Bound carcinogenic potency

Slope Factor The slope factor is used to estimate an upper-bound lifetime probabilit) of an individual dc cloping cancer as a result of exposure to a particular le cl of a potential carcinogen. Also sec Carcinogen Potency Factor (CPF)... 

Qi — The upper-bound estimate of the low-dose slope of the dose-response curve as determined by the multistage procedure. The q, can be used to calculate an estimate of carcinogenic potency, the incremental excess cancer risk per unit of exposure (usually pg/L for water, mg/kg/day for food, and pg/m for air). 

The 95% confidence limits of the estimate of the linear component of the LMS model, /, can also be calculated. The 95% upper confidence limit is termed qi and is central to the US-EPA s use of the LMS model in quantitative risk assessment, as qi represents an upper bound or worst-case estimate of the dose-response relationship at low doses. It is considered a plausible upper bound, because it is unlikely that the tme dose-response relationship will have a slope higher than qi, and it is probably considerably lower and may even be zero (as would be the case if there was a threshold). Lfse of the qj as the default, therefore, may have considerable conservatism incorporated into it. The values of qi have been considered as estimates of carcinogenic potency and have been called the unit carcinogenic risk or the Carcinogen Potency Factor (CPF). 

Based on the evidence reviewed above, EPA has concluded that BCME is a known human carcinogen (EPA Group A). Employing the data of Kuschner et al. (1975), EPA (1988) has calculated an upper bound cancer potency factor (q ) of 220 (mg/kg/day)1. Assuming that a 70-kg adult inhales 20 m3/day, the concentrations of BCME associated with upper bound human risk levels of 10 4, 10 5, 10 6 and 10"7 are 3.4 x 10"7, 3.4 x 10"8, 3.4 x 10 9 and 3.4 x 10 10 ppm, respectively. These values, and doses which have been observed to cause cancer, are plotted in Figure 2-1. 

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