Toxic substances properties

Kersting, K. 1984. Development and use of an aquatic micro-ecosystem as a test system for toxic substances. Properties of an aquatic micro-ecosystem IV. Int. Rev. Hydrobiol. 69 567-607. 

The determination and assessment of toxic substance properties has developed its own science, which cannot be covered here. 

Neady every significant class of dyes and pigments has some members that function as sensitizers. Toxicological data are often included in surveys of dyes (84), reviews of toxic substance identification programs (85), and in material safety data sheets provided by manufacturers of dyes. More specific data about toxicological properties of sensitizing dyes are contained in the Engchpedia under the specific dye classes (see Cyanine dyes Polymethine dyes Xanthene dyes). 

Cationic flocculants are widely used in clearing oil-water, waste, natural and drinking water. At the sarue time they ar e moderately toxic substances which have cumulative properties. For the majority of flocculants, prodused and used in Ukraine, limit admission concentration is 0,l-t-0,4 mg/dm for drinking water and 0,01 mg/dm and less - for natural waters. 

Another section of the EPA, the Office of Prevention, Pesticides, and Toxic Substances (OPPT), has recently updated and harmonized its testing guidelines for evaluating the developmental and reproductive effects of pesticides and industrial chemicals to include an assessment of endocrine disrupting properties. These guidelines will be used in future testing of pesticides under both the Toxic Substances Control Act (TSCA) and the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). 

The nature and intensity of the effect highly depend on the way toxic substances penetrate into the organism. Three main means of penetration are identified inhalation, skin contact, ingestion. Some penetration means are favoured under identical exposure conditions depending on the substance s properties. 

As mentioned above, there are characterization factors for a number of different impact categories, e.g. acidification, eutrophication, climate change, human toxicity and ecotoxicity. However, characterization factors are missing for many additives, especially for human toxicity and ecotoxicity, which makes it difficult to assess the potential impact that a product will cause during its entire life cycle. A major reason that characterization factors are often missing is the lack of data regarding substance properties, such as physical chemical properties and toxicity. 

Extrapolating properties, defined, 16 729 Extra spring copper alloys, 7 723t Extreme ambient conditions, lubrication and, 15 252-256 Extreme-case analysis, 9 547 Extreme environments, solid and liquid lubricants for, 15 256 Extremely low toxic substances, 23 113 Extreme pressure (EP) lubrication regime, 15 214. See also EP entries Extreme purity gases, analyses of, 13 468 Extreme ultraviolet lithography, 15 189-191... 

The Office of Toxic Substances has assembled a team of multi-disciplined scientists to review each of these PMNs and assess the potential risks to human health and the environment posed by commercial manufacture and sale. These assessments are based upon limited firm data on the specific chemical, comparison with structurally similar chemicals of known toxicity, plus estimates of exposure from calculations of the potential number of people involved in manufacturing and processing operations and in consumer use. Most PMNs contain elementary data on physical and chemical properties and obvious acute health effect such as skin... 

Classical bacterial exotoxins, such as diphtheria toxin, cholera toxin, clostridial neurotoxins, and the anthrax toxins are enzymes that modify their substrates within the cytosol of mammalian cells. To reach the cytosol, these toxins must first bind to different cell-surface receptors and become subsequently internalized by the cells. To this end, many bacterial exotoxins contain two functionally different domains. The binding (B-) domain binds to a cellular receptor and mediates uptake of the enzymatically active (A-) domain into the cytosol, where the A-domain modifies its specific substrate (see Figure 1). Thus, three important properties characterize the mode of action for any AB-type toxin selectivity, specificity, and potency. Because of their selectivity toward certain cell types and their specificity for cellular substrate molecules, most of the individual exotoxins are associated with a distinct disease. Because of their enzymatic nature, placement of very few A-domain molecules in the cytosol will normally cause a cytopathic effect. Therefore, bacterial AB-type exotoxins which include the potent neurotoxins from Clostridium tetani and C. botulinum are the most toxic substances known today. However, the individual AB-type toxins can greatly vary in terms of subunit composition and enzyme activity (see Table 2). 

Interestingly, much work has been devoted to the development of substances in the class of cholinesterase inhibitors that have exceedingly high toxicity substances that also have properties (such as volatility and sufficient but not excessive environmental stability) that make them useful as agents of warfare. Most of those now stockpiled were first developed during World War II. Sarin and VX are perhaps the most well-known members of this class of compounds that have been especially designed to kill people. 

Peter Lacouture, Associate Director, Clinical Research, The Purdue Frederick Company, Norwalk, Connecticut Dr. Fumio Matsumura, Associate Director, Toxic Substances Program, Institute of Toxicology and Environmental Health, University of California, Davis, California Dr. Frederick Oehme, Director, Comparative Toxicology Laboratories, Kansas State University, Manhattan, Kansas and Dr. Jack Radomski, Private Consultant, Jonesport, Maine. These experts collectively have knowledge of heptachlor and heptachlor epoxide s physical and chemical properties, toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and quantification of risk to humans. All reviewers were selected in conformity with the conditions for peer review specified in Section 104(i)(13) of the Comprehensive Environmental Response, Compensation, and Liability Act, as amended. 

Environmental fate Chemicals released in the environment are suscephble to several degradahon pathways, including chemical (i.e., hydrolysis, oxidation, reduction, dealkylahon, dealkoxylation, decarboxylahon, methylation, isomerization, and conjugation), photolysis or photooxidahon and biodegradation. Compounds transformed by one or more of these processes may result in the formation of more toxic or less toxic substances. In addihon, the transformed product(s) will behave differently from the parent compound due to changes in their physicochemical properties. Many researchers focus their attention on transformahon rates rather than the transformahon products. Consequently, only limited data exist on the transitional and resultant end products. Where available, compounds that are transformed into identified products as weh as environmental fate rate constants and/or half-lives are listed. 

More than 50,000 chemicals are currently listed in the Toxic Substance Control Act (TSCA) inventory, but physical-chemical properties are available for a relatively small percentage and biological endpoints for even less. The costs associated with thoroughly testing all chemicals are prohibitive, so models are needed to (1) predict the environmental effects of a new chemical, or (2) assess whether the chemical should be subject to a detailed testing regime (J ). Although models are available to... 

Mercury dimethyl is a highly toxic substance by all routes of exposure. Several cases of human poisoning are well documented. (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nJohn Wiley Sons.) The compound can accumulate in the brain and blood of humans. Intake of small quantities can cause death. 

In other words, introduction of ortho substitutions into PBDEs or PCDEs does not create a spatial impediment for the two phenyl rings to assume a semi-flat position respect to each other as it does for PCBs or PBBs. This has implications not only for dioxin-type toxicities, but also for nondioxin-type toxicities. For example, studies have shown that mono- and diortho-substituted PCBs exhibit neurotoxic properties and structure-activity relationships for various neurological end points have been established (see Agency for Toxic Substances and Disease Registry 2000 for details). Although structure-activity relationships have not yet been fully examined for PBBs or PBDEs, it is reasonable to speculate that mono-and diortho-substituted PBDEs may not necessarily follow the neurotoxic potency rankings constructed with mono- and diortho-substituted PCBs. 

Sources of information pertaining to toxic substances indude local and national health organizations in many countries. Several treatises on the subject have been prepared, including the broad spectrum Sax s Dangerous Properties of Industrial Materials, John Wiley Sons, Inc., New York, NY, 2000. This book contains 20.000 entries, each of which gives physical, chemical, and toxicological data about potentially hazardous materials. 

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