The first thing to do is figure out which questions you are trying to answer: What chemicals does this facility release, and what are their well-known health effects? How smoggy is the air in my county? Who has permits to release chromium into the water nationwide? Almost all of the data that's readily available to the public can be found through eight major sources on the World Wide Web. If you want very detailed information about a particular issue or facility, using the Freedom of Information Act (FOIA) at the Federal level or with your state environmental agency can produce much more information. But, for starters, use these sources to help you answer your questions:

Accidents involving toxic chemicals can occur at fixed sites or during transport by road, rail, or sea. EPA's major database for tracking these accidents is a database called Emergency Response Notification System (ERNS), which holds records of phone calls to a nationwide response center. ERNS can be downloaded as a set of files from the EPA Web site, but the best source to search it is a website called RTK NET.

EPA’s Database page http://www.epa.gov/epahome/Data.html

RTK NET http://www.rtk.net/

This information, which is mostly from EPA's Air Quality Subsystem database AQS/AIRS, is best found through EPA's AIRSData site. EPA's Center for Environmental Information and Statistics (CEIS) also has simple air quality profiles for each county in the U.S. If you want to analyze data yourself, the EPA Web site provides a downloadable program called "AIRS Executive."

EPA's AIRSData http://www.epa.gov/airsweb/

EPA's CEIS http://www.epa.gov/ceis/

Compliance with air pollution, water pollution, and hazardous waste laws is tracked in the three main permit databases (see Permits below), with some additional information available about Superfund sites and drinking water sources (see Contaminated Sites and Water quality). In addition, there is a database called DOCKET that tracks enforcement actions by EPA. It is available through RTK NET.

RTK NET http://www.rtk.net/

Some sites have been contaminated by past releases of toxics to the land, and remain dangerous (usually as threats to groundwater, or to people in nearby buildings). "Superfund" sites are major sites that are known to the government. Basic Superfund information is held in a database called CERCLIS, though there are many other related factsheets and smaller databases. The best source for Superfund information is EPA's Envirofacts web page. The most common other hazard of this type is old underground storage tanks. There is generally no national database of these tanks; the only way to find them is to use the Freedom of Information Act (FOIA) for information at the state level or to pay a company to do a real estate search around a particular point.

EPA's Envirofacts http://www.epa.gov/enviro/

Major categories of information about factories are Toxic Releases, Hazardous Waste, and Permits (see sections below). If you are interested specifically in factories in the petroleum refining, iron and steel production, primary nonferrous metals, pulp manufacturing, or automobile assembly.industries, then you may be best off with EPA's Sector Facility Indexing Project (SFIP).

EPA's Envirofacts http://www.epa.gov/enviro/

Quick summaries can be found through EPA's Center for Environmental Information and Statistics (CEIS). The Environmental Defense Fund’s (EDF) Scorecard has a good ranking system that ranks facilities by health hazards within an area, and a comparative risk feature that will sometimes have expert opinion on the worst risks in an area. EPA's Surf Your Watershed is very good for an overall look at water issues within an area; EPA's AIRSdata site is best for air quality. Both EPA's Envirofacts and RTK NET will provide detailed data about facilities within areas.

EPA's CEIS http://www.epa.gov/ceis/

EDF Scorecard http://www.scorecard.org/

EPA's Surf Your Watershed http://www.epa.gov/surf/

EPA's AIRSData http://www.epa.gov/airsweb/

The Environmental Defense Fund’s (EDF) Scorecard is the best site to find out what health effects a chemical can cause, which chemicals can produce a certain health effect, or which chemicals are regulated under a particular law. The EDF Scorecard will provide links to other sites as well.

EDF Scorecard http://www.scorecard.org/

EPA's data on quantities and types of hazardous waste -- its generation, and its destinations, such as incinerators and landfills -- is mainly in the Biennial Reporting System (BRS) database, available through RTK NET and EPA's Envirofacts. The TRI database also has information on generation of waste and transfers of waste from factories. The best source for this is RTK NET, since it lets you search for the destinations as well as the sources of the waste.

