Organic solvents

Abstract

Industrial solvents is a collective term for a large group of chemicals that are volatile organic liquids commonly used to dissolve other organic materials such as oils, fats, resins, rubber, lacquers, waxes, perfumes, and plastic. They have a very wide area of use as exemplified below: Painting; paint manufacturing; floor-laying; production of glass-fiber re-enforced polyester; surface coating; graphic industries; rotogravure printing; dyeing of paper, plastics, and fabrics; metal degreasing; dry cleaning; cleansing; spotting agents; carriers and intermediates in organic synthesis; medium for extraction processes; analytical chemistry. Technical organic solvents are reasonably inexpensive and considerable volumes are used yearly and numerous workers are exposed daily [1-7]. Although mainly treated as a group due to their general properties, solvents are chemically diversified (Fig. 1) and can be classified into different categories according to their physico-chemical characteristics, with examples given in Table 1. Origin and manufacturing techniques of solvents vary. Many originate from petroleum distillates. They may then be used as purified neat chemicals such as the aliphatics and aromatics or in mixtures of various kinds such as thinner (mixture of alcohols, ketones, toluene), naphtha, petroleum ether (mixture of aliphatics), kerosene and white spirit (mixtures of aromatics and/or aliphatics). They may also undergo derivatization by various synthetic methods into halogenated compounds, esters, ethers, alcohols, and similar compounds. Synthesis from other raw materials by various techniques as well as extraction from various natural sources is also common. Table 1 shows threshold limit values (TLVs) for Sweden [8]. Such values are inter alia proposed by the American Conference of Governmental Industrial Hygienists (ACGIH) and various national government agencies and have had great influence in many industrialized countries when reviewing health hazards from solvents and implementing preventive measures. Information on water and lipid solubility and volatility is also of great value when discussing potential risks from solvent exposure. Steadily increasing knowledge of the various adverse effects seen in man and experimental animals has resulted in a gradual decrease in TLVs over the years, e.g., methylene chloride. It has been claimed that the relative importance of the percutaneous route of absorption of solvents has increased as result of these regulatory activities concerning inhalation of solvents. Awareness of environmental and human effects has also led to a change from chlorinated solvents to biologically degradable solvents with altered risk spectra. © 2006 Springer-Verlag Berlin Heidelberg.