title: Lack of total independence of uncertainty factors (UFs): implications for the size of the total uncertainty factor.
abstract: This paper assesses the fundamental assumption that multiple uncertainty factors (UFs) are independent of each other and therefore may be combined through a multiplicative scheme. It is argued that a lack of independence is seen in several cases such as that between the interindividual and less-than-lifetime UFs with respect to an age component and results in an error in double counting of UFs. The paper proposes revised UF values based on the concept of the relationship of independent and interdependent UFs. This uncertainty factor revision is then applied to a large number of contaminants for which EPA either has or has proposed MCLs or DWELs.
authors.affiliation: School of Public Health, University of Massachusetts, Amherst 01003.
authors.forename: E J
authors.initials: EJ
authors.lastname: Calabrese
authors.forename: C E
authors.initials: CE
authors.lastname: Gilbert
mesh_terms: D000367:Age Factors; D000818:Animals; D004812:Epidemiologic Methods; D015386:Hazardous Substances / Q000633:toxicity*; D006801:Humans; D012307:Risk Factors; D013045:Species Specificity; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D015386:Hazardous Substances