The Biological and Environmental Chemistry of Chromium (1994): Sidney A. Katz and Hary Salem. VCH Publishers, Inc., 220 East 23rd Street, New York - 10010, USA, Cost DM 215.
It is paradoxical that lower valency compounds of chromium such as Cr3+ in environmental samples are micro-nutrients whereas hexavalent Cr compounds in food and other items are Carcinogenic. Among the micro-nutrients such as Cu, Pb, Zn and Cd, Cr ranks fourth in Crustal abundance at 100æg/gm with a soluble Cr3+ levels of less than 0.5æg/l in the aquatic system. The book has Nine well defined Sections. The first Section deals with the dual role of Cr at essential as well as at toxic levels. The biological uptake, in terms of biochemical reactions in animals and human beings are adequately discussed in this Section. Over seventy references are also listed here. The second Section deals with the environmental geochemistry of Cr in terms of natural occurrence, its mobility in the hydrosphere, isotopic fractionation and organic legends of interest in biochemistry of Cr. 47 key references are discussed briefly in this Section. The third Section deals with man s use of Cr in a variety of products such as alloys, chemicals and refining activities starting from chromite as a natural geochemical source material. The global distribution of chromite is discussed briefly and the environmental aspects of Cr as used in a number of refractories is discussed based on fifty important references.
The fourth Section deals with geochemical weathering of Cr compounds and anthropogenic addition to the environment due to a variety of human activities. In relation to natural abundances in a variety of rocks and minerals, the emission levels from such industrial activity as coal and oil Combustion, at 1700 tones Cr/yr in its trivalent state is documented in detail. Waste disposal due to electroplating contributes upto 11600 æg/gm of Cr to soil while incinerator fly ash could add another 1600 æg Cr/gm of soils. The aqueous chemistry of inorganic Cr (Cr+3 and Cr+6) compounds is briefly discussed based on 80 references. Section five deals with the toxicology of Cr. The blood Cr, urine elimination, lung levels, skin absorption and Cr uptake due to orthopedic practices are covered in this section. There is a detailed discussion on Transport, metabolism, distribution and elimination of Cr compound via biocarriers have received considerable attention in this section, with a coverage of over 270 references. Experimental data on Cr behaviour in a variety of animals such as rat, human dead bodies, human hair and tissues are illustrated adequately. Occupational hazards in welding industry based on epidemiological survey is briefly discussed. Genotoxicity aspects of Cr compounds in a variety of organisms such as Fish, Rodents, insects as well as at cellular and DNA levels are covered with experimental data. This section accounts for nearly a quarter of discussion in the entire book.
The essentiality of Cr as a minor nutrient is critically evaluated in the sixth section. Glucose and lipid metabolism requires Cr. Supplementing needs of Cr at levels as high as 150-250æg/day for TAN (total parental nutrition) are lucidly documented. Discussion on impaired glucose (Cr bearing) tolerance is interesting. Cr levels in a variety of commonly used spices, such as Turmeric (more than 2 æg/gm) Thyme (about 10 æg/gm) are discussed. Edible corn carries 370 æg Cr/gm whereas greenbeans carry a low level of 40 ægCr/gm. Carbohydrate, lipid and protein metabolism of Cr in human body has been adequately discussed. The nutritional status of Cr is illustrated with tabulated data for a wide variety of food items. More than 160 references are covered in this section.
Section seven elegantly discusses various analytical methods currently employed in Cr estimation in environmental samples. The need for proper preservation of biological samples for Cr estimation is illustrated well.Variety of instrumental techniques such as AAS (sensitivity = 0.06 æg/l), ICP-AES (1æg/l) and SSMS (DL) (0.0005 mg/l) are compared based on U.S.E.P.A. methodology. The desirability of chemical pre-treatment in spectrochemical methods such as AAS, ICP etc are highlighted. Chromatographic approach for species estimation, in view of variable oxidation states of Cr, are discussed in detail. There is also a brief discussion on a variety of reference materials (both geochemical as well as biological). Over 180 references are covered in this section.
The eighth section discusses regulatory aspects of the chromium problems both from the point of view of standards, permissible levels and legal measures to monitor them. Thus, a healthy trend has been set up whereby hard core biogeochemical aspects are discussed along with enforcement Acts, standardization, monitoring and managements. By and large though these Acts (Laws) such as Drinking Water Act of 1974 , "Clean Water Act of 1977", Clean Air Act of 1970 etc. are with reference to North America and Europe, the discussion give us a reasonable basis to evaluate laws applicable and enforceable in the Indian context. Cr limits in environmental samples as accepted in over 25 countries including India are tabulated for ready reference. About thirty reference cover laws and standard in force in many countries. Based on Ninety references, the ninth section elegantly summaries the subtopics in earlier eight sections.
Overall this book, covering about a thousand references is an excellent work on the biogeochemical aspects of an important paradoxical element. A similar approach can be visualized for a few other toxic elements such as Hg, Se etc. A brief discussion on legal aspects of Cr in the environment makes this book, a very interesting reading exercise and is strongly recommended for researchers.
School of Environmental Sciences
Jawaharlal Nehru University
New Delhi - 110067