Reference concentrations

FIGURE 10< 108 The procedure to measure the capture efficiency by the tracer gas method, aj The measurement of the reference concentration in the duct, when the tracer is released direcdy into the duct, fb) The measurement of the concentration in the duct, when the tracer is released from the source, / -= sampling point, 2 = pump, J = analyter, 4 - injection of tracer, 5 = tracer gas flow meter, 6 = tracer gas cylinder. 

Inhalation Reference Concentration (RfC) An estimate (with an uncertainty spanning perhaps an order of magnitude) of the daily exposure of the human population to a chemical, through inhalation, that is likely to be without risk of deleterious effects during a lifetime. 

Table 4. Effect of specific surface area of filler and its concentration on concentration shift factors aci and ac for composites copolymer + ash (the reference concentration 10%)...

Options The analyst elects to first study photometry and place the three reference concentrations symmetrically about the nominal value (= 100%). The initial test procedure consists of using references at 80, 100, and 120% at the beginning of the series, and then a 100% reference after every fifth determination of an unknown sample. 

EPA s Integrated Risk Information System (IRIS) lists an oral reference dose (RfD) of 0.006 mg/kg/day for endosulfan (IRIS 2000). No reference concentration (RfC) for chronic inhalation exposures to endosulfan was reported. 

EPA. 1989c. Interim methods for development of inhalation reference concentrations. Washington,... 

EPA. 1990b. Interim methods for development of inhalation reference concentrations. Washington, DC U.S, Environmental Protection Agency, Office of Health and Environmental Assessment, Office of Research and Development, Environmental Criteria and Assessment Office. EPA600/8-90/066. 

An equilibrium constant expression contains concentrations, each of which has been divided by the reference concentration. For convenience, we omit these reference concentrations when we write the expressions for Q or for. S eq You should remember, however, that the implicit presence of reference concentrations means that K values are dimensionless but that concentrations must be in bar for gases and molarity for solutes. 

C16-0057. State the standard (reference) concentration for each substance appearing in the equilibria of Problem. 

The oral reference dose (RfD) for trichloroethylene is currently imder review by an EPA workgroup (IRIS 1996). No inhalation reference concentration (RfC) has been derived (IRIS 1996). The National Center for Environmental Assessment, EPA has begun an effort to reassess the health risks associated with trichloroethylene. 

CRMs for Contaminants in Environmental Matrices For nearly two decades NIST has been involved in the development of SRMs for the determination of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and chlorinated pesticides in natural environmental matrices such as fossil fuels (Hertz et al.1980 Kline et al. 1985), air and diesel particulate material (May and Wise 1984 Wise et al. 2000), coal tar (Wise et al. 1988a), sediment (Schantz et al. 1990, 1995a Wise et al. 1995), mussel tissue (Wise et al. 1991 Schantz et al. 1997a), fish oil, and whale blubber (Schantz et al. 1995b). Several papers have reviewed and summarized the development of these environmental matrix SRMs (Wise et al. 1988b Wise 1993 Wise and Schantz 1997 Wise et al. 2000). Seventeen natural matrix SRMs for the determination of organic contaminants are currently available from NIST with certified and reference concentrations primarily for PAHs, PCBs, chlorinated pesticides, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofiirans (PCDFs) see Table 3.11. 

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). 

Pretreatment Standards for New Sources recommended exposure level/limit Reference Concentration Reference Dose ribonucleic acid... 

EPA has derived both an oral reference dose (RfD) and an inhalation reference concentration (RfC) for chronic exposure to hydrogen sulfide. The RfD of 0.003 mg/kg/day is based on the NOAEL of 3.1 mg/kg/day for gastrointestinal disturbance in pigs in a study by Wetterau et al. (1964) (IRIS 1998). The NOAEL value of 3.1 mg/kg/day was divided by an uncertainty factor of 1,000 to account for interspecies extrapolation (10), sensitive individuals (10), and subchronic exposure (10) (IRIS 1998). 

EPA. 1994b. Methods for derivation of inhalation reference concentrations and application of inhalation dosimetry. EPA/600/8-90/066F October 1994. 

ATSDR has not derived MRLs for lead. The EPA has not developed a reference concentration (RfC) for lead. EPA has also decided that it would be inappropriate to develop a reference dose (RfD) for inorganic lead (and lead compounds) because some of the health effects associated with exposure to lead occur at blood lead levels as low as to be essentially without a threshold (IRIS 1999). 

Uncertainty Factor (UF)—A factor used in operationally deriving the Minimal Risk Level (MRL) or Reference Dose (RfD) or Reference Concentration (RfC) from experimental data. UFs are intended to account for (1) the variation in sensitivity among the members of the human population, (2) the... 

In order to assess the risk for the population living in Guiyu, the daily intake was compared with the oral reference value for DeBDE. According to EPA (US EPA [30]), the DeBDE daily oral reference and oral slope factor are 7.0E-03 mg (kg day)-1 and 7.0 x 10-4 mg-1 kg day. Inhalatory reference concentration and inhalatory unit risk have not been established. 

The parameter ad is included to allow for catalyst deactivation as shown by Liebman. The data for the example (physical constants) are shown in Table 1. All temperatures and concentrations were scaled using a nominal reference concentration (Ar = 1 x 10-6 gmol cm-3) and a nominal reference temperature (Tr = 100.0 K). 

The Environmental Protection Agency (EPA) inhalation reference concentration (RfC) for -hexane is 0.2 mg/m3 (0.06 ppm by volume). No reference dose (RfD) has been derived for this compound (IRIS 1998). 

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