NOTE: A risk estimate is not the same as a count of actual cancer cases, and by itself it does not prove that any specific cancer was caused by chemicals in the local air. There are significant uncertainties in the scientific procedures used to estimate cancer risks. For more, see Scorecard's overview of hazardous air pollutants.

TOXIC CHEMICAL RELEASES
Over 5 billion pounds of toxic chemicals are released by industry into the nation's environment each year, including 75 million pounds of recognized carcinogens. Scorecard uses data from the U.S. EPA Toxics Release Inventory (TRI) to profile local pollution sources.

For environmental justice analyses, Scorecard uses an indicator of total reported TRI releases in an area. A geographic information system is used to develop an area's indicator by summing environmental releases from all TRI facilities within a census tract or within one mile of the tract boundary.

NOTE: The numerical values for the TRI Release analyses are indicators, not actual pounds released in a county or state. Indicators are considerably higher than the total chemicals released in a county or state because the geospatial allocation can count releases from the same facility multiple times, if that facility is within one mile of multiple census tract boundaries. Note also that not all toxic chemical releases are reported to TRI. For more, see Scorecard's overview of toxic chemical releases.

SUPERFUND SITES
Over 1,300 federal Superfund sites are scheduled for cleanup on the National Priorities List (NPL), commonly known as the federal Superfund program. These are the nation's worst toxic waste sites, and first in line to be cleaned up. Contamination at Superfund sites results from improper handling of waste and toxic materials, often spanning many decades. Some Superfund sites are old waste disposal facilities, while others were various types of industrial production facilities at which unauthorized dumping and inadvertent spills occurred.

For environmental justice analyses, Scorecard uses a measure of the number of Superfund sites per square mile.

NOTE: Proximity to a Superfund site does not necessarily reflect the level of exposure to any chemical at that site, or the level of any other health-related impact from the site. For more, see Scorecard's overview of Superfund.

FACILITIES EMITTING CRITERIA AIR POLLUTANTS
Criteria air pollutants are the six most common air pollutants in the U.S. The poor air quality that many Americans know as smog and soot is actually due to criteria pollutants like ozone and particulate matter. Exposure to criteria pollutants can cause breathing difficulties, aggravate heart and lung disease, and result in premature mortality. Over 100 million people still live in counties with unhealthy air. This pollution comes from mobile, area and point sources.

For environmental justice analyses, Scorecard uses a measure of the number of facilities emitting criteria air pollutants per square mile.

NOTE: Facilities per square mile is a relatively weak indicator of the potential for unhealthy exposures to criteria air pollutants, because it does not capture the amount of chemicals released by a facility, or the importance of other major sources like cars. For more, see Scorecard's overview of smog and particulates.

IMPORTANT NOTE - TEMPORARY DISCREPANCY: Scorecard's environmental justice reports are in the process of being updated to 2000 census data and more current environmental data. The data underlying environmental justice reports will differ from other sections of Scorecard until this update is complete. For example: cancer risks from hazardous air pollutants in environmental justice reports are based on 1990 EPA exposure estimates and 1990 census data, while Hazardous Air Pollutant reports have been updated to 1996 EPA exposure estimates and 2000 census data. Toxic chemical release indicators are based on 1998 TRI data, while Toxic Chemical Release reports have been updated to 2001 data.