POLLUTION LOCATOR|Definitions of Toxics Release Inventory Reporting Categories

This page defines the environmental release and waste management categories used by companies reporting to the Toxics Release Inventory. More on TRI and its limits.

Air Releases

Total releases to air include all TRI chemicals emitted by a plant from both its smoke stack(s) as well "fugitive" sources (such as leaking valves).

Stack Air Releases

Releases to air that occur through confined air streams, such as stacks, vents, ducts or pipes. Sometimes called releases from a point source.

Fugitive Air Releases

Releases to air that do not occur through a confined air stream, including equipment leaks, evaporative losses from surface impoundments and spills, and releases from building ventilation systems. Sometimes called releases from nonpoint sources.

Water Releases

Releases to water include discharges to streams, rivers, lakes, oceans and other bodies of water. This includes releases from both point sources, such as industrial discharge pipes, and nonpoint sources, such as stormwater runoff, but not releases to sewers or other off-site wastewater treatment facilities. It includes releases to surface waters, but not ground water.

Land Releases

Land releases include all the chemicals disposed on land within the boundaries of the reporting facility, and can include any of the following types of on-site disposal:

RCRA Subtitle C Landfills

Wastes which are buried on-site in landfills regulated by RCRA Subtitle C.

Other On-site Landfills

Wastes which are buried on-site in landfills that are not regulated by RCRA.

Land Treatment/Application Farming

Wastes which are applyied or incorporated into soil.

Surface Impoundments

Surface impoundments are uncovered holding ponds used to volatilize (evaporate wastes into the surrounding atmosphere) or settle waste materials.

Other Land Disposal

Other forms of land disposal, including accidental spills or leaks.

Underground Injection

Underground injection releases fluids into a subsurface well for the purpose of waste disposal. Wastes containing TRI chemicals are injected into either Class I wells or Class V wells:

Class I Injection Wells

Class I industrial, municipal, and manufacturing wells inject liquid wastes into deep, confined, and isolated formations below potable water supplies.

Other Injection Wells

Include Class II, III, IV, and V wells. Class II oil- and gas-related wells re-inject produced fluids for disposal, enhanced recovery of oil, or hydrocarbon storage. Class III wells are associated with the solution mining of minerals. Class IV wells may inject hazardous or radioactive fluids directly or indirectly into underground sources of drinking water (USDW), only if the injection is part of an authorized CERCLA/RCRA clean-up operation. Class V wells are generally used to inject non-hazardous wastes into or above an underground source of drinking water. Class V wells include all types of injection wells that do not fall under I-IV. They are generally shallow drainage wells, such as floor drains connected to dry wells or drain fields.

Total Environmental Releases

Total Environmental Releases includes all reported on-site releases to air, water, and land (including underground injection). This total does not include any waste that is transferred off-site, so it does not include any environmental releases that may occur as a result of off-site disposal or treatment.
[Note: In its presentations of TRI data, EPA provides information about "total releases" - the sum of both on-site and off-site releases. Data based on this more expansive definition of releases are available from Scorecard as a component of Total Production-Related Waste reports, but are not appropriate for use when aggregating TRI data to profile releases within specific geographic areas.]

Total Off-Site Transfers

Total off-site transfers are the sum of chemical shipments off-site to other facilities for disposal, recycling, combustion for energy recovery, or treatment. An off-site transfer occurs whenever wastes are sent to a facility that is geographically or physically separate from the facility reporting under TRI. While off-site transfers do not result in environmental releases at the waste-generating facility, they can result in environmental releases at the off-site facility.

