Handbook of Arsenic Toxicology

Swaran Jeet Singh Flora

• Publisher: Academic Press
• Year: 2014
• eBook ISBN: 9780124199552
• Topic: Biological Sciences
• Subtopic: Toxicology
• Index: Biological Sciences

Throughout history, arsenic has been used as an effective and lethal poison. Today, arsenic continues to present a real threat to human health all over the world, as it contaminates groundwater and food supplies. Handbook of Arsenic Toxicology presents the latest findings on arsenic, its chemistry, its sources and its acute and chronic effects on the environment and human health. The book takes readings systematically through the target organs, before detailing current preventative and counter measures. This reference enables readers to effectively assess the risks related to arsenic, and provide a comprehensive look at arsenic exposure, toxicity and toxicity prevention.- Brings together current findings on the effects of arsenic on the environment and human health- Includes state-of-the-art techniques in arsenic toxicokinetics, speciation and molecular mechanisms- Provides all the information needed for effective risk assessment, prevention and countermeasure

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Arsenic

Chemistry, Occurrence, and Exposure

Swaran J.S. Flora, Department of Pharmacology and Toxicology, Defence Research and Development Establishment, Gwalior, India

The presence of arsenic in water bodies depends on pH, the redox condition of the solution, sorption, and exchange reactions. The World Health Organization (WHO) has established a guideline value of a maximum of 10 μg/L for arsenic in drinking water. Historically, arsenic has been used in fertilizers and medicines, and as a wood preservative; however, exposure to it over time may lead to skin diseases, impaired biochemical process, and various types of cancer. Bangladesh and West Bengal in India are the worst affected regions in terms of arsenic levels in water bodies and the magnitude of resultant health problems. In order to prevent arsenic pollution it is essential to understand the geochemical interactions of arsenic with its environment. The mechanism of arsenic release and mobility and its natural attenuation process are the key factors to elucidate the risk of arsenic contamination and to design and implement safe and effective treatment and remediation technologies.

Keywords

arsenic; sources; redox potential; hydrothermal; geothermal; arsenic-bearing minerals

Chapter Outline

1.1 Introduction 1

1.2 Chemistry of Arsenic 2

1.3 Arsenic Minerals and Compounds 8

1.4 Organoarsenicals 11

1.5 Arsenic Mobilization in the Environment 13

1.6 Sources of Arsenic in Biosphere 16

1.7 Arsenic in Hydrothermal and Geothermal Fluids 24

1.8 Arsenic Release from Mining and Mineral Processing 29

1.9 Global Occurrence of Arsenic in Ground Water 32

1.10 Methods of Arsenic Removal from Water 37

1.11 Conclusions 40

References 41

1.1 Introduction

Arsenic, the king of poisons, has influenced the human population more than any other element or toxic compound for thousands of years. Today, millions of people are being chronically exposed to elevated doses of arsenic from air, food, water, and soil. Throughout the history of human progress, arsenic has been seen as a bizarre and frightful element. Toxic effects of arsenic are highly prevalent in both developed and developing countries. Arsenic toxicity has become a principal concern owing to the escalating contamination of air, water, and soil. It has the ability to readily change its oxidation state and bonding configuration, thus showing diverse chemical behavior in the environment and forming large numbers of organic and inorganic compounds. Specific electronic configurations of valence shells with filled s orbitals and half-filled p orbitals enable arsenic to easily donate electrons and overlap in covalent bonds. Naturally, arsenic forms bonds with oxygen and sulfur and generates large numbers of oxides and sulfides. It is also capable of forming large numbers of bio-molecules as it forms stable bonding with the methyl group. The peculiar chemistry of arsenic is the basis for its dual action as a toxin and as a curative.

Drinking water and contaminated soils are the major means by which arsenic gains its entry into the food chain. Most of the arsenic compounds are readily soluble in water and so can easily enter water bodies such as rivers, lakes, and ponds, and by surface runoff. The main pathways of human exposure to arsenic are ingestion of drinking water, consumption of food, and inhalation of air. Among all sources, drinking water has been reported to be the main route of arsenic exposure around the globe [1,2]. Occupational exposure to arsenic is also very common in individuals working in wood preservation, desiccant, chemical warfare agent, pigment, drug and arsenic-based pesticide industries, and those involved in smelting and mining operations and residing in the vicinity of mining areas.

Prolonged exposure to arsenic leads to various dermatological, respiratory, neurological, and reproductive disorders and it is therefore referred to as a carcinogen and mutagenic agent [3,4]. The US Department of Health and Human Services in its 9th Report on Carcinogens listed arsenic compounds as human carcinogens. Arsenic exposure may cause severe health manifestations including cancers, melanosis (hyperpigmentation or hypopigmentation), hyperkeratosis (hardened skin), blackfoot disease (peripheral vascular disorder), gangrene, diabetes mellitus, hypertension, ischemic heart disease, etc. [5,6].

