Nanotechnology-based Sensors for Detection of Environmental Pollution

By Munir Ozturk

Nanotechnology-based Sensors for Efficient Detection of Environmental Pollution discusses the use of nanotechnology to generate sensors capable of performing efficient detection of different types of environmental pollutants. Nanomaterial’s characteristics such as large surface area, good reactivity, and possibility to suffer chemical surface modification to recognize different types of molecules are useful, especially to perform the detection of specific environmental pollutants. Innovative and efficient ways to detect environmental pollution are urgently needed for sustainability and the nanotechnology field has an enormous potential to offer strategic solutions. Nanotechnology-based sensors offer an efficient way of detecting the presence of contaminants and determine its structure and chemical nature is by applying nanotechnology and/or nanobiotechnology.

This book will contain 5 parts: the first one will be dedicated to exploring environmental pollution as a threat to life on Earth and main contaminants (inorganic, organic or pathogens) and the risk they represent to living beings. The second part will be dedicated to nanotechnology allowing pollutants’ detection covering a brief history of nanotechnology-based sensors, different types of nanotechnology-based sensor (optical, electrochemical, and magnetic), nanotechnology-based sensors’ design and fabrication and nano biosensors. The third part will be focused on important specific pollutants (pesticides, heavy metal, dyes, toxic gas, pharmaceutical waste, petroleum hydrocarbons, and pathogenic microbes) and their detection by nanotechnology-based sensors. The fourth part will be dedicated to important nanomaterials in nanotechnology-based sensors, exploring carbon-based and non-carbon-based material in nanoscale (graphene, carbon nanotubes, quantum dots, magnetic nanomaterials, non-magnetic nanoparticles) and also point-of-care sensors and functionalization to generate optimized nanotechnology-based sensors to pollutants’ detection. The fifth and last part of Nanotechnology-based Sensors for Efficient Detection of Environmental Pollution will address relevant practical aspects related to nanotechnology-based sensors, covering advantages and challenges, safety, economic and commercial aspects related to the field and also sustainability, highlighting green nanomaterials on nanotechnology-based sensors.

• Provides a comprehensive, multidisciplinary review of nanotechnology-based sensors
• Supplies readers extensive knowledge on detecting harmful pollutants in different environments using nanotechnology-based sensors
• Presents chapters dedicated to the detection of pollutants different from toxic gas and pharmaceutical products, such as pesticides, heavy metals, dyes, pathogens, and petroleum hydrocarbons
• Introduces information on pollutants and the threats they represent to living beings, nanotechnology-based sensor’s design and fabrication, a brief history of the field, and practical issues related to the field, such as economics, safety, and challenges

• Language: English
• Publisher: Elsevier Science
• Release date: May 9, 2024
• ISBN: 9780443141195

Book preview

Preface

Fernanda Maria Policarpo Tonelli, Arpita Roy, Munir Ozturk and H.C. Ananda Murthy

Biological contaminants as well as organic and inorganic structures are involved in causing one of the world’s most concerning problems: environmental pollution. It threatens the survival of living beings on the Earth and causes instabilities in ecosystems.

So, it is necessary that new manners to efficiently deal with the already existing pollution in air, soil, and water be implemented. It is also necessary to reduce the production of environmental contaminants worldwide. However, to verify if this reduction is occurring and also to localize contaminated areas to perform remediation, it is crucial to determine if pollutants are present, which ones, and in which concentration. In this sense, nanomaterials’ field can contribute offering devices to perform these tasks.

This book discusses the use of nanotechnology to generate sensors capable of performing efficient detection of different types of environmental pollutants. Characteristics of nanomaterials such as large surface area, good reactivity, and possibility to suffer chemical surface modification to recognize different types of molecules are useful especially to perform the detection of specific environmental pollutants.

The chapters are organized in five sections; the first one is dedicated to explore environmental pollution as a threat to life on the Earth, addressing different types of contaminants, the importance of detecting them to sustainability, and their possibility to also be used in an eco-friendly manner to remediate environmental contamination. The second section focuses on different types of nanotechnology-based sensors to detect environmental pollution. The third one covers relevant pollutants that can be detected by these sensors in different types of samples. The fourth section is dedicated to important nanomaterials that can be used in nanosensors and also point-of-care devices for pollutants’ detection. The fifth and last section covers relevant practical aspects related to nanosensors such as safety, economic, and commercial issues related to the field and also sustainability and advantages and challenges associated with this type of sensors.

This book’s main purpose is to offer readers extensive knowledge on nanosensors as strategic tools to detect harmful pollutants present in different types of contaminated samples to allow future interventions such as application of remediation protocols.

We are extremely grateful to all the authors who have contributed chapters in this project and to Elsevier for their generous cooperation in publishing this book.

Section 1

Environmental contaminants

Outline

1 Environmental pollution: a worldwide threat

2 Main inorganic pollutants and their risk to living beings

3 Main organic pollutants and their risk to living beings

4 Main biological contaminants endangering humans’ health

5 The importance of detecting pollutants to sustainability

6 Green carbon-based nanomaterials to environmental remediation

1

Environmental pollution: a worldwide threat

Fernanda Maria Policarpo Tonelli,    Federal University of São João del Rei, Divinópolis, Minas Gerais, Brazil

Abstract

Environmental pollution is a serious issue that is not limited to a small number of countries such as the developing ones. The majority of the world's population currently lives in places in which the level of environmental contamination is considered above the safe one. It is a major worldwide concern and this book will be dedicated to addressing the nanotechnology field contributions by providing nanotechnology-based sensors for the detection of environmental pollutants.

Keywords

Environmental pollution; inorganic pollutants; organic pollutants; harmful anthropogenic actions; toxic contaminants

Environmental pollution is a problem that concerns not only a small number of countries such as the ones that are experiencing development. More than 90% of people in the world live in places in which the pollution level is considered above the safe one (Murray et al., 2020); therefore, it is a major worldwide concern.

However, the intensity of exposure to environmental contaminants depends upon some variables, and poor legislation, overpopulation, and lack of surveillance, are examples of aspects that favor a higher level of exposure in low- and middle-income countries (Mannucci & Franchini, 2017). Sometimes people not even are aware of this exposure and the risks it represents (Muralikrishna & Manickam, 2017); and inside a country, aspects associated with discrimination, especially related to ethnicities, can also favor the exposure of a group of individuals to a higher level of pollution (Tessum et al., 2021).

