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Environmental Toxicity of Nanoparticles

Mohammad Shahadat1,2*, Momina3, Yasmin1, Suzylawati Ismail3, S. Wazed Ali2 and Shaikh Ziauddin Ahammad1┼

1Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, IIT Delhi, India

2Department of Textile Technology, Indian Institute of Technology, IIT Delhi, Hauz Khas, New Delhi, India

3School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus, Pulau Pinang, Malaysia

Abstract
Nanotechnology has played a key role as results of its significant potentials in various fields such as water treatment, agriculture, aerospace, and pharmaceutical industries. Available scientific data on nanomaterials have revealed their applications in consumer and industrial products in day-to-day life. Alternation in the surface properties of particle to minimize size up to nano-level may also found to be responsible for their toxicity. Many governmental agencies including United States National Institute for Occupational Safety and Health and Japan's Ministry of Health have been raised inequity regarding the utilization of nanomaterials for treatment of wastewater. Inhalation of nanoparticles through human beings is found to be less efficiently removed as compared to large one (micro or macro particles) through biological clearance mechanism in different body parts. However, nanoparticles easily transfer to various body organs through the circulatory systems which upsurge several diseases. Therefore, attention is needed to use nanoparticle in water treatment and biological system under control handling because of their toxicity. The present chapter reviews environmental toxicity of nanomaterials in water and their effects on human beings. Additionally, a critical evaluation of challenges and use of nanomaterials to generate clean and safe environment has been discussed.

Keywords: Toxicity, nanomaterials, wastewater, diseases, human health, environment

1.1 Introduction

Nanotechnology deals with the manipulation of matter on an atomic level in preparation of macroscale products along with the dimension of nanoparticle in the range from 1 to100 nm [1]. With the advancement of modern research, nanotechnology has become an integrating technology [2]. Over the past two decades, the term "Nanotechnology" has been inflated and it almost become synonymous for innovative and highly promising things that are obtained from the nanotechnology [3]. Based on innovative physical including chemical and electrical properties, nanoparticles are being widely used in various industries, information and communication system, electronic and computer devices, biotechnology and agriculture [4], aerospace engineering, medicine and medical applications, as additive for food, paints, drinks, ceramics, cosmetics papers, packaging, cancer therapy and biosensor [5]. Liposomes, dendrimers polyethylene glycol are the medical applications of nanoparticles [6]. Applications of nanoparticles have been widely expanded in routine life because of their significant role. Ultimately, nanoparticles and nanocomposite-based materials are beneficial to human beings and society. However, extensive use of nanoparticles is another concern in terms of societal threat to the health of human beings and the environment.

Nanoparticles have been accumulated in body parts through sorption, inhalation and oral ingestion which severely affect the soft tissues (e.g. brain, heart, kindly, liver, etc.) [7]. Small size and high-surface area to volume ratio of nanoparticles make them highly reactive by producing reactive oxygen which is found to be more toxic to the environment. Besides the beneficial role of nanoparticles, scientists have been addressed toxicity of various nanoparticles. Because of 'nano' size, the nanoparticles easily cross any physiological barrier i.e. cell membrane, cell wall and the membrane of cell organelles [8]. It circulates through the vascular system (blood and lymphatic system) and easily translocates from one organ to other and invades the tissue. It makes dysfunction of organs and tissue system by interfering normal cellular processes such as uncontrolled cell proliferation (cancer), premature cell death. Some nanoparticles are beneficial for producing anti-cancerous drug, DNA, monoclonal antibodies and other medicines [4].

