Introduction

Human health risk assessment at EPA is focused on advancing the understanding of the effects that exposure to pollutants have on key biological, chemical, and physical processes that affect human health.

Risk assessments by EPA scientists and their partners provide the foundation for the Agency’s actions to protect public health and the environment. EPA’s human health risk assessment efforts generate health assessments used to determine the potential risk to public health from exposures to environmental contaminants.

This section highlights some of the many accomplishments that EPA scientists and researchers made in 2010 to advance human health risk assessment, including:  ushering in the “next generation” of risk assessment science, the release of an extensive database that provides both a powerful new resource to scientists and a new level of transparency to the public, final integrated science assessments for carbon monoxide and the National Ambient Air Quality Standards, and more.

A New Era for EPA's Integrated Risk Information System (IRIS)

The Agency advances the management of chemical risks.

Over its 40-year history, EPA has embraced the critical role of providing timely, high-quality, and accessible human health risk information on environmental contaminants, especially about contaminants that may endanger the American public. Today, a central aspect of that role is the Agency’s Integrated Risk Information System (IRIS) program.

IRIS is a human health assessment program that evaluates risk information on health effects that may result from exposures to environmental contaminants. Through the IRIS Program, EPA provides the highest quality science-based human health assessments to support the Agency’s regulatory activities to protect the public.

The IRIS database includes more than 540 chemical substances and contains crucial information on ways human health is impacted by exposure to those substances in air, water, and land from contaminated sites and from products. Combined with specific exposure information, government and private entities use IRIS to help characterize public health risks of chemical substances in a site-specific situation, thereby supporting risk management decisions designed to protect public health.

In 2010, EPA continued to implement a revamped and greatly improved IRIS process to ensure scientific quality, integrity, transparency, and timeliness of EPA’s effort to manage chemical risks. The IRIS development process includes a streamlined review schedule, ensuring that the majority of assessments are posted on IRIS within 2 years of the assessment start date.

Ten final IRIS assessments were released in 2010 and significant progress was made on a number of draft assessments—exceeding the average productivity of the program over the last 3 years.

The 10 final IRIS Assessments released in 2010 were:

• Chloroprene
• Cis-1,2-dichloroethlyene
• Pentachlorophenol
• 1,1,2,2-Tetrachloroethane
• Trans-1,2-dichloroethylene
• Hydrogen Cyanide and Cyanide Salts
• 1,4-Dioxane
• Ethylene glycol monobutyl ether (EGBE)
• Carbon Tetrachloride
• Acrylamide

For more information and to access the updated IRIS program, visit: www.epa.gov/iris/index.html.

HERO Streamlines EPA Science Assessments, Marks Milestone in Transparency

An Agency database provides open access to state-of-the-science information used for science assessments.

EPA took a major step in advancing open government and transparency when it announced the launch of the Health and Environmental Research Online (HERO) database in March 2010.

HERO is an open and accessible online database built from a wealth of scientific literature and information. EPA researchers designed the database to provide sophisticated search capabilities and elegant access, review, and analysis of the ever-growing body of scientific literature on which they rely. This includes peer-reviewed journals and literature, as well as technical bulletins, conference proceedings, and other sources that can provide the latest scientific findings as well as insight into emerging directions and trends, yet may be lost in less robust databases.

The database includes more than 300,000 scientific articles. For each reference, HERO contains:

• Reference type.
• Citation elements:  author’s name, title, year of publication, source. Depending on the type of reference, the citation also may include volume, page numbers, URL, 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.
• For “key” studies:  objective, quantitative extracted study data.

HERO provides EPA researchers with a powerful tool to inform the development of risk assessments. The Agency uses risk assessments to integrate exposure and health or ecological effects information into a characterization of the potential for health hazards in humans or our environment. The process is highly interdisciplinary, drawing 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.

HERO is an “evergreen” database, meaning it employs mechanisms to continuously incorporate new science publications. Added references are sorted, classified, and made available through HERO. These efforts keep EPA scientists and others abreast of the rapidly growing body of scientific literature, and help them to meet their mission of assessing state-of-the-science findings to protect human health. 

In addition to supporting Agency researchers, HERO provides the public with an easy way to search and analyze the scientific literature underlying risk assessments used to support EPA decision-making. The database’s systematic, comprehensive search and screening techniques are transparent and open, and the HERO Web site incorporates opportunities and mechanisms to facilitate public and stakeholder participation in the identification of key research. As such, the release of HERO in 2010 marked a key milestone in EPA’s open government directive to conduct business with transparency, participation, and collaboration.

For more information and to participate, visit the HERO Web site at: http://cfpub.epa.gov/ncea/hero/.

EPA Human Health Risk Assessments

2010 Accomplishments In Brief

EPA released the following Human Health Risk Assessment products in 2010:

• Integrated Science Assessment (ISA) for Carbon Monoxide (CO)
  On January 29, 2010, EPA announced the release of the final Integrated Science Assessment (ISA) for Carbon Monoxide (CO). The report presented EPA’s latest evaluation of the scientific literature on the potential human health and welfare effects associated with ambient exposures to CO.
  
