, generation, collection, volumes, recycling methods, disposal and environmental impact will be discussed in the global scenario. Section 3 focusses on the practical realities of solid waste management in Chile, serving as a representative example. With a population of over 18 million and a total area 756,000 km2, this South American country borders the South Pacific Ocean to the west with a coastline of over 6000 km long. Around 90% of the population lives in urban areas, primarily in the metropolitan area of Greater Santiago. Chile is among Latin America's fastest-growing economies in recent decades, enabling the country to significantly reduce poverty. Chile is gradually moving to a circular economy through legislation, long-term plans and the provision of funds from public and private entities and has demonstrated a financial implementation of these objectives.

#### **2. Generation, Management and Disposal of Solid Wastes: A global Overview**

#### *2.1. Municipal Solid Waste (MSW)*

#### 2.1.1. Sources and Composition

Municipal solid waste represents the typical waste generated by households, offices, commercial shops, hotels, schools and other institutions. The major contributors are food waste, paper, plastics, metal, yard waste, cardboard and packing waste glass. It can also include some demolition and construction debris along with small amounts of hazardous and chemical waste, e.g., electric light bulbs, batteries, automotive parts, discarded medicines and chemicals. An overview of the typical sources of MSW and its constituents are given in Table 2 [5].

**Table 2.** Typical sources and compositions of MSW.

 In middle- and lowincome countries, organic waste accounts for more than 50% of the total MSW generated. In high income countries, this percentage reaches 32%, approximately. Recyclable materials range from 10% in low income countries and up to 50% in high income countries. Recovery and recycling of wastepaper has seen a significant increase among the recyclables over time. In high-income countries, one third of the total amount of waste produced is presently recycled or composted [7]. Table 3 summarizes the generation of MSW for different global regions along with projected increases by 2050.

**Table 3.** Generation of MSW by region (2016), and their projection by 2050 [3].

In 2016, the largest amounts of MSW were generated in the East Asia and Pacific Region, with the region generating 468 million tonnes, representing 23% of the total amount of MSW. Waste generation from Sub-Saharan Africa is expected to increase three times by 2050, reaching 516 million tonnes, followed by South Asia with 661 million tonnes by 2050, doubling on the 334 million tonnes produced in 2016. The Middle East and North Africa region will also double their waste by 2050, with an estimated amount of 255 million tonnes.  Factors Influencing MSW Generation

Several factors that affect the volume of MSW that is generated includes population growth, income levels, immigration, industrial and economic development. While population growth is considered to be a critical factor influencing MSW generation [8], EPA has also highlighted income and tax revenue as key factors; electricity consumption was

another compelling factor [9,10]. Sukholthaman et al. found that MSW generation tended to increase with increasing levels of gross domestic product (GDP) and the consumer purchase index [11]. Liu et al. have reported on the impact of consumption patterns on the generation of MSW in China [12]. These researchers investigated the impact of economic development and consumption levels on MSW generation. The highest levels of MSW generation were found to exist in medium to low economic consumption groups. Developing regions with large development potential had fast economic growth rates and generated more MSW compared with developed regions with marginal growth in MSW generation. These findings have been summarized in Table 4 [13].

**Table 4.** Typical factors influencing MSW generation.

#### 2.1.3. Waste Collection and Disposal

In urban areas, MSW collection and transport involves its storage at the generation source and at pick-up points, its collection by crews/trucks driving around the neighbourhood and finally its transport to a disposal station. The collection of MSW is difficult, complex and costly, accounting for up to 60-80% of the total solid waste budget of a typical community. In residential areas, the most common collection methods are via the kerb, an alley or through backyard carry. In a kerb or alley service, the residents carry plastic bags and/or containers to the kerb or collection point and collect the empty container at a later point. The collection of MSW occurs once or twice per week in most communities. Wang et al. have reported on the rural solid waste management in China, observing that the rural solid waste collection services, facilities and equipment were often of a lower quality [14]. High costs and the inconsistent employment of waste collection workers were found to be unsustainable, and hindered the overall quality of waste collection services [15].

The various materials are separated either by the users at the source or separated from the mixed refuse at a central processing facility. Material separation at the source involves separating the material into different components followed by their transportation. Waste separation at the source is carried out by using separate bins for the biodegradable fraction and the recyclables and hazardous waste materials. The active household response for waste separation has generally been quite poor. The separation of material in MSW usually occurs at a central facility. The organic material is shredded and processed through air classifiers, which separate the desired components for further processing and recycling and for classification as a material or an energy resource. For handpicking, a conveyor moves the solid waste along a group of workers who collect a few of the larger components by hand. A mechanized material recovery method utilizes shearers to break open the bags and trammel screens to separate cans, glass and other inorganic material. Magnetic and electromechanical systems are used for separating ferrous and non-ferrous metals.

An overview of waste disposal methods in the USA is shown in Figure 1 [16]. It is estimated that 75–80% of total MSW generated is collected and only 22–28% is processed and treated. A significant proportion of the collected waste is often dumped indiscriminately, clogging the drains and sewer systems [17]. Additionally, due to imperfect waste infrastructure and recycling systems, the recycling rates of MSW in developing provinces are low. All these factors suggest the generation of large MSW volumes in the near future in developing provinces. In contrast, the developed regions have a stable economic development rate and high recycling efficiency rates of MSW. From the perspective of waste clearance volumes, the developed regions will generate less MSW than developing provinces in the near future [18].

**Figure 1.** An overview of MSW disposal and treatment in the USA.

#### *2.2. Industrial Waste*

Industrial activities such as manufacturing processes, mining operations, construction, demolition and the operation of factories produce waste products in the form of materials that have been rendered useless and are no longer required. Industrial wastes include masonry and concrete, dirt and gravel, scrap metal, chemicals, oil, solvents and scrap lumber. Industrial waste can either be solid, semi-solid or liquid in form; they may be hazardous and toxic or may be a non-hazardous waste. Hazardous wastes include, among others explosive wastes, flammable solid wastes, wastes liable to spontaneous combustion, wastes that emit flammable gases on contact with water, oxidising wastes, organic peroxide wastes, infectious wastes and corrosive wastes. [19]. Industrial waste is sometime mixed into municipal waste, making the conduction of accurate assessments difficult. Such waste can pollute the adjacent soil or water bodies thereby contaminating groundwater, rivers or coastal waters [20]. An estimated 7.6 billion tonnes of industrial waste was produced in the USA in 2017. In this overview, we focus our attention on the leading metal processing industries, namely the iron and steelmaking sector and the aluminium industry and the associated waste management.

#### 2.2.1. Iron and Steelmaking Sector

With the ability to adapt to changing conditions regarding raw material availability, energy resources and hot metal demands, ironmaking technology has achieved a high degree of excellence. New challenges, especially with respect to the environment and CO2 emissions, are the main drivers for technological progress in the 21st century. Steel consumption worldwide is increasing steadily, as is its impact on the environment through energy consumption. Steel provides a key input for other industrial sectors that produce

items essential to the functioning of the wider economy, e.g., automobiles, trains, aircrafts, hand tools, complex factory machinery and countless other items.

