Toxicity of solvent

In this subsection, specific operating parameters will be discussed. These includes nutrient media for use during desulfurization process, toxicity of solvent to various biocat-alytic strains, effect of oil/water ratio on biocatalyst as well as desulfurization rates and subsequent separations, biocatalyst density during desulfurization, and finally, the alternative to operate the desulfurization process in batch vs. continuous mode. 

Volatilization of solvent components can become a problem when the system is operated at elevated temperatures or in hot climates. The human toxicity of solvent components is a generally unknown factor and could be a problem in a system enclosed in a building. 

Perhaps the area of environmental pollution most pertinent to solvent extraction processing is that of water pollution and, consequently, the toxicity of solvent extraction reagents to aquatic life then become important. Thus, the primary consideration in the development of water quality criteria for these reagents is to determine their toxicity toward fish and their biodegradability [70]. 

Donelly, K.C. Brown, K.W. Andersson, C.S. Thomas, J.C. Scott, B.R. Bacterial mutagenity and acute toxicity of solvent and aqueous extracts of soil samples from a chemical manufacturing site. Environ. Toxicol. Chem. 1991, 10, 1123-1131. 

Wahlberg JE Percutaneous toxicity of solvents. A comparative investigation in the guinea pig with benzene, toluene, and 1,1,2-trichloroethane. Ann Occup Hyg 19 226-229, 1976... 

Special attention must be given to the hazards involved in the use of solvents, and there is a general tendency to replace solvents that are hazardous, but have long been in use for historical reasons, with less dangerous solvents. For instance, benzene, a very useful solvent but known carcinogen, ought to be and actually often is replaced by the less hazardous toluene or xylene. Table A3 (see the appendices) provides some information concerning the toxicity of solvents on the table as well as their inflammability and the explosive limits of their vapor in air. 

Solvents may be classified according to their polarity into three groups apolar aprotic solvents, dipolar aprotic solvents, and (polar) protic solvents. Examples of these three classifications for some common laboratory solvents are listed in Table 16.1, in order of increasing polarity (indicated by dielectric constant), together with some other solvent properties. For information on the hazards and toxicity of solvents, see Chapter 11. 

Dietary habits can influence the TK and toxicity of solvents in several ways. The mere bulk of food in the stomach and intestine can inhibit systemic absorption of VOCs. Solvents in the GI tract partition into dietary lipids, largely remaining there until the lipids are emulsified and digested. This substantially delays the absorption of VOCs such as CCI4 and its hepatotoxicity. Increased incidences of cancer have been observed in obese humans possibly due to increase in liver CYP2E1 by ketone body formation. Caloric restriction has clearly been shown to reduce the incidence of cancer. Fasting results in increased P450 activities and reduced GSH, which affect the TK and toxicity of VOCs. Food may contain certain natural constituents, pesticides, and other chemicals, which may enhance or reduce the solvent metabolism. 

Many excipients are extracted from or purified by the use of organic solvents. These solvents are normally removed by drying the moist excipient In view of the varying and sometimes unknown toxicity of solvents, it is important that excipient specifications include tests and limits for residues of solvents and other reactants. 

Sax, N. I. (1984) Dangerous Properties of Industrial Materials, 6th edn. Van Nostrand Reinhold, New York. The definitive book on the toxicity of solvents and other organic chemicals. 

In general, peroxides exhibit low toxicity. However, some are moderately toxic. Their irritant action on skin and eyes vary widely. For example. Methyl ethyl ketone (MEK) peroxide is a severe eye irritant, whereas lauroyl peroxide is innocuous to eyes and skin and is nontoxic. As peroxides are a wide class of compounds with several possible organic moieties held by peroxy linkage, the relationship of toxicity with structure cannot be generalized. Also the toxicity of solvents or diluents should be borne in mind when handling commercial peroxide solutions. 

Evaluating the toxicity of solvents provides one metric for comparing potential candidates. This evaluation (usually the LD50 or PEL (permissable exposure level)) allows one to screen out solvents that are environmentally undesirable. In actual practice, the preliminary ranking should incorporate the criteria given in Table V. In general, despite the data available in all the areas listed in Table V, chemists have not... 

Because whole bacterial cells are more complex than enzymes, fliey pose by far greater problems in operating bioproduction processes when organic solvents are present. The most critical problem is the inherent toxicity of solvents to living organisms. As... 

The toxicity of solvents for microorganisms shows positive and negative consequences, e.g. ... 

Specific toxicity of solvents is directly related to their metabolism which is predominantly catalyzed by cytochrome P-450 mixed-function oxidases in the liver or other tissues. 

Interactions may be involved in enhancing or reducing toxicity of solvents. For example Bloch et al. showed that in cases of alcohol abuse an increase in the toxic effects of benzene and other lipophilic petroleum derivatives occurs. Also, it has been shown that benzene inhibits the metabolism of toluene. ... 

Information on the toxicity of solvents may be available in one or more of the following areas ... 

This section is intended to give a broad picture of the similarities and differences between the toxicity of solvents within and across the major chemical groups. It should not be taken as a comprehensive picture of the toxic effects of any specific solvent, for which reference should be made to one of the sources of information indicated in section 5.2.2. Where appropriate, the relevant UK occupational exposure limits (OESs or MELs) [9] are given in brackets after each individually named solvent. 

Two areas of safety are important—toxicity of solvent and flammability. The unit is entirely encased, and has an efficient exhaust system coupled to multiple sensors which trigger audible alarms and eventual shutdown if the... 

---