title: Derivation of human health-based ambient water quality criteria: a consideration of conservatism and protectiveness goals.
abstract: Under the terms of the Clean Water Act, criteria for the protection of human health (Human Health Ambient Water Quality Criteria [HHWQC]) are traditionally derived using equations recommended by the US Environmental Protection Agency (USEPA) that include parameters for exposure assessment. To derive "adequately protective" HHWQC, USEPA proposes the use of default values for these parameters that are a combination of medians, means, and percentile estimates targeting the high end (90th percentile) of the general population. However, in practice, in nearly all cases, USEPA's recommended default assumptions represent upper percentiles. This article considers the adequacy of the exposure assessment component of USEPA-recommended equations to yield criteria that are consistent with corresponding health protection targets established in USEPA recommendations or state policies, and concludes that conservative selections for exposure parameters can result in criteria that are substantially more protective than the health protection goals for HHWQC recommended by USEPA, due in large part to the compounding effect that occurs when multiple conservative factors are combined. This situation may be mitigated by thoughtful selection of exposure parameter values when using a deterministic approach, or by using a probabilistic approach based on data distributions for many of these parameters.
authors.affiliation: National Council for Air and Stream Improvement, Newberry, Florida, USA.
authors.forename: Vickie
authors.initials: V
authors.lastname: Tatum
authors.forename: Paul
authors.initials: P
authors.lastname: Wiegand
authors.forename: Steve
authors.initials: S
authors.lastname: Stratton
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Louch
authors.forename: Ellen
authors.initials: E
authors.lastname: Ebert
authors.forename: Paul
authors.initials: P
authors.lastname: Anderson
mesh_terms: D004781:Environmental Exposure; D004784:Environmental Monitoring; D006801:Humans; D018570:Risk Assessment; D014481:United States; D014484:United States Environmental Protection Agency; D014874:Water Pollutants, Chemical / Q000032:analysis*; D060753:Water Quality / Q000592:standards
chemical_list: D014874:Water Pollutants, Chemical
keywords: Conservatism; Human health; Water quality criteria