In laboratories, a wide variety of chemicals is used in small amounts, with a notable exception for organic solvents which are used in bulk. Each year, a large laboratory consumes a few thousand litres of common solvents (such as acetone, ethanol and chloroform). Several other solvents are used for crystallization purposes and for cleaning equipment and glassware.
This involves a number of risks. Many solvents are flammable and, to a greater or lesser extent, toxic. Exposure of laboratory workers (through the skin or by inhalation of solvent vapour) may produce a variety of toxic effects. Hexane, for example, is neurotoxic and chloroform is harmful to the liver. In addition to benzene, which is carcinogenic, several other widely used solvents (such as chloroform, dichloromethane, 1,4-dioxane and carbon tetrachloride) are under suspicion of causing cancer in humans.