Frequently Asked Questions
Health and Environmental Research Online (HERO) is a database of scientific studies and other references used to develop EPA's risk assessments aimed at understanding the health and environmental effects of pollutants and chemicals. It is developed and managed in EPA's Office of Applied Science and Environmental Solutions (OASES).
Risk assessment is a process in which information is analyzed to determine if an environmental hazard might cause harm to exposed persons and ecosystems. This process is highly interdisciplinary in that it draws from such diverse fields as biology, toxicology, ecology, epidemiology, engineering, geology, statistics, and the social sciences to create a rational framework for evaluating environmental hazards. EPA uses risk assessment as a tool to integrate exposure and health or ecological effects information into a characterization of the potential for health hazards in humans or our environment. Read more about risk assessment at EPA.
For each reference, HERO contains:
- Reference type
- Citation elements: authors, title, year of publication, source. Depending on the type of reference, the citation will also include volume, page numbers, URL, PubMed ID, doi, etc.
- Abstract or brief description
- Topic areas that describe the reference (e.g., carbon monoxide, asthma)
- Assessment(s) in which the reference was used, if relevant. Note that HERO contains references considered for use in assessment development, not just those references actually used or cited.
- For "key" studies: objective, quantitative extracted study data [future enhancement]
- Browsing: You can browse HERO by selecting a project from the Project page. This will take you to the project's reference page where references that are used in the assessment development process are listed.
- Searching: You can search public references in HERO through the Search page. You can either do a simple search or submit more specific searches in the Fielded Search area.
- Exporting: Once you have found what you want, you can export the reference metadata to EndNote reference manager by choosing the reference(s) you want and clicking "Export to File," then selecting "Export to EndNote." Your browser will download an RIS file that you can import into EndNote, or other reference managers compatible with the RIS format.
HERO includes studies used in assessment development, whether cited as a reference or considered for use. Read more about the literature search and literature screening processes.
HERO uses a variety of reference types; the majority of references are original research published in peer-reviewed literature. The field of library and information science provides us with standardized definitions, required and optional fields, and citation formats for each reference type.
HERO covers studies about a broad range of pollutants, chemicals, health and environmental effects. You can browse through these topics on the project page. This list is constantly growing as more studies are added. HERO's goal is to include the scientific literature used in EPA assessments. Contact us with your suggestions for additional data sources you think should be included.
HERO is constantly being updated as new studies are published. We have a team of information specialists who use advanced search techniques to keep studies on relevant topics feeding into HERO. This enables scientists to keep on top of the rapidly-growing body of literature and meet EPA's mission of assessing the state-of-the-science to protect human health and welfare. In addition, EPA has plans to enhance HERO's functionality per your ideas. Contact us to let us know how we can make HERO more useful to you.
HERO revisions are planned to broaden both the features and scope of information included. Future directions include additional data sets, environmental models, and services that connect data and models. Contact us with your ideas for improving HERO.
HERO was developed as part of changes to the National Ambient Air Quality Standards (NAAQS) and Integrated Risk Information System (IRIS) assessment processes. Beginning in 2005 with a revision to the NAAQS Review Process, EPA was tasked with creating a "more detailed and comprehensive science assessment support document, which will eventually be linked to an electronic database of scientific studies... [to] facilitate a more continuous process to identify, compile, characterize, and prioritize new scientific studies." Furthermore, it was deemed "essential that the best science and the greatest transparency inform air quality standards that prevent illness and save lives." More recently EPA Announced a New IRIS Assessment Development Process which is designed to improve "efficiency, scientific integrity, and transparency in a program that plays a vital role in our mission to protect human health and the environment."
Studies are constantly being added to HERO. If a study is not currently included it is either because: a) it has not been used or considered for use in an assessment; b) it has not yet been suggested; or c) it does not fit in the criteria for inclusion. Generally, scientific studies are published in peer-reviewed journals and relate to one of EPA's areas of concern. Contact us to suggest studies.
HERO's focus is on the world's published scientific literature, including studies that are conducted by EPA and its partners. The Science Inventory is a searchable database of research products primarily from EPA's Office of Research and Development. They complement each other.
There are many public and subscription databases of scientific studies. Contact us with your suggestions for sources that we haven't included.
Yes. It would be helpful to include as much of the citation as you can - authors, journal, title, year, volume, pages, etc. Contact us with your suggestions.
HERO is being continually improved in direct response to user suggestions. Contact us with your suggestions.
U.S. Environmental Protection Agency. (2025). HERO (1.7.4.dev0+g2fd50eff4.d20251019; llr 25.10) [Software]. Available from https://heronetnext.epa.gov/. Accessed October 22, 2025.
HERO contains references used or considered by EPA scientists in the development of scientific assessments. Although historically, not all assessments created by the EPA have their references entered in HERO, all references from new assessments will be included in HERO.
Most journal article entries in HERO have a link to a DOI (Digital Object Identifier) . This link will direct you to a journal or publisher website. If the article is free to the public, or you have a subscription to the journal, you can download the PDF. If not, you will usually be offered an option to purchase the individual article. Please note: Copyright laws prohibit distribution of copyrighted material.
Reports, books, book chapters, conference material, and other miscellaneous reference types are included if they were used in the assessment development process. Some of these references provide links to an internet site where the material can be downloaded or purchased.
During assessment development, scientists and collaborators identify relevant literature. In addition, results from comprehensive evergreen literature searches are continuously added.
If you would like to suggest a reference addition, send us the full citation. Please include information about the topic(s) the reference relates to.
HERO launched in March 2009. It contains data from a number of legacy databases used by the EPA -- both digital and paper. EPA is making these references available to the public in the interest of greater transparency and public accountability.
Yes. Any 2 or more fields you enter in a search will be joined as an "and" search and will find only the references meeting criteria in both (or all) fields.
Type the last names of the authors separated by a comma, e.g., Johnson, Patel.
Increasingly, we are producing our published assessments with links back to the reference in HERO. Clicking on a link - which contains the HERO ID - will open up your browser window and take you right to the details for that reference!
After conducting a search in HERO, you will be presented with a list of results. Select the references you want in your list by clicking the box next to each reference. Click the "Create Bibliography" button to produce your list.
References are evaluated for relevance to each assessment, taking several factors into account. Read about the assessment process.
At its core, HERO is a database for references used in EPA scientific assessments. Other components of the HERO Database System help scientists with literature searches, reference classification, and document production.
Constantly! Team HERO is behind the screen busily entering references daily. The evergreen process we employ brings new studies to our attention as they are published.
We are in the process of adding features to HERO that will show information extracted from the most relevant studies used by the various scientific disciplines. You will be able to search and produce reports on these studies both individually and across similar studies.
Tagging in HERO allows you to organize references within a project. These labeled groups can start at a higher level and have infinite lower level tags. The tagging hierarchy can then be viewed from the project page and on individual records.
Use the Project Setup page to request or modify tags for your project.
Use the Import References page under Tools to insert citations, DOI, RIS or other supported forms into HERO and label with your project tags.
For additional information, please see the attached document on Tagging.
A presentation on how to make a 508 compliant document that goes way beyond just that. Use this to figure out how to make a well-structured document that is easy for anyone to use and will lead you to simple 508 compliance.
An intro to LitCiter: This is a summary of information found elsewhere on this site. It also has some additional helpful hints and some best practices.
LitCiting and Tagging References in HERO: A seminar given by Laura Datko-Williams and Adrien Wilkie in September 2013