Due to increasing health concerns and adverse effects of arsenic on humans, US EPA in 2002 reduced the maximum permissible limit of arsenic in drinking water from 50 to 10 μg/L [7]. Despite a number of corrective and preventive measures, the increase of arsenic contamination in ground water continued to develop with the addition of new areas to the list of arsenic- contaminated regions. In view of the global health issues associated with arsenic exposure, it has become essential to understand arsenic sources, geochemistry, interaction with water, and various mechanisms associated with arsenic release into the environment. This chapter deals with the occurrence of arsenic in air, water, and soil, and its chemistry in the entire medium along with its global distribution. The chapter also discusses a number of treatment methodologies for the effective removal of arsenic from ground water and to reduce the global arsenic burden.

1.2 Chemistry of Arsenic

1.2.1 Origin and History

Arsenic has been known since ancient times in its sulfide form. The Greek philosopher Theophrastus knew about two arsenic minerals: bright yellow orpiment (As₂S₃) and red colored realgar (As₄S₄). Greek historian Olympiodorus of Thebes (5th century AD) was the first to obtain white arsenic (As₂O₃) by heating arsenic sulfide. The discovery of the element arsenic is attributed to Albertus Magnus, a German philosopher in the 1200s, who was the first to report the metallic behavior of arsenic. De Mineralibus described pure arsenic being obtained by the heating of orpiment with soap. Arsenic trioxide (As₂O₃), a by-product of copper refining, when mixed with olive oil and heated gives arsenic metal. Chinese scientist Tsao Kan-Mu studied toxicity of arsenic compounds in the 1500s during the Ming dynasty and mentioned their use as pesticides in rice fields. The elemental name is believed to come from the Greek word arsenikos meaning potent. Arsenic ranks as the 20th most common element in Earth’s crust, 14th in the sea, and 12th in the human body.

Humans have been using arsenic since ancient times both as a poison and a curative. It has also been used in pyrotechnics, metallurgy, warfare, and pigmentation, and for decoration. One of the most popular oxides of arsenic (arsenic trioxide) is a tasteless, odorless, white powder used in the past as a chemical warfare agent; however, green colored copper acetoarsenate was traditionally used in wallpapers as a pigment [8].

1.2.2 Atomic Structure and Bonding

Arsenic ranks 33rd in the periodic table, as part of the elements in Group 15, being a member of the nitrogen family. Its atomic number is 33 and its atomic weight is 74.921, placing it as heavier than iron, nickel, and manganese but lighter than silver, lead, or gold. The most stable and non-radioactive isotope of arsenic is arsenic-75 (⁷⁵As) with 33 protons and 42 neutrons inside the...

Table of contents

• Cover image
• Title page
• Table of Contents
• Dedication
• Copyright
• Foreword
• Preface
• Acknowledgements
• List of Contributors
• 1. Arsenic: Chemistry, Occurrence, and Exposure
• 2. Ground Water Arsenic Contamination and Its Health Effects in Bangladesh
• 3. Arsenic and Fluorescent Humic Substances in the Ground Water of Bangladesh: A Public Health Risk
• 4. Arsenic Risk Assessment
• 5. Evaluation of Novel Modified Activated Alumina as Adsorbent for Arsenic Removal
• 6. Health Effects Chronic Arsenic Toxicity
• 7. Changing Concept of Arsenic Toxicity with Development of Speciation Techniques
• 8. Mechanism for Arsenic-Induced Toxic Effects
• 9. Arsenic-Induced Mutagenesis and Carcinogenesis: A Possible Mechanism
• 10. Arsenic Through the Gastrointestinal Tract
• 11. Cutaneous Toxicology of Arsenic
• 12. Arsenic-Induced Liver Injury
• 13. Arsenic and Respiratory Disease
• 14. Arsenical Kidney Toxicity
• 15. Arsenic-Induced Developmental Neurotoxicity
• 16. Developmental Arsenic Exposure Impacts Fetal Programming of the Nervous System
• 17. Health Effects of Prenatal and Early-Life Exposure to Arsenic
• 18. Arsenic, Kidney, and Urinary Bladder Disorders
• 19. Developmental Arsenic Exposure: Behavioral Dysfunctions and Neurochemical Perturbations
• 20. Arsenic and the Cardiovascular System
• 21. Immunotoxic Effects of Arsenic Exposure
• 22. Arsenic and Developmental Toxicity and Reproductive Disorders
• 23. Arsenic and Cancer
• 24. The Association between Chronic Arsenic Exposure and Type 2 Diabetes: A Meta-Analysis
• 25. Arsenic Biosensors: Challenges and Opportunities for High-Throughput Detection
• 26. Medical Countermeasures—Chelation Therapy
• 27. Biochemical and Molecular Basis of Arsenic Toxicity and Tolerance in Microbes and Plants
• 28. Arsenic Contents and Its Biotransformation in the Marine Environment
• Index