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TRI National Analysis

Hazard and Potential Risk of TRI Chemicals

The chemical release data collected and made publicly available in the Toxics Release Inventory (TRI) are reported in pounds, with the exception of dioxin and dioxin-like compounds, which are reported in grams. Pounds or grams of releases, however, is not necessarily an indicator of environmental or human health impacts posed by the chemical releases, 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 to human health and the environment.

Human health risks that may result 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)

Helpful Concepts

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

The likelihood that a toxic chemical will cause an adverse health effect following its release into the environment is often referred to as risk. Risk is a function of hazard and exposure.

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. Other potential sources, such as exhaust from cars and trucks, chemicals in consumer products, and chemical residues in food and water, are not tracked by TRI.

To provide context on the relative hazard and potential for risks posed by certain waste management activities of TRI chemicals (e.g., from releases to the environment), the TRI Program uses EPA’s Risk-Screening Environmental Indicators (RSEI) model.

RSEI is a screening-level model that provides additional context for human health impacts from TRI release data by considering chemical toxicity, the fate and transport of the chemical through the environment, and potential human exposure. For chemicals reported to TRI as released to air or water, transferred to publicly-owned treatment works (POTWs), or transferred off site for incineration, the model produces a RSEI Score, which is a numerical descriptor that provides a relative estimate of potential human health risk to help identify situations of greatest potential risk and evaluate trends over time. RSEI does not currently model other waste management activities or release pathways reported to TRI, such as those associated with land disposal. In addition to RSEI Scores, the model produces RSEI Hazard estimates, also called toxicity-weighted pounds.

RSEI: Risk-Screening Environmental Indicators

  • RSEI Hazard results consider:
    • Quantity of the chemical released
    • Toxicity of the chemical
  • RSEI Scores consider:
    • Quantity of the chemical released
    • Toxicity of the chemical
    • Location of releases
    • Environmental 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 relative potential human health risk. 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.

Important notes about RSEI:

  • RSEI is not a stand-alone source of information for making conclusions or decisions about the risks posed by any particular facility or environmental release of a TRI chemical.
  • RSEI does not assess risk. It provides relative risk rankings from air emissions and water discharges of TRI-listed chemicals.
  • RSEI results should not be used to determine whether a facility is in compliance with federal or state regulations.
  • RSEI results should only be used for screening-level activities, such as:
    • trend analyses comparing potential relative risks from year to year, and
    • ranking and prioritizing chemicals, industry sectors, or geographic regions for strategic planning.
  • RSEI can be used with other data sources and information to help policy makers, researchers, and communities establish priorities for further investigation and to look at changes in potential human health impacts over time.
  • RSEI can help identify situations of greatest potential risk and evaluate trends over time.

This page was published in January 2021 and uses the 2019 TRI National Analysis dataset made public in TRI Explorer in October 2020.

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