Elemental speciation in human health risk assessment.
This book is based on a draft prepared by WHO Task Group on Environmental Health Criteria for Elemental Speciation in Human Health Risk Assessment under the supervision of Dr Inge Mangelsdorf of Fraunhofer Institute, Hanover, Germany and Dr A. Aitio, International Programme on Chemical Safety, WHO, Geneva, Switzerland, held on November 15-18, 2005 at Fraunhofer Institute of Toxicology and Experimental Medicine, Hanover, Germany.
The book is directed at risk assessors and regulators, to emphasize the importance of consideration of speciation which is hardly taken into consideration as a part of most hazard and risk assessments. Further, the book points at the significance of analysis of speciation of elements to increase knowledge on the effect of speciation on mode of action and also to increase understanding of health effects. Speciation is the evaluation of chemical form and distribution of the elements, which play an important role in their toxicity and bioavailability. The areas of speciation analysis have undergone a continued evolution and development for the last two decades. The rapid development of inorganic instrumental analysis mainly driven by the development of atomic spectrometry enabled the analysts to look into the role of trace elements in different areas, such as health and environment, geochemistry and material sciences, to name some. This book provides a comprehensive description of the major areas involved in elemental speciation with the following chapters: structural aspects of speciation; analytical techniques and methodology; bioaccessibility and bioavailability; toxicokinetics and biological monitoring; molecular and cellular mechanisms of metal toxicity; and health effects. In addition, individual chapters are devoted to elemental speciation and mechanism of actions of most of the elements (chromium, manganese, iron, zinc, cobalt, nickel, copper, arsenic, selenium, cadmium, mercury and lead) in detail. Apart from this, role of tin, barium, palladium, platinum, thallium is also discussed in health effects chapter. The book contains an important chapter entitled, "Structural aspects of speciation" where it clearly explained electronic and oxidation states, nuclear (isotopic) composition, inorganic compounds and complexes, organometallic compounds, organic and macromolecular complexes of various elemental species. The book successfully pointed out that the distribution, mobility and biological availability of chemical elements depends not simply on their concentration but, critically, on the chemical and physical association which they undergo in natural systems. However, the book does not point out some of the error sources in analysis of speciation, e.g., incomplete extraction from solid samples, degradation reactions, matrix-dependent recovery of extraction, lack of adequate internal standards, matrix effects, poor sensitivity of analytical techniques, etc. Actually the most difficult area of speciation remains the provision of a truly representative sample and the ability to transfer this to a suitable measurement technique whilst ensuring that the speciation profile remains intact.
Fundamental understanding of trace element behaviour, the realistic formulation of historical perspectives of trace element contamination, an assessment of environmental transformation processes and a thorough appraisal of environment-related health problems and diseases are well documented in this book. The book explains the toxicokinetics and toxicodynamics of elements influenced by carriers, valence state and isotopes, particle size, element ligands, organic versus inorganic element species and biotransformations with resultant health effects.
The book also reflects on understanding of some of the most important forms of an element, the transformation between forms and various consequences in terms of risk assessment, toxicity or biological activity. Different elemental species might not only differ quantitatively in their characteristics (e.g., toxicity) but also qualitatively (toxic versus essential). While Cr (III) compounds do have some positive biological activity and are therefore considered to be essential, Cr (VI) compounds are carcinogenic. Inorganic As (III) trioxide ([As.sub.2][O.sub.3]) is also a carcinogenic but it was found to be effective in the treatment of certain forms of leukaemia. The methylated forms of arsenic are found to be far less toxic than the inorganic arsenic compounds. Methylated mercury, by contrast, is much more toxic than inorganic mercury. The book successfully highlighted molecular mechanisms of metal toxicity and carcinogenesis in respective chapters. Chronic exposure of many heavy metals and metalderivatives is associated with an increased risk of cancer, although the mechanisms of tumour genesis are largely unknown. Major areas of focus in this book include exposure assessment and biomarker identification, role of ROS or oxidative stress in carcinogenesis, mechanisms of metal-induced DNA damage, metal signaling, metal-protein interactions and the effects of different elemental species on immune system.
In conclusion, this is an excellent reference book and presents a comprehensive insight on the toxicological evaluation of elemental species and their intended usage pattern and possible human exposure, and provides an extensive bibliography. The text is clearly written and presents a vast amount of sound technical information. This book should be useful to all toxicologists, scientists, medical practitioners involved in regulatory agencies and is a good guide to those who are engaged in basic medical research on heavy metals or trace elements.
Kusal K. Das
Environmental Health Research Unit
Department of Physiology
Al Ameen Medical College
Bijapur 586 108, India
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|Author:||Das, Kusal K.|
|Publication:||Indian Journal of Medical Research|
|Article Type:||Book review|
|Date:||Apr 1, 2008|
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