Reference dose , oral

Oral reference doses by chemical name for 535 substances EPA s IRIS (Integrated Risk Information. System) http //www.epa.gOv/ngispgm3/iri.s/... 

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

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. 

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. 

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). 

The EPA has derived an oral reference dose (RfD) of 2.00x10 Vig/kg/day for mirex (IRIS 1994). The RfD is based on liver cytomegaly, fatty metamorphosis, angiectasis, and thyroid toxicity in rats (NTP 1990). No reference concentration is available for mirex. Neither a reference dose nor a reference concentration exist for chlordecone. 

An oral reference dose (RfD) is currently pending by EPA (IRIS 1995). 

EPA has verified a chronic oral reference dose (RfD) for disulfoton of 4x10-5 mg/kg/day (IRIS 1994). The RfD is based on the LOAEL of 0.04 mg/kg/day for cholinesterase inhibition in rats treated with disulfoton in the diet for 2 years (Hayes 1985). 

The ehronie-duration oral reference dose (RfD) for ehloroform is also 0.01 mg/kg/day, based on the LOAEL for liver effeets in dogs administered 15 mg/kg/day ehloroform (Heywood et al. 1979 IRIS 1996). 

Oral reference doses and inhalation reference concentrations (RfDs and RfCs, respectively) for chronic noncarcinogenic health effects... 

OSHA = Occupational Safety and Health Administration PEL = permissible exposure limit ppm = parts per million REL = recommended exposure limit RfC = inhalation reference concentration RfD = oral reference dose STEL = short-term exposure limit TLV = threshold limit value TWA = time-weighted average... 

The ERA has calculated a subchronic oral reference dose (RfD) of 7x10 mg/kg/day for carblon tetrachloride based on a NOAEL of 1 mg/kg/day (converted to 0.71 mg/kg/day based on intermittent exposure) for rats in a 12-week study (Bruckner et al. 1986 ERA 1989b IRIS 1993). The critical effect was liver toxicity. A chronic oral RfD of 7x10 mg/kg/day was also calculated based on the same NOAEL used for the subchronic RfD. The ATSDR has calculated an acute inhalation MRL of 0.2 ppm based on a LOAEL of 50 ppm for liver effects in an acute 4-day rat inhalation study (David et al. 1981), and an intermediate inhalation MRL of 0.05 ppm based on a NOAEL of 5 ppm for liver effects in an intermediate-duration (187-192 days) inhalation study in rats (Adams et al. 1952). The ATSDR has also calculated an acute oral MRL of 0.02 mg/kg/day based on a LOAEL of 5 mg/kg/day over 10 days for liver effects in the rat (Smialowicz et al. 1991), and an intermediate oral MRL of 0.007 mg/kg/day based on a NOAEL of 1 mg/kg/day over 12 weeks (converted to 0.71 mg/kg/day based on intermittent exposure) for liver effects in the rat (Bruckner et al. 1986). 

The oral reference dose (RfD) for nickel is 0.02 mg/kg/day (IRIS 1996). The RfD is based on the 5-mg-nickel/kg/day NOAEL identified in the Ambrose et al. (1976) 2-year study in rats. The effect level in this study was 50 mg/kg/day, a dose associated with changes in body and organ weights. The RfD was calculated using an uncertainty factor of 300 (10 for interspecies extrapolation, 10 to protect sensitive individuals, and 3 to account for inadequacies in reproductive studies) (Ambrose et al. 1976 RTT 1988a, 1988b). EPA (IRIS 1996) states that the RfD is at a level that will not sensitize individuals to nickel, but that it may not protect individuals who are already sensitized to nickel. 

In several instances, biomonitoring data have confirmed health effects of environmental exposures and have validated public-health policies. For example, population data on blood lead concentrations that were associated with adverse health effects provided the impetus for the U.S. Environmental Protection Agency (EPA) regulations reducing lead in gasoline. Methylmercury concentrations in blood and hair that were correlated with neurodevelopmental effects provided the rationale for EPA s revision of the oral reference dose. In those examples, the biomonitored concentrations of chemicals could be shown to be related to adverse health effects because of the body of epidemiologic, toxicologic, and clinical... 