The industry is continuing to expand, with the application advanced high–strength steels for transport systems, bridges, pylons, construction sector, infrastructure, housing, manufacturing, agriculture and energy [21]. As a permanent material that can be continuously recycled without losing its properties, steel is fundamental to a successful circular economy. The steel industry amounts for 10.7% of national GDP in the USA. Furthermore, China accounts for 31% of steel's value-added contribution, with the USA and Japan accounting for 11% and 10% respectively [22]. The global steel production in 2020 is shown in Table 5, along with the production levels of the top five countries.

**Table 5.** Global steel production (in million tonnes) in 2020. Contributions from the top five steel producing countries are shown.

During the process of ironmaking, the iron ore is converted into different types of iron through several processes (Figure 2). The blast furnace is the most commonly used process and produces pig iron which composed of around 92-94% of iron and 3-5% of carbon along with smaller amounts of other elements. However, pig iron has limited uses, and most of this iron arrives at steel mills, where it is converted into various steel alloys by reducing the carbon content and adding other alloying elements to acquire steel specific properties. Steelmaking uses both recycled materials as well as pig iron from the blast furnace.

**Figure 2.** A schematic representation of iron and steelmaking processes.

This industry focuses on reducing raw material consumption and reusing the waste produced in various iron/steelmaking operations. In the 1970/1980s, modern steel plants generally required 1.44 tonnes of raw material to produce 1 tonne of steel; this number has been reduced to ~1.15 tonne of inputs to make 1 tonne of steel as of 2020, thereby achieving a 21%reduction. However, more than a billion tonnes of waste was produced by the iron and steel sector in 2020, largely due to a significant increase in overall steel production. A brief overview of major solid waste products produced during various iron/steel production processes is provided along with techniques used for their disposal in the next section [23–27].

**Coke making—**These wastes include coal dust, coke dust, tar sludge and acid sludge. Coal dust is recycled through the coal blend and/or by its addition to the sinter charge mix. Tar sludge is added to the coal blend to improve its density. Acid sludge has to be neutralized before its disposal.

**Sinter making—**The solid wastes generated are dusts and sludges. Dusts are generated at the sinter machine building's floors, in cyclones and the ESP (Electrostatic precipitator). Sludge is generated at the clarifier of the water treatment plant. These materials are recycled back into sinter making, either by blending them with iron ore fines or briquetting.

**Pellet plant—**The major wastes here are dusts and undersized green pellets. These wastes are generally reused as pellet feed materials.

**Blast furnace iron making (BF)—**The generated wastes include dusts, burden screenings at the stock house, cast house runner jams, cast house muck, blast furnace slag, flue dust, sludge, refractory waste and hot metal ladle skulls. Dusts and burden screenings are recycled into sinter making by blending them with the iron ore fines in the raw material yard or by being briquetted. Cast house runner jams are either sold as iron scrap for re-melting or recycled in the steel melting shop. Cast house muck is dumped as land-fill material. The air-cooled BF slag is either dumped at landfills or used for road repairs within the steel plant. Refractory waste is reused by the refractory manufacturer in the manufacture of mortars.

**Iron making by direct reduction (DRI)—**The main solid wastes are char, dusts (both coal and iron) and under sized and reject DRIs. Coal dusts and chars are used in the power plants as fuel for the boiler. Iron dust can also be sold to the cement manufacturers. Under-sized DRIs are briquetted and used in a steel melting shop; DRI rejects are recycled back into the process.

**Basic oxygen steel making (BOS)**—The main solid wastes include converter slag, scrap, waste refractories, converter muck and gas cleaning plant sludge. Most of these waste materials are produced in a mixed condition, therefore extensive sorting is required prior to their recycling. The plant sludge is dried and blended with the iron ore fines as raw material and are briquetted and reused in sinter making. The converter slag is recycled as a replacement for limestone in the sinter mix. The converter slag can also be used in road repairs, as railway track ballast and as soil conditioner. Scrap and refractory wastes from the converter muck are removed and a balance is used for landfill. There are two types of refractory wastes: magnesium carbon refractories from converter linings, and the other types are from refractory ladles. Alumina based refractory wastes can be used for manufacturing mortars.

**Electric Arc Furnace (EAF) steel making**—The typical waste products include GCP dust, slag, scrap and waste refractories. Presently, there is not a well-established method for recycling EAF slag. The grinding and processing of EAF is energy intensive due to its high iron oxide content. It has been used for making roads and ceramic tiles.

Other solid waste contributions come from continuous casting, rolling mills and lime calcining, which primarily includes casting scales, refractory scrap, slag, muck, mill scale, limestone and dolomite screenings, lime dust and lime fines.

#### 2.2.2. Aluminium Sector

Currently, aluminium (Al) is the second most widely used metal in the world. To meet the needs and challenges of the 21st century, the production of Al has increased form 1000 tonnes in 1900s to 58 million tonnes in 2016. Being strong, lightweight and durable, Al is increasingly used in the transport sector towards the aim of a partial replacement of steel, which is heavier. A high strength-to-weight ratio means it is particularly useful as a structural material, weighing around 65% less than steel. Lightweight Al also contributes

to an increased fuel economy in vehicles from cars to armored tanks. Aluminium is extremely important for the aviation sector, e.g., Airbus A380 uses up to 66%Al in its airframe and a Boeing 747 can use up to 75 tonnes of Al. There is a significant usage of Al in the shipping sector including in military applications, in building and construction, for domes for gymnasiums, schools, storage facilities, industrial roof systems, multi-purpose arenas, packaging, aluminium cans, food containers, wrapping foils, etc. [28]. The global production of aluminium is summarized in Table 6 [29].

**Table 6.** Global aluminium production (in thousand tonnes) in 2019. Contributions from the top five aluminium producing countries are shown.

Bauxite is a key aluminium ore containing ~30–54% alumina (Al2O3) along with mixtures of silica, iron oxides, titanium dioxide and several impurities. Around 95% of Al is produced from bauxite ore using the Bayer's process worldwide. In the Bayer process, bauxite is washed in a hot solution of sodium hydroxide, which leaches Al in the form of Al(OH)3; it is later calcined to form Al2O3. Red mud (RM), also known as bauxite residue, is a solid waste biproduct of the alumina recovery process. Producing one tonne of alumina consumes up to 2–3 tonnes of bauxite and generates ~0.4–2 tonnes of RM depending on the source/location of the ore; the global average of RM produced is 1.3 tonnes per tonne of alumina [30,31].

Global bauxite resources are estimated to be ~55 to 75 billion tonnes with reserves in Africa (32%), Oceania (23%), South America and the Caribbean (21%) and Asia (18%). With the production of primary aluminium increasing to 47 million tonnes, an estimated 150 million tonnes of RM are being produced in various aluminium plants across the world [32]. The nearly 3 billion tonnes of RM, presently stored in vast waste reserves, represents large industrial waste scenarios around the globe [33]. Several red mud incidents in different countries have also been tabulated in various publications [34].