RTK NET http://www.rtk.net/

EPA's Envirofacts http://www.epa.gov/enviro/

EPA's Envirofacts has extensive real-time mapping capabilities. The Environmental Defense Fund’s (EDF) Scorecard also has real-time maps that have less information but are easier to use. EPA's Surf Your Watershed provides watershed maps, and most of the other sites have some kind of static maps available. If you want to produce detailed maps on your own computer, you can download the free EPA Landview program from RTK NET.

EPA's Envirofacts http://www.epa.gov/enviro/

EDF Scorecard http://www.scorecard.org/

EPA's Surf Your Watershed http://www.epa.gov/surf/

RTK NET http://www.rtk.net/

Most pollution in the U.S. is permitted by law. Generally, each facility must have one or more permits (to release to the air, to the water, or to handle hazardous waste). Information about these permits, and compliance with them, is kept in the Air Facility Subsystem (AFS/AIRS), Permit compliance System (PCS), and RCRA Information System (RCRIS) databases, for air, water, and hazwaste respectively. The best source for air permit data is EPA's AIRSData site. For water permits, the best source is EPA's Envirofacts. Both Envirofacts and RTK NET are good sources for hazwaste permit information from RCRIS.

EPA's AIRSData http://www.epa.gov/airsweb/

EPA's Envirofacts http://www.epa.gov/enviro

RTK NET http://www.rtk.net/

EPA has many fragmented pesticide databases available for download through the EPA Web page. The most useful searchable site is Environmental Working Group’s (EWG's) Foodnews site, which will show which pesticides are in which foods.

EWG http://www.ewg.org/

EPA’s Database page http://www.epa.gov/epahome/Data.html

The Toxics Release Inventory (TRI) database is the best and mostly widely used source for this information. It provides estimates of actual release amounts, rather than permit levels. For complete TRI data, the best source is RTK NET. If you want TRI data linked with other EPA data, the best source is EPA's Envirofacts. For TRI data linked with information on health effects of chemicals, the best source is the EDF Scorecard.

RTK NET http://www.rtk.net/

EPA's Envirofacts http://www.epa.gov/enviro/

EDF Scorecard http://www.scorecard.org/

Data on sources of drinking waters is kept in EPA's Safe Drinking Water Information system (SDWIS) database, available through EPA's Envirofacts and Environmental Working Group’s (EWG) "Where You Live". Data on quality of surface water (rivers, lakes, etc.) is best accessed through EPA's Surf Your Watershed site.

EPA's Envirofacts http://www.epa.gov/enviro/

EWG http://www.ewg.org/

EPA's Surf Your Watershed http://www.epa.gov/surf/

EDF Scorecard http://www.scorecard.org/

Has subset of latest toxic release information, with very extensive health effect and regulatory info.

EPA's AIRSData http://www.epa.gov/airsweb/

Run by EPA's air pollution office; has info on general air quality and air pollution from individual sites.

EPA's CEIS http://www.epa.gov/ceis/

Environmental statistics; look under "Environmental Profiler" for county data summaries.

EPA’s Database page http://www.epa.gov/epahome/Data.html

Source for a large number of downloadable data files.

EPA's Envirofacts http://www.epa.gov/enviro/

Info from seven major EPA databases, with very good linkage between databases.

EPA's SFIP http://es.epa.gov/oeca/sfi/access.htm

Conjoined pollution, compliance, and production data for facilities in 5 major industries.

EPA's Surf Your Watershed http://www.epa.gov/surf/

Has wide variety of water quality and ecological information on surface waters.

EWG http://www.ewg.org/

Has "Where You Live" source for environmental and other data; "Foodnews" for pesticides in foods.

RTK NET http://www.rtk.net/

Has detailed information from EPA toxic release and many other databases.