Hazard and Risk of TRI Chemicals in the 2015 TRI National Analysis
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Among other information, the Toxics Release Inventory (TRI) provides data about environmental releases of toxic chemicals from industrial facilities throughout the United States, measured in pounds. Pounds of releases, however, is not an indicator of any health risks posed by the chemicals. Although TRI data generally cannot indicate to what extent individuals have been exposed to toxic chemicals, TRI can be used as a starting point to evaluate exposure and the potential risks TRI chemicals pose to human health and the environment.
The human health risks resulting from exposure to toxic 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.
It is important to keep in mind that while TRI often includes information on a large portion of the toxic chemicals used by industry, it does not cover all facilities, all toxic chemicals, or all sources of TRI chemicals in communities. For example, potential sources of chemical exposure that are not covered by TRI include exhaust from cars and trucks, chemicals in consumer products, and chemical residues in food and water.
The hazard of a toxic chemical is its ability to cause an increased incidence of adverse health effects (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 publicly available Risk-Screening Environmental Indicators (RSEI) model, a screening-level model that uses simplifying assumptions to fill data gaps and reduce the complexity of calculations in order 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 chronic human health risk. 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 weighttoxicity weightThis weight is a proportional numerical weight applied to a chemical based on its toxicity. The toxicity of a chemical is assessed using EPA-established standard methodologies. For each exposure route, chemicals are weighted based on their single, most sensitive adverse chronic human health effect (cancer or the most sensitive noncancer effect). In the absence of data, the toxicity weight for one pathway is adopted for the other pathway. The range of toxicity weights is approximately 0.02 to 1,400,000,000.. They do not include any exposure modeling or population estimates.
- RSEI risk scores are estimates of potential human risk based on pathway-specific modeling of chemical concentrations at specific points in the environment, like in the air around a facility or in the water downstream from a facility.
Note that the RSEI model should be used for screening-level activities such as trend analyses that compare relative risk 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.
Top chemicals released§ in 2015, ranked in order by...
|Pounds Released||RSEI Hazard
(estimated dose*toxicity*exposed population)
|1. Nitrate compounds||1. Chromium and compounds||1. Chromium and compounds|
|2. Methanol||2. Cobalt and compounds||2. Nickel and compounds|
|3. Ammonia||3. Arsenic and compounds||3. Cobalt and compounds|
|4. Sulfuric acid||4. Nitroglycerin||4. 1,3-Butadiene|
|5. Hydrochloric acid||5. Nickel and compounds||5. Arsenic and compounds|
|Why are the rankings different?|
§This includes chemicals released on-site to air and water by TRI facilities, or transferred and released off-site to air and water by POTWs and incinerators.
This page was published in January 2017 and uses the 2015 TRI National Analysis dataset made public in TRI Explorer in October 2016.