The link:  http://toxnet.nlm.nih.gov/ TOXNET 

Tool 
There exist a number of tools on Internet that allows a user to search for chemical, physical and environmental properties of chemicals and materials. As an example, TOXNET is a publicly available search tool that does not require the users to be registered available at is managed by U.S. National Library of Medicine and National Institutes of Health. Purpose TOXNET is a search tool for a cluster of databases on toxicology, hazardous chemicals, and related areas. 

Description
TOXNET searches following databases: 

• HSDB - Hazardous Substances Data Bank - Broad scope in human and animal toxicity, safety and handling, environmental fate, and more. Scientifically peer-reviewed. 
• IRIS - Integrated Risk Information System - data from the EPA in support of human health risk assessment, is focusing on hazard identification and dose-response assessment. 
• GENE-TOX - Peer-reviewed mutagenicity test data from the Environmental Protection Agency (EPA) 
• CCRIS - Chemical Carcinogenesis Research Information System - carcinogenicity, mutagenicity, tumor promotion, and tumor inhibition data provided by the National Cancer Institute (NCI). 
• Multiple Tox. - Database integrated search 
• TOXLINE - Extensive references to literature on biochemical, pharmacological, physiological, and toxicological effects of drugs and other chemicals. 
• DART/ETIC - Developmental and Reproductive Toxicology and Environmental Teratology Information Center - Current and older literature on developmental and reproductive toxicology. 
• TRI - Toxics Release Inventory, annual estimated releases of toxic chemicals to the environment. 
• ChemIDplus - Numerous chemical synonyms, structures, regulatory list information, and links to other databases containing information about the chemicals.

To search for information; enter any combination of words, chemical names, and numbers, including Chemical Abstracts Services (CAS) Registry Numbers (RN). The result of a search is a list of hits on each database. Evaluation of the result is left to the user. 

Use 
Easy to use but the evaluation of the found documents can be difficult. The tool is more for experts searching for specific data.