About ITER


Frequently Asked Questions

What is ITER?


ITER (International Toxicity Estimates of Risk) is a free Internet database of human health risk values for over 680 chemicals of environmental concern from several organizations worldwide.  ITER is the only Internet database that provides this data in a table format that allows side-by-side comparisons of risk values from different organizations.  Below the table is a synopsis that includes an explanation for any differences among the organizations' values.


plusHow do I search ITER?

ITER is currently available in two locations: 


“Original ITER” is located at www.tera.org/iter and “ITER on TOXNET” is located at http://toxnet.nlm.nih.gov/. Listed below is the description for searching “Original ITER”. 


For a discussion on how to search ITER on TOXNET, please see www.tera.org/iter/tomasulo. Please note that both versions of ITER contain the same data, however, the TOXNET version has enhanced search functions.

Searching the “Original ITER” Database

To search the “Original ITER” database, go to www.tera.org/iter and click on Search Original ITER. Enter a chemical name, portion of a name, or CAS number. (NOTE: CAS numbers are the most effective way to search because it avoids the confusion about which chemical name is being used). You can also select from a list of all chemicals. When your search results have been returned, you can view the chemical data online or you can generate and print a report for a chemical.


What's included on ITER?

ITER contains data from national and international organizations worldwide. ITER provides links to these organizations for more detailed information.  ITER currently contains data from:


bullet Agency for Toxic Substances and Disease Registry (ATSDR)

ATSDR derives minimal risk levels (MRLs), which are found in the Agency's Toxicological Profiles. 

bullet Health Canada

Health Canada develops Tolerable Intakes/Concentrations and Tumorigenic Doses/Concentrations for Priority Substances under the Canadian Environmental Protection Act (CEPA).  These risk values for Health Canada are included on ITER.

bullet International Agency for Research on Cancer (IARC)

We are currently adding IARC's data to ITER.  Look for announcements about this on ITER’s “What’s New” page.

IARC evaluates the cancer weight of evidence for chemicals over a wide range of human exposures and classifies chemicals according to potential for carcinogenicity.  The results of IARC analyses are published Monographs.  IARC cancer classification groups and detailed descriptions of these groups can be found in the Preamble to each monograph and at http://monographs.iarc.fr/ENG/Preamble/index.php  The IARC evaluation considers the evidence of carcinogenicity in humans, the evidence of carcinogenicity in experimental animals, and other data relevant to the evaluation of carcinogenicity and its mechanisms.


bullet NSF International  


NSF International, an independent, not-for-profit organization, derives action levels [the total allowable concentration (TAC), single product allowable concentration (SPAC), and short-term exposure level (STEL)] for contaminants detected in laboratory testing of products in contact with drinking water and food.  The basis for the action levels is the oral reference dose (RfD) for non-cancer risk assessment and the appropriate risk level for carcinogen risk assessment. U.S. EPA non-cancer and cancer risk assessment procedures are followed and a risk assessment document is prepared.


bullet National Institute of Public Health and the Environment (RIVM), The Netherlands

RIVM develops human-toxicological risk limits (i.e., maximum permissible risk levels, MPRs) for a variety of chemicals based on chemical assessments that are compiled in the framework of the Dutch government program on risks in relation to soil quality.  The MPRs updated in 2001 have been added to ITER.


bullet Texas Commission on Environmental Quality (TCEQ)


TCEQ derives risk values called Effects Screening Levels (ESLs), inhalation Reference Values (ReVs), and inhalation Unit Risk Factors (URFs), which are published in Development Support Documents (DSDs).  DSDs summarize how chemical-specific toxicity values were derived based on published guidelines (RG-442, TCEQ Guidelines to Develop Toxicity Factors).


bullet U.S. Environmental Protection Agency (EPA )


EPA derives risk values called reference concentrations (RfCs), reference doses (RfDs) and cancer assessments. All of these risk values from EPA’s Integrated Risk Information System (IRIS) are included on ITER


bullet Independent parties whose risk values have undergone peer review


Risk values developed by other parties (e.g. industry, consulting groups, government, universities, etc.) that do not meet the criteria for having their own column on ITER (such as having data for at least 40 chemicals) are included on ITER under the ITER PR column or the IPRV column after they have undergone an independent peer review.  


