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Toxicity reference dose

Threshold limit value (TLV) American Conference of Governmental Industrial Hygienists No official standing widely used by industry Toxicity reference dose (RfD) Environmental Protection Agency Official regulatory... [Pg.236]

For carckiogen pesticides (70,71), animal testkigs are subject to maximum tolerated doses (M I L)). M I D is the maximum amount of a substance that can be administered to an experimental animal without causkig extreme health consequences, such as death, to occur but while continuing to produce some measurable toxic effects. Current regulatory theory holds that carckiogen effects do not have a threshold and caimot be related to reference doses. [Pg.235]

The measure used to describe the potential for noncarcinogenic toxicity to occur in an individual is not expressed as tlie probability of an individual suffering an adverse effect. The EPA does not at tlie present time use a probabilistic approach to estimate tlie potential for noncarcinogenic healtli effects. Instead, tlie potential for non carcinogenic effects is evaluated by comparing an exposure level over a specified time period (e.g., lifetime) witli a reference dose derived for a similar exposure period. Tliis ratio of exposure to toxicity is called a liazard quotient and is described below. (The reader is referred to Chapter 11 for additional details on tlie material tliat follows). The noncancer liazard quotient assumes tliat tliere is a level of exposure (i.e., RfD) below which it is unlikely for even sensitive populations to experience adverse healtli effects. [Pg.398]

The potential for noncarcinogcnic health effects is evaluated by comparing iui exposure level over a specified lime period (c.g., lifetime) with a reference dose derived for a similar exposure period. The ratio of exposure to toxicity in called a liazard quotient and, when it is greater tlien unity tlierc is a higher level of concern for potential noncancer effects. [Pg.419]

Acute toxicity In vitro Mammalian systems Aquatic vertebrates and invertebrates Plants IC/EC50 in appropriate test species Use of appropriate indicators of acute toxicity, for example, EPA guidance values, reference doses, and so on... [Pg.37]

Chronic toxicity Mammalian systems Carcinogenicity Neurotoxicity De ve 1 opm e nta l/rep rod u cti ve toxicity Aquatic vertebrates and invertebrates Plants Mutagenicity, increased tumours Reproduction and growth Cancer slope factors Reference doses, and so on IC50, EC50... [Pg.37]

PEL Pg pmol PHS PMR ppb ppm ppt REL RfD RTECS sec SCE SIC SIR SMR STEL STORET TLV TSCA TRI TRS TWA u.s. UF yr WHO wk permissible exposure limit picogram picomole Public Health Service proportionate mortality ratio parts per billion parts per million parts per trillion recommended exposure limit Reference Dose Registry of Toxic Effects of Chemical Substances second sister chromatid exchange Standard Industrial Classification Standardized incidence ratio standard mortality ratio short term exposure limit STORAGE and RETRIEVAL threshold limit value Toxic Substances Control Act Toxics Release Inventory total reduced sulfur time-weighted average United States uncertainty factor year World Health Organization week... [Pg.228]

The purpose of this chapter is not to discuss the merits, or lack thereof, of using plasma cholinesterase inhibition as an adverse effect in quantitative risk assessments for chlorpyrifos or other organophosphate pesticides. A number of regulatory agencies consider the inhibition of plasma cholinesterase to be an indicator of exposure, not of toxicity. The U.S. Environmental Protection Agency, at this point, continues to use this effect as the basis for calculating the reference doses for chlorpyrifos, and it is thus used here for assessing risks. [Pg.36]

NPDES = National Pollutant Discharge Elimination System NTP = National Toxicology Program OSHA = Occupational Safety and Health Administration OW = Office of Water PCB = Polychlorinated Biphenyl RfD = Reference Dose STEL = Short-term Exposure Limit TLV = Threshold Limit Value TSCA = Toxic Substances Control Act TWA = Time Weighted Average WHO = World Health Organization... [Pg.165]

Pg pmol PHS PMR ppb ppm ppt REL RID RTECS picogram picomole Public Health Service proportionate mortality ratio parts per billion parts per million parts per trillion recommended exposure limit Reference Dose Registry of Toxic Effects of Chemical Substances... [Pg.210]

