Harmful Natural Chemicals and Radiation in the Environment

Stories, History and What You Need to Know

Raymond Poon

• Publisher: WSPC
• Year: 2012
• Print ISBN: 9789814412933
• eBook ISBN: 9789814412957
• Topic: Medicine
• Subtopic: Biochemistry in Medicine

This unique volume provides in layman's terms, without sacrificing scientific facts, the health hazards and potential dangers of naturally occurring substances that are around us everyday. The comprehensive coverage includes compounds (e.g. arsenic, lead), gases (e.g. hydrogen sulphide, ozone) and all forms of natural radiations (e.g. heat, radon). Readers will find this book both informative and entertaining because facts and important data are introduced and interpreted in the form of history, stories and scientific summaries. Each chapter concludes with a practical guide that readers will find useful.

Harmful Naturally Occurring Substance and Radiation, which is fully referenced with up-to-date articles, may be used as a textbook for undergraduates and as an introductory textbook for post-graduates in biochemistry, environmental science, toxicology, medical science, and health care. People interested in personal and public health and earth issues will find this book a thought-provoking and revealing read. The book may also be a source of information for policy makers, public health officials, city planners and environmental engineers.

Contents:

• Aluminum
• Arsenic
• Copper
• Ethylene
• Lead
• Mercury
• Nitrate
• Carbon Dioxide and Oxygen
• Toxic Gases of Nature
• Hardness of Water
• Fundamentals and History of Radiation and Radioactivity
• Effect of Ionizing Radiation on Health
• Ultraviolet Radiation
• Heat

Readership: Undergraduates and graduates, general public, professionals, others (policy makers, public health officials, urban planners, environmental engineers).

CHAPTER 1

ALUMINUM

Aluminum in Nature

Aluminum is a silvery-white, malleable and ductile metal in Group 13 (III) of the periodic table. Aluminum is the third most abundant element (after oxygen and silicon), and the most abundant metal, making up about 8% by weight of the Earth’s solid surface. Aluminum in its elemental form is not found in nature because it is highly reactive and is rapidly oxidized to oxides or combined with other element to form aluminum compounds. Aluminum compounds are found everywhere. Clay, for example, is composed of aluminum, silicon and oxygen with trace amount of other metals. Feldspar is aluminum silicate found in igneous rocks. Corundum, a mineral next only to diamond in its hardness, is a form of aluminum oxide. Bauxite, which contains up to 55% aluminum oxide (alumina), is the major raw material for the extraction of aluminum. Some gemstones are aluminum oxides whose specific color is determined by the type of trace metals they contain, e.g. chromium imparts the characteristic red color to ruby, while the violet color of sapphire is due to iron and titanium.

Use of Aluminum

Aluminum metal is used in beverage cans, cooking utensils, tin foils and coins. Alloys of aluminum are strong, light-weight, easy to shape and weld, and corrosive-resistant. Therefore, aluminum is extensively used in the car and aircraft industries, in the building trades, and in decorative arts and jewelry. Aluminum is an ingredient in some solid fuels, rocket propellants and explosives. Interestingly, aluminum compounds are also used as fire retardants and as foaming agents in fire extinguishers. Because of its excellent reflective and low radiant properties, aluminum foils and alloys are extensively exploited in spacecraft and space suits. Aluminum is used in power lines, electrical conductors, cables and wiring. Aluminum sulfate (alum) is used as mordant in the dye industry and in large quantity as coagulant in water treatment. Corundum is second in hardness to diamond and an important industrial abrasive. Aluminum oxide is employed in laboratories and industies for separating mixtures. Some of the aluminum-containing products are in close contact with our body, e.g. jewelry, dental crowns and denture materials, cosmetics and antiperspirants. A wide variety of aluminum products are food additives; some are foaming, emulsifying and anti-caking agents, while others are added for the purpose of pH and color adjustment. Aluminum may be present in various concentration in medicinal products such as antacid, buffered aspirins, and adjuvant for vaccines.

From the early 1940s to late 1970s, inhalation of aluminum particles was experimented as a therapy for silicosis,^75,76 a worldwide occupational lung disease caused by breathing in air contaminated by crystalline silicon dioxide or silica.⁷⁷ The rationale for such a therapeutic procedure was that aluminum can coat the silica particles thus reducing their solubility and reactivity toward lung tissues. For a time, miners in Australia, the United States and Canada liable to silica dust exposure were sprayed with an aluminum mist before they entered the work area. However, the effectiveness of aluminum therapy for the prevention or amelioration of silicosis has not been unequivocally demonstrated.^77,88 Furthermore, concern was raised that the experimental procedure undermined the importance of primary preventive measure, namely the reduction of silica dust in workplace air.⁷⁸