This problem is not new, has different causes (Fig. 1–1), and is receiving increasing attention due to the threat it poses to living beings and ecosystems as a whole (Ukaogo et al., 2020). In the last decades, the number of urbanized/industrialized cities has increased at a fast pace, causing an increase in the: amount of waste produced, CO2 emission, population growth, and transboundary movement (Muhammad et al., 2022); it has also resulted in the landscape’s transformation and in the rapid consumption of non-renewable resources (Vallero & Vallero, 2019). The consequent increase in food and energy demands provoked an enhancement in agricultural activities (involving the use of pesticides and other harmful substances) and in the burning of fossil fuels. Mining and exploration of minerals also contributed to an enhancement in environmental pollution, especially the one associated with inorganic contaminants such as heavy metals [such as mercury (Streets et al., 2019)]. These exploratory activities also impaired soil fertility and caused the destruction of vegetation and reduction in biodiversity (Feng et al., 2019).

Figure 1–1 Main causes of environmental pollution.

The contaminants, due to their toxicity, are associated with an increased risk of death of living beings (especially humans) (Lind et al., 2019). In fact, they are also, directly and indirectly, responsible for a large number of deaths (around nine million) worldwide every year (Fuller et al., 2022; Zhou et al., 2023). Besides that, chronic diseases (Pavuk et al., 2019) and undesired alterations in DNA (Julvez et al., 2019) or in specific tissues such as the nervous one (Pessah et al., 2019) are examples of pollution harmful consequences. Cancer deaths, only in 2020, approximated ten million (Ferlay et al., 2023), and this group of diseases is closely associated with pollution and climate change. Exposure to toxic contaminants (organic and/or inorganic), to some infectious agents and to UV radiation are examples of factors that can favor cancer development and that are consequences of pollution as same as climate change (Hiatt & Beyeler, 2020). It is important to mention that environmental contaminants may also interfere with fetal development due to pregnant women’s exposure to pollution (Ouidir et al., 2020); these substances can cause alteration that will continue till adulthood, such as attention-deficit/hyperactivity disorder (Lenters et al., 2019).

The contaminants of diverse chemical nature can be present in the air (indoor and outdoor ones), water, and/or soil (Bakshi & Abhilash, 2019; Iloms et al., 2020; Zhang et al., 2023). The three of them can be altered, through humans’ actions, to contain chemical substances that are not originally present in their composition and that decrease their quality, being harmful to living beings. As air pollutants, it is possible to highlight organic compounds and nitrogen and sulfur oxides (Fazakas et al., 2023). When it comes to water and soil, domestic/medical wastes, pesticides, and heavy metals deserve special attention (Tonelli & Tonelli, 2020a, 2020b). All this scenario has contributed to the increase in the quantity and diversity of pollutants present in the environment. Emerging pollutants continue to be identified and the threats they represent continue to be elucidated (Sauvé & Desrosiers, 2014). Nowadays, for example, it is possible to find microplastics in products such as cosmetics and food as a consequence of environmental pollution (Auta et al., 2017; Cox et al., 2019; Provencher et al., 2019). In fact, atmospheric transportation has taken these particles even to the Arctic and the Alps (Bergmann et al., 2019).

Another severe consequence of pollution that deserves attention and that endangers the world is climate change; it is related to the increasing pollution level, especially the air pollution (Manisalidis et al., 2020; Moore, 2009). Global warming brings concerning consequences to ecosystems as a whole (Marlon et al., 2019). When it comes to oceans, for example, the increase in atmospheric CO2 causes a reduction in water pH and the consequent elimination of coral reefs and other marine living beings [including the ones that could be useful sources of new useful molecules such as drugs (Ercolano et al., 2019)]. The melting of glaciers, the increase in water level, and the toxic algae blooms are some of the negative consequences (Landrigan et al., 2020; Trainer et al., 2019).

Water scarcity is another serious issue that deserves attention and that is associated to pollution; it is estimated that by 2050, more than 50% of the world’s population will suffer from this scarcity and the increasing production of pollutants has the potential to worsen this situation (Boretti & Rosa, 2019).

An increase in mortality associated with some diseases can also be attributed to pollution. For example, not only lung cancer as a consequence of fine particles (Guo et al., 2017) but also diabetes (Eze et al., 2014), cardiovascular diseases (Bourdrel et al., 2017; Burroughs Peña & Rollins, 2017), respiratory allergies (D'Amato et al., 2016), diseases associated to vectors that had their natural habitat endangered (Lindh et al., 2019), intoxication involving pollutants (Assi et al., 2016), among other illnesses.

It is urgent to dedicate attention to environmental pollution considering the development of efficient devices to detect pollutants, protocols to remediate already existing contamination, but also strategies to enhance the population’s sense of respecting sustainability principles and legislations capable of avoiding new pollutant's emissions. Sustainable development needs to become a reality for the sake of living beings’ health and survival and ecosystems’ balance; transformations need to achieve all human beings, not excluding people from the so-called marginalized communities (Jennings et al., 2021).

This book is dedicated to addressing mainly the first mentioned aspect: detecting environmental contaminants. It focuses on the nanotechnology field contributions by providing nanotechnology-based sensors for the detection of environmental pollution: an important step in the fight against environmental contamination.

References

Assi et al., 2016 Assi MA, Hezmee MNM, Haron AW, Sabri MYM, Rajion MA. The detrimental effects of lead on human and animal health. Veterinary World. 2016;9(6):660–671 https://doi.org/10.14202/vetworld.2016.660-671http://www.veterinaryworld.org/Vol.9/June-2016/20.pdf.

Auta et al., 2017 Auta HS, Emenike CU, Fauziah SH. Distribution and importance of microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions. Environment International. 2017;102:165–176 https://doi.org/10.1016/j.envint.2017.02.013.

Bakshi and Abhilash, 2019 Bakshi M, Abhilash PC. Nanotechnology for soil remediation: Revitalizing the tarnished resource. Nano-materials as photocatalysts for degradation of environmental pollutants: Challenges and possibilities India: Elsevier; 2019;345–370 https://doi.org/10.1016/B978-0-12-818598-8.00017-1.

Bergmann et al., 2019 Bergmann M, Mützel S, Primpke S, Tekman MB, Trachsel J, Gerdts G. White and wonderful? Microplastics prevail in snow from the Alps to the Arctic. Science Advances. 2019;5 https://doi.org/10.1126/sciadv.aax1157.

Boretti and Rosa, 2019 Boretti A, Rosa L. Reassessing the projections of the World Water Development Report. npj Clean Water. 2019;2 https://doi.org/10.1038/s41545-019-0039-9.

Bourdrel et al., 2017 Bourdrel T, Bind MA, Béjot Y, Morel O, Argacha JF. Cardiovascular effects of air pollution. Archives of Cardiovascular Diseases. 2017;110(11):634–642 https://doi.org/10.1016/j.acvd.2017.05.003http://www.elsevier.com/wps/find/journaldescription.cws_home/714079/description#description.

