Drinking Water and Health, Volume 1 (1977) / Chapter Skim
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IV SOLID PARTICLES IN SUSPENSION
IV SOLID PARTICLES IN SUSPENSION
Pages 135-204
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From page 135... ...
However, there is widespread concern over the biological effects of the asbestos mineral fibers that occur in water, since similar fibers are known to be carcinogenic when air heavily laden with them is inhaled for many years. In view of this concern that such fibers as occur in water may be injurious to health, their occurrence, characterization, analysis, and biological ejects are reviewed in some detail.
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From page 136... ...
, and chemical analysis (Weaver and Pollard, 1973~. The layer-lattice clay minerals, in themselves, do not appear to have
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From page 137... ...
, is still open to question and is the subject of extensive study at the present time. If layer-lattice clay minerals have deleterious e~ects on human health, they are probably indirect, through adsorption, transport, and release of inorganic and organic toxicants, bacteria, and viruses.
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From page 138... ...
With regard to phosphate, it is likely that its interactions with calcium ion and amorphous hydroxides of Fe3+ and A13+ and with allophane are more important than adsorption by clay minerals in affecting its concentration in natural waters. In addition to adsorption by simple ion exchange, much work indicates the retention of transition and heavy metals at clay mineral surfaces via
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From page 139... ...
in which The hydroxides and hydrous oxides of iron, manganese, and aluminum are often components of the clay fraction of sediments and have important e~ects on pollutant concentrations in natural waters. They often exist as coatings on the surfaces of other minerals and thus may exert chemical activity far out of proportion to their total concentrations.
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From page 140... ...
Another important factor is the nature of the exchange cation. Thus, for example, transition metal cations on the exchange complex, that have unfilled a'orbitals, will interact strongly with electron-supplying groups of organic molecules.
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From page 141... ...
Hydrogen bonding between water molecules directly solvating exchangeable cations and polar functional groups, such as carbonyl, on organic molecules. The water molecules thus act as a "bridge" between the cation and organic species.
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From page 142... ...
Aromatic molecules such as benzene will complex via pi electrons with clay minerals saturated with Cu2+, under mildly desiccating conditions. Under more vigorous dehydrating conditions, a radical cation of benzene is formed that will react with molecular benzene to give polymers containing phenyl groups as well as fragmented benzene rings (Doner and Mortland, 1969~.
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From page 143... ...
It is obvious that clays eroded from soil surfaces into streams and lakes will probably be, to some degree, complexed with organic matter. Humic acids, a constituent of soil organic matter, may be strongly adsorbed by clays, presumably by interaction with positive sites on the edges of clay particles or with polyvalent cations on the cation exchange complex acting as "bridges." Schnitzer and Kodama (1967)
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From page 144... ...
Noncommercial deposits of asbestos minerals are also relatively com mon. The standard definitions of the Glossary of Geology (American Geological Institute, 1972; second printing, 1973)
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From page 145... ...
. Table IV-3 summarizes the basic properties of the asbestos minerals.
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From page 146... ...
146 DRINKING WATER AND H"LTH TABLE IV-2 List of Some Minerals That May Occur in AcicularFibrous Form. Major Element Stoichiometry Has Been Simplified in Many Cases.
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From page 147... ...
Anthophyllite may have a value similar to that of chrysotile, and the other amphibole asbestos minerals may have values similar to those of cummingtonite (Parks, 1967~. As the pH of the medium falls below the isoelectric point, the surface charge of suspended particles tends to become more positive.
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From page 150... ...
~ , , SOLUBILITY Acid dissolution of asbestos minerals has often been studied in order to test resistance to corrosion (Cotterell and Holt, 1972; Spell and Leineweber, 1969; Choi and Smith, 1971~. In general, the resistance to
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From page 151... ...
Asbestos minerals generally occur in metamorphic retrograde deposits. Chrysotile occurs in low-grade metamorphic deposits, and the amphiboles occur in slightly higher-grade metamorphic deposits.
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From page 152... ...
