Lifetime excess risk

Another quantitative estimate of gastrointestinal cancer risk has been calculated based on the incidence of benign intestinal pol q)s in male rats exposed to 500 mg/kg/day of chrysotile (65% >10 [Jm long) in the diet (EPA 1985a). This calculation indicates that the lifetime excess risk from ingesting water containing... 

Concentration (f/mL) corresponding to lifetime excess risk level of 10 0.0005 0.005... 

A5.2.2.9 The competent authority will need to establish what level of risk is acceptable to implement such an approach to consumer product labelling for chronic effects. For example, CPSC recommends labelling for a cancer hazard if the lifetime excess risk exceeds one-in-a-million from exposure during reasonably foreseeable handling and use. ... 

On the basis of available evidence, the Committee on the Biological Effects of Ionizing Radiations (called BEIR V Committee) has recommended use of a lifetime excess risk (i.e., normal risk has been subtracted) of 0.08 per 100 rad for death from y-ray- or X-ray-induced cancer. This risk applies to the average person in the United States population (all ages considered) exposed to doses up to 10 rad, when... 

The risk estimates proposed by ICRP (1991) and UNSCEAR (2000) - for use in radiation protection - provide simple and robust estimates for the lifetime excess risk to die from radiation-induced cancer. But they facilitate only an overall, not an organ-specific estimate and are aimed at age- and gender-averaged groups of persons, such as the working population or the whole population of a country. 

Lifetime excess risks, also referred to as lifetime attributable risks (Kellerer et al. 2001, BEIR VII 2006), LAR, are calculated by means of site-specific risk models, site-specific baseline rates on cancer incidence (or cancer mortality), and life-table data to account for competing risks ... 

Fig. 7.4. Lifetime excess risk at 1 Sv organ dose in dependence on age at exposure for those cancer sites attributing most to the total excess lifetime risk according to BEIR VII risk models and German life tables and German cancer incidence rates...

Where IR, = individual inluilalion excess lifetime cancer risk from pollutant i... 

The EPA classifies all radionuclides, including americium, as Group A (known human) carcinogens (EPA 1997b). Lifetime excess total cancer risk per unit intake or exposure for ingestion, inhalation, and external exposure to 241 Am and 243Am are included in Table 8-1. The EPA has not derived reference concentrations (RfCs) or reference doses (RfDs) for americium (IRIS 2001). 

Ingestion—lifetime excess total cancer risk/pCi 241 Am 243Am 3.28x10-10 3.27x1 O 10 ... 

Because the theoretical excess lifetime cancer risk for dimethylhydrazines was estimated from nonverified potency estimates and because AEGLs are applicable to rare events or single, once-in-a-lifetime exposures in a limited geographic area with a small population, the AEGL values based on noncarcinogenic endpoints were considered to be more appropriate. 

For the range of human doses illustrated in Figure 8.1 (Close-up) we would say that the upper bound on excess lifetime cancer risk lies in the range of 0.000 000 8 (8 in 10 million, or 8x10 ) to 0.000 008 (8 in one million, or 8xl0 ). Actual risks are unknown, bnt are not likely to exceed these upper bound limits. Excess lifetime cancer risk means the risk incurred over a full lifetime above that incurred in the absence of exposure to the carcinogen. 

If people receive this dose of methylene chloride each day for a full lifetime, then according to the EPA dose-response model, the upper bound on excess lifetime cancer risk is ... 

The WHO considers in its drinking-water quality guidelines, in relation to genotoxic carcinogens, that a lifetime cancer risk for consumers of less than 10 represents a tolerable risk (WHO 1996). Guideline values associated with excess lifetime cancer risks of 10 and 10 are also presented for the genotoxic carcinogens to emphasize the fact that each country should select its own appropriate risk level. 

The relative risk is calculated as a measure of response and is then used to calculate the excess lifetime cancer risk expressed as unit risk (associated with a lifetime exposure to 1 p,g/m ). 

The BEIR III risk estimates formulated under several dose-response models demonstrate that the choice of the model can affect the estimated excess more than can the choice of the data to which the model is applied. BEIR III estimates of lifetime excess cancer deaths among a million males exposed to 0.1 Gy (10 rad) of low-LET radiation, derived with the three dose-response functions employed in that report, vary by a factor of 15, as shown in Ikble 6.1 (NAS/NRC, 1980). In animal experiments with high-LET radiation, the most appropriate dose-response function for carcinogenesis is often found to be linear at least in the low to intermediate dose range (e.g., Ullrich and Storer, 1978), but the data on bone sarcomas among radium dial workers are not well fitted by either a linear or a quadratic form. A good fit for these data is obtained only with a quadratic to which a negative exponential term has been added (Rowland et al., 1978). 

Table 6.1 —Lifetime excess cancer mortality from a single exposure to 10 rad oflow-LET radiation per miOion males, as estimated with the absolute risk projection model and various dose-response models ...

Table. 2—Estimated lifetime excess cancer mortality from low-LET radiation per million males, as estimated by different dose-response models and risk projection models ...

Table IV lists the results of risk calculations provided in the preliminary proposal for the substances that were proposed as potential carcinogens in the regulatory context at that time (44). 1,1-Dichloroethylene was later converted to a listing of equivocal evidence of carcinogenicity. The table includes calculations made by the USEPA CAG and the NAS Safe Drinking Water Committee. These calculations attempt to project concentrations of each chemical in drinking water that, if consumed for a lifetime (70 years) at the rate of 2 L of water per day would contribute an excess lifetime cancer risk of up to 1 in 100,000 and up to 1 in 1,000,000. The quality of evidence of carcinogenicity ranging from sufficient in humans to limited in animals is also included for each chemical. Provisional ADI values calculated from chronic toxicity data only are included for the sake of comparison.

Compound Adjusted ADIa (pg/L) Projected Upper Limit Excess Lifetime Cancer Risk Concentration in Drinking Water (nfl/L) Quality of Evidence... 

Waste would be classified as exempt if the concentrations of hazardous substances are sufficiently low that it poses no more than a negligible risk to a hypothetical inadvertent intruder at a municipal/industrial landfill for nonhazardous waste. A negligible risk, or the associated dose, is a value so low that further efforts at risk reduction generally are unwarranted (e.g., an excess lifetime cancer risk less than about 10 4 or doses of noncarcinogenic hazardous substances substantially less than nominal thresholds for induction of health effects in the general population). 

The term unacceptable is used to describe excess lifetime cancer risks from exposure to radionuclides greater than a value in the range of about 10 1 to 10 3, the particular value depending on the exposure situation. Such risks normally must be reduced regardless of cost or other circumstances and, thus, are properly interpreted as intolerable (de manifestis). 

A negligible dose or risk from exposure to radionuclides has not been established in regulations under AEA. However, based on recommendations of NCRP and IAEA, excess lifetime cancer risks on the order of 1CP4 or less generally could be considered negligible. 

Excess lifetime cancer risks considered negligible have values in the range of about 1CU4 to 10 6 or below, depending on the exposure situation intakes of noncarcinogenic hazardous chemicals less than RfDs are considered negligible. 

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