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TRI National Analysis

Hazard and Potential Risk of TRI Chemicals

Among other information, the Toxics Release Inventory (TRI) Program provides data about environmental releases of TRI chemicals from industrial facilities throughout the United States, measured in pounds. Pounds of releases, however, is not an indicator of health risks posed by the chemicals, as described in EPA's Factors to Consider When Using Toxics Release Inventory Data. Although TRI data generally cannot indicate to what extent individuals have been exposed to chemicals, TRI can be used as a starting point to evaluate exposure and potential risks TRI chemicals pose to human health and the environment.

The human health risks resulting from exposure to chemicals are determined by many factors, as shown in the figure below. TRI contains some of this information, including what chemicals are released from industrial facilities; the amount of each chemical released; and the amounts released to air, water, and land.

Overview of Factors that Influence Risk

Overview of factors that influence risk (emissions, fate, exposure, toxicity, and risk of adverse effect)

It is important to keep in mind that while TRI includes information on many chemicals used by industry, it does not cover all facilities, all chemicals, or all sources of TRI chemicals in communities. For example, potential sources of exposure to chemicals not tracked by TRI include exhaust from cars and trucks, chemicals in consumer products, and chemical residues in food and water.

Helpful Concepts

The hazard of a toxic chemical is its ability to cause an adverse health effect(s) (e.g., cancer, birth defects). Toxicity is a way to measure the hazard of a chemical.

The risk of a toxic chemical is the chance of adverse health effects occurring as a result of exposure to the chemical. Risk is a function of hazard and exposure.

To provide information on the potential hazard and risk posed by disposal or other releases of TRI chemicals, the TRI Program uses EPA's Risk-Screening Environmental Indicators (RSEI) model. RSEI is a screening-level model that uses simplifying assumptions to fill data gaps and reduce the complexity of calculations to quickly evaluate large amounts of data. RSEI includes TRI data for on-site releases to air and water, transfers to Publicly Owned Treatment Works (POTWs), and transfers for off-site incineration. RSEI does not currently model other release pathways, such as land disposal.

RSEI produces hazard estimates and unitless risk “scores,” which represent relative risks to human health following chronic exposure to a TRI chemical. Each type of result can be compared to other results of the same type.

RSEI: Risk-Screening Environmental Indicators

RSEI results consider more than just chemical quantities released.

  • RSEI hazard results also consider:
    • Toxicity of the chemical
  • RSEI scores also consider:
    • Location of releases
    • Toxicity of the chemical
    • Fate and transport
    • Human exposure pathway
  • RSEI hazard estimates consist of the pounds released multiplied by the chemical's toxicity weight. They do not include any exposure modeling or population estimates.
  • A RSEI risk score is an estimate of potential risk to human health. It is a unitless value that accounts for the magnitude of the release quantity of a chemical, the fate and transport of the chemical throughout the environment, the size and locations of potentially exposed populations, and the chemical’s inherent toxicity.

Note that the RSEI model should only be used for screening-level activities such as trend analyses that compare potential relative risks from year to year, or ranking and prioritization of chemicals or industry sectors for strategic planning. RSEI does not provide a formal risk assessment, which typically requires site-specific information, more refined exposure information, and detailed population distributions.

This page was published in March 2019 and uses the 2017 TRI National Analysis dataset made public in TRI Explorer in October 2018.

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