Carcinogen Potency Factor

Carcinogen Potency Factor (CPF) A CPF is the slope of the dose-response cun e at very low exposures. The dimensions of a CPF, are expressed as the iin erse of daily dose (mg/kg-day)". ... 

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)... 

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). 

Among the many different types of ARARs are ambient or chemical-specific requirements, which can be levels set by other laws, such as MCLs, National Ambient Air Quality Standards (NAAQS), or CWA, CAA, and TSCA regulations, and the long-term remedial action would have to meet those goals. Because not that many ambient or chemical-specific requirements have been established, other types of ARARs must usually be identified. An alternative is for the USEPA to use carcinogenic potency factors or reference doses to set the proper level of treatment. It must be remembered, though, that each ARAR is specific to the remedial activity and not the pollutant. 

Davidson KA, Faust RA. 1996. Oral carcinogen potency factors for benzene and some of its metabolites. Fund Appl Toxicol Suppl. The Toxicologist 30(1) 114. 

Boyce, C. P. (1998). Comparison of approaches for developing distributions for carcinogenic potency factors. Hum Ecol Risk Assess 4, 527-589. 

Schneider et al. (2002) also examined the use of the TEF approach on the data from the Culp et al. (1998) study, and from several other studies using dermal or lung application of PAH mixtures of known composition. They used the TEF derived by Brown and Mittehnan (1993) (Table 10.4) and concluded that the benzo[a]pyrene equivalency factors do not adequately describe the potency of PAH mixtures and lead to underestimation of the carcinogenic potencies in most cases. 

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. 

Biodegradability Evaluation and Simulation System (German) Federal Institute for Health Protection of Consumers and Veterinary Medicine BenchMark Dose Biomagnification Factor Carcinogenic potency in mice Carcinogenic potency in rats... 

Inhalation unit risks have been derived for sulfur mustard directly from experimental animal data as weU as from an analysis of the relative carcinogenic potency of sulfur mustard in comparison with that of known carcinogens for which there are both long-and short-term data. Epidemiological and long-term animal data are not available to directly derive an oral slope factor for sulfur mustard. Estimates of the oral slope factor are made from the inhalation unit risk and from the relative potency method. 

The U.S. EPA (1991) identified an "inhalation" unit risk of 8.5 x 10 per fig/w , derived from the Weibull time-to-tumor model, as the most appropriate estimate of the carcinogenic potency of sulfur mustard. This unit risk can be converted to a slope factor by normalizing the value for a 70 kg man inhahng 20 m of air per day. The resulting slope factor is 0.3 (ug/kg/day). ... 

The estimated comparative carcinogenic potency can be used to derive a slope factor (SF) or qi for sulfur mustard. The slope factor converts the estimated daily intake averaged over a lifetime exposure to incremental risk of an individual developing cancer. Because the slope factor is an upper 95th percentile confidence limit on the probability of response based on experimental animal data, the carcinogenic risk will generally be an upper-bound estimate. 

In the absence of human or animal oral dose-response data, the relative potency approaches developed by Watson et al. (1989) and U.S. EPA (1991) are considered to be appropriate methods for estimating the tnmorigenic potency of sulfur mustard by the oral route of exposure. The oral slope factor derived by Watson et al. is approximately one order of magnitude less than the one derived from the relative potency estimated by U.S. EPA (1991). In the emerging area of relative potency analysis, a factor of 10 difference represents a good fit. There is no significant difference between the estimates of sulfur mustard carcinogenic potency relative to B(a)P pnblished by Watson et al. (1989) and U.S. EPA (1991). 

Carcinogenic Effects. Specific petroleum hydrocarbon indicator compounds that have EPA cancer potency factors are assessed these are benzene and benzo(a)pyrene. EPA relative potency factors can be used for benz(a)anthracene, indeno(l,2,3-cd)pyrene, dibenz(a,h)anthracene, chrysene, benzo(b)fluoranthene, and benzo(k)fluoranthene. 

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