Recommendations for advancing media preparation methods used to assess aquatic hazards of oils and spill response agents

Thomas Parkerton, Michel Boufadel, Trond Nordtug, Carys Mitchelmore, Kat Colvin, Dana Wetzel, Mace G. Barron, Gail E. Bragin, Benjamin de Jourdan, Jennifer Loughery

Research output: Contribution to journalReview articlepeer-review

8 Scopus citations


Laboratory preparation of aqueous test media is a critical step in developing toxicity information needed for oil spill response decision-making. Multiple methods have been used to prepare physically and chemically dispersed oils which influence test outcome, interpretation, and utility for hazard assessment and modeling. This paper aims to review media preparation strategies, highlight advantages and limitations, provide recommendations for improvement, and promote the standardization of methods to better inform assessment and modeling. A benefit of media preparation methods for oil that rely on low to moderate mixing energy coupled with a variable dilution design is that the dissolved oil composition of the water accommodation fraction (WAF) stock is consistent across diluted treatments. Further, analyses that support exposure confirmation maybe reduced and reflect dissolved oil exposures that are bioavailable and amenable to toxicity modeling. Variable loading tests provide a range of dissolved oil compositions that require analytical verification at each oil loading. Regardless of test design, a preliminary study is recommended to optimize WAF mixing and settling times to achieve equilibrium between oil and test media. Variable dilution tests involving chemical dispersants (CEWAF) or high energy mixing (HEWAF) can increase dissolved oil exposures in treatment dilutions due to droplet dissolution when compared to WAFs. In contrast, HEWAF/CEWAFs generated using variable oil loadings are expected to provide dissolved oil exposures more comparable to WAFs. Preparation methods that provide droplet oil exposures should be environmentally relevant and informed by oil droplet concentrations, compositions, sizes, and exposure durations characteristic of field spill scenarios. Oil droplet generators and passive dosing techniques offer advantages for delivering controlled constant or dynamic dissolved exposures and larger volumes of test media for toxicity testing. Adoption of proposed guidance for improving media preparation methods will provide greater comparability and utility of toxicity testing in oil spill response and assessment.

Original languageEnglish (US)
Article number106518
JournalAquatic Toxicology
StatePublished - Jun 2023

All Science Journal Classification (ASJC) codes

  • Aquatic Science
  • Health, Toxicology and Mutagenesis


  • Media preparation
  • Oil toxicity testing
  • Passive dosing
  • Water accommodated fraction


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