ITER PR Column

The ITER PR column contains data from those organizations whose risk values have undergone peer review through TERA’s ITER Peer Review process (https://tera.org/Peer).  This independent peer review is convened by TERA through its Peer Review Program, and if the expert panel concurs with an assessment, it can be made available to the public on the ITER database.  Over two-dozen independent risk values have been included in the ITER PR column.  Most of the independent values can only be found on ITER. 


IPRV Column

The IPRV column contains data from those organizations that do not meet the criteria for having their own column (such as having data for at least 40 chemicals) and whose risk values have undergone peer review outside TERA’s ITER Peer Review process. 

Risk values are principally used as guidance or regulatory levels against which human exposures from contamination of air, food, soil, and water can be compared. The information on ITER is useful to risk assessors and risk managers needing human health risk values to make risk-based decisions. ITER allows the user to compare a number of key organizations' values and to determine the best value to use for the human exposure situation being evaluated.


How do I view chemical data?


If you would like to view the data for a chemical, click on its chemical name.  This will take you to the Level 1 table for that chemical, which contains red and gray circles for each organization and category (noncancer oral, cancer oral, noncancer inhalation, or cancer inhalation).  The red circles indicate that ITER contains data, and the gray circles indicate that ITER does not contain data for that particular organization or category.  (Note:  In some cases the organization may have data available but it has not yet been prepared for inclusion in ITER.  See the above section, entitled “What is ITER” to determine which organizations’ data is currently being added to ITER).  Click on the red circles to go to the Level 2 table, which displays the key elements for each organization’s risk value along with a synopsis explaining any differences among risk values.  At the bottom of the Level 2 table, you can click on the green circle(s) to go to Level 3 and obtain more information about a particular organization’s risk value (including a source and/or link for further information about that particular assessment).


How do I generate a report?

If you want to generate and print a report, click on the CAS number and the entire record for that chemical will be available to print.  You will first see the Level 1 table for that chemical with the red and gray circles to indicate whether or not ITER has data for that organization or category.  By clicking on a risk value category (noncancer oral, cancer oral, noncancer inhalation, or cancer inhalation), you will get both the Level 2 and Level 3 data for that chemical for all of the organizations on ITER.  You will then need to print each risk value category separately.

How was this information compiled?


The values and text on ITER have been extracted from existing published documents and data systems of the original health organizations.  TERA staff compiles information on the risk values into a consistent format, so that users can readily make comparisons across organizations.  In some cases, the organization itself extracts and prepares data for ITER.  TERA staff performs necessary conversions so that direct comparisons can be made when appropriate, and write the synopsis text to help explain the similarities and differences between the values of the different organizations.  The following explains the sources for ITER data.


ATSDR information was extracted from the ATSDR Toxicological Profile for each chemical.  Toxicological Profiles are published in both draft and final forms by ATSDR.  For information call the ATSDR TOX-INFO LINE at (404) 639-6000 or see http://www.atsdr.cdc.gov/toxprofiles/index.asp.


Health Canada information was extracted from Assessment Reports prepared by Environment Canada and Health Canada under the CEPA Priority Substances Program.  These reports provide an assessment of risks to human health and are chemical specific.  The most recent assessment reports, Environment Canada and Health Canada’s Canadian Environmental Protection Act, 1999:  Priority Substances List Assessment Reports, are available online at http://www.hc-sc.gc.ca/ewh-semt/pubs/contaminants/psl2-lsp2/index-eng.php.  Earlier reports were included in a 1994 publication, Evaluation of Risks to Health from Environmental Exposure in Canada. In: Environmental Carcinogenesis and Ecotoxicology Reviews, Part C of Journal of Environmental Science and Health. C12(2).  This publication summarized the assessments of risks to human health of 44 Priority Substances that were written to fulfill the requirements of the CEPA.  More detailed assessment reports and supporting documentation are available from the corresponding authors of each respective manuscript.  New assessments will continue to be added as they are released.