  CO is one of six principal (or criteria) pollutants for which EPA must establish National Ambient Air Quality Standards (NAAQS) to protect public health, including for “sensitive” populations such as asthmatics, children, and the elderly. Periodically, EPA reviews the scientific basis for these standards by preparing an ISA. The ISA and supplementary annexes, in conjunction with additional technical and policy assessments, provide the scientific basis for EPA decisions on the adequacy of the current NAAQS and the appropriateness of possible alternative standards.
  
  Together with the final ISA for Particulate Matter (PM), which was released in late 2009, the completed CO assessment led to the posting of the revised and fully implemented NAAQS process. 

• Perspectives on the Application of Mechanistic Information in Chemical Hazard and Dose-Response Assessments
  On September 29, 2010, EPA released a project summary called, Perspectives on the Application of Mechanistic Information in Chemical Hazard and Dose-Response Assessments. The summary lists several EPA articles reviewing approaches for applying mechanistic information in human health risk assessment and exploring opportunities for progress in this area.
  
  The report was the result of an EPA-initiated multidisciplinary project to critically review methods for applying mechanistic information in human health risk assessment and to explore strategies for progress in this area. The project examined approaches for interpreting observed effects in laboratory animals and their human relevance based on hypothesized modes of action. In addition, a critical aspect of the project was to explore issues pertinent to toxicity-pathway based risk assessment.
  
  
• Potential for Incorporation of Genetic Polymorphism Data in Human Health Risk Assessment
  On September 19, 2010, EPA released a project summary called, Potential for Incorporation of Genetic Polymorphism Data in Human Health Risk Assessment. The summary lists several EPA articles that evaluated the potential impact of genetic polymorphisms in 10 metabolizing enzymes on the variability in enzyme function across ethnically diverse populations.
  
  The work presented focuses on the contribution of genetic polymorphisms to the variability in host metabolism and defense mechanisms by evaluating polymorphisms in 10 enzyme systems, including three Phase I metabolic enzymes (CYP2E1, CYP2D6, PON1), four Phase II metabolic enzymes (SULTs, UGTs, GSTs, NATs), and three detoxification enzymes (ALDH2, EH, NQO1).

• An Exposure Assessment of Polybrominated Diphenyl Ethers (PBDEs)
  On May 24, 2010, EPA released the final report An Exposure Assessment of Polybrominated Diphenyl Ethers (PBDEs). The report provides a comprehensive assessment of exposure to this class of persistent organic pollutants, often used as flame retardants, for people living in the United States. Individual chapters address:  the production, use, and lifecycle of PBDEs; environmental fate; environmental levels; and human exposure.
  
  
• An Approach to Using Toxicogenomic Data in U.S. EPA Human Health Risk Assessments:  A Dibutyl Phthalate Case Study
  On January 13, 2010, EPA announced the availability of a final report titled, An Approach to Using Toxicogenomic Data in U.S. EPA Human Health Risk Assessments:  A Dibutyl Phthalate Case Study. The report features the application of genomic technologies (e.g., transcriptomics, genome sequence analysis) to study effects of environmental chemicals on human health and the environment.
  
  It describes an approach to evaluating toxicogenomic data for use in risk assessment and a case study of dibutyl phthalate (DBP). A multidisciplinary team of scientists developed the approach for utilizing genomic data in risk assessment and performed the DBP case study.
  
  The principles of the approach include examining the genomic and toxicity data sets together, defining a set of questions to direct the evaluation, and performing new analyses of genomic data, when relevant. The report includes the development of exploratory methods and preliminary results from genomic data analyses. In addition, recommendations, research needs and future directions for applying genomic data to risk assessment were identified. The approach and case study may be used as a template for evaluating and analyzing genomic data in future chemical assessments as well as by researchers performing genomic studies for use in risk assessment.

Draft Scientific Report on Dioxin Toxicity Released

EPA released a draft scientific report, EPA's Reanalysis of Key Issues Related to Dioxin Toxicity and Response to NAS Comments for independent external review and public review and comment.

The public release of the draft scientific report marked a significant milestone toward the completion of the Agency's dioxin reassessment. It provides EPA's response to the key recommendations and comments included in the National Academy of Sciences (NAS) 2006 report. In addition, the report includes new analyses on potential human effects that may result from exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

This comprehensive human health and exposure risk assessment on dioxin, one of the most toxic environmental contaminants, aims to protect the health of the American public.

Health Science Information on Formaldehyde and Trichloroethylene (TCE) Toxicity

EPA completed comprehensive examination of the health science information on formaldehyde and trichloroethylene (TCE) toxicity and released external review drafts for public comment. Formaldehyde is important both to public health and to a number of upcoming residual risk rulemakings under the Clean Air Act. TCE is one of the most common pollutants of concern at Superfund sites in the United States and also can be found in drinking water and in air emissions.