Review of Fluoride in Drinking Water: Status, Issues, and Solutions by A. K. Gupta and S. Ayoob

The book deals with fluoride in drinking water, which is a topic of great interest to public health, especially in developing countries of Africa and Asia. The subject matter of the book spans eight chapters addressing virtually all essential elements from an environmental science and engineering perspective.

A global perspective on fluoride in drinking water is provided in the first chapter. Beginning with a sketch of the drinking water scenario the chapter discusses geogenic pollutants in groundwater, fluoride in humans, and genesis of fluoride in groundwater. The chapter concludes with a number of key points, such as, for example, the main source of fluoride is the parent rock, around 200 million people from 35 countries will be at risk of fluorosis by 2025, and 99% of the absorbed fluoride in humans gets deposited in bones and teeth. On the whole, the chapter is nicely written and provides a lot of useful information.

Chapter 2 discusses the scenario of fluoride pollution. Beginning with an overview of the global scenario, the chapter discusses the fluoride scenario in Africa and Asia and the Indian scenario, and concludes with five key points illustrated by the fluoride belt from Eritrea to Malawi along the East African Rift; fluoride rich zones spanning across China, Northern Thailand, India, Afghanistan, Iran, Iraq, and Turkey; 20 states in India affected by fluoride with Rajasthan, Gujarat, and Andhra Pradesh being the worst affected; and high fluoride concentration in Tanzania, South Africa, Kenya, Ghana, and Sudan.

Dental fluorosis is the subject matter of Chapter 3. Introducing the adverse effects of fluoride on human health, the chapter treats dental effects of fluorosis detailing tooth decay, prevention of dental caries, and the role of fluoride in dental decay; history and occurrence of dental fluorosis; and development of dental fluorosis encompassing physical symptoms of dental fluorosis, issues of dental fluorosis, and prevention of dental fluorosis. The concluding part contains 12 key points, such as the less than disputable evidence for the necessity of fluoride for humans, acceptable level of fluoride in drinking water to prevent dental caries, ecological imbalance of the physiological equilibrium of dental minerals and oral microbial biofilms being a causative factor, and fluorosis as one of the most pervasive health problems.

Skeletal fluorosis constitutes the theme of Chapter 4. It covers the action of fluorosis on bones, fluoride exposure level and skeletal fracture, skeletal fluorosis, crippling skeletal fluorosis, fluoride level, and ensuing effects on skeletal fluorosis; significance of other factors; and recent developments. The chapter concludes with the 15 main points of the chapter, such as that the toxic response of fluoride is mostly reflected in its effects on the human skeletal system, chemical composition and physical structure of human bones are altered by fluoride, increased doses of fluoride reduce mechanical properties of bones, and the most acute forms of skeletal fluorosis observed in India have been with osteosclerosis of the spine and associated osteoporosis of the limb bones.

Chapter 5 discusses stress effects of fluoride on humans, including nonskeletal fluorosis, fluoride and cancer, fluoride and the gastrointestinal system, and other health effects. It is summarized with eight key points, such as interaction of fluoride with soft tissues, organs, and other systems; enhanced oxidative stress owing to acute fluoride toxicity; disturbance in the lipid metabolism in the blood of patients; and connection between fluoride in drinking water and kidney and bladder cancer, to name a few.

Fluoride in the environment and its toxicological effects are dealt with in Chapter 6. Introducing the sources of environmental exposure, the chapter discusses environmental transport, distribution, and transformation; environmental levels and human exposure; fluoride from dental products, and fluoride from food and beverage; fluoride in soil; fluoride in tobacco and masala; fluoride from occupational exposure; total fluoride exposure; effects of fluoride on laboratory animals and in vitro systems; effect of fluoride on aquatic organisms; effect of fluoride on plants; effect of fluoride on animals; and guidelines, values, and standards. The chapter concludes with 11 key points, such as: natural processes of weathering, dissolution of minerals, volcanic eruptions, and marine aerosols are responsible for the release of fluoride into the environment; workers in many heavy industries are routinely exposed to high levels of fluoride; industrial emission is a major source of fluoride exposure; and fluoride exposure affects the photosynthesis and respiration of plants, among others.

An overview of defluoridation techniques is given in Chapter 7. Beginning with coagulation including lime, magnesium oxide, and calcium and phosphate compounds, the chapter discusses coprecipitation of fluoride including alum, and alum and lime; adsorption including bone and bone charcoal, clays and soils, carbonaceous and other adsorbents, alumina, activated alumina, and other alumina-based absorbents; electrochemical methods including electrocoagulation and electrosorption; membrane processes including reverse osmosis, nanofiltration, and electrolysis; and a summary of defluoridation techniques. The chapter concludes with 13 key points, such as defluoridation techniques that are generally practiced are coagulation, adsorption/ion exchange, electrochemical methods, and membrane processes; defluoridation potential of activated carbon is found to be poor; and a lasting solution of defluoridation is yet to be found.

A case study on adsorptive removal of fluoride from groundwater by adsorbent alumina cement granules is dealt with in Chapter 8. Introducing reagents and adsorbate, synthesis of adsorbent, instrumentation, and characterization of the adsorbent, the chapter goes on to discussing batch studies, including the effect of process parameters, equilibrium studies, and column studies; theoretical and mathematical formulations including adsorption capacity, kinetic modeling, rate limiting steps, and adsorption equilibrium and isotherms; factors influencing adsorption; behavior of adsorption columns; analysis and modeling of breakthrough curves; and regeneration. It then discusses results on characterization of the adsorbent, kinetic studies, the rate limiting step, fluoride removal mechanism, isotherm studies, and a summary of the case study.

On the whole, the book is nicely written book and Professors Gupta and Ayoob deserve a lot of applause for writing this very useful book. The book will be useful to graduate students, college faculty, water supply managers, and those dealing with environmental science and engineering issues.