The study reported in the volume continues the assessment and evaluation procedures established in the earlier volumes which identified chemical and biological contaminants associated with drinking water distribution systems and the health implications of deficiencies in those systems. An evaluation of information on the toxicity of selected inorganic and organic contaminants and SNARL's were provided when appropriate. Some of the compounds were reviewed for the first time in the report; others had been reviewed in earlier volumes of the series. For the latter compounds, discussions were limited mainly to information that had become available after the earlier reports had been published, although the committee occasionally cited older references that were not previously assessed. Twenty-one compounds are reviewed in Chapter 2. Chapter 3 contains an evaluation of epidemiological data on exposure to arsenic and asbestos in drinking water.