Arsenic Medical and Biological Effects of Environmental Pollutants (1977) / Chapter Skim
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7 Summary and Conclusion
7 Summary and Conclusion
Pages 216-226
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From page 216... ...
, and aluminum strongly adsorb or form insoluble precipitates with arsenites and arsenates is important in the control of arsenic pollution. The ability of various molds and bacteria to convert arsenic compounds to various methyl 216
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From page 217... ...
The largest use of arsenic is in the production of agricultural pesticides, in the categories of herbicides, insecticides, desiccants, wood preservatives, and feed additives. Arsenic trioxide was the raw material for the older inorganic pesticides, including lead arsenate, calcium arsenate, and sodium arsenite.
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From page 218... ...
Safe disposal of arsenic wastes still constitutes a major administrative and technologic problem. The major sources of arsenical wastes are residues in empty pesticide containers; surplus pesticides stored by government agencies, manufacturers, state and municipal facilities, and users; and soil contaminated by extensive use of arsenical pesticides.
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From page 219... ...
Bacteria and fungi can metabolize inorganic arsenic salts to form methylated derivatives. Algae can biosynthesize complex organic arsenicals that are associated with the lipid fraction of these microorganisms.
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From page 220... ...
The mechanism of action of phenylarsonic animal feed additives remains obscure, and these compounds are for the most part absorbed and excreted without metabolic change. Toxicoses caused by the phenylarsonates are manifested by an entirely different syndrome from those caused by the inorganic and aliphatic organic arsenicals.
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From page 221... ...
One of the first symptoms of plant injury by sodium arsenite is wilting caused by loss of turgor, whereas the symptoms due to arsenate do not involve rapid loss of turgor, at least through the early expression of toxicity. The chvtotoxicity of organic arsenical herbicides is characterized by .
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From page 222... ...
Proper examination of the skin of people subjected to chronic low-dose arsenic exposure has the potential for providing valuable information related to the dose and duration of exposure necessary to cause changes in given populations. In a word, these benign skin lesions may be regarded as sensitive indexes of exposure to an agent that has potentially serious consequences.
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From page 223... ...
The absence of a useful animal model is a serious handicap to the study of arsenic as a skin carcinogen and is probably due to metabolic differences between humans and the animals tested so far. The failure to induce skin cancer in test animals is perhaps not surprising, inasmuch as neither melanosis nor keratosis has been duplicated in animals and these effects appear to be inseparably linked to the tumorigenic action of arsenic in the skin of man.
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From page 224... ...
Until recently, total arsenic was usually determined calorimetrically, by either the molybdenum blue method or the silver diethyldithiocarbamate method. Arsenic is now usually determined by atomic absorption, with the sample solution introduced into a flame as an aerosol or deposited as a droplet inside a tube or on a metallic strip, which is then strongly heated.
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From page 225... ...
Industrial effluents have been shown to contain arsenic, but the self-purifying tendency of rivers and streams and improved quality of wastewater discharges should help to minimize this problem. The use of arsenical pesticides in food crops declined greatly after introduction of the chlorinated hydrocarbon and organophosphorus chemicals.
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From page 226... ...
Clearly, the ecologic uncertainties about arsenic compounds deserve more effort and attention.
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