The Hall–Héroult process is the main process used for smelting aluminium, and involves dissolving alumina in molten cryolite, and electrolyzing the molten salt bath in a purpose-built cell. The electrolysis takes place at 940–980 ◦C and produces 99.5–99.8% pure aluminium [35,36]. An aluminium smelter produces 40–60 kg of mixed solid wastes per tonne of product, with spent cathodes, spent pot, cell linings comprising the major fraction of waste. The linings consist of 50% refractory material and 50% of carbon. Over the useful life of the linings, the carbon becomes impregnated with aluminium and silicon oxides (averaging 16% of the carbon lining), fluorides (34% of the lining), and cyanide compounds (about 400 ppm). The contamination levels in the refractories element of failed linings are generally low. The other by-products for disposal include skim, dross, fluxing slags, and road sweepings [37–39].

Extensive efforts have been made to process, recycle and reutilize red mud waste. Key challenges in processing RM include high alkalinity (pH: 10–13), small particle sizes (≤75 μm), large volumes and high transportation costs [40,41]. Landfilling and dumping around the industrial plants have been the standard practice worldwide. Vast amounts of stockpiled RM can also be toxic and very hazardous [42]. Deep sea dumping and storage in ponds has also been attempted. Poorly designed storage dams are likely to fail under certain circumstances, resulting in local and environmental contamination. Many efforts are being made to find economically viable and environmentally sustainable solutions to the RM problem. However, most options can only accommodate for a small fraction of the red mud generated globally [43].

The recycling of aluminium requires only 5% of the energy necessary to smelt it from the alumina and a small fraction of greenhouse gases are emitted during aluminium recycling compared with the production of primary aluminium. Properly treated and sorted aluminium scrap can be used to produce different types of goods at low cost given that these scraps already contain some of the alloying elements required for certain applications. Aluminium recycling plants can be found all over the world, but are significant concentrated in Europe, the USA and Japan [44,45].

#### **3. Waste Management in Chile: Current Status**

Chile is gradually moving toward a Circular Economy (CE) system. The evolution towards sustainable development and CE is taking place in conjunction with legislation, long-term plans and funds, support and financial implementation from public and private entities. The current national situation regarding waste management and the new *Waste Management Framework* has encouraged the processing of copper mining tailings and prohibited the commercial use of plastic bags. While Chile has a wide variety of resources, mineral resources are the most valuable in economic terms as the national economy is, to a great extent, driven by the mining sector. A wide variety of wastes are generated by the diverse industries in the country. National laws classify waste residues depending on their nature as hazardous waste or non-hazardous waste. The non-hazardous waste is further categorized into industrial waste (IW), municipal solid waste (MSW) and sewage sludge (SS). According to the Chilean Ministry of the Environment, 19.6 million tonnes of total waste were generated in 2018, 97.3% of which were non-hazardous waste. These figures do not include radioactive residues, gangue, low grade minerals, leaching gravel, tailings or slags produced in mineral processing. [46].

This section presents the current status of waste management in Chile and the initiatives towards a more sustainable economy. Waste management activities, waste characterization, regulatory measures, challenges and opportunities and initiatives towards a circular economy will be discussed.

#### *3.1. Waste Management: Legislations and Regulations*

All countries need to develop a common criteria for the environmental management of waste residues, technical guidelines, regulations with respect to environmental requirements, a holistic management criteria for the minimization of waste generation, and their application during the productive cycle towards clean technologies and circular economy [47]. Chile is a signatory to several international conventions and agreements on waste management and sustainable development. Some of the efforts made by Chile include:

Chile is a member of the OECD, United Nations and The Southern Common Market (MERCOSUR for its Spanish abbreviation), all committed to promote sustainable development. Chile has also subscribed to the Basel Convention as well as to the Stockholm's agreement. Basel Convention establishes mandatory actions for hazardous waste management and appropriate disposal as well as legislation for transboundary movement of waste [48]. The Stockholm convention provides an agreement to protect both human health and the environment from harmful persistent organic pollutants (POP's) [49]. Chile is devoted to eliminating or minimizing the release of POP's to the soil, water and air [50].

The Latin American *"Agreement of Environmental Management of Special Residues and After Use Responsibility"* (Acuerdo de Gestión Ambiental de Residuos Especiales y Responsabilidad Post Consumo), signed during the fourth extraordinary meeting of MERCOSUR's Ministries of the Environment, established the commitment to incorporating production patterns and sustainable consumption, with the objective of minimizing the quantity and harmfulness of waste generated [51]. This agreement also established the term "*special residues of universal generation waste*" based on their environmental impact, hazardous characteristics, risks or potential harmful damage to the environment; such wastes require special environmental management and need to be separated from other residues. Universal wastes include hazardous wastes produced by the households and several businesses including televisions, computers and various electronic devices, batteries, fluorescent lamps, mercury thermostats, mercury containing equipment.

The policy of integrated solid waste management was promulgated in 2005 with the objective to ascertain that all activities related to the management of solid wastes should be carried out with minimal risks for human health and the environment. The following regulatory procedures have been developed for managing and for the disposal of hazardous electronic waste: Law 19,300 provides the *general basis for the environment* [52]; the Basel Convention concerns the transboundary movement of hazardous waste and its elimination; Law 20,920 concerns *Waste Management Framework, Extended Producer Responsibility (EPR)* law [53]; and *promotion for the recycling law, sanitary standard DS 148*, provides regulations for recycling funds [54], among others.

#### *3.2. Waste Management Initiatives*

The Chilean government has undertaken several campaigns to increase awareness about recycling. The plan "*Santiago recycles"* began in 2017, and is believed to be one of the most ambitious projects concerning reuse in the country. With a budget of ~5 million euros, the aims of the project were to educate people, build waste management facilities and to make Santiago a more sustainable city [55]. The implementation of the *Waste Management Framework* has provided formal pathways to the producers of lubricants, electric and electronic equipment, batteries, packaging, and rubber tires on their management during the manufacturing process, commercialization, and at their end-of-life, encouraging their use as a resource elsewhere. Extended producer responsibility (EPR) has increased activities to appropriately manage and process these types of wastes. A number of private entities have started businesses for collection and storage, while other companies use these components as B grade raw materials for reuse while minimizing the environmental impact [56].

To avoid the contamination of land and the ocean, a law was approved in 2018 prohibiting the commercial use of plastic bags in the whole territory, with Chile being the first country in Latin America that prohibits plastics use. In 2019, the campaign to reduce single use plastics was launched, particularly plastic straws, and also a campaign to avoid cigarette butts being disposed of in public spaces and/or directly in the soil. The creation of the Circular Economy Office in the Ministry of the Environment was the result of all the actions adopted in waste minimization, management, valorization and recycling [57]. These measures, however, did not include the waste produced by the mining industry. Two key wastes, namely MSW and mining waste, will be discussed in the following sections.

