Toxicity dispersion methods

Various state guidelines, for example the Toxicity Dispersion (T5Q)s) method used by the New Jersey Department of Environmental Protection (NJ-DEP). 

TXDS Acute Toxic Concentration. Some states have their own exposure guidelines. For example, the New Jersey Department of Environmental Protection (NJ-DEP) uses the Toxic Dispersion (TXDS) method of consequence analysis for the estimation of potentially catastrophic quantities of toxic substances as required by the New Jersey Toxic Catastrophe Prevention Act (TCPA) (Baldini and Komosinsky, 1988). An acute toxic concentration (ATC) is defined as the concentration of a gas or vapor of a toxic substance that will result in acute health effects in the affected population and one fatality out of 20 or less (5% or more) during a 1 hr exposure. ATC values as proposed by the NJ-DEP arc estimated for 103 extraordinarily hazardous substances, and are based on the lowest value of one of the following ... 

The chemical and physical phenomena involved in chemical process accidents is very complex. The preceding provides the elements of some of the simpler analytic methods, but a PSA analyst should only have to know general principles and use the work of experts contained in computer codes. There are four types of phenomenology of concern 1) release of dispersible toxic material, 21 dispersion of the material, 3) fires, and 4) explosions. A general reference to such codes is not in the open literature, although some codes are mentioned in CCPS (1989) they are not generally available to the public. 

A test to determine the biodegradation rate of the dispersant and the biodegradation rate of the dispersant-oil mixture has been proposed [1302]. The test method is intended to supplement the toxicity tests and the effectiveness tests, which evaluate the performance of oil spill dispersants. 

U.S. EPA defines MNA as the reliance on natural processes, within the context of a carefully controlled and monitored site cleanup approach, to achieve site-specific remediation objectives within a time frame that is reasonable compared to that offered by other more active methods. The natural processes include biodegradation, dispersion, dilution, sorption, volatilization, stabilization, and transformation. These processes reduce site risk by transforming contaminants to less toxic forms, reducing contaminant concentrations, and reducing contaminant mobility and bioavailability. Other terms for natural attenuation in the literature include intrinsic remediation, intrinsic bio-remediation, passive bioremediation natural recovery, and natural assimilation. 30... 

One method of overcoming the detrimental solvent dewetting effects is to use liquid C02 as the solvent for nanoparticle dispersions [52], since C02 does not experience the dewetting instabilities due to its extremely low surface tension [53]. In this case, nanoparticles must be stabilized with fluorinated ligands [30, 33, 54—65] or other C02-philic ligands [60,66-76], such that they will disperse in the C02 prior to dropcasting. These fluorinated ligands tend be toxic and environmentally persistent and, typically, only very small nanoparticles can be dispersed at low concentrations. 

In a QRA study the consequences of these releases are quantified using dispersion modeling and a detailed analysis to determine the downwind consequences as a result of fires, explosions, or toxicity. In a LOPA study the consequences are estimated using one of the following methods (1) semi-quantitative approach without the direct reference to human harm, (2) qualitative estimates with human harm, and (3) quantitative estimates with human harm. See footnote 6 for the detailed methods. 

Both nanospheres and nanocapsules are prepared from either a polymerization reaction of dispersed monomers or from a solvent dispersion procedure using preformed polymers. In many instances, the latter procedure using preformed polymer is desirable, as potential reactions between drug and monomer are avoided and the potential toxicity of residual monomers, surfactant, and initiator is reduced [37], The final properties of nanoparticles, such as their size, morphology, drug loading, release characteristics, and biodisti-bution, are all influenced by the method of preparation [38],... 

The number of studies on the health effects of fullerenes and carbon nanotubes is rapidly increasing. However, the data on their toxicity are often mutually contradictory. For example, the researchers from universities of Rice and Georgia (USA) found that in aqueous fullerene solutions colloidal nano-C particles were formed, which even at low concentration (approximately 2 molecules of fullerene per 108 molecules of water) negatively influence the liver and skin cells [17-19]. The toxicity of this nano-C aqueous dispersion was comparable to that of dioxins. In another smdy, however, it was shown that fullerene had no adverse effects and, on the contrary, had anti-oxidant activity [20]. Solutions of prepared by a variety of methods up to 200 mg/mL were not cytotoxic to a number of cell types [21]. The contradiction between the data of different authors could be explained by different nano-C particles composition and dispersion used in research. 

XVIII) Laboratory Disposal of LA by the Method Used at the du Pont s Plant at Pomp-ton Lakes, NJ. Disperse slowly with stirring ca 1 g sample in ca 16 ml of 25% aq ceric ammonium nitrate soln and allow to stand. Fumes from the decompn are not toxic... 

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