. Construction DEMO Cement products 69~o Floor tile loo Paper products 756 Paint and caulking 2~o Transportation 3% Textiles 2% Plastics loo Other 6% Redistribtion of asbestos minerals to the environment depends on the extent to which the material is conserved or sequestered in the processes of mining, manufacturing and consumption.
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From page 153... ...
, but this hypothesis has not been substantiated for areas where asbestos minerals occur naturally and that have not been disturbed by man. Asbestos cement pipe is used in some localities to transport drinking water and there has been some concern over the release of fibers from these pipes (Wright, 1974~.
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From page 154... ...
, the total emissions of asbestos (chrysotile) in the United States can be estimated to be about equal to the fibrous emission into western Lake Superior cited above, on a mass basis.
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From page 155... ...
Several workers have shown details of variations in structure in asbestos minerals, and these variations must be compared with smallscale cleavage fibers from nonasbestos deposits (Chisholm, 1973; Hartman, 1963; Hutchinson et al., 1975; Ruud et al., 1976~. ASBESTOS FIBER SAMPLING AND ANAYLSIS Introduction Several methods have been used to identify fibrous or acicular particulates of asbestos minerals and determine their concentrations in air, water, mineral samples and biological tissue.
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From page 156... ...
For optical microscopy, asbestos fibers are defined as those particles of length greater than 5 ,um and a length-to-diameter ratio of 3 to 1 or greater. This method may not be specific for asbestos mineral fibers (by fiber definition)
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From page 157... ...
The amphibole mineral fibers are generally straighter in appearance than those from chrysotile. Selected area diffraction patterns for the amphibole asbestos minerals may be similar in appearance; therefore, casual visual observation of these patterns is sufficient only for classification of the fiber as being "an amphibole asbestos" (Larger et al., 1974; Cook et al., 1974; Clark and Ruud, 1975~.
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From page 158... ...
However, these materials may easily be distinguished using selected area electron diffraction (Ruud et al., 1976; Langer et al., 1975~. Transmission electron microscopes equipped with energy dispersive X-ray detectors allow simultaneous observation of morphology, crystal structure, and elemental composition.
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From page 159... ...
This technique, however, is still in the research phase and has not been developed to the reliability of a general analytical method. It must be recognized that, with the exception of the technique described above, X-ray diffraction methods are not capable of differentiating between asbestos mineral fibers and their nonfibrous mineral counterparts.
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From page 160... ...
There is no direct epidemiological evidence on the ejects of various other types of fibrous minerals, some of which may perhaps find their way into drinking water. The fact that exposure to air heavily polluted with asbestos mineral fibers often leads to the diseases mentioned above does not necessarily indicate that drinking water contaminated with an equally large number of such fibers may lead to the same diseases or perhaps some other diseases.
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From page 161... ...
However, the hypothesis is tenable to the degree that it cannot be ruled out of consideration without evidence to the contrary. It is important to note that workers exposed to air containing large numbers of asbestos minerals fibers inevitably ingest such fibers.
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From page 162... ...
and by Elmes and Simpson (1971~. This, taken together with the data presented in Table IV-6, strongly suggests that ingestion of asbestos mineral fibers can result in an increased risk of cancer of several sites.
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From page 163... ...
An even lower risk might not become apparent for a much longer period of time and then it would be difficult if not impossible to pinpoint the cause. Experimental Studies As discussed above, epidemiological studies of the population exposed have failed to detect any increase in gastrointestinal cancer that might be ascribed to the asbestos mineral fibers contained in some drinking water.
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From page 164... ...
Reports such as these have, without resolving the matter, lent interest to the question whether or not human ingestion of asbestos may be accompanied by similar effects. Experimental investigations with animals of the toxic effects of asbestos mineral fibers have not yet led to the development of an experimental model system that reproduces the putative effects of ingestion of such fibers by man.
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From page 165... ...