IARC information was extracted from the Summary and Evaluations in the IARC Monographs for each chemical.  IARC Monographs are available at http://monographs.iarc.fr


NSF International information is compiled from compound specific oral risk assessment documents prepared by NSF International.  The complete documents are available from the NSF bookstore at http://www.techstreet.com/cgi-bin/browsePublisher?publisher_id=133&subgroup_id=13180.


RIVM (The Netherlands) information was extracted from RIVM's 2001 document entitled, Re-evaluation of human-toxicological maximum permissible risk levels (RIVM report 711701025).  This report can be found at http://www.rivm.nl/bibliotheek/rapporten/711701025.html

TCEQ information was extracted from the Development Support Documents (DSDs). These documents can be found at http://www.tceq.texas.gov/toxicology/dsd/final.html.


U.S. EPA information was extracted from the Integrated Risk Information System (IRIS). IRIS is EPA's official source for agency consensus risk values.  IRIS is available on-line at http://www.epa.gov/iris. For additional information about IRIS, contact the U.S. EPA Risk Information Hotline at (301) 345-2870 or at  Hotline.IRIS@epamail.epa.gov.


Independent parties’ information is derived from their risk assessment documentation, which has undergone independent peer review (see https://tera.org/Peer).


What are TERA’s plans for expanding ITER?


We are currently adding cancer classifications from IARC and  plan to add data from the International Programme on Chemical Safety (IPCS), a member of the World Health Organization.


ExpandHow is ITER sponsored?


ITER was developed by TERA as a public service, to provide the international risk assessment community with easy access to the health risk values of many organizations and to provide a way to distribute independently derived peer-reviewed values. We are extremely grateful to our sponsors, without whom ITER would not have been possible. Additional support is needed to both maintain and expand ITER, and to continue providing ITER as a free service to the risk assessment community.


TERA has received support from a number of diverse organizations to help support the development and continual growth of the ITERdatabase.  Concurrent Technologies Corporation (CTC), a non-profit organization that develops and transfers leading edge technology to help the U.S. be more competitive in the world market place, collaborates with TERA by housing the original ITER database on its server and by providing technical support.  The Specialized Information Services (SIS) Division of the National Library of Medicine (NLM) collaborates with TERA to display ITER on its TOXNET compilation of databases.  This Division of NLM is responsible for information resources and services in toxicology, environmental health, chemistry, HIV/AIDS, and specialized topics in minority health.  Other groups have supported ITER through funds or in-kind activities.  These sponsors have included:


-         The Acrylonitrile Group, Inc.

-         The American Chemistry Council

-         Duke Energy

-         Concurrent Technologies Corporation(CTC)

-         Cytec Industries Inc.

-         Formaldehyde Epidemiology, Toxicology, and Environmental Group, Inc. (FETEG)

-         Health Canada

-         Metal Finishing Association of Southern California

-         National Institute of Public Health and the Environment (RIVM), The Netherlands

-         National Library of Medicine

-         Nickel Producers Environmental Research Association (NiPERA)

-         Noblis

-         NSF International

-         Syracuse Research Corporation

-         Texas Commission on Environmental Quality (TCEQ)

-         TERA developmental reserve funds

-         U.S. Borax


ITER was developed by TERA as a public service, to provide the international risk assessment community with easy access to the health risk values of many organizations and to provide a way to distribute independently derived peer-reviewed values.  We are extremely grateful to these sponsors without whom ITER would not have been possible. 



Duke Energy


Through the Cinergy Foundation, Cinergy contributes one percent of its pretax profits to local communities in support of the arts, education, human services and community development. In 1997, the Cinergy Foundation contributed over $5.2 million to charitable causes within its service territory. Cinergy understands its responsibility and is proud to be an active leader in the community. For more information, please visit www.duke-energy.com.


Cytec Industries Inc.