TRI tracks off-site transfers to various types of facilities:

Publicly Owned Treatment Works

A POTW is a wastewater treatment facility that is owned by a state or municipality. Wastewaters from facilities reporting under TRI are transferred through pipes or sewers to a POTW. Treatment or removal of a chemical from the wastewater depends upon the nature of the chemical, as well as the treatment methods present at the POTW. In general, chemicals that are easily utilized as nutrients by microorganisms, or have a low solubility in water, are likely to be removed to some extent. Chemicals that are volatile and have a low solubility in water may evaporate into the atmosphere. Not all TRI chemicals can be treated or removed by a POTW. Some chemicals, such as metals, may be removed, but are not destroyed and may be disposed of in landfills or discharged to receiving waters; transfers of metals and metal compounds to POTWs are categorized as off-site releases.


Toxic chemicals in waste that are transferred off-site for disposal generally are released to land at an off-site facility or are injected underground.

Energy Recovery

Toxic chemicals in waste sent off-site for purposes of energy recovery are combusted off-site in industrial furnaces (including kilns) or boilers that generate heat or energy for use at that location. Treatment of a chemical by incineration is not considered to be energy recovery.


Toxic chemicals in waste that are sent off-site for the purposes of recycling are generally recovered by a variety of recycling methods, including solvent recovery and metals recovery. The choice of the recycling method depends on the toxic chemical being sent for recycling. Once they have been recycled, these chemicals may be returned to the originating facility for further processing or made available for use in commerce.


Toxic chemicals in waste that are transferred off-site may be treated through a variety of methods, including biological treatment, neutralization, incineration, and physical separation. These methods typically result in varying degrees of destruction of the toxic chemicals. Not all TRI chemicals can be treated in ways that prevent their ultimate release to the environment. Transfers of metals and metal compounds to treatment by solidification/stabilization are categorized as off-site releases.

Total Production-Related Waste

Total production-related waste is the sum of all non-accidental chemical waste generated at a facility, prior to any form of on-site or off-site waste management. It is the sum of on-site environmental releases (minus quantities from non-routine, one-time events), on-site waste management (recycling, treatment, and combustion for energy recovery), and off-site transfers for disposal, treatment, recycling or energy recovery.

Released On-and Off-Site

The total quantity of TRI chemicals that were released to the environment or disposed of at the facility (directly discharged to air, land, and water, and injected underground) or sent off-site for disposal. This quantity is the sum of the amounts reported in Sections 5 and 6 of Form R (releases plus transfers to disposal and transfers to POTWs of metals and metal compounds) less any amount(s) associated with non-routine events. [Note: EPA TRI reports label this category as "total releases."]

Energy Recovery On-Site

The quantity of TRI chemicals that were combusted in some form of energy recovery device, such as a furnace, kiln or boiler. The amount reported represents the amount destroyed in the combustion process, not the amount that entered the energy recovery unit. For example, 100,000 pounds of toluene entered a boiler that, on average, combusted 98% of the toluene. Any remaining toluene was discharged to air. A total of 98,000 pounds is reported as combusted for energy recovery (the remaining 2,000 pounds is reported as released to air).

Energy Recovery Off-Site

The quantity of TRI chemicals that left the facility boundary for energy recovery at an off-site location.

Recycling On-Site

The quantity of TRI chemicals recovered at the facility by recycling and made available for further use. The amount reported represents the amount exiting a facility's recycling unit. It is not the quantity that entered an on-site recycling or recovery operation. For example, 3,000 pounds of a listed chemical enters a recycling operation. Of this, 500 pounds of the chemical are in residues from the recycling operation that are subsequently sent off-site for disposal. The quantity reported as recycled on-site would be 2,500 pounds.

Recycling Off-Site

The quantity of TRI chemicals that left the facility boundary for recycling at an off-site location.

Treated On-Site

The quantity of TRI chemicals destroyed in on-site waste treatment operations. For example, if 100,000 pounds of benzene were combusted in an incinerator that destroyed 99% of the benzene, the facility would report 99,000 pounds as treated on-site (the remaining 1,000 pounds would be reported as released to air).

Treated Off-Site

The quantity of TRI chemicals that left the facility boundary and was sent to POTWs or other off-site locations for treatment at off-site locations.