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Department of Environmental Health

Risk Science Center (RSC)

Human Health Risk Assessment


Risk Assessments

The Risk Science Center scientists combine a practitioner’s knowledge of the issues and pitfalls involved in the development of human health risk assessments, together with cutting-edge toxicology expertise, to develop state-of-the-science assessments.  Our research, aimed at improving risk assessment methods particularly in the areas of dose-response and mode of action, further enhance our analyses.  In solving risk problems for a diverse array of government and private sponsors, we apply a collaborative philosophy that emphasizes partnership building, allowing us to expand our pool of expertise, build on multiple perspectives, and ensure the use of the best science.  These strengths form the basis for our development of independent and science-driven analyses for a range of risk assessment products such as screening-level assessments, dossiers for HPV and REACH, occupational assessments, and in-depth evaluations considering mechanistic data and using sophisticated modeling techniques. 

Project Spotlight


Expertise: Occupational Toxicology

Our Center's goal is to work cooperatively with other organizations’ efforts to see that OELs are developed to support advances in risk assessment methods and the protection of worker health..... 

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Expertise: Toxicology Reviews

Our staff have a detailed understanding of the latest developments in risk science and toxicology and how it is applied practically in risk assessment.  Our staff have developed or reviewed the documentation for hundreds of non-cancer and cancer risk assessment values....

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Expertise: Screening Assessments

Information needs vary with the complexity of risk management decisions. Screening level assessments are an important component of proactive risk assessment for setting priorities for more detailed evaluations and for comparative risk ranking.  We have developed such screening assessments for many sponsors.....

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Wheat 246

Expertise: Product/Site Assessment

We provide integrated toxicology support for product safety evaluation and characterization of environmental site-related risks through our extensive network of international experts in exposure modeling ....  

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Recent Projects

  • Acrylamide – a detailed analysis of the mode of action and dose-response characterization of mammary tumors, thyroid tumors, and tunica vaginalas mesotheliomas observed in chronic rat bioassays has been conducted.  Key Publications:
  • Dourson M, Hertzberg R, Allen B, Haber L, Parker A, Kroner O, Maier A, Kohrman M. 2008. Evidence-based dose-response assessment for thyroid tumorigenesis from acrylamide. Reg Tox Pharm 52(3): 264-289
  • Haber LT, Maier A, Kroner OL, Kohrman MJ. 2009. Evaluation of human relevance and mode of action for tunica vaginalis mesotheliomas resulting from oral exposure to acrylamide. Reg Tox Pharm 53(2): 134-149.
  • Maier A,Kohrman MJ, Hertzberg R, Allen B, Haber LT, Dourson M.  Reevaluation of Dose-Response Options for F344 Rat Mammary Tumors for Acrylamide – Additional Insights Based on Mode of Action.  Food and Chemical Toxicology.  Submitted March 2009.
  • Alachlor and Acetochlor Environmental Degradates – an expert peer panel process is being used to provide an evaluation of the current data in support of reference dose development for the environmental degradates of these two pesticides.
  • Bromopropane – an analysis of issues and considerations for developing an occupational exposure limit for 1-bromopropane was developed.  The analysis relied on benchmark concentration modeling and consideration of neurological versus reproductive toxicity as alternative critical endpoints.  
  • Chlorpyrifos – an analysis was developed regarding the interpretation of epidemiology studies for chlorpyrifos exposure to assess potential impacts on children and on issues pertaining to cholinergic and non-cholinergic modes of action as the appropriate basis for developing a point of departure for risk assessment. 
  • Chloropicrin – novel dose-response methods to take advantage of the availability of severity-graded data for individual subjects at multiple time points were applied to characterize the sensory irritant potential of chloropicrin.  The assessment was developed in support of potential fence-line acute airborne exposure limits.  
  • Dermal -  a project is underway to apply the National Institute for Occupational Safety and Health’s weight of evidence procedures to assign notations that inform workers of potential systemic toxicity, direct skin effects, and sensitization potential from dermal exposures to chemicals.
  • Diacetyl - A toxicology review and issues analysis related to the availability of data to support OEL development for the butter-flavoring chemical, diacetyl, is under development.  In particular, evaluation of issues related to interspecies extrapolation and effects of peak versus cumulative exposure are being considered.
  • HPV, REACH, and screening Assessments - The Risk Science Center provides support to a variety of sponsors in cataloging, critically evaluating, and developing robust data summaries, test plans, and risk assessment documents.  We apply the latest guidance and novel systematic approaches to evaluate and present read-across strategies.
  • IDLH – Immediately Dangerous to Life or Health (IDLH) values are 30-minute airborne concentrations developed to protect against severe irreversible effects or effects that might impair escape from exposure environments should respiratory protection or other control measures fail.  IDLH methods research and documentation supporting new values are being developed.
  • IRIS and Other EPA Toxicology Reviews – The Risk Science Center provides support for development of comprehensive toxicology reviews and risk assessment values for U.S. EPA as well as private sponsors. 
  • MITC – a comprehensive dose-response assessment has been conducted to characterize the irritant potential of methyl isothiocyanate using benchmark concentration modeling of human sensory irritation data and in-depth examination of interspecies variability in respiratory tract irritation.  
  • Occupational Exposure Limits for Pharmaceuticals – published OELs are not available for most pharmaceuticals.  To ensure that workers in the pharmaceutical industry are adequately protected we have develop systematic approaches for hazard banding as well as provisional and final OEL development for a variety of sponsors. 
  • Perchlorate – Our scientists have worked with interested parties to develop and promote research programs for studies on ammonium perchlorate.  A protocol review panel reviewed the protocols of the initial round of studies before they were initiated. The resulting research has led to data to supporting ongoing analyses of dose-response issues, including the development of RfDs by several groups. 
  • RDX – exposure and environmental fate data are being analyzed to develop an estimate of the percentage contribution (i.e., Relative Source Contribution, RSC) for RDX (Royal Demolition Explosive) exposure from drinking water exposure.