#### *3.3. Municipal and Industrial Wastes*

Chile, considered a relatively high-income country, has a population of ~19 million inhabitants. The average generation of MSW per day per capita in Chile is about 1.15 kg, slightly higher than the world's average of 0.74 kg waste per capita [58]. Of the overall amount of MSW produced, 44.9% of MSW was generated in the metropolitan region of Santiago, the capital city of Chile which is home to 41.1% of the country's population. Considerably lower levels of MSW were produced by the Valparaíso, Bío-Bío and Coquimbo regions, accounting for 10.6%, 9.3% and 5.2%, respectively. Approximately 8 million tonnes of MSW is generated in Chile every year; the waste collection rate is almost 100%; the volume of waste rose by 30% during the period 2000–2010.

Household waste is generally collected door-to-door in plastic bags, whereas recyclables are primarily collected at central collection points equipped with containers. Kerb-side collection is still quite limited, with household waste collected on the kerb-side and then transferred into the rear of a compactor truck [59]. The overall efficiency and cost effectiveness is limited as not all citizens are regularly serviced, leading to negative impacts on the environment and the society. The waste is mainly composed of food and green waste, which accounts for 58% of the total waste generated. The remaining waste includes dry recyclables, paper and cardboard (13%), plastics (12%), glass (4%), metal (3%), and up to 15% of organic waste. Approximately 50% of the waste is disposed in sanitary landfills, however, the use of open dumps account for ~27% of disposal and processing. A further 15% of the MSW is transferred to controlled landfills. The normal collection system transports all the mixed waste to a transfer station or to a landfill [60].

Because they comprise a relatively small fraction of the overall waste, hazardous waste, medical waste and e-waste are generally disposed of along with MSW. Only 5% of the MSW is sent to recycling facilities and less than 1% waste is composted due to limited material separation. Recycling and composting are still emerging treatments and the extent of their usage varies significantly across the country. A new strategy proposes recycling up to 66% of organic waste by 2040, by reducing the level of organic waste produced encouraging its separation in houses, offices, schools and markets, and through the use of infrastructure, equipment and logistic systems that allow the organic residues to be used as a resource in the production of soil enhancers and electric or thermal energy [61,62].

Several methods and recovery systems are currently used in Santiago for recycling the organic fraction of MSW. These include sorted collection at source, separation at source for drop-off collection and sanitary landfills. [63]. Sorting prior to collection at the source involves the sorting of recyclables at home before collection by a municipal service or by informal collectors.  Informal collectors, numbering in excess of 60,000 collect around 2-10 tonnes/month/person of recyclables, and account for ~76% of the total recyclables collected [64]. Project Santiago Recycles introduced the separation of recyclables at the origin for their drop-off collection at solitary bell-shaped container stations associated with charity institutions, and 'clean point' stations with a larger drop-off area for containers of different types of recyclable waste. Recycled waste collected at the largest clean point in Santiago experienced a156% increase between 2009 and 2014. In 2009, there were three sanitary landfills in Santiago and two transfer stations; several dumpsites have been closed in the metropolitan region.

Among the key productive sectors of the Chilean economy are the manufacturing industry, electricity, gas and water supply, livestock industry, agriculture, mining, the wood industry and the fishing industry. As reported by the 'Ministry of Environment' 10.5 million tonnes of non-hazardous industrial waste was generated in 2018 representing ~50% of the total waste produced. The manufacturing industry was the largest waste producer, producing 4.2 million tonnes, followed by the electricity, gas and water supply industry which produced 2.2 million tonnes. The construction industry, real-estate activity sector and commerce respectively produced 0.67, 0.67 and 0.61 million tonnes of waste. The agriculture, livestock, hunting and forestry sectors produced total of 0.61 million tonnes of waste. Smaller amounts of waste were generated by the fishing, small mine & pit, transport, storage & communication sectors, which produced 0.48, 3.61 and 0.3 million tonnes, respectively. A further 0.2 million tonnes of waste were produced by other sectors. Regarding sewage sludge, a 57.8% was generated in the metropolitan Santiago area, which amounted to 198,000 tonnes in 2018. The amount of hazardous waste increased considerably between 2006 and 2018 from 26,840 tonnes (in 2006) to 612,427 tonnes (in 2018) [46,65,66]. This waste was mainly produced in the Antofagasta region, and the Metropolitan region. The large amounts generated in the Antofagasta region, located in the north of Chile, can be attributed to mining activities and other associated services.

#### *3.4. Copper Mining Waste*

#### 3.4.1. General Information

Chile is the world's largest producer of copper, with high-quality mineral resources located in northern Chile which has resulted in the installation of mineral processing plants over the last century (see Table 7). The copper mining industry is Chile's main economic sector, contributing to 11% of its GDP during last 10 years. Copper and its associated by-product exports represent the biggest revenue source for the country [67]. Copper production, however, produces millions of tonnes of waste; mining is generally considered as highly contaminating and unsustainable. Several measures have been implemented to optimize processes, dispose residues in an appropriate and safe manner, and to develop valorization processes.

Legislative regulations are essential to establish the responsibilities and duties of mining companies, through an exploratory and exploitative concession. Laws such as '*Closure of Mining Activities and Installations'* (Law 20.551) provide protection to the environment and to the population, as well as the mitigation of negative effects generated during the mine's lifespan and its closure [68]. Rule D28, which has been operational since December 2018, establishes the maximum permitted emissions of SO2, arsenic, mercury and particulate matter for copper foundries. They are required to capture more than 95% of these particulate emissions [69]. The program "Alta Ley" was created by *Fundación Chile*, a non-profit organization to co-ordinate the framework of these improvements. The program developed a technological road map called 'From Copper to Innovation' which reports areas of work focused on correcting, renewing and improving the mining industry. The most important challenges include ore grades, water resources, energy resources, waste generation, gas and fine dust emissions, among others [70].

**Table 7.** Global copper mining (in million tonnes) in 2020; contributions from top five copper mining countries are shown [71].

#### 3.4.2. Typical Mining Wastes

Several types of wastes are produced during mining depending on the type of mineral exploited and its processing route. Mine waste, low grade ores and gangue represent the largest volumes of solid residues produced by the Chilean copper mining industry. Several million tonnes of soil must be removed to process valuable minerals/ores. For example, in an open pit operation, up to 500 tonnes of material may need to be removed for each tonne of copper produced. However, most of these wastes are inert materials and rocks with little environmental impact. Only a small fraction (up to 1%) may require specialist disposal. The physical stability of mining and metallurgical wastes plays a crucial role in their impact on the environmental. The chemical aspects and mineralogical composition of ores and mining waste determine the chemical stability, degradation and associated environmental impact.

A schematic representation of copper extraction routes from oxide and sulfide ores is provided in Figure 3.