Burroughs Peña and Rollins, 2017 Burroughs Peña MS, Rollins A. Environmental exposures and cardiovascular disease: A challenge for health and development in low- and middle-income countries. Cardiology Clinics. 2017;35(1):71–86 https://doi.org/10.1016/j.ccl.2016.09.001http://www.elsevier.com/inca/publications/store/6/2/3/2/8/2/index.htt.

Cox et al., 2019 Cox KD, Covernton GA, Davies HL, Dower JF, Juanes F, Dudas SE. Human consumption of microplastics. Environmental Science and Technology. 2019;53(12):7068–7074 https://doi.org/10.1021/acs.est.9b01517http://pubs.acs.org/journal/esthag.

D'Amato et al., 2016 D'Amato G, Pawankar R, Vitale C, et al. Climate change and air pollution: Effects on respiratory allergy. Allergy, Asthma and Immunology Research. 2016;8(5):391–395 https://doi.org/10.4168/aair.2016.8.5.391http://www.e-aair.org/Synapse/Data/PDFData/9999AAIR/aair-8-391.pdf.

Ercolano et al., 2019 Ercolano G, De Cicco P, Ianaro A. New drugs from the sea: Pro-apoptotic activity of sponges and algae derived compounds. Marine Drugs. 2019;17 https://doi.org/10.3390/md17010031.

Eze et al., 2014 Eze IC, Schaffner E, Fischer E, et al. Long-term air pollution exposure and diabetes in a population-based Swiss cohort. Environment International. 2014;70:95–105 https://doi.org/10.1016/j.envint.2014.05.014.

Fazakas et al., 2023 Fazakas E, Neamtiu IA, Gurzau ES. Health effects of air pollutant mixtures (volatile organic compounds, particulate matter, sulfur and nitrogen oxides)—A review of the literature. Reviews on Environmental Health 2023; https://doi.org/10.1515/reveh-2022-0252http://www.degruyter.com/view/j/reveh.

Feng et al., 2019 Feng Y, Wang J, Bai Z, Reading L. Effects of surface coal mining and land reclamation on soil properties: A review. Earth-Science Reviews. 2019;191:12–25 https://doi.org/10.1016/j.earscirev.2019.02.015.

Ferlay et al., 2023 Ferlay ME, Lam MC, Mery MP, et al. Global cancer observatory: Cancer today. 2020 Lyon: International Agency for Research on Cancer; 2023;.

Fuller et al., 2022 Fuller R, Landrigan PJ, Balakrishnan K, et al…. Pollution and health: A progress update. The Lancet Planetary Health. 2022;6(6):e535–e547 https://doi.org/10.1016/s2542-5196(22)00090-0.

Guo et al., 2017 Guo Y, Zeng H, Zheng R, et al. The burden of lung cancer mortality attributable to fine particles in China. Science of the Total Environment. 2017;579:1460–1466 https://doi.org/10.1016/j.scitotenv.2016.11.147.

Hiatt and Beyeler, 2020 Hiatt RA, Beyeler N. Cancer and climate change. The Lancet Oncology. 2020;21(11):e519–e527 https://doi.org/10.1016/S1470-2045(20)30448-4http://www.journals.elsevier.com/the-lancet-oncology/.

Iloms et al., 2020 Iloms E, Ololade OO, Ogola HJO, Selvarajan R. Investigating industrial effluent impact on municipal wastewater treatment plant in vaal, South Africa. International Journal of Environmental Research and Public Health. 2020;17 https://doi.org/10.3390/ijerph17031096https://www.mdpi.com/1660-4601/17/3/1096/pdf.

Jennings et al., 2021 Jennings V, Reid CE, Fuller CH. Green infrastructure can limit but not solve air pollution injustice. Nature Communications. 2021;12 https://doi.org/10.1038/s41467-021-24892-1http://www.nature.com/ncomms/index.html.

Julvez et al., 2019 Julvez J, Smith GD, Ring S, Grandjean P. A birth cohort study on the genetic modification of the association of prenatal methylmercury with child cognitive development. American Journal of Epidemiology. 2019;188(10):1784–1793 https://doi.org/10.1093/aje/kwz156.

Landrigan et al., 2020 Landrigan PJ, Stegeman JJ, Fleming LE, et al…. Human health and ocean pollution. Annals of Global Health. 2020;86(1):1–64 https://doi.org/10.5334/aogh.2831https://agh.ubiquitypress.com/articles/10.5334/aogh.2831/galley/3144/download/.

Lenters et al., 2019 Lenters V, Iszatt N, Forns J, et al. Early-life exposure to persistent organic pollutants (OCPs, PBDEs, PCBs, PFASs) and attention-deficit/hyperactivity disorder: A multi-pollutant analysis of a Norwegian birth cohort. Environment International. 2019;125:33–42 https://doi.org/10.1016/j.envint.2019.01.020.

Lind et al., 2019 Lind PM, Salihovic S, Stubleski J, Kärrman A, Lind L. Association of exposure to persistent organic pollutants with mortality risk: An analysis of data from the prospective investigation of vasculature in uppsala seniors (PIVUS) study. JAMA Network Open. 2019;2 https://doi.org/10.1001/jamanetworkopen.2019.3070.

Lindh et al., 2019 Lindh E, Argentini C, Remoli ME, et al. The Italian 2017 outbreak chikungunya virus belongs to an emerging aedes albopictus-adapted virus cluster introduced from the Indian subcontinent. Open Forum Infectious Diseases. 2019;6 https://doi.org/10.1093/ofid/ofy321http://ofid.oxfordjournals.org/?code=ofid&homepage.x=83&homepage.y=5&.cgifields=code.

Manisalidis et al., 2020 Manisalidis I, Stavropoulou E, Stavropoulos A, Bezirtzoglou E. Environmental and health impacts of air pollution: A review. Frontiers in Public Health. 2020;8 https://doi.org/10.3389/fpubh.2020.00014.

Mannucci and Franchini, 2017 Mannucci P, Franchini M. Health effects of ambient air pollution in developing countries. International Journal of Environmental Research and Public Health. 2017;14 https://doi.org/10.3390/ijerph14091048.

Marlon et al., 2019 Marlon JR, Bloodhart B, Ballew MT, et al. How hope and doubt affect climate change mobilization. Frontiers in Communication. 2019;4 https://doi.org/10.3389/fcomm.2019.00020http://www.frontiersin.org/journals/communication#.

Moore, 2009 Moore FC. Climate change and air pollution: Exploring the synergies and potential for mitigation in industrializing countries. Sustainability. 2009;1(1):43–54 https://doi.org/10.3390/su1010043http://www.mdpi.com/2071-1050/1/1/43/pdf.

