Catalyzing a Core Repository for Chemical Toxicity Values

Overview of ITER+:

Human Health Risk Assessments require the use of chemical toxicity values (also known as reference values and others shown in Table 1) to qualitatively understand exposure data or be used for a quantitative risk assessment. Currently, these values are developed by a number of authoritative bodies and/or risk assessors and reside in a variety of locations. Searching for these toxicity values can be time and resource-intensive. Toxicity values for any chemical identified from different sources can vary in scientific quality, and often additional expertise may be needed to develop new or peer reviewed or revise toxicity values for screening level exposure assessments and/or site specific risk assessments. ITER+ is working to develop a one-shop stop for all chemical toxicity values.



To build upon the existing data housed within the International Toxicity Estimates for Risk Assessment (ITER) database and include additional toxicity values needed for exposure screening and risk assessment.  ITER includes peer-reviewed human-health toxicity values and is searched using the Toxicology Data Network (TOXNET) on the National Library of Medicine’s website  (

ITER+ is a collaborative public/private partnership providing a systematic and transparent quality evaluation of risk assessment information from REACH database* for determining the addition of new credible values into TOXNET. The addition of REACH* toxicity values (DNELs) will require the chemical to have:

1) a DNEL value available in the ECHA database;
2) assessment factors with sufficient details;
3) key study information, i.e. experimental design, dosimetry and critical effect(s);
4) point of departure values (i.e., LOAEL/NOAEL/BMDL); and
5) DNEL value is reproducible using all the data from the ECHA database based on DNEL derivation guidance.

A working group will curate REACH data DNELS and derived minimal effect levels (DMEL). An expert ITER+ Advisory Committee (DAC) will provide a systematic and transparent high quality assurance (QA) with the intent to broaden the ITER database to include new chemicals. The methods used for chemical toxicity values QA are available by clicking here.

Monthly meetings between the advisory committee and the working group will facilitate discussions of these QA’s. Meeting notes are available by clicking here.

These additions will enable chemical risk analysts to use the ITER+ database/TOXNET as their initial ‘go to library’ site prior to undertaking a full literature search.

Table 1. Terminology Used for
Chemical Toxicity Value’s

  • Acceptable Daily Intake (ADI)
  • Cancer Slope Factor (CSF)
  • Derived Minimal Effect Level (DMEL)
  • Derived No Effect Level (DNEL)
  • Effects Screening Levels (ESLs)
  • Exposure Limits
  • Maximum Contaminant Level Goals (MCLGs)
  • Maximum Permissible Risk levels, (MPRs)
  • Minimal Risk Level (MRL)
  • Provisional Peer Reviewed Toxicity Value (PPTRV)
  • Reference Concentration (RfC)
  • Reference Dose (RfD)
  • Risk Value
  • Single Product Allowable Concentration (SPAC)
  • Tolerable Concentration (TC)
  • Tolerable Daily Intake (TDI)
  • Tolerable Intake (TI)
  • Total Allowable Concentration (TAC)
  • Toxicity Estimate for Risk
  • Toxicity Reference Values (TRVs)
  • Toxicity Value



Centralizing authoritative chemical toxicity values from worldwide organizations in a curated, cosmopolitan database will foster the prediction of toxicity from exposure to consumer products by removing one of the current barriers in the use of screening level toxicity values finding credible values! Increasing the number of chemical toxicity values by ITER+ will also reduce repetitive toxicity testing costs, and provide an opportunity for upgrading older toxicity values via a high quality systematic and transparent process. Updates from this ITER+ project can be found on the ITER University of Cincinnati webpage by clicking here.

Toxicity Values

*A survey of ITER users indicated that the inclusion of European risk values would be the most desired database enhancement.





The are a number of ways to you can help make this happen:

  1. Funding
    We are looking for funding partners to help bring this public good to market.
    This is a project that will benefit many in the risk community, but the cost is
    more than an individual organization should bear.
  2. Endorsement
    If you think this is a good idea that needs to happen, but funding and/or time
    is not available, please consider offering your organizational support with an
    official endorsement.
  3. In-Kind Support
    ITER+ will be a significant undertaking, we could use your help! Roles may
    include everything form data compilation to peer review.
  4. Spread the Word!
    Please share this effort with colleagues who may find this of interest.


Let us know how you can help!

For more information, please contact Jeanelle Martinez,

Projects Partners





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