TRI and Estimating Potential Risk

The Toxics Release Inventory (TRI) provides useful data about environmental releases of toxic chemicals from industrial facilities throughout the United States, measured in pounds (or grams for dioxins). These data can serve as a starting point for evaluating potential risks to human health and the surrounding environment. 

Risk Concepts

Risk is the probability of harm to human health or the environment resulting from exposure to an environmental stressor.

Risk Assessment is an evaluation of the potential for a problem to occur and the scientific analysis of its threat to public health and the environment.

On this page:

What are the factors that influence risk determinations?

Many factors determine whether or to what extent the risks to human health or the environment from TRI-listed chemicals, some of which are summarized in the figure below. For additional information on the range of factors associated with health risks, visit EPA's main risk assessment webpage.

Overview of Factors that Influence Risk

Diagram describing the factors that influence risk: exposure source, environmental fate, population, exposure route, level of exposure, and toxicity.

Is my health at risk because of TRI chemical emissions?

The quantities of chemicals released into the environment are not an indicator of risks to human health because these quantities alone do not indicate the extent of exposure to these chemicals. Other factors, as shown in the figure above, should be accounted for including other sources of releases, the toxicity of the chemical emitted, environmental fate of chemicals, exposure routes, levels of exposure and surrounding populations.   

While TRI data includes a large portion of the chemicals used by industry, it does not cover all facilities, all toxic chemicals, or all sources of TRI chemicals emitted into the environment. For example, exhaust from cars and trucks, emissions from agricultural activities, chemicals in consumer products, and chemical residues in food and water are potential sources of chemical exposure not covered by TRI.

Additionally, TRI data does not tell us about the frequency of chemical releases and the level of hazard potential varies among the chemicals on the TRI chemical list. For example, exposure to small quantities of a certain TRI chemical may pose a greater risk of causing harm than exposure to large quantities of another TRI chemical.

How can I find out about the toxicity of certain chemicals?

Toxicity and Hazard

The toxicity of a substance refers to its potential to harm living organisms. Toxicity is a function of exposure concentration and duration, and varies by species, age and condition of exposed organisms.

The hazard of a chemical is its inherent ability to cause an adverse effect on health (e.g., cancer, birth defects). TRI calculates hazard as pounds multiplied by toxicity weights.

The TRI Program uses ‘relative toxicity weights’ that describe each chemical’s toxicity relative to other TRI-reported chemicals. Given data limitations about frequency and unknown exposure, conservative assumptions are applied. The toxicity weights for each TRI listed chemical or category are based on human health effects associated with long-term exposure and the single most sensitive effect for the pathway (oral or inhalation)—that is, the effect that happens at the lowest dose. 

For most chemical categories, TRI assumes the most toxic form of the chemical, except for chromium and chromium compounds, polycyclic aromatic compounds, and mercury and mercury compounds, where multiple toxicity weights are used. To determine the hazard potential of TRI chemical emissions, TRI multiplies the toxicity weight(s) of the chemical by the pounds released.  These hazard quantities are available in various TRI tools including TRI Toxics Tracker and EPA’s Risk Screening Indicators dashboard (EasyRSEI).

To learn more about how the TRI Program derives toxicity weights, refer to the RSEI Toxicity Weights webpage.

For More Information

Other resources that have information about TRI chemicals and the effects of exposure on human health and the environment include:

How can TRI data help me understand relative risk?

TRI data can be used as a starting point—along with other resources such as EPA’s Risk-Screening Environmental Indicators (RSEI) model—to evaluate potential exposure and risks to human health and identify where further investigation may be warranted.

A RSEI Score is a calculated estimate of relative potential human health risk. It is a unitless value that accounts for the amount of a chemical released to air or water, what happens to the chemical in the environment, size, and location(s) of potentially exposed populations, and the chemical’s toxicity weight.

The RSEI model incorporates information from TRI on the amount of chemicals released along with factors such as how chemicals change and where they go as they move through the environment, each chemical’s relative toxicity, and the potential for human exposure.  People are  most likely to be exposed to TRI chemicals through the air or water, so RSEI focuses on releases to air and water, including releases to air from waste incinerators and releases to water following transfers to publicly owned treatment works (POTWs). Using these waste management quantities reported to TRI, the RSEI model produces two primary results—hazard-based values (RSEI Hazard) and risk-related scores (RSEI Score)—that enable screening-level comparisons of relative potential harm and potential risks to human health from TRI chemicals.

While these values provide greater insight on potential health impacts than TRI release quantities alone, RSEI Hazard or RSEI Score values are not estimates of human health risks from industrial emissions of TRI chemicals. Rather, these values are offered for relative comparisons, such as the analysis of trends over time or comparison of sectors. Studies and analysis using RSEI data can be used to help establish priorities for further investigation and to look at changes in potential human health impacts over time.

  • Note that the RSEI model should only be used for screening-level activities such as trend analyses that compare potential relative risk per 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.
  • RSEI provides an ability to analyze the relative contribution of chemicals and industrial sectors to human health impacts and RSEI results serve as an analytical basis for setting priorities for further risk analysis, pollution prevention, regulatory initiatives, enforcement targeting, and chemical testing requirements.
  • For information about the risk assessment process, visit EPA's main risk assessment webpage.

How is EPA working to minimize risk from toxic chemicals in my community?

EPA works with state and tribal partners to:

  • regulate how and to what extent facilities store, use, handle, release and dispose of toxic chemicals;
  • encourage facilities to prevent or reduce pollution at the source; and
  • publish TRI data to create a strong incentive for companies to improve environmental performance.

In general, industrial facilities that operate in compliance with environmental regulations have controls in place that reduce the potential risks their operations pose to human health and the environment.

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Last updated on January 15, 2025