Muhammad et al., 2022 Muhammad I, Ozcan R, Jain V, Sharma P, Shabbir MS. Does environmental sustainability affect the renewable energy consumption? Nexus among trade openness, CO2 emissions, income inequality, renewable energy, and economic growth in OECD countries. Environmental Science and Pollution Research. 2022;29(60):90147–90157 https://doi.org/10.1007/s11356-022-22011-1https://www.springer.com/journal/11356.

Muralikrishna and Manickam, 2017 Muralikrishna IV, Manickam V. Analytical methods for monitoring environmental pollution Elsevier BV 2017;495–570 http://doi.org/10.1016/b978-0-12-811989-1.00018-x.

Murray et al., 2020 Murray CJL, Aravkin AY, Zheng P, et al…. Global burden of 87 risk factors in 204 countries and territories, 1990–2019: A systematic analysis for the Global Burden of Disease Study 2019. The Lancet. 2020;396(10258):1223–1249 https://doi.org/10.1016/s0140-6736(20)30752-2.

Ouidir et al., 2020 Ouidir M, Buck Louis GM, Kanner J, et al. Association of maternal exposure to persistent organic pollutants in early pregnancy with fetal growth. JAMA Pediatrics. 2020;174 https://doi.org/10.1001/jamapediatrics.2019.5104.

Pavuk et al., 2019 Pavuk M, Serio TC, Cusack C, Cave M, Rosenbaum PF, Birnbaum LS. Hypertension in relation to dioxins and polychlorinated biphenyls from the anniston community health survey follow-up. Environmental Health Perspectives. 2019;127 https://doi.org/10.1289/EHP5272https://ehp.niehs.nih.gov/doi/pdf/10.1289/EHP5272.

Pessah et al., 2019 Pessah IN, Lein PJ, Seegal RF. Neurotoxicity of polychlorinated biphenyls and related organohalogens. Acta Neuropathologica. 2019;138(3):363–387.

Provencher et al., 2019 Provencher JF, Ammendolia J, Rochman CM, Mallory ML. Assessing plastic debris in aquatic food webs: What we know and don’t know about uptake and trophic transfer. Environmental Reviews. 2019;27(3):304–317 https://doi.org/10.1139/er-2018-0079.

Sauvé and Desrosiers, 2014 Sauvé S, Desrosiers M. A review of what is an emerging contaminant. Chemistry Central Journal. 2014;8 https://doi.org/10.1186/1752-153x-8-15.

Streets et al., 2019 Streets DG, Horowitz HM, Lu Z, Levin L, Thackray CP, Sunderland EM. Five hundred years of anthropogenic mercury: Spatial and temporal release profiles*. Environmental Research Letters. 2019;14 https://doi.org/10.1088/1748-9326/ab281f.

Tessum et al., 2021 Tessum CW, Paolella DA, Chambliss SE, Apte JS, Hill JD, Marshall JD. PM2.5 polluters disproportionately and systemically affect people of color in the United States. Science Advances. 2021;7 https://doi.org/10.1126/sciadv.abf4491https://advances.sciencemag.org/content/7/18/eabf4491.

Tonelli and Tonelli, 2020a Tonelli FCP, Tonelli FMP. Causes and effects of pesticide and metal pollution on different ecosystems. Bioremediation and biotechnology: Degradation of pesticides and heavy metals. Vol. 2 Springer 2020a; https://doi.org/10.1007/978-3-030-40333-1_1https://link.springer.com/book/10.1007/978-3-030-40333-1.

Tonelli and Tonelli, 2020b Tonelli FCP, Tonelli FMP. Concerns and threats of xenobiotics on aquatic ecosystems. Bioremediation and biotechnology: Persistent and recalcitrant toxic substances. Vol. 3 Springer 2020b; https://doi.org/10.1007/978-3-030-46075-4_2https://link.springer.com/book/10.1007/978-3-030-46075-4.

Trainer et al., 2019 Trainer VL, Moore SK, Hallegraeff G. Pelagic harmful algal blooms and climate change: Lessons from nature’s experiments with extremes. Harmful Algae. 2019;91:1–14.

Ukaogo et al., 2020 Ukaogo PO, Ewuzie U, Onwuka CV. Environmental pollution: Causes, effects, and the remedies. Microorganisms for sustainable environment and health Nigeria: Elsevier; 2020;419–429 https://doi.org/10.1016/B978-0-12-819001-2.00021-8https://www.sciencedirect.com/book/9780128190012/microorganisms-for-sustainable-environment-and-health.

Vallero and Vallero, 2019 Vallero DJ, Vallero DA. Land pollution waste: A handbook for management United States: Elsevier; 2019;631–648 https://doi.org/10.1016/B978-0-12-815060-3.00032-3https://www.elsevier.com/books/handbook-of-electronic-waste-management/prasad/978-0-12-817030-4.

Zhang et al., 2023 Zhang Y, Wang M, Shi T, Huang H, Huang Q. Health damage of air pollution, governance uncertainty and economic growth. International Journal of Environmental Research and Public Health. 2023;20 https://doi.org/10.3390/ijerph20043036.

Zhou et al., 2023 Zhou L, Wang Y, Wang Q, et al. The interactive effects of extreme temperatures and PM2.5 pollution on mortalities in Jiangsu Province, China. Scientific Reports. 2023;13 https://doi.org/10.1038/s41598-023-36635-x.

2

Main inorganic pollutants and their risk to living beings

Onali Pasqual¹, Anushka Rathnayake¹, Gobika Thiripuranathar¹ and Sagarika Ekanayake²,    ¹College of Chemical Sciences, Institute of Chemistry Ceylon, Rajagiriya, Sri Lanka,    ²Department of Biochemistry, Faculty of Medical Sciences, University of Sri Jayewardenepur, Nugegoda, Sri Lanka

Abstract

Inorganic pollutants are compounds with components other than carbon in their molecular structure and in addition to natural processes, human activities, including industrial processes, agriculture, transportation, etc., discharge different inorganic pollutants into the environment. Among, heavy metals could be considered the most harmful inorganic pollutants in the environment. These are released via both natural and anthropogenic sources. Anthropogenic sources are recognized as the key source of contamination. These heavy metals contaminate all natural environmental resources including water, soil, and air and the effects of these pollutants on people, animals, and plants are rather severe. For instance, heavy metals bioaccumulate and give rise to numerous health issues, including cancer, renal damage, and neurological diseases to mention some. The hazards posed by inorganic pollutants could be reduced by a mix of governmental activities, such as emission standards and pollution controls, and individual deeds, like consuming less energy and buying eco-friendly products. In addition, it is quite important to regulate the levels of these pollutants in the environment by using appropriate remediation methods. Chemical precipitation, chemical coagulation and flocculation, bioremediation, membrane filtration, ion exchange, electrochemical methods, and bioremediation are some of the available effective remediation methods. It is important to notice that nanotechnology offers several promising ways for utilizing these toxic heavy metals in minor quantities, their removal from contaminated water and soil, recovery from waste, and detection and monitoring in the environment. Therefore, it is vital to consider the potential benefits of nanotechnology through novel research and innovation in both reducing utilization and remediation due to heavy metals.

