Water-borne mutagens

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Introduction
01 Cancer
02 Ozone
03 Urban air
04 Air pollutants
05 Blue-green algae
06 Water mutagens
07 Contamination
08 Chernobyl
09 Radon
10 Medical geology
11 Renal hazards
12 Organohalogens
13 Estrogens
14 Food hazards
15 Mycotoxins
16 Poisoning
17 Genetics
18 Risk

Ordering

(Excerpt from Chapter 6)

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Water: A unique substance

Water is essential to all life on earth and dominates the chemical composition of all biota. All animals, including humans, are more than 50% water by weight. Its necessity and ubiquity rest on its unique chemical and physical properties. Water has an incredibly high specific heat, exceeded by few known substances. As a result, water is thermally stable, with temperature changes occurring only very gradually. The latent heat of vaporization is also extremely high, and large energy inputs are required before liquid water can be changed to a vapor. Consequently, water exists primarily as a liquid at common temperatures and pressures. The density of water also reveals interesting and unique properties. Water is over 700 times more dense than air and achieves a maximum density at slightly less than 4^o C. This high density causes many substances to be relatively buoyant, thus reducing the amount of energy required to move heavy materials across large distances (e.g., lumber).

Water is the only common substance that expands when it freezes. Pure ice at 0^o C is actually about 8.5% lighter than liquid water. This allows ice to float on water and causes surface waters to freeze from the top down. Water also exhibits the highest surface tension of any known liquid except mercury. In other words, the molecular attractions between adjacent water molecules at the air-water interface favor adhesion to the liquid phase. The resulting tension is sufficient to support particles and organisms of considerable size. Finally, water is an excellent solvent capable of dissolving a wide range of substances. Consequently, it is an effective medium for the transfer and movement of dissolved materials required by all organisms.

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Paul A. White is presently a visiting research scientist at the Atlantic Ecology Division of the U.S. Environmental Protection Agency in Narragansett, Rhode Island, USA. He completed his Ph.D. in 1995 at McGill University in Montreal, Quebec, Canada. His current research efforts are largely focused on determining the sources, identity and health hazards of genotoxic substances in municipal wastewaters and surface waters.

David M. DeMarini is a genetic toxicologist in the Environmental Carcinogenesis Division of the U.S. Environmental Protection Agency in Research Triangle Park, North Carolina, USA. He received his Ph.D. from Illinois State University in Normal, Illinois, USA, in 1980. His current research is on the types of mutations induced by complex mixtures and the influence of genotype on susceptibility to the genotoxic effects of various environmental mutagens, such as disinfection by-products.