The oral reference dose (Oral RfD) is an estimate of the daily exposure of a person to a contaminant that is likely to be without appreciable risk of a deleterious non-carcinogenic effect during a lifetime (USEPA http //www.epa.gov/iris/). Oral RfD values for POP concentrations in seafood types are presented in Table 16.5, together with the daily intake of POPs from seafood consumed in Singapore. Daily intakes of POPs from seafood are below the oral RfD. The cancer benchmark concentration (Dougherty et al., 2000) represents the exposure concentration at which a lifetime cancer risk equates to one excess cancer death in one million persons. This level is defined as the public health protective concentration in the Congressional House Report to the Food Quality Protection Act of 1996 in the USA. Cancer benchmark concentrations were exceeded for DDTs, heptachlor, and PCBs (See Table 16.5). The cancer hazard ratio is the ratio of the MDI for a specific contaminant relative to the cancer benchmark concentration. The cancer hazard ratio represents the extent to which average daily exposure exceeds the benchmark concentration. The cancer hazard ratio of seafood consumption... 

A chronic oral reference dose (RfD) of 0.00002 mg/kg/day has been derived and verified by EPA for white phosphorus (IRIS 1993). The RfD is based on aNOAEL of 0.015 mg/kg/day for parturition mortality and forelimb hair loss in rats gavaged with 0.015 mg/kg/day in a one-generation reproduction study (Condray 1985). 

RfC = inhalation reference concentration RfD = oral reference dose STEL = short-term exposure limit ... 

Several military bases contaminated with chemical-warfare agents as a result of storage and past disposal practices are slated to be closed pursuant to the Base Realignment and Closure Act. Before those military bases can be transferred to civilian use, contaminated soil and water must be cleaned to levels that are considered safe. To help make decisions on restoration required at contaminated sites and on the potential uses of the former military installations (e.g., for housing, occupational, or wildlife purposes), the U.S. Army developed interim chronic oral reference doses and, where appropriate, oral slope factors for six chemical-warfare agents that are likely to be encountered at contaminated sites. Similar information for inhalation exposure is under development. 

To ensure that chemical contamination is rednced to safe concentrations at stockpile and NSCM sites before they are used for residential, occupational, or wildlife purposes, the U.S. Army requested that health-based exposure limits for GA, GB, GD, VX, sulfur mustard, and lewisite be developed to protect the pnblic and the environment. Oak Ridge National Laboratory (ORNL) was asked to conduct the health risk assessments and propose chronic oral reference doses (RfDs) and, where... 

Opresko, D.M., R.A. Young, R.A. Faust, S.S. Talmage, A.P. Watson, R.H. Ross, K.A. Davidson, and J. King. 1998. Chemical warfare agents Estimating oral reference doses. Rev. Environ. Contam. Toxicol. 156 1-183. 

Dourson, M.L. 1994. Methods for establishing oral reference doses (RfDs). Pp. 51-61 in Risk Assessment of Essential Elements, W. Mertz, C.O. Abernathy, and S.S. Olin, eds. Washington, D.C. ILSI Press. 

The estimated oral NOAEL of 161 g/kg/day can be used to estimate a human oral reference dose (RfD) by first adjusting the NOAEL for a 7 days/week exposure period by using a factor of 5/7 i.e., 5/7 x 161 /rg/kg = 115 /ig/kg/day, and then applying the result to the following EPA formula ... 

ORAL REFERENCE DOSE FOR GB 4.1 Cholinesterase Inhibition as an RfD Endpoint... 

The LOAEL of 0.06 //g/kg/day can be used to estimate a human oral reference dose (RfD) by using the following formula ... 

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