The Knovel and CRC collections of online handbooks have mutiple titles which cover aspects of chemical exposure. They are good for getting up to speed on particular chemicals or techniques. Sometimes the articles include bibliographies you can mine for further information. The other two listed are standard works which are now available online.
These sources are all listed in the SearchWorks online catalog. Most of these collections of articles do not have full text included, but link out to the articles. If you need a refresher on searching these, check the left sidebar under "Research Skills" for the "Find articles" refresher.