**Figure 3.** A schematic representation of copper extraction routes for oxide and sulfide ores [72].

A few of the focal waste sources are provided in the next section. Low grade ores are sometimes dumped separately for processing at a later stage. Metal dissolution, acid generation, bacterial leaching and effluents can lead to environmental issues at the dump sites. Froth flotation is a method that is used to concentrate copper sulfide ores by fine grinding the ore and the separation of the gangue. This process generates large amounts of tailings containing the gangue minerals and a portion of sulfides (mainly pyrite). The tailings are characterized by fine grained minerals, with a high water fraction and a high pH value. Abandoned tailing ponds constitute very serious environmental challenges. These are solid wastes produced after the flotation process, which are milled and have a fine particle size. Approximately 98% of the rock that is finely milled is disposed of, and only 2% of the rock contains copper [73]. With ore grades becoming poorer, higher volumes of rock must be removed to maintain production levels. This means that larger quantities of material will be disposed of, either as gangue or tailings. It has been estimated that copper tailings will double in size by 2035 [74]. Tailings are one of the biggest solid residues generated during the processing of copper minerals. It has been estimated that 60 to 100 tonnes of tailings are generated per 1 tonne of copper produced. The latest studies indicate that the cumulative volumes of tailings would reach ~7,900Mm3 with a total mass of ~10,600Mt, corresponding to 742 deposits in the country. Out of 742 deposits, 104 are active, 463 inactive and 173 have been abandoned [75]. The various metallurgical wastes produced during copper processing include spent leached ore, slags, pyrometallurgical dust and gas cleaning residues. The high temperature processing of copper concentrates involves smelting, converting and refining. During these stages, slags are produced and represent the largest volumes of residues generated, with 2 to 5 tonnes of slags per 1 tonne of copper produced. Less than 1 ton of SO2 is also formed as a gaseous biproduct [76].

#### 3.4.3. Waste Disposal and Environmental Initiatives

As the mining industry represents the major activity in the country and generates huge amounts of residues, several measures have been taken to improve its waste and resource management. Regarding tailings generation, conventional tailings represent potential water losses and/or evaporation which is a serious issue for their appropriate disposal and management. The disposal of thickened tailings has three clear advantages, namely, good water recovery, low percolation and low fine-dust emissions. The rules pertaining to the disposal of thickened tailings have been established as per the '*Closure of Mining Activities and Installations'* law [77]. An increase in tailings generation will generate significant physical, chemical and territorial storage issues. A study in the Coquimbo region of three types of industries, i.e., mining, wastewater treatment and agriculture found that their associated wastes can cause sludges and dam sediments to encapsulate and neutralize tailings, thereby reducing the environmental impact of their storage [78].

A few accidents have occurred due to the relative instability of tailing dams. The risks are associated with the breaking off of the tailing retaining wall followed by land floods. This can occur as a result of natural events or operational design issues. In Chile, the latest risk event occurred in the 1960's when a tailing dam collapsed. It is important to assess the percolation and environmental impact of the tailing dams. These can cause harmful effects on health, water and soil. The law requires that tailings be managed in a way that they are physically and chemically stable once disposed of, and as such control is a highly important factor in preventing risks associated with natural disasters.

With regard to slags, two processing plants for slags have been built by CODELCO, one is located in El Teniente division and the other in El Salvador. These are floatation plants that recover copper and generate filtered tailings. There has also been some research on slag treatments. Investigations have confirmed the presence of Fe-C-Cu alloys and precious metals, which could be processed further to recover metals. Additionally, inert slags could be used for cement production. It has also been possible to recover iron and molybdenum from copper slags by selective reduction due to their chemical affinities [79–81]. All these byproducts are being studied and used as construction materials; chemical and physical

studies have demonstrated that that have similar characteristics to the materials used in the construction industry. This is a clear example of a circular economy, as the residues produced in one industry could provide the raw material needed for a different industry, thereby enhancing the pyrometallurgical capacity in the region as well as expertise in the mining field [47].

#### *3.5. Other Solid Wastes—Electronic Waste, Plastics*

In addition to the consistent efforts to improve waste management for MSW and in the mining sector, Chile has made significant improvements in managing other wastes as well. Chile is the second biggest producer of electronic waste (e-waste) in Latin America, producing 8.9 kg of e-waste per capita per year [82]. The highest e-waste producers in Latin America are Brazil and Mexico, generating 1.5 and 1 Mtons, respectively; Chile is estimated to have produce ~200,000 tonnes of e-waste in 2018 [83]. Although this amount is much lower than the amounts produced by Brazil and Mexico, Uruguay and Chile were among highest e-waste producers per inhabitant in 2016, generating 10.8 and 8.7 kg per capita, respectively. While the typical annual growth worldwide is 3–4%, the estimated growth of e-waste in Latin America in 2018, was 5%. One of the key factors contributing to a high e-waste generation in Chile is directly related to the GDP rise during previous years. In 2012, the per capita income in Chile was 18,354 USD as compared to 1, 292 USD in Haiti. Higher income levels lead to a higher acquisition of electronic goods and the consequent generation of e-waste [84].

A typical recycling chain for e-waste consists of four steps: collection, dismantling, mechanical/physical processing and metallurgical processing [85]. Chile has developed an urban mining sector with a focus on the first two stages of the chain, i.e., collection and disassembly. The valuable components of e-waste, such as printed circuit boards (PCBs), are currently sent overseas where the material is processed. Any plastics separated from the e-waste are formally processed in the country. Some initiatives are currently being developed to implement the recovery of metals from PCBs locally. The validation of a high temperature pyrolysis process is currently being pursued through a collaboration between the Chilenter Foundation and Universidad Andrés Bello [86–88]. The purpose of this project is to concentrate valuable metals into a reduced fraction, while other components are retained as a non-metallic fraction to be used as a raw material for purposes such as carbon and energy resource. Chile has the potential of recovering valuable metals from e-waste as it has the largest pyrometallurgical capacity in the region, as well as expertise in the mining field [47].

As Chile consumes large amounts of plastic products, waste plastics are recycled at a considerable rate in the country. As a priority product considered in the *Waste Management Framework*, if packaging is created using plastic, then the extended producer responsibility plays an important role in controlling the type and quantity of plastic being used for fabrication and its subsequent disposal. Another important measure promoted by the Chilean government is to prohibit the commercial use of plastic bags in the whole of its territory, making Chile the first country in Latin America to prohibit their use [89]. Action has been taken to avoid the contamination of the land and especially the ocean across the whole country. It is important to mention that Chile has 4,300 km of coast. The Government has also launched a campaign to reduce the use of plastic straws, which has increased awareness regarding environmental impact of single-use plastics and has therefore minimized their use, either by avoiding them or by replacing them with glass or steel straws.

#### **4. Concluding Remarks**

An in-depth overview has been presented on solid waste management in relation to the global scenario, and a further special report on waste management in Chile has been presented. Given the wide variety of wastes being produced, there is no single method to manage all wastes. For example, one of the major issues in managing MSW is its collection from various households, offices and institutes, and its transportation to central processing areas. This feature represents one of the costliest aspects of waste management operations. Biodegradable organic wastes, inert wastes and the mixed nature of waste and their sorting presents additional challenges. The collection of waste is not a major issue for industrial wastes as most of it is produced locally at industrial sites. However, large volumes and relatively inert wastes, some of which may be hazardous, poses a major challenge. Through various related government projects and legislation, Chile is making very sincere multipronged efforts to manage wastes produced by its population, its industries and the mining sector. Continuous sustained efforts, an education of its populace, an awareness of waste hazards and the creation of waste management infrastructures provides the solution for sustainable waste management, the recovery of resources and a circular economy.

