Benzenes acute toxicity

Mono-substituted benzene, acute toxicity, Photobacterium phosphoreum, QSAR. 

Many very hazardous solvents, such as benzene and carbon tetrachloride, were widely used until the 1970s. The situation was very similar for the use of pesticides. Among the toxic pesticides that were still in wide use 20 years ago were chlorophenols, DDT, lindane, and arsenic salts, all of which are classified as human carcinogens as well as being acutely toxic. Fortunately, use of these kinds of very toxic chemicals is now limited in the industrialized world. However, because the number of chemicals used in various industries continues to increase, the risks of long-term health hazards due to long-term exposure to low concentrations of chemicals continues to be a problem in the workplace. 

In discussing the enviromnental fate of technical DDT, the main issue is the persistence of p,p -DDT and its stable metabolites, although it should be bom in mind that certain other compounds— notably, o,p -DDT and p,p -DDD—also occur in the technical material and are released into the environment when it is used. The o,p isomer of DDT is neither very persistent nor very acutely toxic it does, however, have estrogenic properties (see Section 5.2.4). A factor favoring more rapid metabolism of the o,p isomer compared to the p,p isomer is the presence, on one of the benzene rings, of an unchlorinated para position, which is available for oxidative attack. p,p -DDD, the other major impurity of technical DDT, is the main component of technical DDD, which has been used as an insecticide in its own right (rhothane). p,p -DDD is also generated in the environment as a metabolite of p,p -DDT. In practice, the most abundant and widespread residues of DDT found in the environment have been p,p -DDE, p,p -DDT, and p,p -DDD. 

So acrylic acid would bear R25 (LD50 o-n 34 mg/kg) R22 (LD50 o-r 235 340 353 355) or no code (LD50 o-r 2590). Benzene, toluene, 1-propanol, dichloromethane, etc., can be either R22 or have no code by ingestion depending on the values (labour regulations actually chose not to allocate any acute toxicity code to them). 

In addition to the chemicals included on the other lists, the CDC also included heavy metals such as arsenic, lead, and mercury volatile solvents such as benzene, chloroform, and bromoform decomposition products such as dioxins and furans polychlorinated biphenyls (PCBs) flammable industrial gases and liquids such as gasoline and propane explosives and oxidizers and all persistent and nonpersistent pesticides. Agents included in this volume are limited to those that are most likely to pose an acute toxicity hazard. 

Basak, S. C., Gute, B. D., Lucic, B., Nikolic, S., Trinajstic, N. A comparative QSAR study of benzamidines complement-inhibitory activity and benzene derivatives acute toxicity. Comput. Chem. 2000, 24, 181-191. 

Gute, B. D., Basak, S. C. Predicting acute toxicity of benzene derivatives using theoretical molecular descriptors A hierarchical QSAR approach. SAR QSAR Environ. Res. 1997, 7, 117-131. 

At the initial stages of a release, when the benzene-derived compounds are present at their highest concentrations, acute toxic effects are more common than they are later. These noncarcinogenic effects include subtle changes in detoxifying enzymes and liver damage. Generally, the relative aquatic acute toxicity of petroleum will be the result of the fractional toxicities of the different hydrocarbons present in the aqueous phase. Tests indicate that naphthalene-derived chemicals have a similar effect. 

Naphthalene and its homologs are less acutely toxic than benzene but are more prevalent for a longer period during oil spills. The toxicity of different crude oils and refined oils depends not only on the total concentration of hydrocarbons but also the hydrocarbon composition in the water-soluble fraction (WSF) of petroleum, water solubility, concentrations of individual components, and toxicity of the components. The water-soluble fractions prepared from different oils wiU vary in these parameters. Water-soluble fractions (WSFs) of refined oils (e.g.. No. 2 fuel oil and bunker C oil) are more toxic than water-soluble fraction of crude oil to several species of fish (killifish and salmon). Compounds with either more rings or methyl substitutions are more toxic than less substituted compounds, but tend to be less water soluble and thus less plentiful in the water-soluble fraction. 