Several animal feeding studies with asbestos are reported to have shown no increase in cancer with this route of exposure (Bonser and CIayson, 1967; Smith, 1973; and Gross et al., 1974~. The asbestos minerals tested included crocidolite, ch~ysotile, and "amosite." However, none of these studies would be considered adequate under modern constructs of chronic toxicity testing (National Academy of Sciences, 1975; Sontag et al., 1976)
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From page 166... ...
In this approach, large quantities of mineral fibers, of various size distributions, are injected into the pleural or peritoneal cavity. Stanton et al.
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From page 167... ...
, these may be similarly unreactive, and this may account for failure to detect any increased incidence of various gastrointestinal cancers related to ingestion of mineral fibers in water.
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From page 168... ...
Research on the unresolved problems of the chronic ejects of ingesting asbestos mineral fibers therefore merits strong support. ORGANIC PARTICULATES IN WATER The organic particulate matter found in natural water systems may be classified as follows: 1.
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From page 169... ...
Humic acid is the component that is soluble in strong base but insoluble in strong acid, fulvic acid is soluble in both acid and base; and humin is insoluble in both acid and base. Humic acids contain phenolic, quinoid, polycarboxylic aromatic
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From page 170... ...
The presence of these aggregates will have a marked eject on the way humic acids interact with pollutants in natural water systems, and this will be discussed later. Fulvic acids are generally believed to be similar in structure to humic acids but of lower molecular weight.
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From page 171... ...
In addition to interactions with metals, humic acids and other natural organic polyelectrolytes can interact strongly with other organic components in natural water systems. These interactions can be of two types: incorporation of organic molecules into humic acids during their formation, and reaction of organic compounds with humic acids after their formation.
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From page 172... ...
Martin has not postulated a mechanism for the conversion of the phenols, quinones, and aromatic acids into humic acids, but it is likely that free radical polymerization reactions play a major role in this conversion. The free radicals that polymerize into humic acid molecules probably arise either from enzymatic reactions or photolysis.
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From page 173... ...
When considering these types of interactions it must be kept in mind that humic acids form molecular aggregates; changes in the degree of aggregation will probably modify these interactions. Mechanisms of Interaction Physical Interactions Adsorption a.
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From page 174... ...
A careful study of the interactions of humic acids with enzymes should give a new insight into the biochemical reactions that take place in soil-water systems. Municipal and Industrial Wastes Municipal and industrial waste disposal is a major source of organic particulate matter in natural waters that serve as sources for drinking water.
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From page 175... ...
In combined sanitary storm sewage systems untreated sanitary sewage may be discharged into a receiving stream during periods of high storm sewage flow. Organic matter supplied to natural waters by sanitary sewage-treatment plants and treatment facilities for food-processing plants undergoes degradation relatively rapidly.
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From page 176... ...
found a positive correlation between the organic carbon concentration, iron oxide concentration, and trace metal concentrations in the sediments. Since many of the communities around Lake Michigan take their drinking water from the lake, the high trace metal and pesticide concentrations in the suspended sediments could pose a problem if the coagulation and filtration processes used in water treatment are not adequate to remove them from the water.
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From page 177... ...
It would therefore be expected that some of the organic debris in natural waters would contain elevated levels of hydrophobic pollutants; however, there do not appear to be any studies in the literature that deal with this matter. Organic Colloids Organic polyelectrolytes that are very similar to the soil humic and fulvic acids have been isolated from surface and groundwaters.
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From page 178... ...
However, in an unfractionated sample, the aggregates will contain a diversity of different types of molecules. Even molecules that are quite different from humic acids can be incorporated into the aggregates; Wershaw et al.
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From page 179... ...
MICROORGANISMS AND SUSPENDED PARTICLES IN WATER The tendency of microorganisms to form aggregates and to become concentrated at the surfaces of solid particles, rather than to be uniformly and individually dispersed, may have important consequences for their survival and for their reactions to the various processes of water treatment. It is doubtful that many of these microbial agglomerates will pass through an efficiently operating water-treatment process, but a large segment of the population ingests surface water that has had only partial treatment (i.e., disinfection)
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From page 180... ...
