Learn the Issues
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Timeline of Actions on HFCs
The Kigali amendment to phase down HFCs was the result of years of negotiation by parties to the Montreal Protocol, with numerous HFC amendment proposals submitted by North America, Island States, India, and the European Union.
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Section 20: Radionuclides
There is no HRS score pathway for radionuclides, but there are special considerations that come into play within each of the four pathways when radioactive substances are present.
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Section 19: Soil Exposure - Nearby Population Threat
Learn about soil exposure and nearby population threat, which assesses the relative risk that nearby individuals (residents, students, and day care children) may travel to the site and come into contact with hazardous substances.
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Section 18: Soil Exposure - Resident Population Threat
The soil exposure pathway for evaluating HRS scores evaluates the potential threats to humans and terrestrial environments posed by direct, physical contact with hazardous waste or contaminated soil.
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Section 17: Air - Waste Characteristics & Targets
The air migration pathway for evaluating HRS scores evaluates the likelihood of release of hazardous substances into the atmosphere and how many people and sensitive environments could be exposed to hazardous substances carried in the air.
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Section 16: Air - Likelihood of Release
Learn about the air migration pathway for evaluating HRS scores and the likelihood of hazardous gas and particulate substance release.
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Section 15: Surface Water - Ground Water to Surface Water Component
Learn about surface water targets, which can be threatened by the release of contaminated ground water.
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Section 13: Surface Water - Human Food Chain Threat
Learn about how surface water releases can threaten the human food chain.
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Section 12: Surface Water - Drinking Water Threat
Learn about how surface water releases can threaten the safety of drinking water.
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Section 11: Surface Water - Likelihood of Release
Learn about the surface water pathway, the most complex pathway for evaluating Hazard Ranking System (HRS) scores.
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Section 10: Ground Water - Waste Characteristics & Targets
Learn about the waste characteristics factor category in the ground water pathway, which is made up of two components: the toxicity/mobility of the most hazardous substance associated with the site and the hazardous waste quantity at the site.
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Section 9: Ground Water - Likelihood of Release
Learn how EPA evaluates an identified aquifer's likelihood of release factor category for the purpose of scoring the ground water pathway.
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Section 8: Ground Water - Aquifers
Learn about issues surrounding aquifers, the basic unit of evaluation in the HRS ground water pathway.
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Section 7: Targets
Learn about targets, the third factor category in the HRS pathway score equation. Targets are the people, resources, or sensitive environments that could be affected by the site.
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EPA to Begin Hazardous Waste Cleanup at Goo Smoke Shop Site in Clinton Township, Michigan
EPA News Release: EPA to Begin Hazardous Waste Cleanup at Goo Smoke Shop Site in Clinton Township, Michigan
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Section 6: Likelihood of Release
Learn about the likelihood of Release (LR) factor category, which is evaluated based on the factors of observed release and potential to release.
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Provisional Models and Tools Used in EPA’s Pesticide Endangered Species Biological Evaluations
This document provides an overview of the Environmental Protection Agency’s (EPA) ecological risk assessment process for the evaluation of potential risk to endangered and threatened (listed) species from exposure to pesticides.
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Section 5: Waste Characteristics
Learn about the calculation process for substance-specific factors, the chemical characteristics of the hazardous substances found at a site that are available to migrate from the site sources.
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Section 4: Source Characterization
Learn about source characterization for Superfund sites. Although the Hazard Ranking System (HRS) is designed to score releases and sites, sources and areas of observed contamination play a crucial role in determining HRS pathway scores.
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Section 3: HRS Structure
Read about the the four pathways for evaluating a Hazard Ranking System (HRS) score: ground water migration, surface water migration, soil exposure, and air migration.