Organic exposure

Corrosion resistance is inferior to that of austenitic stainless steels, and martensitic steels are generally used in mildly corrosive environments (atmospheric, fresh water, and organic exposures). 

The martensitic alloys contain 12 to 20 percent chromium with controlled amounts of carbon and other additives. Type 410 is a typical member of this group. These alloys can be hardened by heat treatment, which can increase tensile strength from 550 to 1380 MPa (80,000 to 200,000 Ibf/in ). Corrosion resistance is inferior to that of austenitic stainless steels, and martensitic steels are generally used in mildly corrosive environments (atmospheric, freshwater, and organic exposures). In the hardened condition, these materials are very susceptible to hydrogen embrittlement. 

GB interferes with neural synapses. It causes overstimulation of the nervous system, which in turn causes over-reactivity in the muscles and malfunctioning of various body organs. Exposure to GB will result in massive congestion of enzymes and fluids in all the major organs, throughout the nervous system, and within the brain. Those who survive exposure may suffer permanent neurological damage.1... 

Although QSARs, QSPRs, and MMMs generate screening data, which provide a much-improved focus on the risks associated with environmental contaminants, organism exposure must be confirmed by direct determination of contaminant identities and measurement of concentrations in water or air or estimated... 

Some introductory comments on the conceptual basis of SPMD uptake (ku) and release (ke) rate constants and the associated sampling rates (i.e., Rs) are in order. The can be conceptualized as the volume of air or water cleared of chemical per unit sampler mass or volume per unit time (e.g., mL g d or mL mL d ) and Rs is the volume of air or water cleared per unit time (e.g., L d ). Thus, the only difference between ku and Rs is that Rs is not normalized to a unit mass or unit volume of sampler. In the context of organism exposure (see Section l.L), the SPMD is equivalent to the encounter volume times the fractional bioavailability of the chemical (which excludes dietary uptake). The release rate constant (d ) is equal to kuK J. 

Three areas of methodolc stressed here are of special concern for the study of air pollution effects on v etation growth of the test organisms, exposure facilities, and instrumentation. First, to determine the effects of air pollutants on many plant species, one must have a good understanding of the best cultural conditions for a given test crop some results reflect the use of poor test specimens. Second, dynamic... 

When appropriate chemical-specific data are available, a CSAF can be used to replace the relevant default sub-factor for example, suitable data defining the difference in target organ exposure in animals and humans could be used to derive a CSAF to replace the uncertainty sub-factor for animal to human differences in toxicokinetics (a factor of 4). The overall UF would then be the value obtained on multiplying the CS AF(s), used to replace default sub-factor(s), by the remaining default sub-factor(s) for which suitable data were not available. In this way, chemical-specific data in one area could be introduced quantitatively into the derivation of a tolerable intake, and data would replace uncertainty. 

A number of potential risks are associated with plant-based pharmaceuticals these include allergen exposure to the public, pollen transfer to wild species, nontarget organism exposure due to persistence of genetically engineered material in the environment, interspecies gene flow, and contamination of nontransgenic crops intended for human consumption. The role of risk analysis with respect to the impact of plant-based biopharmaceuticals on human health and the environment are discussed in this chapter. 

Environmental (External—Organism Exposure to Food Allergen)... 

For humans, the key issues relate to the demonstration that significant accumulation does not occur in a food organism. Exposure from the food organism is dependent on factors such as how much is eaten and how frequently, other sources of exposure, and the impact of preparation and cooking (e.g., the USEPA produces guidance relating to whole fish, fish fillet, cooked and uncooked fish USEPA 2000). Guidelines... 

Alternative route is acceptable if similar metabolism and systemic as well as target organ exposure (e.g., lung for inhalation agents) can be demonstrated (exposure may be derived from pharmacokinetic data)... 

For some organisms, exposure to oxygen in air represents a toxic gas (Chatigny et al., 1989). 

Jones C.W. and Koros W.J., Carbon molecular sieve gas separation membranes—II. Regeneration following organic exposure. Carbon 52 1427 (1994). 

The vast majority of carbon disulfide released into the environment is in the atmosphere. Therefore, terrestrial wildlife and birds in the vicinity of a release have the highest potential for primary exposure. Aquatic organisms would have a minimal exposure potential from an air release, but if the release is from a spill or an end-of-pipe discharge that empties into a water body, then the potential for aquatic organism exposure would be high. 

CN is a white solid with low vapor pressure that can be dispensed as a fine powder or as a jet or stream of solution from small or large spray tanks, as well as aerosols or smokes by pyrotechnic generation. Its solubility in water is limited, but it is soluble in organic and chlorinated organics. Exposure of eyes, nose, mouth, skin, and respiratory tract produces irritation and pain. If swallowed, CN may produce vomiting. 

In chronic toxicity studies, liver and kidneys were the principal target organs. Exposure to 1,2-dichloroethane by gavage for 78 weeks induced a significant increase in the incidence of tumors at several sites in both rats and mice. Inhalation exposure of rats or mice did not show significant increases in tumor incidence. However, repeated dermal or intraperitoneal application of 1,2-dichloroethane resulted in an increase in lung tumors in mice. 

As mentioned earlier, exposure to a pollutant by a host organism constitutes the initial stage in the manifestation of toxicity. In a mammalian organism, exposure of the body occurs through dermal or eye contact, through inhalation, or through ingestion. 

Dr. J. Bruckner and his colleagues at the University of Georgia are collaborating with EPA scientists to develop more accurate PBPK models for prediction of time integrals of target organ exposure to... 

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