, and Kononova (1966~. These studies demonstrated that the most extensive microbial growth takes place in nature on the surfaces of particles and inside loose floes of solid particles.
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From page 181... ...
Lammers isolated and fractionated various organic and inorganic particle species occurring in natural waters. Studies of this kind could help to elucidate the composition and concentration of microbial particulates in water.
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From page 182... ...
A review of viral problems facing water treatment plant operators is presented by Taylor (1974~.
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From page 183... ...
Color in water is due primarily to the presence of natural organic matter; it may also be caused by certain industrial wastes and by some metallic complexes. Color is measured by determining light adsorption.
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From page 184... ...
Removal of Particulates MINERAL FIBERS Pilot-scale filtration experiments for the removal of amphibole and chrysotile fibers from the Duluth water supply have been conducted (Black and Veatch, Consulting Engineers, 1975; Logsdon and Symons, 1975~. Amphibole fibers were easily removed by coagulation and filtration.
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From page 185... ...
salts. Humic acids were readily removed, but a significant fraction of the fulvic acid component was not removed by either coagulant.
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From page 186... ...
The problem is at present hypothetical, i.e., no data are available. ORGANIC COAGULANTS Many synthetic organic materials have been approved for use in water treatment for removal of particulates.
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From page 187... ...
Measurements of turbidity do not give complete information about the size, number, mass, or type of the particles that scatter or absorb light. Small particles (those less than about 0.1 ,um in maximum dimension, single viruses and many asbestos mineral particles)
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From page 188... ...
Such particles may also have other substances and microorganisms attached to them. Small particles of some materials, such as the asbestos minerals, may have the potential to affect human health directly when they are ingested, and there is widespread concern over the biological effects of such substances.
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From page 189... ...
Epidemiological studies of cancer death rates in Duluth, Minn., where the water supply has been contaminated with mineral fiber, have so far not revealed any increase with time, in comparison with death rates in other areas. Contamination of the Duluth drinking water began less than 20 yr ago, however, and since many cancers have long latency periods, these negative epidemiological findings do not exclude the possibility that an increase might appear within the next 5 to 15 yr.
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From page 190... ...
Although many of the clay or natural organic particulates, in themselves, may not have deleterious ejects when ingested by humans, they may exert important health ejects through adsorption, transport, and release of inorganic and organic toxicants, bacteria, and viruses. The clay or organic complex with a pollutant may be mobilized by erosion from the land, or complexes may form when eroded particulate matter enters a stream containing pollutants.
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From page 191... ...
3. Epidemiological studies of time trends in death rates should be conducted in areas that have high concentrations of mineral fibers in drinking water.
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From page 192... ...
1961. The X-ray Identification and Crystal Structures of Clay Minerals.
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From page 193... ...
1976. Asbestos minerals and their nonasbestos analogs.
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From page 194... ...
1976. Selected area electron diffraction and energy dispersive X-ray analysis for the identification of asbestos fibers, a comparison.
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From page 195... ...
1970. Identification of asbestos fibers by microscopical dispersion staining.
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From page 196... ...
Press, London. Biological Effects of Asbestos Minerals, Epidemiological Findings Anderson, H.A., R
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From page 197... ...
17:260-271. Biological Effects of Asbestos Minerals, Experimental Studies Ampian, S.G.
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From page 198... ...
1972. Biologic differences in response to long and short asbestos fibers.
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From page 199... ...
1971. Structural hypotheses of soil humic acids.
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From page 200... ...
1971. Inhibition by soil humic acids of naive and acetylated proteolytic enzymes.
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From page 201... ...
1971. Role of humic acids of marine origin and their different molecular weight fractions in complexing di- and trivalent metals.
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From page 202... ...
1973a. The fractionation of humic acids from natural water systems.
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From page 203... ...
1976. Measurements of 'turbidity' and related characteristics of natural waters.
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From page 204... ...
Water Supply Research Division, U.S. Environmental Protection Agency, Cincinnati, Ohio.
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