Monohydric Alcohols—C1 to C6

This chapter reviews both linear and branched monohydric aliphatic C1 to C6 alcohols. The C7 to C20 monohydric alcohols are covered in Chapter 78. The low molecular weight alcohols, including methanol, ethanol, 1-propanol, and isopropanol are used extensively in industry (16). These alcohols exist as volatile liquids at ambient temperatures, and exposure can occur in both industrial and nonindustrial environments. This review discusses primarily dermal and inhalation routes of exposure, which are the major routes of occupational exposure to alcohols. Many of the high-production alcohols such as methanol, ethanol, propanols, and butanols cause adverse effects when ingested; ingestion, however, is not a major route of occupational exposure. There are some alcohols that have produced adverse effects in humans, including death, in an occupational environment. Nevertheless, alcohols have been used extensively in the workplace generally with few or minor problems. Occasionally, methanol, ethanol, and the propanols produce a skin sensitizing response in humans. In some, but not all, cases the sensitization response was considered to be due to contaminants and not to the alcohol itself. A common property of some of the alcohols is to produce local irritation to the skin, eyes, and respiratory tract, and the effect or potency varies for the type of alcohol. Many alcohols produce minimal or no adverse effects in humans, possibly because of low exposure combined with the low toxicity potential of the alcohol. Few alcohols produce neuropathic effects in humans. Abuse of products containing methanol and ethanol has produced some indications of neurotoxicity in humans, but nothing has been reported in an occupational environment. 2-Hexanol produces neurotoxicity by the oral and intraperitoneal routes in animals, but there is no evidence of such an effect having occurred in the workplace. There is no clear evidence that occupational exposures to alcohols represent a carcinogenic risk to humans. Based on epidemiological data, there is an association between the manufacture of ethanol and isopropanol by the strong acid process (a process no longer used in the United States) and an excess of upper respiratory tract cancer in humans. The effect has been attributed to by-products such as dialkyl sulfates and sulfuric acid, not the alcohols themselves. Some of these alcohols such as ethanol and isopropanol can enhance the toxic effects of various chemicals, particularly hepatotoxins. It is thought that the effects may be due largely to an inductive effect of the alcohol on microsomal enzymes, particularly the cytochrome P450 system, which may allow a greater metabolic conversion of the hepatotoxin to its toxic metabolite. Keywords: Methanol; Inhalation studies; Ethanol; 1-Propanol; Isopropanol; Butanols; Amyl alcohols; Hexanols