Risk-specific dose

Risk-specific doses are derived from the slope factor or unit risk to estimate the dose associated with a specific risk level, for example a one-in-a-million (10 ) increased lifetime risk. Risk below the POD is typically approximated by multiplying the slope factor by an estimate of exposure, i.e., Risk = Slope Factor X Exposure. For exposure levels above the POD, the dose-response model is used instead of this approximation. 

DHHS Risk-specific dose for total TEQs 0.057 pg/kg/day PHS 1992... 

EPA. 1988a. A cancer risk-specific dose estimate of 2,3,7,8-TCDD. Washington, DC U.S. Environmental Protection Agency, Office of Research and Development, Office of Health Effects Assessment. EPA report no. 600/6-88/007Aa. 

Cancer risk-specific doses and screening values for end points other than cancer are essentially equivalent from a risk assessment perspective. 

Risk specific doses Unit risk Risk specific dose 2.4x1 O 7 g/m3 4.2x101 g/m3 EPA 2001 40CFR266, Appendix V... 

EPA 2001h. Risk specific doses. U.S. Environmental Protection Agency. Cocfe ofFederal Regulations. 40 CFR 266, Appendix V. http //ecfrbackaccess.gpo.gpv/otcgi/cfr/. September 24, 2001. 

The unit risk is defined as the upper bound additional lifetime cancer risk associated with exposure to either 1 pg 1 in water or 1 pg m in air. The dose or exposure concentration associated with a given risk can also be calculated by rearranging terms in the slope factor equation shown above to solve for the dose term. The result is termed the risk specific dose (or concentration). The risk specific dose is often used as the basis for the exposure criteria for carcinogens. 

Linear extrapolation of the cancer incidence with dose rate without a threshold, leading to the determination of a risk per unit dose, and a corresponding dose corresponding to a specified risk level [risk-specific dose (RSD), e.g., the era s IV-nitrosodimethylamine, (ERA 2009a)]. This approach is used by the ERA for chenucals that are known to act via a mutagenic MOA, and for chemicals for which the MOA is not known, as a health-protective default. 

The health assessment chapters of these documents contain the available dose-response data from animal experiments and human epidemiology studies for the chemical or class of chemicals of concern. By assessing the risks associated with various doses, acceptable daily intakes (ADIs - for systemic toxicants) or risk-specific doses (for carcinogens) were derived. These levels were divided by appropriate exposure assumptions (e.g., estimated average water consumption) to derive a criterion. 

After the human potency has been calculated, the risk-specific dose (RSD, in mg/day) associated with an upper limit estimate of the excess lifetime cancer risk (e.g., 10 or 1 in 100,000 people) is determined in Equation 2 ... 

RCRA, 40CFR266 Appendix 5 risk specific doses R7... 

With regard to carcinogenicity, a weight-of-the-evidence evaluation suggests that dioxin and related compounds (CDDs, CDFs, and dioxin-like PCBs) are likely to present a cancer hazard to humans [157]. While major uncertainties remain, efforts of this reassessment to bring more data into the evaluation of cancer potency have resulted in a risk-specific dose estimate (1 x 10 risk or one additional cancer in one million exposed) of approximately 0.01 pg TEQ/kg body weight/day. This risk-specific dose estimate represents a plausible upper bound on risk based on the evaluation of animal and human data. "True" risks are not likely to exceed this value, may be less, and may even be zero for some members of the population. 

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