**Author Contributions:** Conceptualization, original draft: R.C. and R.K.; Supervision and resources: Y.K., I.B.; Formal analysis: J.B.K. and P.S.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


**2. Principles of erythrocyte morphology**

Circulating red cells are formed from bone marrow stem cells. Stem cells are pluripotent; they self-replicate and differentiate to specialized cells in circulation through different lineages. Red cells are formed from the myeloid stem cell lineage (colony forming unit—granulocytes, erythroid, myeloid and megakaryocytes). The earliest recognizable red cell precursor in the bone marrow is the pronormoblast. The pronormoblast undergoes series of maturation to become the orthochromatic normoblast. Upon extrusion of its nucleus, the late normoblast becomes the shift reticulocytes, which is released into the circulation. Finally, DNA remnants and other chromatin materials in the reticulocytes is removed by the pitting action of the spleen, hence the mature red cells.

Erythrocytes cannot be seen with the naked eyes. Typically, morphology of red cells is performed on peripheral blood smears, once there is an indication. Erythrocyte morphology is either indicated by a clinical request or laboratory flags. Examples of clinical indications for peripheral blood film/erythrocyte morphology are listed in **Table 1**.

Erythrocyte morphology may also be indicated when significant deviations from the normal are seen in the laboratory during blood work (full blood count) irrespective of a clinical request. For instance, a significantly reduced haemoglobin level with low MCV and raised RDW may suggest iron deficiency anaemia. This is an indication for red cell morphology and other ancillary investigation for iron deficiency.

Blood for peripheral blood film is collected through venipuncture. Anticoagulant of choice is the potassium EDTA. Specimens should be analysed as

**9**

*Erythrocyte Morphology and Its Disorders DOI: http://dx.doi.org/10.5772/intechopen.86112*

Cytoplasm with RNA and nuclear Remnants (e.g. polychromasia, basophilic stippling's)

**Table 2.**

**Cell component Colour** Chromatin (including H-J bodies) Purple

Mature red cells Pink

*Romanowsky staining characteristics of red cell components.*

tion, preferably in the first hour.

**3. Red cell morphologic disorders**

soon as possible, preferably within 2 hours of blood collection. Samples not analysed immediately should be stored at 2–6°C in a refrigerator, or the blood smear should be made, dried and fixed, for subsequent staining with Romanowsky dyes. Asides automated slide makers, the commonest method for preparation of peripheral blood film is the slide 'wedge' or push technique. This technique typically requires microscope slides, pipette/blood dropper, spreader slide and the blood specimen to be analysed. Standard precautions must be observed to prevent transmission of infectious pathogens such as human immunodeficiency virus and hepatitis viruses. Quality control measures will include ensuring proper anticoagulant: blood ratio, sample processing/analysis within sample viability period and adequate mixing of the blood before smearing. Each slide must be labelled with at least two patient identifiers such as name and laboratory, and date of procedure. Once the smear is air-dried in about 5–10 minutes, fixation of the blood tissue is another very important step. Fixation helps to preserve the architecture of the cells, which ensures good morphology. A dried slide should be fixed within 4 hours of prepara-

In polychromatic red cells, RNA produces a blue colour, which offsets the pink colour imparting a purple tinge Basophilic stippling: appears as blue granules dispersed within the cytoplasm in a punctate appearance

For routine morphology, the glass slides are stained with Romanowsky dyes. Romanowsky dyes are differential stains composed of both acidic and basic components. The acidic component is eosin and the basic part is azure B or polychrome methylene blue. Examples of Romanowsky stains include Leishman stain, Jenner, Wright stain, May-Grunwald-Giemsa stain and Giemsa stain. Generally, the eosin part of the dye binds to the basic component of the cell such as the haemoglobin molecules in the red cell and stains it pink. The basophilic part of the dye binds to the acidic component of the cells such as the nucleus and stains it blue. Other components of the cells appear in different colour shades that contrasts and compares with the dye. The term, azurophilic is used to describe a neutral to sky-blue colour shade. For instance, the cytoplasm of a neutrophil is described as azurophilic in colour. Furthermore, the characteristic staining quality of different red cell components is presented in **Table 2**. Staining procedure and the stain contact time depends on the type of dye in use. Staining protocols are contained in standard laboratory texts and reagent manuals. Red cell morphology should be examined at the monolayer region of the film which is 2–4 × 10 fields from the feathered edge. In this place red cells are randomly distributed with most lying singly and only a few overlapping. If area is too thin, the RBCs will appear flat with no central pallor. If too thick, false rouleaux may be reported and morphology may be difficult to evaluate because red cells are packed.

The haemato-morphologist reviews the red cell morphology under the compound microscope and notes any significant abnormalities for reporting/diagnosis

#### **Table 1.**

*Clinical indications for peripheral blood film.*

#### **Table 2.**

*Erythrocyte*

picture with paucity of red cells, numerous red cell fragments, increased polychro-

Circulating red cells are formed from bone marrow stem cells. Stem cells are pluripotent; they self-replicate and differentiate to specialized cells in circulation through different lineages. Red cells are formed from the myeloid stem cell lineage (colony forming unit—granulocytes, erythroid, myeloid and megakaryocytes). The earliest recognizable red cell precursor in the bone marrow is the pronormoblast. The pronormoblast undergoes series of maturation to become the orthochromatic normoblast. Upon extrusion of its nucleus, the late normoblast becomes the shift reticulocytes, which is released into the circulation. Finally, DNA remnants and other chromatin materials in the reticulocytes is removed by the pitting action of the

Erythrocytes cannot be seen with the naked eyes. Typically, morphology of red cells is performed on peripheral blood smears, once there is an indication. Erythrocyte morphology is either indicated by a clinical request or laboratory flags. Examples of clinical indications for peripheral blood film/erythrocyte morphology

Erythrocyte morphology may also be indicated when significant deviations from the normal are seen in the laboratory during blood work (full blood count) irrespective of a clinical request. For instance, a significantly reduced haemoglobin level with low MCV and raised RDW may suggest iron deficiency anaemia. This is an indication for red cell morphology and other ancillary investigation for iron deficiency. Blood for peripheral blood film is collected through venipuncture.

