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Basic Information

On March 29, 2005, EPA issued Guidelines for Carcinogen Risk Assessment (Cancer Guidelines), replacing the 1986 cancer risk assessment guidelines.  The revised Cancer Guidelines provide a process to EPA scientists for assessing possible cancer risks and are intended to make greater use of the increasing scientific understanding of the processes of cancer development. 

The Cancer Guidelines recommend assessing risks to potentially sensitive people and to people at specific lifestages (for example, children) differently than to the rest of the population.  This recommendation led to the development of the Supplemental Guidance for Assessing Susceptibility from Early-Life Exposure to Carcinogens (Supplemental Guidance), which describes possible approaches that EPA could use in assessing cancer risks to children under age 16.  EPA issued the document separately from the Cancer Guidelines so that it can be updated more easily as scientific understanding about the effects of early life exposures develops.

EPA recommends that EPA risk assessors use the new Cancer Guidelines and the Supplemental Guidance when they prepare cancer risk assessments.  They are recommended for use:


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Application of Cancer Guidelines and Supplemental Guidance to Risk Assessment

The Cancer Guidelines emphasize the importance of mode of action (MOA) in assessing cancer risk.  The MOA determination is used in applying the Supplemental Guidance to characterize risks from early-life exposures to chemicals with a mutagenic MOA for carcinogenesis.

Mutagenic Mode of Action for Carcinogenesis Determination

When conducting cancer assessments, assessors can determine the mode of action by implementing the MOA framework described in the Cancer Guidelines and summarized in the Supplemental Guidance.  View a flow chart for early-life risk assessment using mode of action framework (MOA Framework Flow Chart) (PDF) (1 pg, 438K).  The Science Policy Council (SPC) Cancer Guidelines Implementation Workgroup described in an October 2005 memo a process for completing a weight of evidence determination for MOA and communicating the results (Communication I) (PDF) (8 pp, 651K).  It is important to note that a mode of action determination is something that will typically be done by the IRIS program or the Superfund Technical Support Center as part of a hazard identification and dose-response assessment.

The three possible conclusions from a weight of evidence evaluation regarding a mutagenic MOA for carcinogenesis are:

Early Lifestage Adjustments

The mutagenic MOA determination is used in applying the Supplemental Guidance to characterize cancer risks from early-life exposures (see Supplemental Guidance MOA Framework Flow Chart (PDF) (1 pg, 438K)):

For additional information on implementing the MOA framework and Supplemental Guidance into each of the four risk assessment steps (Hazard Characterization, Dose-Response Assessment, Exposure Assessment, Risk Characterization), see the SPC Workgroup memo on a process for completing a weight of evidence determination for MOA and communicating the results (Communication I) (PDF) (8 pp, 651K).

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