title: Quantitative Assessment of Current Risks to Harlequin Ducks in Prince William Sound, Alaska, from theExxon ValdezOil Spill.
abstract: Harlequin Ducks (Histrionicus histrionicus)were adversely affected by theExxon Valdezoil spill (EVOS) in Prince William Sound (PWS), Alaska, and some have suggested effects continue two decades later. We present an ecological risk assessment evaluating quantitatively whether PWS seaducks continue to be at-risk from polycyclic aromatic hydrocarbons (PAHs) in residualExxon Valdezoil. Potential pathways for PAH exposures are identified for initially oiled and never-oiled reference sites. Some potential pathways are implausible (e.g., a seaduck excavating subsurface oil residues), whereas other pathways warrant quantification. We used data on PAH concentrations in PWS prey species, sediments, and seawater collected during 2001-2008 to develop a stochastic individual-based model projecting assimilated doses to seaducks. We simulated exposures to 500,000 individuals in each of eight age/gender classes, capturing the variability within a population of seaducks living in PWS. Doses to the maximum-exposed individuals are ∼400-4,000 times lower than chronic toxicity reference values established using USEPA protocols for seaducks. These exposures are so low that no individual-level effects are plausible, even within a simulated population that is orders-of-magnitude larger than exists in PWS. We conclude that toxicological risks to PWS seaducks from residualExxon Valdezoil two decades later are essentially non-existent.
authors.affiliation: Harwell Gentile & Associates, LC, Port Orange, FL, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Harwell
authors.forename: John H
authors.initials: JH
authors.lastname: Gentile
authors.forename: Keith R
authors.initials: KR
authors.lastname: Parker
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Murphy
authors.forename: Robert H
authors.initials: RH
authors.lastname: Day
authors.forename: A Edward
authors.initials: AE
authors.lastname: Bence
authors.forename: Jerry M
authors.initials: JM
authors.lastname: Neff
authors.forename: John A
authors.initials: JA
authors.lastname: Wiens
keywords: Exxon Valdez oil spill; PAHs; Prince William Sound; ecological risk assessment; ecotoxicology; individual-based models; seaducks