Uncertainty Factor

{
  "id": "MLC-T-ENV-029004",
  "term": "Uncertainty Factor",
  "field": "Environment",
  "definition": "1. One of several, generally 10-fold, default factors used in operationally deriving the RfD and RfC from experimental data. The factors are intended to account for (1) variation in susceptibility among the members of the human population (i.e., inter-individual or intraspecies variability); (2) uncertainty in extrapolating animal data to humans (i.e., interspecies uncertainty); (3) uncertainty in extrapolating from data obtained in a study with less-than-lifetime exposure (i.e., extrapolating from subchronic to chronic exposure); (4) uncertainty in extrapolating from a LOAEL rather than from a NOAEL; and (5) uncertainty associated with extrapolation when the database is incomplete.\n\n2. A number (equal to or greater than one) used to divide NOAEL or LOAEL values derived from measurements in animals or small groups of humans in order to estimate a NOAEL value for the whole human population.\n\n3. One of several factors used in calculating the reference dose from experimental data. UFs are intended to account for (1) the variation in sensitivity among humans; (2) the uncertainty in extrapolating animal data to humans; (3) the uncertainty in extrapolating data obtained in a study that covers less than the full life of the exposed animal or human; and (4) the uncertainty in using LOAEL data rather than NOAEL data.\n\n4. The value (often a default value of 10) used as a divisor of a NOAEL, LOAEL, or benchmark dose to calculate a RfC or RfD. Uncertainty factors are applied as needed for extrapolation of results in experimental animals to humans, inter-individual variability including sensitive subgroups, extrapolation from a LOAEL to a NOAEL, extrapolation of results from subchronic exposures to chronic exposures, and database inadequacies.\n\n5. Mathematical adjustments for reasons of safety when knowledge is incomplete. For example, factors used in the calculation of doses that are not harmful (adverse) to people. These factors are applied to the lowest-observed-adverse-effect-level (LOAEL) or the no-observed-adverse-effect-level (NOAEL) to derive a minimal risk level (MRL). Uncertainty factors are used to account for variations in people’s sensitivity, for differences between animals and humans, and for differences between a LOAEL and a NOAEL. Scientists use uncertainty factors when they have some, but not all, the information from animal or human studies to decide whether an exposure will cause harm to people [also sometimes called a safety factor].\n\n6. One of several, generally 10-fold factors, used in operationally deriving the Reference Dose (RfD) from experimental data. UFs are intended to account for (1) the variation in sensitivity among the members of the human population; (2) the uncertainty in extrapolating animal data to the case of humans; (3) the uncertainty in extrapolating from data obtained in a study that is of less-than-lifetime exposure; and (4) the uncertainty in using LOAEL data rather than NOAEL data.\n\n7. One of several, generally 10-fold, default factors used in operationally deriving the RfD and RfC from experimental data. The factors are intended to account for variation in susceptibility among the members of the human population (i.e., inter-individual or intraspecies variability).\n\n8. One of several numeric factors used in operationally deriving criteria from experimental data to account for the quality or quantity of the available data. [40 CFR 132.2 (CFR 2013)]\n\n9. One of several, generally 10-fold, default factors used in operationally deriving the RfD and RfC from experimental data. The factors are intended to account for (1) variation in susceptibility among the members of the human population (i.e., inter-individual or intraspecies variability); (2) uncertainty in extrapolating animal data to humans (i.e., interspecies uncertainty); (3) uncertainty in extrapolating from data obtained in a study with less-than-lifetime exposure (i.e., extrapolating from subchronic to chronic exposure); (4) uncertainty in extrapolating from a LOAEL rather than from a NOAEL; and (5) uncertainty associated with extrapolation when the database is incomplete. [EPA 2003, EPA 2004]\n\n10. Reductive factor by which an observed or estimated no-observed-adverse effect level (NOAEL) is divided to arrive at a criterion or standard that is considered safe or without appreciable risk. [IPCS/OECD 2004]\n\n11. Mathematical adjustments for reasons of safety when knowledge is incomplete. For example, factors used in the calculation of doses that are not harmful (adverse) to people. These factors are applied to the lowest-observed-adverse-effect-level (LOAEL) or the no-observed-adverse-effect-level (NOAEL) to derive a minimal risk level (MRL). Uncertainty factors are used to account for variations in people’s sensitivity, for differences between animals and humans, and for differences between a LOAEL and a NOAEL. Scientists use uncertainty factors when they have some, but not all, the information from animal or human studies to decide whether an exposure will cause harm to people [also sometimes called a safety factor]. [ATSDR 2004]\n\n12. The value (often a default value of 10) used as a divisor of a NOAEL, LOAEL, or benchmark dose to calculate a RfC or RfD. Uncertainty factors are applied as needed for extrapolation of results in experimental animals to humans, inter-individual variability including sensitive subgroups, extrapolation from a LOAEL to a NOAEL, extrapolation of results from subchronic exposures to chronic exposures, and database inadequacies. Acronym: UF",
  "abbreviation": "UF",
  "synonyms": [
    "UFS"
  ],
  "subject": "Science and research",
  "references": [
    "Integrated Risk Information System (IRIS) Glossary; EPA 2003, EPA 2004",
    "Drinking Water Technical & Legal Terms",
    "Terms of Environment",
    "Benchmark Dose Software (BMDS) Glossary of Terms",
    "ATSDR 2004",
    "RAIS 2004",
    "Adapted fromIntegrated Risk Information System (IRIS) Glossary",
    "40 CFR Appendix C to Part 132 (CFR 2013)",
    "MRA Thesaurus"
  ],
  "url": "https://mlchart.com/terminology/environment/uncertainty-factor/"
}