Anticoagulant of choice is the potassium EDTA. Specimens should be analysed as

• Features of congenital haemolytic anaemias such as splenomegaly, jaundice or bone pains • Suspected chronic or acute myeloproliferative disease, e.g. Chronic myeloid leukaemia

• Features of hyperviscosity syndrome as in paraproteinaemias, leukaemic hyperleucocytosis,

• Evaluation of disseminated intravascular coagulopathy and other red cell fragmentation syndromes

A clinical request for a PBF may be prompted by the following indications:

• Unexplained anaemia, leucopenia or thrombocytopenia • Unexplained leukocytosis, lymphocytosis or monocytosis

• Suspected organ failure such as renal disease, liver failure

• Advanced malignancies with possible bone marrow involvement

• Suspected chronic lymphoproliferative such as chronic lymphocytic leukaemia

• Severe bacterial sepsis and parasitic infections

• Suspected cases of nutritional anaemia

*Clinical indications for peripheral blood film.*

• Advanced lymphoma with leukaemic spills

• Unexplained jaundice or haemolysis

polycythaemia

matic red cells suggests a micro-angiopathy or fragmentation syndrome. This chapter aims to discuss principles of red cell morphology, as well as describe red cells in terms of morphology, identify morphologic abnormalities

associated with different disease conditions.

**2. Principles of erythrocyte morphology**

spleen, hence the mature red cells.

are listed in **Table 1**.

**8**

**Table 1.**

*Romanowsky staining characteristics of red cell components.*

soon as possible, preferably within 2 hours of blood collection. Samples not analysed immediately should be stored at 2–6°C in a refrigerator, or the blood smear should be made, dried and fixed, for subsequent staining with Romanowsky dyes.

Asides automated slide makers, the commonest method for preparation of peripheral blood film is the slide 'wedge' or push technique. This technique typically requires microscope slides, pipette/blood dropper, spreader slide and the blood specimen to be analysed. Standard precautions must be observed to prevent transmission of infectious pathogens such as human immunodeficiency virus and hepatitis viruses.

Quality control measures will include ensuring proper anticoagulant: blood ratio, sample processing/analysis within sample viability period and adequate mixing of the blood before smearing. Each slide must be labelled with at least two patient identifiers such as name and laboratory, and date of procedure. Once the smear is air-dried in about 5–10 minutes, fixation of the blood tissue is another very important step. Fixation helps to preserve the architecture of the cells, which ensures good morphology. A dried slide should be fixed within 4 hours of preparation, preferably in the first hour.

For routine morphology, the glass slides are stained with Romanowsky dyes. Romanowsky dyes are differential stains composed of both acidic and basic components. The acidic component is eosin and the basic part is azure B or polychrome methylene blue. Examples of Romanowsky stains include Leishman stain, Jenner, Wright stain, May-Grunwald-Giemsa stain and Giemsa stain. Generally, the eosin part of the dye binds to the basic component of the cell such as the haemoglobin molecules in the red cell and stains it pink. The basophilic part of the dye binds to the acidic component of the cells such as the nucleus and stains it blue. Other components of the cells appear in different colour shades that contrasts and compares with the dye. The term, azurophilic is used to describe a neutral to sky-blue colour shade. For instance, the cytoplasm of a neutrophil is described as azurophilic in colour. Furthermore, the characteristic staining quality of different red cell components is presented in **Table 2**.

Staining procedure and the stain contact time depends on the type of dye in use. Staining protocols are contained in standard laboratory texts and reagent manuals. Red cell morphology should be examined at the monolayer region of the film which is 2–4 × 10 fields from the feathered edge. In this place red cells are randomly distributed with most lying singly and only a few overlapping. If area is too thin, the RBCs will appear flat with no central pallor. If too thick, false rouleaux may be reported and morphology may be difficult to evaluate because red cells are packed.

#### **3. Red cell morphologic disorders**

The haemato-morphologist reviews the red cell morphology under the compound microscope and notes any significant abnormalities for reporting/diagnosis in light of patient clinical context. Red cell morphology is evaluated in terms of size, shape, colour, distribution and intra cytoplasmic inclusions. In general, red cells have a fairly uniform variation in size, with a red cell distribution width of 11–15% in normal individuals. Abnormal variations in sizes and shape are termed anisocytosis and poikilocytosis, respectively [1].


**2. Literature review**

to technological advancements across all industries. Not only more people connect to the internet every day, also devices actively communicate with one another, coined under the term "the internet of things". Moreover, recent initial public offerings of well-known internet companies such as Groupon, LinkedIn, Facebook, Alibaba Group Holding Limited and funding support programs in the United States, the European Union and China drive the interest

When looking at the development of certain equity indices in the United States, Germany and China, the rates show record or close to record peaks as seen on **Figure 1**. For the Nasdaq Composite Index such rates were last seen during the dot-com bubble while the Deutscher Aktien Index 30 is almost twice as high as during the dot-com bubble and before the recent financial crisis of 2008. For the China Securities Index 300, the sources from the Bloomberg database even state price-to-earnings ratios as high as 220 times reported

Bringing these circumstances into a global context, an artificial economic boost was created after the crisis that made equity indices soar—just like before the dot-com bubble. Hence, the question arises how the situation as of December 2015 is different if it is at all. Are there signs

The dot-com bubble is one of the most disputed bubbles that occurred in the last decades. Each bubble can be modelled according to some rules. Welfare analysis with empirical prediction is subject to examine [3]. Also, the pure statistical tests are suitable to describe bubble [4]. But alternative assessment can be provided by another angle of view on bubbles [5].

of investors for lucrative opportunities.

94 Financial Management from an Emerging Market Perspective

of an asset price bubble as some research argues [1, 2]?

Moreover, market bubbles are related to market volatility in general [6].

**Figure 1.** Increase of indices' values across regions. Source: Own elaboration by the authors.

profits.

Since the current situation of peaking indices is too new to expect extensive research on this topic, there are currently only a few similar articles available to the knowledge of the author [7, 8]. Their research, however, is either limited to a single stock, market or pursues another approach. Furthermore, the eventual assessment of a bubble can only happen in retrospect while today's perspective can only try to catch the market sentiment and interpret some key economic indicators.

#### **2.1. Asset price bubble**

By the definition of the majority of literature, an asset price bubble is characterised by a substantial deviation from the fundamental value of the asset [9]. On the other hand, according to the efficient market hypothesis, there are three levels of efficiency: weak, semi-strong, strong—which represent the incorporation of information into the price of securities [10]. Hence, under certain assumptions such as that investors perceive information uniformly, securities should trade at their fair value and deviating from the fundamental value should not be possible with respect to the level of efficiency. Despite the critique and controversy of the efficient market hypothesis in recent decades it was confirmed again in 2009 [11]. Nevertheless, severe price deviations did occur and cannot be explained by the efficient market hypothesis. Hence these deviations represent a key flaw in this hypothesis on which much of economy theory relies. In theory, rational investors are expected to base their valuations on fundamentals such as the intrinsic value of an asset which can be approximated by the discounted sum of future cash flows [12]. Since nobody can predict the future, however, projections of future cash flows are likely to be highly subjective. To tackle this issue, the assessment of a bubble can be mainly approached from two dimensions: magnitude and time.

While it is recognised that measuring the fundamental value at the very moment of the occurrence is hardly possible [13]. Therefore, it is suggested that a bubble should be measured by deviations of expected and realised returns over a defined period of time—even decades [14]. Obviously, this can only happen in retrospect since returns cannot be predicted with certainty, especially during times of turmoil in the markets [15].

