Learn the Issues

What is a HEPA filter?

HEPA is a type of pleated mechanical air filter that is common in portable air cleaners, also known as air purifiers. It is an acronym for " high efficiency particulate air " filter, as officially defined by the U.S. Department of Energy. This type of air filter can theoretically remove…

Last published: January 13, 2026

Soak Up the Rain: Rain Gardens

Find resources and learn how to site, design, install, and maintain a rain garden - a cost effective and beautiful way to reduce polluted stormwater runoff.

Soak Up the Rain: Rain Barrels

Find resources and learn how to install, use and maintain a rain barrel to collect rain water when it rains and help to reduce stormwater runoff from your property.

Soak Up the Rain: Permeable Pavement

Learn how permeable pavements work to help soak up the rain and reduce runoff. Find information on how to select, install and maintain permeable pavement surfaces.

Risk Assessment

How the EPA conducts risk assessment to protect human health and the environment. Several assessments are included with the guidelines, models, databases, state-based RSL Tables, local contacts and framework documents used to perform these assessments.

Exploration of Aging and Toxic Response Issues: Final Report

Most physiological functions undergo deterioration with increasing adult age and this deterioration undoubtedly increases vulnerability to harmful environmental agents.

Human Health Risk Assessment

This site will be linked off of the risk Microsite and will be where the 4 steps to HHRA, the guidelines to HHRA, links to models, tools, databases and HHRA examples.

Conducting a Human Health Risk Assessment

This page provides the step-by-step instructions to how the EPA conducts a human health risk assessment with additional links to models, tools, databases and related products.

EPA Approves Permits for Wabash Carbon Services Underground Injection Wells in Indiana’s Vigo and Vermillion Counties

EPA issued permits that allow Wabash Carbon Services LLC to construct two wells for injection and storage of carbon dioxide underground

Geographic Locations: United States

Papers Addressing Scientific Issues in the Risk Assessment of Metals

To inform the consideration of metals properties, and to engage the external scientific community, the Agency commissioned external experts to lead the development of a series of issue papers.

Methods for Identifying a Default Cross-Species Scaling Factor (Rhomsberg, 2004)

Provides a rationale for selecting default cross-species extrapolation factors with which to scale oral doses across species for non-carcinogenic endpoints.

Antimicrobial Exposure Assessment Task Force II (AEATF II) Volume 5: Governing Document for a Multi-Year Antimicrobial Chemical Exposure Monitoring Program (interim draft document with changes)

This document describes the overall scope of the AEATF II program, demonstrates the need for additional human exposure monitoring data and explains the proposed methodology for the exposure monitoring studies proposed for conduct by the AEATF II.

External Review Draft: Harmonization in Interspecies Extrapolation: Use of BW 3/4 as Default Method in Derivation of the Oral RfD

Recommends procedures, inclusive of default procedures, that will be used to estimate oral exposures in terms of human equivalents for all toxicologic endpoints.

Issue Paper on the Human Health Effects of Metals

This paper discusses issues important to consider in developing a framework for performing human health assessments for exposure to metals and metal compounds

Antimicrobial Exposure Assessment Task Force II (AEATF II) Volume 5: Governing Document for a Multi-Year Antimicrobial Chemical Exposure Monitoring Program (interim draft document)

Describes the overall scope of the AEATF II program, demonstrates the need for additional human exposure monitoring data and explains the proposed methodology for the exposure monitoring studies proposed for conduct by the AEATF II.