Shipping Emissions and Air Quality Impacts

International merchant vessels constitute a significant source of atmospheric pollutants, emitting sulphur oxides, nitrogen oxides, particulate matter and black carbon, alongside carbon dioxide and short-lived climate forcers. These emissions degrade air quality in coastal and port regions, contribute to acid deposition, exacerbate respiratory and cardiovascular illnesses, and influence regional and global climate through aerosol–cloud interactions and radiative forcing. Recent regulatory measures, including sulphur content caps and designated emission control areas, have driven shifts towards low-sulphur fuels and exhaust aftertreatment, yet residual emissions of ultrafine particles and nitrogen oxides persist. Emerging pathways to near-zero shipping involve carbon-neutral drop-in fuels, advanced engine designs and integrated well-to-wake assessments that balance climate, health and economic objectives. Satellite and airborne monitoring advances are enhancing the spatial resolution of emission inventories, informing policy interventions and technological deployment to mitigate both local air quality concerns and broader climate trade-offs.

Research from Nature Portfolio

Analyses of exhaust gas cleaning systems reveal that while onboard scrubbers enable continued use of heavy residual oils at lower fuel cost, their wash-water discharge imposes substantial ecotoxicity burdens on marine environments, calling for tighter discharge standards or alternative compliance strategies. Economic modelling indicates that private incentives for scrubber installation have eclipsed investments in cleaner fuels or engine retrofits, despite pronounced environmental harm. Complementary studies on low-sulphur marine fuels demonstrate significant reductions in particulate matter exposures and associated premature mortality and childhood asthma, but also a marked decrease in aerosol cooling potential, yielding a modest increase in net warming. These findings underscore the need for shipping policies that jointly target greenhouse gases and air pollutants to optimise public health and climate outcomes.

Shipping Emissions and Air Quality Impacts publication trend

The graph below shows the total number of articles in shipping emissions and air quality impacts across all publications each year (not limited to Nature Index journals).

Technical terms

Particulate Matter (PM2.5): Fine inhalable aerosol particles with aerodynamic diameter ≤2.5 µm, capable of penetrating deep into the respiratory tract.

Nitrogen Oxides (NOx): A collective term for nitric oxide and nitrogen dioxide, formed during high-temperature combustion and contributing to ozone formation and respiratory irritation.

Sulphur Oxides (SOx): Gaseous pollutants, primarily sulphur dioxide, produced from sulphur in marine fuels, leading to acid deposition and aerosol formation.

Black Carbon (BC): Light-absorbing carbonaceous particulate matter emitted from incomplete combustion, with strong warming potential and health impacts.

Exhaust Gas Cleaning System (Scrubber): A deck-mounted apparatus that removes sulphur compounds and some particulates from ship exhaust by scrubbing gases with water or chemical solutions.

Radiative Forcing: The change in net energy flux in the atmosphere caused by greenhouse gases or aerosols, influencing climate warming or cooling.

Well-to-Wake Emissions: Total greenhouse gas and pollutant emissions accounting for fuel production, transport and final combustion in engines.

References

1. Reduction in greenhouse gas and other emissions from ship engines: Current trends and future options. Progress in Energy and Combustion Science (2023).
2. Limited efficiency of wet scrubbers in reducing the environmental impact of ship-emitted particles. Environmental Chemistry Letters (2025).
3. Strong economic incentives of ship scrubbers promoting pollution. Nature Sustainability (2024).
4. Sensitivity analysis for the detection of NO2 plumes from seagoing ships using TROPOMI data. Remote Sensing of Environment (2024).
5. Cleaner fuels for ships provide public health benefits with climate tradeoffs. Nature Communications (2018).
6. Airborne emission measurements of SO2 , NOx and particles from individual ships using a sniffer technique. Atmospheric Measurement Techniques (2014).