Several diseases like autoimmune, dermatitis, colon and cervical cancer, gastrointestinal (colon cancer, Crohn's), heart, liver, lung diseases (asthma, bronchitis, lung cancer), neurological disorder (Parkinsons's diseases, Alzheimer's diseases) may associated with the exposure of nanoparticles [9]. Reduction in fossil fuel combustion had severe impact on global human exposure to nanoparticles, resulted limiting deforestation and desertification [7]. Nanostructured fixed particles (computer devices), microchip electronics, printed devices and some other are not found harmful to human, but, free nanoparticles (non-structured nanoparticles) are detrimental for health. The toxicity of nanoparticles depends on its properties such as sizes, shapes, surface charge, types, number of particles, agglomeration, aggregation, composition, crystallinity, surface functionalization, etc. [7]. These factors affect the chemical reactivity of materials, as well as their mechanical, optical, electric, and magnetic properties. Two primary factors cause nanomaterials to behave significantly different than bulk materials such as surface effects (causing smooth properties scaling due to the fraction of atoms at the surface) and quantum effects (showing discontinuous behavior due to quantum confinement effects in materials with delocalized electrons) [10].

1.1.1 Toxicity of Nanoparticles in Wastewater Bodies

Several wastewater treatment technology and treatment plants are in practiced since 1700 to date. It is found that 70-80% wastewater directly disposed into the main water stream. From early 1900s, different treatment technologies-activated sludge process (ASP), trickling filter, hybrid anaerobic reactor (HAR), Sequencing batch reactor (SSBR), Membrane bioreactor (MBR), Constructed wetland, and Nanofiltration have treated through adsorption, precipitation, ion-exchange, evaporation, osmosis, filtration, floatation, settling, bio-flocculation, nitrification-denitrification, nanofiltration by nanoparticles have been adopted to treat wastewater [11-13]. Among all treatment technologies, nanofiltration is considered as a cost-effective method having great efficiency to reduce total dissolved solids (TDS), heavy metals, nitrites, sulphates, color, turbidity of water, and reducing of bacterial abundance. Because of tiny size (less than 1 µm), high surface area, agglomeration capacity, these nanoparticles are used in medicine and health care products, electronics, and ultraviolet resistant items. However, besides the advantages of nanoparticle, the exposure of copper, iron, gold, manganese, titanium, silica and other carbon-based nanomaterials to water bodies became another cause of water pollution. Thus, involvement of nanoparticles to water pollution has become a serious global issue owing to their detrimental effects to the environment which results in disturbance of the eco-system [14, 15].

Nanoparticles have exhibited toxic manifestations through different mechanisms which outburst a number of diseases such as allergy, fibrosis, nephrotoxicities, hematological toxicities, hepatological toxicities, splenic toxicities, pulmonary toxicities, neurotoxicities, and splenic toxicities in humans. Not only the nanoparticles of metal oxides found to be toxic for humans, but, the nanoparticles obtained from anthropogenic activities, natural and environmental sources are also found carcinogenic for the environment [16]. The harmful health effects of different nanoparticles including metalloid, non-metalloids, anthropogenic and natural resources are listed in Table 1.1. An outline regarding the negative effects of nanoparticles to human beings is shown in Figure 1.1.

1.1.2 The Effect of Nanoparticles Toxicity on Human Health

Nanotechnology is one of the emerging fields having potential applications in many areas. However, leaching of toxic nanoparticles to the aqueous and terrestrial environment is important cause of concern [40, 41]. Besides the synthesis, these nanoparticles also exist in the environment from natural and anthropogenic sources [42]. Nanoparticles in soil and water are referred as colloids, whereas in air it is referred as ultrafine particles [42]. These are also employed in drug delivery system to send proteins, drugs, to the target site in the treatment of diseases [4, 43, 44]. The recent advances in nanotechnology also brought up their opportunities in water treatment, since the current water treatment technologies are no longer sustainable due to inconvenient and improper distribution and discharge practices. Therefore, the efficient and multifunctional processes by nanotechnology provide excellent performance which can be affordable by wastewater treatment industries [45]. Adsorption, membrane processes, use of photocatalyst, sensing and monitoring water quality are some of the current potential techniques in wastewater treatment where nanomaterials are being employed [45-47]. However, very few information is available on the hazards of nanomaterials...