History

Although aluminum compounds are as old as earth itself, the elemental metallic form was not known to the world until the 19th century. In 1825, the Danish scientist Hans Christian Ørsted succeeded in isolating a reasonably pure form of elemental aluminum by reacting anhydrous aluminum oxides with a reactive potassium mixture.¹ Aluminum is tightly bound to other elements such as oxygen and it takes tremendous amounts of energy to separate these bonds and extract the elemental metal. The separation process was time-consuming and costly, and the aluminum produced was considered a precious metal; a major use was to be fashioned into jewelry items. In 1886, the American Charles Martin Hall and the Frenchman Paul Héroult separately invented the electrolytic reduction process for the production of aluminum from alumina extracted from bauxite.¹ Although the Hall–Héroult process made large scale production possible, aluminum was still an expensive metal because, at that time, the cost of electricity required for the electrolytic process was high. For example, the aluminum block used to cap the Washington Monument in 1884 costs $16 per pound, the same as the then prevailing market price of silver.² It was not until the turn of the 20th century, when the generation of electricity becomes less costly, that widespread application of aluminum in fabrication, industry and consumer goods began. For this reason aluminum is often called the metal of the 20th century.

Aluminum in Air, Water and Food

Air. Aluminum found in the atmosphere is predominantly in particulate forms. Because aluminum accounts for 8% of the Earth’s crust, much of the atmospheric source of aluminum originates from natural erosion of soil and rocks and volcanic activity.³ Anthropogenic sources account for about 13% of atmospheric aluminum⁴ and these include aluminum production, coal combustion, exhaust from motor vehicle combustion, mining and agricultural activities, and other industrial activities. Airborne aluminum levels range from 0.0005 μg/m³ over Antarctica to more than 1 μg/m³ in industrialized areas.⁵

Water. Aluminum occurs ubiquitously in natural waters as a result of the weathering of aluminum-containing rocks and minerals. Atmospheric deposition is another natural source of aluminum input to surface water. Anthropogenic sources such as mining activity, industrial and municipal discharges, surface run-off, may also contribute to aluminum in surface water. Wet and dry deposition of atmospheric aluminum to surface water is a constant input.^3,5 Low pH facilitates mobilization and solubility of aluminum; acidic mine drainage and acid rain for example, cause an increase in the dissolved aluminum content of surrounding waters.^6,7 Aluminum concentration in drinking water varies widely from country to country and from region to region. In an analysis of drinking water from New York City and 25 states in the U.S., the aluminum concentrations were found to range from undetectable to 1.029 mg/L.⁸ In the city of Xi’an, China, total aluminum concentrations in drinking water were found to range from 0.051–0.417 mg/L.⁹ In the Kirazli region of Turkey,¹⁰ aluminum concentration as high as 15 mg/L has been reported in water that may be used for drinking purpose. Treatment of drinking water with alum or other aluminum-based coagulant for water treatment may contribute to the aluminum concentration in drinking water.^3,9 Normally, the contribution of drinking-water to the total oral exposure to aluminum is about 4%.⁵ The World Health Organization does not set a limit for aluminum on drinking water. Instead, it has derived “practicable levels” of

0.1 and

0.2 mg/L for large and small facilities, respectively, based on optimization of the coagulation process in water treatment plants that use aluminum-based coagulants.¹¹

Food. Food is the main source of aluminum intake.¹² Foods such as spinach, tea and some herbs contain high concentrations of aluminum. Some foods with high amounts of aluminum-based additives (e.g. processed cheese, grain products, cream substitutes, and grain-based desserts) contribute significantly to the amount of aluminum we ingest. Cooking with aluminum utensils and drinking beverages from aluminum containers may also add to our oral intake of aluminum. Adult dietary intake of aluminum in industrialized countries ranged from approximately 1.9–11 mg/day. Infant intakes of aluminum in Canada, the United Kingdom, and the USA ranged from 0.03–0.7 mg/day.^5,12

Potential Hazards and Health Effect

As much as aluminum is a 20th century metal, aluminum-related diseases are justifiably being called 20th century diseases. Indeed, concerns about known and potential adverse effects related to aluminum continue with the widespread use of aluminum in the 20th century and beyond. The followings are some representative cases that provide insight into the real and putative hazards of aluminum.

Dialysis Encephalopathy. Between late 1960s and the 1980s, many kidney disease patients undergoing dialysis came down with a disease called dialysis encephalopathy¹³ or dialysis dementia.¹⁴ According to George Dunea,¹⁵ the disease appeared so suddenly that “it was mysterious and frightening indeed. Patients coming to dialysis would look at each other in fear and wonder whose turn would come next. Consumer groups came to the hospital wondering what was going on. At first, we had no idea what was happening...”. An association of aluminum with dialysis enceph...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• Dedication
• ACKNOWLEDGMENT
• PREFACE
• CONTENTS
• INTRODUCTION
• Chapter 1 Aluminum
• Chapter 2 Arsenic
• Chapter 3 Copper
• Chapter 4 Ethylene
• Chapter 5 Lead
• Chapter 6 Mercury
• Chapter 7 Nitrate
• Chapter 8 Carbon Dioxide and Oxygen
• Chapter 9 Toxic Gases of Nature
• Chapter 10 Hardness of Water
• Chapter 11 Fundamentals and History of Radiation and Radioactivity
• Chapter 12 Effect of Ionizing Radiation on Health
• Chapter 13 Ultraviolet Radiation
• Chapter 14 Heat
• Note
• Index