Use of dispersants during marine pollution response
The National Plan for Maritime Environmental Emergencies (the National Plan) provides for dispersant use, but strict rules and processes apply.
Chemical dispersants are one of the response tools available during oil spill responses.
Dispersants break up surface slicks, preventing the oil reaching coastal and shoreline environments, and reducing the direct exposure of marine mammals and birds to surface oil slicks.
The surface slick is broken up into microscopic-sized oil droplets enclosed within a film of the dispersant.
These droplets are effectively weightless in water and readily disperse into the water column through wave and current energy. Here the oil is diluted many tens of thousands of times, and is eventually eaten by oil eating bacteria and other micro-organisms.
Dispersant use is provided for under the National Plan for Maritime Environmental Emergencies (the National Plan).
Strict rules and processes apply to dispersant use and only Oil Spill Control Agents (OSCA) registered products can be used. A net environmental benefit analysis (NEBA) is required to ensure dispersant is an appropriate and approved response strategy.
Monitoring oil and dispersant use ensures effective application, and that dispersant use is stopped when no longer effective.
There are risks associated with dispersant use.
AMSA and the National Plan recognise the risks, plan for them, and work to minimise their effects.
All dispersants are tested for human health effects and eco-toxicity before OSCA registration and use. Some marine areas are recognised as unsuitable for dispersant use, such as areas near particularly sensitive ecosystems (e.g. coral reefs) or in shallow water (where effective dilution is less likely).
AMSA has an ongoing programme to improve its knowledge of dispersants, their uses and risks. This page links to key documents to assist with dispersant understanding, grouped by function and process.
Documents which may assist with understanding about dispersants in general and Australia’s approach specifically:
- Dispersants – an overview for responders [ PDF: 2.22Mb]
- OSCAs and dispersants – redeveloping the Australian approach [ PDF: 628Kb]
- Continual improvement in Australia’s dispersant response strategy [ PDF: 2.22Mb]
Approval and acceptance
The National Plan recognises dispersant use in maritime (shipping-related) spills around Australia could be a very effective means to prevent major environmental damage. However, oil weathers (changes) once spilled and over time can become too viscous (thick) for dispersants to work.
It is imperative that application occurs quickly.
Dispersants are tested before being accepted and purchased for National Plan response stockpiles. The Oil Spill Control Agents (OSCA) Policy ensures they meet health and environmental standards.
- Dispersants are registered by AMSA as Oil Spill Control Agents
- The offshore petroleum sector approves dispersants differently
- AMSA purchases new dispersant stocks through tender processes.
Storage and logistics
AMSA holds significant stockpiles of dispersants and spray equipment around the country.
Some are in high risk areas to enable easy access and quick response. Some are in areas where logistics allow rapid transport to the spill location.
To ensure rapid responses, AMSA has 24/7 contracts with fixed wing spraying contractors using aircraft able to carry up to 3.5 tonnes of dispersant up to 350km offshore.
To assist with safety, accuracy and effectiveness, other aircraft and observers are used for on-site direction and monitoring.
- Where are AMSA’s dispersant and equipment stockpiles?
- How does the aircraft contract arrangements work?
Approval to apply dispersant
The use of dispersants in a National Plan response must be approved by the relevant Incident Controller and/or statutory authority.
The benefits to the clean-up activites and the affected environment must be supported by solid evidence from monitoring, testing and expert advice. As response circumstances change over time, approval for use is regularly re-assessed and documented.
A formal, documented process will include:
- the need and likely effectiveness
- expert opinion and testing
- alternatives considered
- environmental effects of the oil and the oil/dispersant mix
- safety issues for the public or operators.
This is generally known as a net environmental benefit analysis (NEBA). AMSA has a version of this for dispersant use (and other OSCAs).
It is a clear, well-documented decision-making process called the Protocol for Obtaining Approval for the Application of Oil Spill Control Agents to Oil at Sea or on Shorelines.
The protocol provides simple decision-trees: one each for “at sea” and “shoreline” use, depending on what OSCA is required.
In a second stage, another simple decision-tree is used for conducting a rapid net environmental benefit assessment, adapted from international best practice. Checklists of the required processes, information and decision points complete the guideline.
- Decision-making Guide - Should a dispersant be used in this response?
- Will dispersant likely be effective in this case?
Monitoring – assessing when to stop and did it work?
Effective monitoring of dispersant use is difficult, as none, some, most or all of the oil eventually goes into the water column.
Aerial observation by trained and experienced observers has the primary means of monitoring. Reliably measuring oil in the water column is also difficult. If the dispersant worked as intended, the volumes and concentrations of oil are very low and hard to find.
AMSA and the Commonwealth Scientific and Industral Research Organisation (CSIRO) have collaborated to develop towable measuring devices able to do in-situ, real-time oil and dispersant monitoring, and three-dimensional mapping.
Combined with the new oil Spill Monitoring Handbook and CSIRO’s expertise in monitoring in the field, and responders can now be more confident in answering the very important questions:
- Did it work?
- Should we stop spraying?
- Where did it all go?
Understanding and communicating the benefits and risks of dispersant use
Under the National Plan, AMSA has three main roles related to dispersants:
- Gatekeeper – determining the acceptability of dispersants for National Plan response use under the OSCA Policy
- Responder – the use dispersant in a response
- Advisor – we provide technical, risk and benefit information about dispersants to all other National Plan dispersant users and interest groups.
Driven by a combination of new, local and international knowledge, we are improving our knowledge of dispersants in four significant areas:
- risk assessment
- public information.
Foremost amongst public concerns about hazards are issues to human health and the environment.
In 2013 AMSA started a process to identify these areas of concern and information gaps by seeking the expertise and advice of two of Australia’s peak, independent, expert bodies to provide their advice:
- The National Industrial Chemicals Notification and Assessment Scheme (NICNAS - the Australian government's regulatory body for industrial chemicals), was asked to assist with a human health hazard assessment. NICNAS produced two reports:
- Chemicals used as oil dispersants in Australia: Stage 1. Identification of chemicals of low concern for human health (April 2014)
- Chemicals used as oil dispersants in Australia: Stage 2. Summary report of the human health hazards of oil spill dispersant chemicals (October 2014)
- NICNAS Stage 2 - Appendix to Summary of Heal Assessment of Oil Dispersant Chemicals
- CSIRO was asked to undertake an assessment of the state of knowledge about ecotoxicology.
AMSA is presenting the results of these studies as part of its commitment to being transparent and inquisitive about dispersant use as a response strategy. An AMSA preamble page has been inserted at the head of each report to ensure its context is explained and to describe how AMSA and the National Plan are addressing the findings and recommendations.
To ensure all National Plan responders and decision-makers are aware of the risks and benefits of dispersant use, AMSA undertakes regular training and information sessions.
Information on education events, such as the National Response Team dispersant information session, is provided below. For information on the content or running of the CSIRO/AMSA dispersant masterclass, please contact AMSA.
Links for responders
- NOAA ADIOS2
- National Plan Oil Spill Dispersant Effectiveness Test - Field Kit (Nat-DET) Operational Guide [ PDF: 496Kb]
- Dispersant Effectiveness Test - checklist [ PDF: 700Kb]
- Environment, science and technical network tools and resources