Cytec Industries Inc. is a global specialty chemicals and materials technology company with 1999 sales of $1.4 billion. Its growth strategies employ technologically based customer solutions for markets which include: aerospace, plastics, industrial coatings, mining, paper and water treatment.  Please emailINFO@GM.Cytec.com for further information.




Noblis is a nonprofit science, technology and strategy organization that helps clients solve complex systems, process and infrastructure problems. From a unique impartial stance, Noblis does “what's right and what works best” for its clients and the public good.  Noblis is passionate about making a difference and improving lives. And Noblis has the sophisticated knowledge of science, technology, economics and regulatory processes to find cost-effective, practical and sound solutions to extremely complex and potentially harmful environmental challenges.

Please contact Andrew Rak atandrew.rak@noblis.org or visit uswww.noblis.org for additional information.


NSF International


NSF International (formerly the National Sanitation Foundation), founded in 1944, is an independent, not-for-profit organization offering third party certification to 43 NSF/ANSI Standards covering consensus requirements for drinking water treatment chemicals, components, and purification devices, food service equipment, and other products.  NSF-ISR is a world leader in management systems registrations.  The Toxicology Group, LLC provides consulting services in areas including human and ecological risk assessment and regulatory affairs.  Coupled with state-of-the-art chemical, physical, and microbiology laboratory facilities, these groups provide cost effective risk management solutions in many areas of public health and the environment.


Please contact Clif McLellan atmclellan@nsf.org or visit http://www.nsf.org/ for further information.


Syracuse Research Corporation


Syracuse Research Corporation (SRC) is a not-for-profit organization dedicated to providing scientific and technical support in environmental science, information technology, technology policy and advanced electronics engineering. The Environmental Science Center at SRC develops and applies quantitative exposure and risk assessments for environmental chemicals, analysis of toxicological literature, and structuring of environmental and toxicological databases. SRC supports the efforts of ITER to disseminate worldwide health risk assessment information.



plusHow can I support ITER?


Thank you for your interest in helping support ITER, the only comprehensive Internet database of international risk values. We believe ITER is a great resource for international risk assessment information and hope you do too. As a nonprofit [501(c)(3)] organization, TERA funds ITER through grants and donations. TERA has been able to develop ITER as a free Internet database thanks to contributions of time, resources, and money, as well as through partnerships, from organizations such as those listed on our sponsors page.


bullet Financial Support

bullet In-Kind Support

bullet Feedback and Ideas for Improvements and Expansion


You can help TERA expand this database through your financial or in-kind support, or through your ideas and feedback. We greatly appreciate any support you offer, and recognize that it will benefit the entire risk assessment community and beyond.


TERA plans to expand the ITER database to include additional data from other countries and international organizations. Currently, ITER contains risk values and/or cancer classifications for 680+ chemicals from:


bullet Agency for Toxic Substances & Disease Registry (ATSDR),

bullet Health Canada, 

bullet International Agency for Research on Cancer (IARC) [in progress],

bullet NSF International,

bullet National Institute of Public Health and the Environment (RIVM), The Netherlands,

bullet Texas Commission on Environmental Quality (TCEQ),

bullet U.S. Environmental Protection Agency (U.S. EPA), and

bullet Independent parties whose risk values have undergone peer review.


Your support will help us make risk assessment information readily available to people around the world, and will ultimately help protect public health. Please remember that your financial and in-kind contributions are also tax-deductible.


Thank you for your support!


plusHow do I cite ITER?


General citation:


TERA (Toxicology Excellence for Risk Assessment).  2010.  International Toxicity Estimates for Risk (ITER) Database.  Online.  Cincinnati, OH.  Available at: www.tera.org/iter.


Citing a specific chemical:


TERA (Toxicology Excellence for Risk Assessment).  2010.  International Toxicity Estimates for Risk (ITER) Database.  Benzene (CAS 71-43-2).  Online.  Cincinnati, OH.  Available at: www.tera.org/iter.


Can I make a suggestion?


TERA is interested in feedback on the content and format of ITER, as well as your suggestions for adding other organizations to ITER. Please send us your comments to Oliver Kroner.