Toxic exposure lethal concentration

Health and Safety Factors. VDE is a flammable gas its combustion products are toxic. Liquid VDE on contact with the skin can cause frostbite. Acute inhalation toxicity of VDE is low median lethal concentrations (LC q) for rats were 128,000 ppm after a single 4-h exposure (52) and 800,000 ppm after a 30-min exposure (53). Cumulative toxicity is low exposure of rats and mice at levels of up to 50,000 ppm for 90 days did not cause any... 

The LC q (lowest possible lethal concentration) has been reported to be 23 ppm for a 30 min exposure time (mouse), 53 ppm for an exposure time of 100 min (rat, rabbit, and guinea pig), and 200 ppm for an exposure time of 10 min (monkey). No toxic effects were reported upon exposure to 1 ppm for 7 h/d over 55 days. The oral LD q (rat) of ketene is 1300 mg/kg, the low level of toxicity probably being due to the almost immediate formation of acetic acid and other acetates in the digestive tract. 

Health, Safety, and Environmental Factors. Sulfur dioxide has only a moderate acute toxicity (183). The lowest pubHshed human lethal concentration is 1000 ppm for 10 months. The lowest pubHshed human toxic concentration by inhalation is 3 ppm for 5 days or 12 ppm for 1 hour. The lowest pubHshed human lethal concentration is 3000 ppm for 5 months. In solution (as sulfurous acid), the lowest pubHshed toxic dose is 500 flg/kg causing gastrointestinal disturbances. Considerable data is available by other modes of exposure and to other species NIOSH standards are a time-weighted average of 2 ppm and a short-term exposure limit of 5 ppm (183). 

Lethal concentration 50 (LC50) is the vapour concentration of a substance in air, which kills 50% of the animals exposed. This estimate comes from a protocol that was statistically controlled. This value depends on the animal chosen for the experiments and exposure time. The three animals that are most commonly used are in descending order rat, mouse and rabbit. It is a parameter that estimates risk level by inhalation, which is the most important means of penetration involving toxic substances in the work place. 

CNC is a formulation of chloroacetophenone. Like CN, CNC has a pronounced lacrimatory effect, resulting in a natural reflex to shut the eyes. It is similarly irritating to the skin, especially the face and such exposed portions of the body where sweat accumulates. The same rashes caused by CN will be caused by CNC. CNC has a slightly more powerful choking effect than CN. Eye toxicity remains about the same as CN. Some sensitive individuals may experience nausea upon exposure. CNC can form lethal concentrations in closed or confined spaces, although concentrations in open are highly unlikely ever to do so. 

The acceptable limits for toxic exposure depend on whether the exposure is brief or prolonged. Lethal concentration for airborne materials and lethal dose for non-airbome materials are measured by tests on animals. The limits for brief exposure to toxic materials that are airborne are usually measured by the concentration of toxicant that is lethal to 50% of the test group over a given... 

Table III presents the results of calculating the "time to lethal concentration" for each one of the PVC products investigated. The toxic potency values used for all the materials are based on 30 min exposures in the NBS cup furnace toxicity test, in the Non-Flaming mode, the one most relevant to this scenario.

Data on acute exposures of humans to both isomers of dimethylhydrazine are limited to case reports of accidental exposures. Signs and symptoms of exposure include respiratory irritation, pulmonary edema, nausea, vomiting, and neurologic effects. However, definitive exposure data (concentration and duration) were unavailable for these accidents. The limited data in humans suggest that the nonlethal toxic response to acute inhalation of dimethylhydrazine is qualitatively similar to that observed in animals. No information was available regarding lethal responses in humans. In the absence of quantitative data in humans, the use of animal data is considered a credible approach for developing AEGL values. 

Exposures resulting in nonlethal, irreversible effects of dimethylhydrazine were not well defined. For most studies, responses were described in terms of no visible signs of toxicity or lethality. However, Weeks et al. (1963) described nonlethal (but reversible) effects in dogs exposed to 1,1-dimethylhydrazine at varying concentrations. In this study, dogs were exposed to 1,1-dimethylhydrazine at 1,550 ppm or 4,230 ppm for 5 min or 360, 400, or 1,530 ppm for 15 min. The highest cumulative exposures at each of two exposure periods (Ct =352-383 ppm-h) were associated with marked tremors, convulsions and death, while the lower concentration exposures at each of two periods caused behav... 

LCt inhy. 3000-5000 mg-min/m3 (230-380 ppm for a 2-min exposure). This toxicity estimate is from an older source (ca. 1952) and has not been updated. Current sources do not provide an estimate on a lethal concentration. 

Lethal human toxicity values have not been established or have not been published. However, based on available information, exposure to concentrations above 500 ppm can rapidly incapacitate and kill exposed individuals. 

The New Jersey Department of Environmental Protection uses the TXDS method of consequence analysis to estimate potentially catastrophic quantities of toxic substances, as required by the New Jersey Toxic Catastrophe Prevention Act (TCPA). 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 1 fatality out of 20 or less (5% or more) during a 1-hr exposure. ATC values, as proposed by the New Jersey Department of Environmental Protection, are estimated for 103 extraordinarily hazardous substances and are based on the lowest value of one of the following (1) the lowest reported lethal concentration (LCLO) value for animal test data, (2) the median lethal concentration (LC50) value from animal test data multiplied by 0.1, or (3) the IDLH value. 

HFC-134a has very low acute inhalation toxicity. In rats, lethal concentrations during exposure periods of 15 min to 4 h ranged from >500,000 to >800,000 ppm (Collins 1984 Silber and Kennedy 1979a). Concentrations at 200,000 ppm and greater induce anesthetic-like effects (Larsen 1966). Monkeys, dogs, and mice recovered without adverse effects from anesthetic doses of 270,000 (mice) to 800,000 ppm (dogs), the latter exposures at up to 5 h (Shulman and Sadove 1967). 

Ballantyne, B. 1983. The influence of exposure route and species on the acute lethal toxicity and tissue concentrations of cyanide. In Developments in the Science and Practice of Toxicology. Elsevier Science Publishers, New York, pp. 583- 586. 

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