Benzene is shipped in tank cars, tank trucks, barges, and drums. Transfers from one vessel to another are in dosed systems because benzene is a poisonous substance with acute toxic effects. It ll kill you in 5—10 minutes if you breathe too much. Red DOT flammable liquid labels are required. 

Drew, R.T. and Fonts, J.R. The lack of effects of pretreatment with phenobarbital and chlorpromazine on the acute toxicity of benzene in rats, Toxicol. Appl. Pharmacol, 27 1) 183-19Z, 1974. 

Burden, F. R., and Winkler, D. A. (2000) A quantitative structure-activity relationships model for the acute toxicity of substituted benzenes to Tetrahymena pyriformis using Bayesian-regularized neural networks. Chem. Res. Toxicol. 13,436-440. 

Benzene is widely used for its solvent properties and as an intermediate in the synthesis of other chemicals. The 1999-2000 recommended threshold limit values are given in Table 57-1. The acute toxic effect of benzene is depression of the central nervous system. Exposure to 7500 ppm for 30 minutes can be fatal. Exposure to concentrations larger than 3000 ppm may cause euphoria, nausea, locomotor problems, and coma vertigo, drowsiness, headache, and nausea may occur at concentrations ranging from 250 to 500 ppm. No specific treatment exists for the acute toxic effect of benzene. 

Capello et al.16 applied LCA to 26 organic solvents (acetic acid, acetone, acetonitrile, butanol, butyl acetate, cyclohexane, cyclohexanone, diethyl ether, dioxane, dimethylformamide, ethanol, ethyl acetate, ethyl benzene, formaldehyde, formic acid, heptane, hexane, methyl ethyl ketone, methanol, methyl acetate, pentane, n- and isopropanol, tetrahydrofuran, toluene, and xylene). They applied the EHS Excel Tool36 to identify potential hazards resulting from the application of these substances. It was used to assess these compounds with respect to nine effect categories release potential, fire/explosion, reaction/decomposition, acute toxicity, irritation, chronic toxicity, persistency, air hazard, and water hazard. For each effect category, an index between zero and one was calculated, resulting in an overall score between zero and nine for each chemical. Figure 18.12 shows the life cycle model used by Capello et al.16... 

Kaiser, K.L.E., Palabrica, V.S., Ribo, J.M. (1987) QSAR of acute toxicity of mono-substituted benzene derivatives to photobacterium phosphoreum. In QSAR in Experimental Toxicology II. Kaiser, K.L.E., Editor, pp. 153-168, D. Reidel Publishing Co., Dordrecht, Holland. 

Karabunarliev, S., Mekenyan, O.G., Karcher, W., Russom, C.L., and Bradbury, S.P., Quantum-chemical descriptors for estimating acute toxicity of substituted benzenes to the guppy (Poecilia reticulata) and fathead minnow (Pimephales promelas), Quant. Struct.-Act. Relat., 15, 311-320, 1996b. 

Benzene can have both chronic and acute toxic effects. The risk of acute effects is low, since acute symptoms occur only at 1000 ppm or higher. Chronic vapor inhalation at the level of 25 to 50 ppm can cause changes in blood chemistry, and co/ rmoa7 exposure at 100 ppm can cause severe blood disorders. The OSHA exposure limits for benzene vapor are 1 ppm as an 8-hour time-weighted average and a ceiling of 50 ppm for no more than 10 min. In order to reach the level of 10 ppm in a laboratory of 750 m volume, 23 g of liquid benzene would have to evaporate into a closed atmosphere. Thus the hazards associated with the infrequent use of liquid benzene in a well-ventilated laboratory are very low. 

Toxicity. Toluene has about the same acute toxicity as benzene but is a less serious industrial hazard. The maximum permissible atmospheric concentration of toluene is 100 ppm. Exposure to air concentrations of 10000 to 30 000 ppm may cause unconsciousness within a few minutes. A blood concentration of more than lOpg/ml may be lethal although higher concentrations have been found in habitual abusers. 

Gute, B.D. and Basak, S.C. (1997). Predicting Acute Toxicity of Benzene Derivatives Using Theoretical Molecular Descriptors A Hierarchical QSAR Approach. SAR QSAR Environ.Res., 7,117-131. 

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