Keywords

Inorganic pollutants; heavy metals; water contamination; soil contamination; health consequences; remedial actions

2.1 Introduction

Inorganic pollutants are chemical substances that do not contain carbon atoms. These are created by nature or by human activities and are frequently found in urban runoff, mining, and industrial waste. Humans, animals, and plants are affected due to the negative consequences of exposure to these contaminants. The types of inorganic pollutants that pollute the environment are mainly heavy metals, trace elements, mineral acids, metal compounds, inorganic salts, sulfates, and cyanides which are present in the environment in higher concentrations than the desirable levels (Wasewar et al., 2020). Among them, heavy metals are chemical elements, having a specific gravity at least five times that of water, and those are the major inorganic pollutants found in the environment when considering their adverse effects (Prasher, 2009).

Even at very low concentrations, they are harmful to nature and could significantly affect both humans and animals (Vardhan et al., 2019). Some heavy metals, such as copper (Cu) and chromium (Cr), are crucial for biochemical functions in the human body; however, in higher doses, they are also harmful and may cause acute or chronic toxicities (Engwa et al., 2019). Lead (Pb), mercury (Hg), and cadmium (Cd) are other examples of hazardous heavy metals that could harm human health. Heavy metal toxicity in human beings is mainly due to oxidative stress leading to biological molecular damage (enzymes, proteins, and nucleic acids). Moreover, they cause behavioral issues, learning impairments, and developmental delays. Excessive exposure to heavy metals may cause carcinogenesis, neurotoxicity, and cellular toxicity in vital human organs such as the liver, lungs, and kidneys (Engwa et al., 2019). Therefore, it is crucial to minimize heavy metal exposure to human beings. Heavy metal sources are mainly twofold; geogenic or anthropogenic, where vegetation decomposition, chemical weathering of rocks with their constituent minerals, and atmospheric dry or wet deposition are natural sources, while anthropogenic sources are mining, discharge of industrial effluents, industrial emissions, and fertilizers (Madhav et al., 2020).

Heavy metal poisoning not only poses adverse health effects but also has a negative impact on the ecosystem. For instance, heavy metals harm or kill plants, animals, and microorganisms, which disturb ecosystems. Moreover, they lower soil and water fertility, which makes it more difficult for plants to grow and for aquatic life to thrive. In general, heavy metal removal is essential for preserving both the environment and human health. With varying degrees of success, there are various treatment options existing to remove heavy metals from the environment and to treat heavy metal-contaminated wastewater prior to release into the environment (Vardhan et al., 2019). Overall, exposure to inorganic pollutants has harmful effects on living beings, and it is essential to minimize human exposure to these chemicals through reducing the usage by moving toward nanoscale developments, proper waste management, and pollution control measures. This chapter highlights the pollution brought about in the environment by inorganic pollutants, their characteristics, sources, and their adverse effects on living beings.

2.2 Inorganic pollutants and their sources

Heavy metals are a group of metals that have a higher atomic density, typically higher than 4000 kg/m³ and nearly all are harmful to living beings even at very low concentrations (Vardhan et al., 2019). Some of the heavy metals commonly found in the environment are Cr, manganese (Mn), iron (Fe), cobalt (Co), Cu, zinc (Zn), arsenic (As), molybdenum (Mo), Cd, tin (Sn), Hg, and Pb (Briffa et al., 2020). This chapter focuses on commonly found heavy metals in the environment including; Cu, Hg, Pb, Cd, and Cr.

2.2.1 Copper (Cu)

Copper (Cu) is an important metal with numerous industrial applications. The Earth’s crust contains relatively abundant amount of Cu. Pure Cu is a good heat and electrical conductor with a relatively high melting point. In nature, Cu occurs in various forms, such as native Cu, copper sulfides (CuS), copper carbonates (CuCO3), and copper oxides (CuO), and these are introduced into the environment through both natural and anthropogenic activities (Patterson, 1971). Copper’s mineral or surface-sorbed state, solubility, and particle size are likely to play a role in bioavailability in soils or suspended particulates in water. Copper acetate and copper sulfate are considerably more soluble and thus more bioavailable than CuO, CuS (e.g., chalcopyrite), and other less-soluble minerals. Additionally, clay minerals, hydrous iron, and manganese oxides are powerful soil adsorbents that strongly bond with Cu in soil and sediments, reducing its solubility and mobility (Royer & Sharman, 2020).

Cu mining operations, metal and alloy production, electrical production, home and agricultural pesticides and fungicide use, leather processing, ceramic industry, and automotive brake pads are examples of sources of anthropogenic Cu in the environment, while volcanic eruptions, windblown dust, and forest fires could be mentioned as few examples of natural sources of Cu pollution (Izydorczyk et al., 2021; Rehman et al., 2019; Shrivastava, 2009). Exposure to high levels of Cu could be lessened by avoiding cooking acidic food in Cu cookware, choosing Cu-free plumbing fixtures, being cautious about Cu-containing dietary supplements, and wearing gloves when handling Cu as it could be absorbed through the skin (Georgopoulos et al., 2001). Cu is also a crucial trace mineral for human health as it is used by the human body for a variety of vital processes such as energy generation in the body, building connective tissues & blood vessels by supporting collagen synthesis, and by being a cofactor of many enzymes (Krupanidhi et al., 2008; Shi et al., 2021). Moreover, Cu can stimulate genes, support the immunological and nervous systems, and aid in brain development. However, exposure to high doses of free Cu ions causes damage to cellular components (Oe et al., 2016). Therefore, actions for reducing the levels of Cu in the environment are quite important.

2.2.2 Mercury (Hg)

Mercury (Hg) is the only metal in the periodic table that is liquid (quick-silver) at room temperature and pressure. It is the most common metal implicated in industrial poisoning. With no nutritional or biological role, Hg is the second most toxic mineral on earth (Ozuah, 2000). Hg compounds are mainly classified into three categories; metallic mercury (Hg°), inorganic mercury (Hg²+), and organic mercury (e.g., methyl mercury: CH3Hg+). All these forms of Hg have been found to be toxic with no recognized biological benefits unlike Cu (Gochfeld, 2003). Mercuric salts are known to be more toxic than mercurous salts. Also, organic mercury complexes are more toxic than inorganic salts and their formation occurs under both environmental conditions and within the animal body (Langford & Ferner, 1999).

