Exposure, chemical acute

For a variety of reasons it is difficult to precisely evaluate toxic responses caused by exposures (particularly acute ones) to hazardous chemicals. Five of these toxic responses are briefly discussed below. 

Acute Exposure, Chemical—Exposure to a chemical for a duration of 14 days or less, as specified in the Toxicological Profiles. 

Chemical injuries to the liver depend on the type of toxic agent, the severity of intoxication, and the type of exposure, whether acute or chronic. The six basic types of liver damage are fatty liver, necrois, hepatobiliary dysfuntions, viral-hke hepatitis, and (on chronic exposure) cirrhosis and neoplasia. A number of organic chemicals and drugs induce fatty liver and hver necrosis. 

In the safety evaluation of chemicals, acute toxicity tests are those that evaluate effects occurring within about 7 days of a single dose, and sub-chronic toxicity tests evaluate toxicity resulting from short-term repeated dosing or exposure, often 28 days up to 90 days. Chronic toxicity tests are those that evaluate effects occurring after much longer exposures, at least six months and possibly up to the lifetime in experimental animals. 

The acute dermal irritation is the study of reversible inflammatory changes in the skin of test animals following the application of a test chemical. Acute dermal corrosion is the study of irreversible tissue damages in the skin following the application of a test chemical. In the evaluation of toxic characteristics of a chemical, determination of the irritant or corrosive effects on mammal skin is an important study step. Information derived from this test indicates the existence of hazards likely to arise from skin exposure to the test chemical. 

Acute bronchitis Inflammation of the tubes that carry air into the lungs Acute dermal toxicity Adverse effects occurring within a short time of dermal application of a singular dose of a test chemical Acute exposure Exposure to chemical substances for 14 days duration or less, as specified in the protocol... 

Cohort study A study in which a group of people with a past exposure to chemical substances or other risk factors are followed over time and their disease experience compared to that of a group of people without the exposure Colic Acute abdominal pain, especially in infants... 

If more than 300 citations are found using any form of chemical identification, the references may be enriched in relevance and quality by adding any number of the following characterizations of the desired data to the search strategy short-term threshold limit permissible exposure limit acute toxicity ocular terms inhalation terms dermal terms... 

Current pesticide management practices can result in three categories of human exposure situations—acute, chronic high or occupational, and chronic low or incidental. Pesticide exposure, whether direct or via chemical trespass from treated areas, can be reduced, if not eliminated entirely, by utilizing ... 

Physical and Chemical Properties - Physical State at 15 C and 1 atm. Solid Molecular Weight 78.08 Boiling Point at 1 atm. Not pertinent Freezing Point Not pertinent Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 3.18 at 20 °C (solid) Vtpor (Gas) Density Not pertinent Ratio of Specific Heats of Vapor (Gas) Not pertinent Latent Heat of Vaporization Not pertinent Heat of Combustion Not pertinent Heat of Decomposition Not pertinent. Health Hazards Information - Recommended Personal Protective Equipment For dust only Symptoms Following Exposure Little acute toxicity General Treatment for Exposure Usually no treatment needed Toxicity by Inhalation (ThresholdUnut Value) Not pertinent Short-Term Exposure Limits Not pertinent Toxicity by Ingestion Late Toxicity Data not available V(q>or (Gas) Irritant Characteristics Not pertinent Liquid or Solid Irritant Characteristics No reciable hazard. Practically harmless to the skin O r Threshold Not pertinent. 

A. Acute exposure causes burning of the eyes, nose, and throat lacrimation and cough. Laryngospasm may occur. Wheezing may be seen in normal subjects as well as asthmatics. Chemical bronchitis is not uncommon. With a very high-level exposure, chemical pneumonitis and noncardiogenic pulmonary edema may occur. 

Steps 4 and 5 are not straightforward activities, especially when it comes to long-term effects, i.e. the development of occupational diseases. For accidental exposures to acute toxic/corrosive chemicals, the risk-estimation matrix of Table 22.5 can be used. A similar matrix for use with other chemical exposure assessments is shown in Table 23.2. The application of it involves a number of crucial decisions concerning ... 

Clearance of foreign materials (particles) from the lung and airways depends on the function of macrophages, ciliated cells and secretory cells, and on the physical and chemical properties of the alveolar cells. All these are affected by ozone exposure. Single acute exposure of animals and humans to ozone concentrations less than 0.6 ppm have been shown to accelerate clearance of particles from the tracheobronchial tree whereas acute exposures to ozone levels greater than 0.6 ppm caused a delay in particles clearance [79, 261]. Repeated exposures (2 h daily for 14 days) to 0.1 ppm ozone gave rise to acceleration in alveolar clearance of latex particles but had no effect on tracheobronchial clearance. These results, related to morphological studies, are consistent with certain adaptation [278-283]. 

The third of the major hazards and the one with the greatest disaster potential is the release of toxic chemicals. The hazard posed by toxic release depends not only on the chemical species but also on the conditions of exposure. The high disaster potential from toxic release arises in situations where large numbers of people are briefly exposed to high concentrations of toxic material, i.e., acute exposure. However, the long-term health risks associated with prolonged exposure at low concentrations, i.e., chronic exposure, also present serious hazards. 

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