Start with the first phrase of your topic: "mercury poisoning." Columbia Encyclopedia (part of Bookshelf with Microsoft Word) gives two subject listings: for Mercury (obviously the planet, not the car) and mercury--but no listing for mercury poisoning. The article on mercury includes several topics highlighted and underlined which you can click, jumping to related articles--on pollution and environmentalism among others. Before following these leads, jot down any keywords to use for your search as well as any facts of general information that piqued your interest.

You could then go to the Science Citation Index, Medline, or Business Index (on CD-ROMs, installed in designated computers in many libraries. When you are asked to type the words to search for, select some of the keywords you jotted down. See Understanding Where the Information Is: Databases.

With a topic such as mercury poisoning, you will probably use more articles than books to get your information. However, check the library catalog as well--using some of the keywords for a subject search, as well as the names of any experts you came across for a search by author (to see if your library has any books written by these experts).