Despite its toxicity, Hg has multiple applications in the world due to its unique properties. Hg amalgam has been utilized for dental care for many years, and it has long been used to refine different metals (Brownawell et al., 2005). Moreover, Hg has been utilized in electric appliances like lighting fixtures and dry batteries as well as measurement devices, such as thermometers, barometers, and blood pressure monitors. Some countries continue to employ substantial amounts of metallic Hg as a catalyst in the electrolysis-based manufacturing of caustic soda. In addition, numerous products, including mercurochrome, agricultural chemicals, and mildew-proofing agents have utilized Hg compounds which could be classified as sources of Hg released into the environment (Driscoll et al., 2013; Ebinghaus et al., 1999; Hylander & Goodsite, 2006). Ingestion of Hg poses several serious health risks to humans including; neurological damage, kidney damage, respiratory problems, cardiovascular problems, and skin problems (Park & Zheng, 2012). Exposure to Hg could be minimized by avoiding eating high-Hg fish, being cautious about dental fillings, avoiding Hg-containing skin-lightening creams, choosing Hg-free vaccines, and proper disposal of broken Hg-containing products, such as fluorescent light bulbs, thermometers, and batteries (Ratcliffe et al., 1996; Tchounwou et al., 2003).

2.2.3 Lead (Pb)

Lead (Pb) is another toxic heavy metal with no known biological or nutritional function similar to Hg (Ali et al., 2019). Pb is recognized as one of mankind’s oldest environmental and occupational toxins, which was first identified by ancient Greeks (Witkowski & Parish, 2001). Pb is a mineral frequently found in the earth’s crust and released into the environment through erosion, volcanic eruptions, and rock weathering. However, due to human activities, including mining, smelting, and burning fossil fuels, the amount of Pb in the environment has considerably increased, causing widespread contamination of air, soil, and water. Pb could be found in the environment in multiple chemical forms. Inorganic Pb variants such as lead oxide (PbO), lead sulfide (PbS), lead nitrate [Pb(NO3)2], and lead carbonate (PbCO3) are typically found in Pb ores, batteries, and other industrial applications (Yang et al., 2020). Organic Pb variants such as tetraethyl lead (TEL), trimethyl lead (TML), and lead acetate (LA) are typically found in gasoline, hair dyes, and other cosmetic products (Tuncel et al., 2002).

Some primary sources of Pb released into the environment include industrial activities, transportation, construction, and consumer products (Flegal & Smith, 1995; Paoliello & De Capitani, 2005). Pb has many applications due to its distinctive combination of qualities, including high density, low melting point, and excellent malleability. Some common applications of Pb include; batteries, radiation shielding, electronics, plumbing, and ammunition (Cheng & Hu, 2010) all of which release this inorganic contaminant to the environment. Pb could build up over time in both the environment and living beings. Pb exposure could have serious health consequences, especially for young children, including cognitive impairment, neurological damage, and developmental delays. It is therefore, controlled as a dangerous metal and measures are taken to minimize its environmental distribution. Ingestion of Pb could be minimized by using personal protective equipment when working with Pb, avoiding Pb-containing paints, and Pb-containing ceramics and other products (Tong et al., 2000).

2.2.4 Cadmium (Cd)

It is a soft, bluish-white metal having numerous applications in various industries. Some important applications of Cd include batteries, paint pigments, metal plating, nuclear reactors, semiconductors, and medical appliances. Cd exists in the environment in various chemical forms such as cadmium oxide (CdO), cadmium chloride (CdCl2), cadmium sulfide (CdS), and cadmium carbonate (CdCO3) (Usuda et al., 2011). Cd is naturally present on Earth’s crust in trace amounts, however, it could enter the environment via various natural and man-made sources, including mining and industrial activities, fertilizers and sewage sludge, tobacco smoke, and food and water contaminated with Cd (Hutton, 1983; Pinot et al., 2000).

Cd is primarily discharged into the environment from various sources, including Ni-Cd batteries, coatings and platings, plastic stabilizers, fossil fuel combustion, phosphate fertilizers, and waste incineration. In addition, the concentration of Cd in the environment is also influenced by activities such as Zn, Pb, and Cu mining, production of both ferrous and nonferrous metals, and cement production (Rahman & Singh, 2019). Exposure to high levels of Cd can lead to many harmful health effects, including cancer, kidney damage, bone damage, cardiovascular diseases, gastrointestinal problems, and nervous system damage (Bernard, 2008; Genchi et al., 2020; Sharma et al., 2015). Hence, adequate laws and best management practices must be implemented in industrial and agricultural operations to diminish the emission of Cd into the environment. In addition, people are able to lessen their exposure to Cd by abstaining from tobacco use, selecting low-cadmium meals, and properly discarding batteries and other cadmium-containing devices (Mezynska & Brzóska, 2018; Nawrot et al., 2006).

2.2.5 Chromium (Cr)

Chromium (Cr) is a naturally occurring element that is present in rocks, soil, and minerals that make up the Earth’s crust. Natural processes like weathering and erosion could also cause it to escape into the environment. Cr is an important element that has many practical applications in various industries, as well as an essential element for human health and nutrition. Cr metal has various applications, including in stainless steel production, the aerospace industry, leather tanning, paints and pigments production, dietary supplements, and environmental remediation. As Cr is also widely employed in many industrial processes, there are considerable man-made sources of Cr in the environment. Some common sources of environmental Cr include industrial emissions, disposal of waste and landfills, and pesticides and fertilizers (Kimbrough et al., 1999; Saha et al., 2011). Furthermore, natural phenomena like tectonic and hydrothermal events lead to the release of small amounts of Cr⁴+ from the Earth’s crust (Rahman & Singh, 2019). Around 75% of locations worldwide that are polluted with Cr⁴+ are situated mainly in South Asian nations (McCartor & Becker, 2010).

Cr is essential for human health in small amounts (trace element). Cr is known to support insulin action and normal glucose and lipid metabolism (Striffler et al., 1995). However, excessive exposure to Cr could be hazardous. The type of the element, the exposure route, and the duration of exposure all contribute to the toxicity of Cr. Hexavalent chromium (Cr⁶+) and trivalent chromium (Cr³+) are the two most prevalent types. Long-term exposure to Cr⁶+ could cause numerous health issues since it is more hazardous than Cr³+ (Huvinen et al., 2002). However, Cr³+ could still be dangerous when exposed to large doses (Shekhawat et al., 2015). To lessen these negative impacts, it is crucial to control and reduce the release of Cr into the environment. Exposure to Cr can be minimized by avoiding Cr-containing cleaning agents and paints, using protective gear when working with Cr, proper disposal of Cr-containing products, and maintaining a balanced diet which helps the body to remove toxins (Mishra et al., 2010; Mishra & Bharagava, 2016).