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. [Pg.224]

The more classical approach to assess the presence of marine biotoxins in seafood is the in vivo mouse bioassay. It is based on the administration of suspicious extracted shellfish samples to mice, the evaluation of the lethal dose and the toxicity calculation according to reference dose response curves, established with reference material. It provides an indication about the overall toxicity of the sample, as it is not able to differentiate among individual toxins. This is a laborious and time-consuming procedure the accuracy is poor, it is nonspecific and generally not acceptably robust. Moreover, the mouse bioassay suffers from ethical implications and it is in conflict with the EU Directive 86/609 on the Protection of Laboratory Animals. Despite the drawbacks, this bioassay is still the method of reference for almost all types of marine toxins, and is the official method for PSP toxins. [Pg.32]

According to the definitions provided in the OECD test guidelines (TG 420 and 423), acute oral toxicity refers to those adverse effects that occur following oral administration of a single dose of a substance or multiple doses given within 24 h. [Pg.108]

Barlow, S. 2005. Threshold of Toxicological Concern (TTC). A tool for assessing substances of unknown toxicity present at low levels in the diet. ILSI Europe Concise Monograph Series. Europe, Bmssels, Belgium ILSI. http //europe.ilsi.org/publications/Monographs/ThreshoIdToxicoIogicaIConcem.htm Barnes, D., G. Daston, J. Evans, et al. 1995. Benchmark dose workshop Criteria for use of a benchmark dose to estimate a reference dose. Regul. Toxicol. Pharmacol. 21 296-306. [Pg.204]

Dourson, M.L., L.A. Knauf, and J.C. Swartout. 1992. On reference dose (Rfd) and its underl3dng toxicity data base. Toxicol. Ind. Health 8 171-183. [Pg.293]

SSLs are risk-based concentrations derived from standardized equations combining exposure information assumptions with US-EPA toxicity data. For the ingestion, dermal, and inhalation pathways, toxicity criteria are used to define an acceptable level of contamination in soil, based on a one-in-a-million (10 individual excess cancer risk for carcinogens and a Hazard Quotient (HQ) of 1 for noncarcinogens. The hazard quotient is defined as the ratio of an exposure estimate over the Reference Dose or Concentration (Section 5.1), i.e., HQ = Exposure/(RfD or RfC). [Pg.364]

There are of course many mathematically complex ways to perform a risk assessment, but first key questions about the biological data must be resolved. The most sensitive endpoint must be defined along with relevant toxicity and dose-response data. A standard risk assessment approach that is often used is the so-called divide by 10 rule . Dividing the dose by 10 applies a safety factor to ensure that even the most sensitive individuals are protected. Animal studies are typically used to establish a dose-response curve and the most sensitive endpoint. From the dose-response curve a NOAEL dose or no observed adverse effect level is derived. This is the dose at which there appears to be no adverse effects in the animal studies at a particular endpoint, which could be cancer, liver damage, or a neuro-behavioral effect. This dose is then divided by 10 if the animal data are in any way thought to be inadequate. For example, there may be a great deal of variability, or there were adverse effects at the lowest dose, or there were only tests of short-term exposure to the chemical. An additional factor of 10 is used when extrapolating from animals to humans. Last, a factor of 10 is used to account for variability in the human population or to account for sensitive individuals such as children or the elderly. The final number is the reference dose (RfD) or acceptable daily intake (ADI). This process is summarized below. [Pg.242]

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). [Pg.138]

Maximum Contaminant Level NIOSH = National Institute for Occupational Safety and Health ODW = Office of Drinking Water OERR = Office of Emergency and Remedial Response OSHA = Occupational Safety and Health Administration OSW = Office of Solid Wastes OTS = Office of Toxic Substancesl OWRS = Office of Water Regulations and Standards PEL = Permissible Exposure Limit RfD = Reference Dose ... [Pg.134]


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See also in sourсe #XX -- [ Pg.232 , Pg.237 , Pg.290 ]




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