The Development of New Toxicity Testing and Approval Processes for Oil Spill Treatment Products in the UK

Current experimental protocols for the toxicity assessment of oil spill treatment products in the UK have been established since the 1970s. To address health and safety, cost and scientific robustness issues the UK approach for dispersant testing and approval has been reviewed and updated for implementation during 2020. To provide more robust scientific advice for the risk assessments that enable effective decision making on the use of oil remediation products in the event of a spill there has been a focus on methods that already have internationally accepted protocols. Standardisation of dispersant testing will promote more effective cross-institute comparisons of toxicity data and will enable further harmonisation of approaches in the future. It is preferable that environmentally relevant test species are used but, as the scientific literature provides little conclusive evidence of a taxa-specific trend in sensitivity, species selection based on sensitivity alone was not justified. Eight dispersants, commonly stockpiled in the UK, were tested independently and in combination with a representative crude oil (Kuwait). Testing of dispersants in combination with oil has historically provided more variable results so this study has considered the benefits of this versus product only testing. Core test species included the harpacticoid copepod, Tisbe battagliai, and the algae, Skeletonema sp., as both have cost-effective internationally standardised methods, whilst also being environmentally representative and using test species easily cultured under laboratory conditions with no seasonality. Other candidate test species, such as oyster embryos, had limitations in applicability due to seasonal issues. Fish testing was not considered as there was no ethical reasoning for vertebrate testing due to the absence of taxa-specific toxicity. Results showed that, if oil is excluded from the assessment, Skeletonema sp. and Tisbe battagliai, can produce reliable, reproduceable and interpretable results. When running the T. battagliai test, independently on multiple occasions, without oil, dispersant 1, 2 and 3 had EC50 results that were not statistically different. This suggests that product only testing is suitable for ranking products based on toxicological hazard. The redevelopment of the UK guideline to use standardised testing and the selection of appropriate, environmentally relevant test organisms will increase the quality and reliability of data used to underpin the UK oil spill treatment testing and approval scheme. The adoption of this approach will enable an approved list of products for use in UK waters to be maintained. However, the decision for dispersant use in any given scenario will need to be underpinned through expert advice applying a risk assessment approach taking account a range of incident-specific physical and environmental sensitivity information.