2.3 Inorganic metals and pollution

Inorganic substances, which may contain hazardous heavy metals and elements could be found either in their pure form or combined with other elements (Wilcox, 2005). They are likely the most ancient toxins recognized by humans (Goyer & Clarkson, 2001). These compounds are typically present in a solid state, but under certain circumstances, they may also exist as a gas if finely divided or have a high vapor pressure (e.g., Hg and hydrogen sulfide), or as a liquid if soluble in water (Wilcox, 2005).

Metals are distinct from other harmful substances as they are neither created nor destroyed by humans (Andrade et al., 2017). Nonetheless, the impact of metals on human health is influenced by human activities in two significant ways: firstly, through environmental transmission, which includes human or anthropogenic contributions to air, water, soil, and food, and secondly, by changing the chemical or biochemical form of the element (Beijer & Jernelöv, 1986). Metals may infiltrate a water source through industrial and consumer waste or even as a result of acidic rain breaking down soils and releasing heavy metals into streams, lakes, rivers, and groundwater (Verma & Dwivedi, 2013). When a substance is absorbed and stored in living organisms at a rate faster than it could be degraded or eliminated, it will accumulate. Heavy metals are well known to bioaccumulate in human beings (Nabawi et al., 1987). Exposure to heavy metals induces toxicity, reduces mental and central nervous function, causes fatigue, and damages vital organs such as the lungs, kidneys, liver, and blood composition. Over time, prolonged exposure could lead to a slow degenerative process that affects the physical, muscular, and neurological systems, mimicking the symptoms of Alzheimer’s disease, Parkinson’s disease, muscular dystrophy, and multiple sclerosis (Amirah, 2013). Hence, inorganic contaminants have the potential to contaminate water, air, and soil, creating hazards for all living organisms in the long term.

2.3.1 Water pollution

Water pollution due to heavy metals is a rising concern worldwide, as it poses a serious threat to human health and the environment. Heavy metals such as Pb, Cd, Hg, and Cr are persistent pollutants that do not break down naturally and could accumulate in water bodies over time. Water contamination is mainly due to urbanization and industrialization, where metals are accumulated in the water bodies during the transportation of water. Even trace amounts of heavy metals in water bodies might be highly toxic to human beings and other ecosystems (Briffa et al., 2020). The presence of heavy metals in aquatic environments is a significant global issue due to their toxic nature, prevalence, and resistance to degradation (Adaikpoh et al., 2005).

Intensive agricultural operations may also contribute to polluting the groundwater with pesticides and chemical fertilizers (Kurwadkar, 2019). Since heavy metals bioaccumulate, if one organism is affected, the entire food chain will have its’ effects causing humans to have the highest threat due to the fact that they are at the top of almost all the food chains (Briffa et al., 2020). Raw sewage contains high levels of heavy metals, which do not degrade during sewage treatment. These metals are either eliminated in the final effluent or present in the resulting sludge. The characteristics and pollutants of the sewage released into the water body rely on the sewage treatment processes. Hence, to overcome the issues caused by untreated sewage being discharged into rivers and oceans, numerous measures have been implemented. Stricter regulations have been put in place, and innovative technologies such as membrane filtration, UV disinfection, reverse osmosis, nanofiltration, electrocoagulation, and adsorption have been developed to minimize the amount of pollutants being released into water bodies. Sewage treatment has also become a crucial aspect of water pollution control (Briffa et al., 2020). In surface waters, these pollutants exist in solution form or suspension form and are usually transported to greater distances depending on the stability and the physical state of the pollutants, as well as the wind and currants (Briffa et al., 2020). Persistent pollutants have the potential to infiltrate the food chain via marine creatures like fish. Hence, it could result in the contamination of predators, including larger fish, birds, mammals, and even humans, as they travel across different ecosystems while carrying the pollutant (Walker et al., 2005).

2.3.2 Soil pollution

Heavy metal pollution of soil is a global environmental problem that has gained significant attention due to growing concerns about the safety of agricultural produce (Li et al., 2019). Soil contamination with heavy metals and metalloids could occur from various sources such as industrial activities, mining, application of fertilizers and pesticides, livestock waste, and other waste materials that contain high amounts of these metals. These types of contamination pose risks to humans and ecosystems, either by direct ingestion or contact with contaminated soil, through introduction into the food chain, or by reducing the quality of food through phytotoxicity, which affects both the safety and marketability of the food (Santás-Miguel et al., 2022).

The origin of heavy metals in soil can be traced back to the parent material. Approximately 95% of the Earth’s crust is made up of igneous rocks, which are generally rich in heavy metals like Cu, Cd, nickel (Ni) and cobalt (Co). The natural processes of meteoric, biogenic, terrestrial, and volcanic activities, erosion, leaching, and surface winds introduce heavy metals from rocks into the soil environment (Li et al., 2019). The anthropogenic impact of heavy metal loading into the soil is mainly caused by contamination from metallurgical plants, waste disposal, and agricultural treatments. The metallurgical activities that produce gaseous and particulate matter emissions, wastewater, and biosolid wastes, have a significant impact on the environment (Dudka & Adriano, 1997). Industrial wastewater, sewage sludge, chemical fertilizers, and weathering of soil minerals are the main ways the soil is polluted with inorganic pollutants (Edelstein & Ben-Hur, 2018).

Soil pollution by heavy metals has various impacts on human health, depending on the type and concentration of the metal, the duration and route of exposure, and individual factors such as age, genetics, and lifestyle (Mahurpawar, 2015). Heavy metals are often present in contaminated soils at concentrations higher than necessary for nutrients or normal levels. This leads to their uptake by plants and accumulation to harmful levels. Exceeding the permissible limits of heavy metals negatively affects the growth of beneficial soil microorganisms such as nodule bacteria and rhizobia while they could also cause problems for living organisms including microbes, plants, and humans when they enter the food chain (Zaidi et al., 2014).

If crops are cultivated in contaminated areas and irrigated with wastewater containing high levels of heavy metals, the concentration of heavy metals near the root zone increases. As a result, the plant system absorbs these heavy metals along with nutrients, and accumulates in various parts of the plant, especially in the roots and leaves (Sandeep et al., 2019). The uptake of heavy metals via plant roots is a crucial pathway for these contaminants to enter the food chain. The absorption of heavy metals by plants and their subsequent accumulation as they move up the food chain poses a risk to the health of both animals and humans (Sharma et al., 2006). Heavy metals can indirectly enter the human body through animals that graze on grasses grown on contaminated soils. Studies have shown that soil contamination can be transmitted to plants through water, which could ultimately lead to an increase in heavy metal concentrations in the bodies of animals that consume these plants. This increase in heavy metal concentrations could also be seen in animal by-products such as raw milk, further increasing the risk of toxicity to humans (Ziarati et al., 2018). Furthermore, exposure to heavy metals such as Pb, Cd, As, and Ni via various direct and indirect pathways through contaminated soil increases the risk of various cancers, including lung, bladder, liver, kidney, and skin (Mahurpawar, 2015).