Beyond the pure stock price, another crucial factor according to equity asset valuation is often taken into account: the price-to-earnings ratio or earnings in general. Commonly speaking, the higher the price-to-earnings ratio increases without substantial news to support a higher valuation, the harder it becomes to justify prices if there is little evidence for future returns other than the pure belief—for instance speculation.

Differentiating a plausible market development and an irrational bubble remains the subject of collective research on expectations and actual future cash flows. In retrospect, only the burst of a bubble, indicated by a substantial depreciation of prices, gives reason to assume that there was one in the first place. That is because a permanent change would require a fundamental reason and not constitute a bubble due to the lack of deviation. Also, there can be an overlap with different types of business cycles. This issue relates to the second dimension by which a bubble has to be assessed – time.

For example, there is an argument that the actual dot-com bubble was quite short and only lasted from 1998 to 2000 [16]. Even though, this might be the time of the actual substantial price deviation, it is important to take into account the circumstance which led to it in the first place. Therefore, a five-stage approach that was described and later refined is favoured in this paper [17]. This is supported by another research, which used a three-stage to five-stage approach, too [18].

Since a single value or theory is unlikely to explain the workings of a complex event of an asset price bubble which is the interplay of irrational humans and algorithm driven economics, it is more likely the combination of these factors.

#### **2.2. Explanations for the occurrence of asset price bubbles**

Even though there currently is no guaranteed empirical method to detect an asset price bubble [19], especially in real time, there are still again mainly two methods to approach this issue [20]. The first one is based on rational expectations of the efficient market hypothesis, and the second one on behavioural finance.

Firstly, there are empirical and technical models that are based on the efficient market hypothesis [21, 22]. Even though, such models are able to provide sufficient explanatory power, they are for example limited to historic data [23], certain stocks or companies [24] or more generally, to certain assumptions which were true in the past. Most importantly they lack the major factor of irrational human behaviour that can be observed in certain situations at the stock market, especially during uncertainty due to politics or the introduction of an innovation. Under the category of rational expectations also fall the established economic theories that take into account monetary policies, investment and consumption cycles. For example, there is also an evidence for connecting the emergence of bubbles with the credit creation policies [25].

Secondly, there are qualitative metrics which take into account soft factors such as the current sentiment of the market and irrational human behaviour, including biases as coined under the term behavioural finance. Psychological factors, especially during turbulent times, gain importance while traditional measures lose in relevance [26]. Concepts like herding behaviour and greater-fool theory trump rational economic assumptions such as the efficient market hypothesis and investors willingly forego arbitrage opportunities. Also, soft factors such as human capital, strategic alliances, joint ventures and internet popularity gain in importance [27–29]. Since only forecasts about future cash flows can be made, expectations play an integral role to the development of the market. For example, there is a study showing that during the dot-com bubble financial analysts were more optimistic about internet stocks [30]. Especially in such circumstances fundamental values start to become irrelevant to investors [31]. Also, it must be taken into account that even though there might be an asset price bubble, it can be necessary due to circumstances to ride that bubble instead of acting rationally against the majority of market participants [32]. After all there is nothing so dangerous as the pursuit of a rational investment policy in an irrational world. The financial sector plays also a significant role here [33, 34]. A good example is technical analysis with the Federal Reserve System model which is extensively criticised by theorists for their flaws but used by practitioners nevertheless. The sheer beliefs and usage of such concepts substantially influence the market even without sound academic background [35]. Furthermore, restrictions like short selling, set by a higher body or lock-in periods for stock options, may skew and alter the economic normalisation processes [36]. Moreover, history shows that politicians are reluctant to take countermeasures before an imminent economic threat can be proven because acting on a false alarm would result in a loss in economic output which in consequence would have negative transitioning effects throughout society [37, 38].

So, taking into account the irrational human behaviour is an important factor. Therefore, a holistic combination of both theories efficient market hypothesis and behavioural finance is expected to yield a better result for the explanation and assessment of a bubble formation.

#### **2.3. Other effects**

For example, there is an argument that the actual dot-com bubble was quite short and only lasted from 1998 to 2000 [16]. Even though, this might be the time of the actual substantial price deviation, it is important to take into account the circumstance which led to it in the first place. Therefore, a five-stage approach that was described and later refined is favoured in this paper [17]. This is

Since a single value or theory is unlikely to explain the workings of a complex event of an asset price bubble which is the interplay of irrational humans and algorithm driven econom-

Even though there currently is no guaranteed empirical method to detect an asset price bubble [19], especially in real time, there are still again mainly two methods to approach this issue [20]. The first one is based on rational expectations of the efficient market hypothesis, and the

Firstly, there are empirical and technical models that are based on the efficient market hypothesis [21, 22]. Even though, such models are able to provide sufficient explanatory power, they are for example limited to historic data [23], certain stocks or companies [24] or more generally, to certain assumptions which were true in the past. Most importantly they lack the major factor of irrational human behaviour that can be observed in certain situations at the stock market, especially during uncertainty due to politics or the introduction of an innovation. Under the category of rational expectations also fall the established economic theories that take into account monetary policies, investment and consumption cycles. For example, there is also an

evidence for connecting the emergence of bubbles with the credit creation policies [25].

Secondly, there are qualitative metrics which take into account soft factors such as the current sentiment of the market and irrational human behaviour, including biases as coined under the term behavioural finance. Psychological factors, especially during turbulent times, gain importance while traditional measures lose in relevance [26]. Concepts like herding behaviour and greater-fool theory trump rational economic assumptions such as the efficient market hypothesis and investors willingly forego arbitrage opportunities. Also, soft factors such as human capital, strategic alliances, joint ventures and internet popularity gain in importance [27–29]. Since only forecasts about future cash flows can be made, expectations play an integral role to the development of the market. For example, there is a study showing that during the dot-com bubble financial analysts were more optimistic about internet stocks [30]. Especially in such circumstances fundamental values start to become irrelevant to investors [31]. Also, it must be taken into account that even though there might be an asset price bubble, it can be necessary due to circumstances to ride that bubble instead of acting rationally against the majority of market participants [32]. After all there is nothing so dangerous as the pursuit of a rational investment policy in an irrational world. The financial sector plays also a significant role here [33, 34]. A good example is technical analysis with the Federal Reserve System model which is extensively criticised by theorists for their flaws but used by practitioners nevertheless. The sheer beliefs and usage of such concepts substantially influence the market

supported by another research, which used a three-stage to five-stage approach, too [18].

ics, it is more likely the combination of these factors.

96 Financial Management from an Emerging Market Perspective

second one on behavioural finance.

**2.2. Explanations for the occurrence of asset price bubbles**

There are argues that there may be many reasons to cause asset price bubbles [39]. There are several research papers which take also nonfinancial but rather information technology oriented factors into account that might influence investors' decisions when buying technology stocks. The reasoning behind such measures is the Anglo-Saxon approach which focuses on growing big and gaining market share at high costs in the beginning while becoming profitable later [40]. Such factors include, for example, page views or visitors and sales in contrast to traditional measures such as earnings before interest, taxes, depreciation and amortisation or net income [41, 42].