Abstract
This Evidence Review Note (ERN) provides an evidence-led assessment of the relevance and proportionality of offshore air quality within the Environmental Impact Assessment (EIA) of UK offshore wind farm (OWF) projects. Developed through the Offshore Wind Evidence and Knowledge Hub (OWEKH), the ERN draws on a structured review of 79 published UK offshore wind EIAs and associated scoping reports, alongside stakeholder input and relevant policy and guidance.
The review examined the treatment of offshore air quality across OWF projects spanning more than two decades. No recent standalone chapters titled ‘Offshore Air Quality’ were identified. Where air quality chapters were included, these predominantly addressed onshore construction-related effects, with offshore emissions either scoped out at the scoping stage or addressed briefly within broader air quality chapters.
Offshore air quality effects associated with construction, operation, maintenance and decommissioning activities were considered, including vessel and helicopter exhaust emissions, temporary offshore plant and generators, and minor operational turbine or platform-related emissions. These were consistently predicted to be negligible or minor, and not to give rise to likely significant effects. None of the OWF EIAs reviewed identified significant residual effects on offshore air quality following the application of standard controls and good practice. No mitigation specific to offshore air quality was required, and no significant cumulative effects were identified.
The review also confirms that relevant emissions from marine vessels are subject to established international and national regulatory controls. These include MARPOL Annex VI and associated emission standards, and provide an additional management framework for offshore emission sources.
The full evidence base demonstrates that offshore air quality can be successfully scoped out of project-level EIA for offshore wind developments, in the absence of unusual site-specific circumstances or material changes in emissions arising from project parameters. Continued inclusion of extended discussion in scoping reports does not appear proportionate to the level of risk identified. Accordingly, this ERN recommends that offshore air quality should be scoped out of EIA for offshore wind projects. It should be supported by a concise, evidence-based justification at the scoping stage that explicitly references this ERN. This approach promotes proportionality, reduces unnecessary reporting, improves consistency across projects, and maintains alignment with statutory EIA requirements.
OWEKH ERNs are maintained as live documents and will be updated as new evidence, monitoring data, policy changes or sector learning emerge. This ensures our guidance remains robust, transparent and evidence-based.