2.3.3 Air pollution

Atmospheric pollutants are substances that are not typically found in the air and exist in higher concentrations than considered acceptable, or are present in specific atmospheric layers in an unusual manner (Molina & Segura, 2021). The increase in global population has led to a significant environmental issue on a worldwide scale air pollution which has been aggravated by the growth of industrialization and urbanization (Masindi & Muedia, 2018). Air pollution is primarily attributed to gases, such as carbon monoxide, methane, volatile organic compounds, and particulate matter (PM) (Molina & Segura, 2021). The majority of atmospheric PM is made up of inorganic ions, including nitrate, sulfate, mineral dust, and heavy metals such as Cd, As, Cr, and Pb. Among these heavy metals, Pb and As appear to be the most prevalent in atmospheric PM (Su et al., 2022). Air pollution has been intensified by the dispersion of dust and particulate matter, which could be attributed to both natural and anthropogenic processes (Soleimani et al., 2018). Naturally occurring processes that contribute to the release of these particles into the air include dust storms, soil erosion, volcanic eruptions, and rock weathering, while anthropogenic sources are more linked to industrial and transportation activities (Briffa et al., 2020).

Numerous research studies have demonstrated that heavy metals are the primary components of PM that lead to negative health effects when inhaled (Wang et al., 2018). Atmospheric PM containing heavy metals can be deposited onto plant leaves or in the soil as well, which could indirectly affect humans through atmospheric heavy metal pollution leading to health risks associated with heavy metal toxicity (Molina & Segura, 2021). Other than atmospheric heavy metal pollution, some heavy metals can enter the body through tobacco smoking as well. The accumulation of several heavy metals, including Cd, Cr, Pb, and Ni, in tissues and fluids could occur as a result of smoking tobacco (Ashraf, 2012).

Various industrial activities typically lead to the emission of airborne pollutants such as Pb and Cd. While food is the primary source of heavy metal toxicity in the general population, inhalation is a significant factor in areas heavily contaminated by these metals (Meshref et al., 2014). Soil and dust contaminated with Pb from industrial sources lead to an elevated level of Pb in the air (Laidlaw et al., 2016) exposing living beings to contamination. Pb is a toxic heavy metal that causes a range of health effects in humans, including developmental delays and cognitive impairments (Masindi & Muedia, 2018). Hg can be released into the atmosphere through anthropogenic sources like coal-fired power plants and waste incineration, as well as natural sources like volcanic eruptions. Coal combustion is a major source of Hg emissions globally (Pacyna et al., 2010). Anthropogenic sources of Cr pollution include industrial processes like electroplating and leather tanning. Industrial emissions are a major source of chromium pollution in the atmosphere (Kumar & Chopra, 2015). For a variety of purposes, including assessing exposure and health risk, determining the concentration of pollutants in indoor air is essential. The inorganic pollutant content in the air is assessed using different methods, such as passive sampling and active sampling (Villanueva et al., 2022).

2.4 Health effects and harm to living beings

The impact of inorganic pollutants on human health occurs in two ways: firstly, by increasing the level of heavy metals found in air, water, soil, and food, and secondly, by altering the chemical composition of an element’s structure (Jaishankar et al., 2014). Heavy metals can be harmful to human beings in higher doses which may cause acute or chronic toxicities due to accumulation in the body. However, some heavy metals such as Cu and Cr are essential for various physiological and biochemical functions in humans (Engwa et al., 2019) in trace amounts. Generally, even extremely minute amounts of the majority of other heavy metals are hazardous to the body. Certain heavy metals, like Pb, Cd, and As, enter the body via the digestive system. Others, such as Hg and Cd enter the body by inhalation, while others, like Pb, could be absorbed through the skin. Numerous heavy metals are transported throughout the body (Florea & Büsselberg, 2006) and compartmentalized into cells and tissues of the human body, where they bind to proteins and nucleic acids, causing damage and disrupting their normal cellular functions (Engwa et al., 2019). Due to the health hazards of these inorganic metals regulatory limits in foods are imposed worldwide. The regulatory limits imposed by various organizations on the heavy metals of interest in this study are summarized in Table 2–1.

Table 2–1

ppm, Parts per million; mg, milligram; EPA, Environmental Protection Agency; OSHA, Occupational Safety and Health Administration; FDA, Food and Drug Administration; WHO, World Health Organization.

Heavy metal ions could cause direct damage to the cells by inducing conformational changes in biomolecules, while they may cause indirect damage by forming reactive oxygen and nitrogen species, including superoxide radicals, hydrogen peroxide, and nitric oxide (Valko et al., 2005). Production of free radicals, results in cellular oxidative stress, and damage biological molecules such as enzymes, proteins, lipids, and nucleic acids, which is the key for both neurotoxicity and carcinogenesis. The imbalance between free radical production and antioxidant generation to detoxify the reactive intermediates is the cause of oxidative stress in cells (Jaishankar et al., 2014).

Each type of heavy metal has a specific mechanism of free radical generation. During prolonged exposure, some heavy metal toxicities may be acute, while others may develop into chronic disorders that could harm vital organs such as the kidney, liver, lungs, brain, and endocrine system (Engwa et al., 2019). Chronic toxicity gradually leads to degenerative processes in the muscles, body, and brain that are comparable to those found in conditions including Parkinson’s disease, multiple sclerosis, muscular dystrophy, and Alzheimer’s disease, and long-term exposure might also cause cancers (Järup, 2003). Heavy metals have been found to have an impact on cellular organelles such as mitochondria, nuclei, lysosomes, and cell membranes. Metal ions interact with DNA and nuclear proteins, which cause site-specific damage, subsequently leading to DNA damage, cell cycle modulation, and carcinogenesis. The metal-mediated free radicals may induce DNA base alterations which cause oxidative damage and carcinogenesis (Briffa et al., 2020).

2.4.1 Harmful health effects of copper (Cu)

Cu is classified as an essential element required as a cofactor for many enzyme functions including cellular energy (ATP) generation. Cu toxicity is categorized as primary if it occurs due to an inherited metabolic disorder or secondary if it is caused by high intake, increased absorption, or reduced excretion due to underlying pathological conditions (Bomzon et al., 2023). Accidental consumption or use of contaminated water sources, copper-containing creams for burns, acidic foods cooked in uncoated copper cookware, and suicide attempts are common causes of Cu toxicity. Ingestion of 10–20 g of Cu could be lethal. Copper sulfate (CuSO4) is easily accessible and used in farming as a pesticide, in the leather industry, and in making homemade glue. Burning CuSO4 is a common practice among Buddhists and Hindus, and the bright blue color of hydrated CuSO4 crystals could attract children and lead to inadvertent poisoning (Gamakaranage et al.,