Figure 4. This world map was drawn by Flemish
          cartographer Abraham Ortelius in 1570. 
           Today, satellites  give us essentially complete knowledge of the earth’s surface
          so that one can zoom-in to see a house. In 1570, a map of the world
          was needed even though information was limited. Today, we can map the
          knowledge domain of occupational toxicology realizing that knowledge
          is incomplete and accuracy will increase as we learn more.
          The map of Ortelius shows that information was fairly
          complete for Europe but incomplete for the western hemisphere.
          Likewise, there are areas in the knowledge domain of hazardous
          chemicals and occupational diseases in which the information is
          relatively complete or incomplete. From animal experiments, case
          reports, and epidemiological studies, we now have fairly complete
          information about the potential adverse effects of the most commonly
          used chemicals, for example, the several hundred chemicals profiled by
          ACGIH. Metals are typically profiled as groups, for example,
          "arsenic and inorganic compounds." See this list
          of diseases caused by metal compounds.
          For occupational diseases, see this list
          in Haz-Map. There is little doubt about the occupational nature of
          205 of the 239 diseases in Haz-Map. There is a consensus in occupational
          medicine textbooks that these occupational diseases are caused by
          specific
          hazardous agents, and the diseases can be prevented by good occupational
          hygiene practices. The debatable categories are occupational cancers,
          reproductive diseases, and "more research needed." A rule in
          Haz-Map accepts as established occupational cancers all designated as
          "known human carcinogens" by IARC (International Agency for
          Research in Cancer) and which occur after occupational exposure.
          Like a mapmaker, the domain expert who designs an intelligent
          database first outlines the domain and then adds details, starting
          with the most prominent features. The intended use of the map
          determines the content. Instead of simply passing on the explosion of
          information, it could be intelligently mapped prior to dissemination.
          The CDC has called the product of this kind of mapping process,
          "synthesized, knowledge-based information." [MMWR, Feb18,
          2000/49(06); 118-120.]