Cleaner air milestone reached as Southampton cuts nitrogen dioxide levels by 30%

Southampton has reached a major milestone in improving air quality, with nitrogen dioxide (NO₂) levels across the city falling by 30% following years of sustained action to reduce pollution.

Southampton City Council announced the improvement after the latest assessments by the Government’s Joint Air Quality Unit confirmed the city has met the conditions of the national Nitrogen Dioxide Programme. Monitoring at 69 locations shows NO₂ levels dropped significantly between 2019 and 2024, with no sites exceeding the annual legal limit of 40 micrograms per cubic metre (µg/m³) in the past two years.

The council said the progress marks a key step towards creating a healthier and greener city for residents, following concerns raised in 2017 when pollution levels reached a critical point.

More than £6 million has been invested in measures designed to transform travel and reduce emissions. These include the construction of major new cycling routes on key corridors, contributing to a 17% increase in cycling usage, upgrades to traffic signals to improve flow and reduce congestion, and the retrofitting of 145 buses to Euro VI emission standards in partnership with Bluestar.

Additional improvements include the expansion of rapid charging infrastructure for taxis, support for low-emission vehicles, and delivery and freight consolidation schemes carried out with the Port of Southampton to reduce commercial vehicle trips. A comprehensive Green City communications campaign has also encouraged residents to adopt cleaner and healthier travel choices.

Many of these initiatives — such as the Southampton Cycle Network, upgraded buses and strengthened taxi emission standards — will remain in place permanently.

A spokesperson for Associated British Ports said: “At the Port of Southampton, we are committed to operating sustainably, from being the first UK Port to provide shore power for cruise ships, generating over 50% of the power the port uses each year from our own solar panels, to expanding our use of electric vehicles and fuel-efficient pilot launch vessels. These investments are already reducing emissions across the port and demonstrate our commitment to continue to deliver cleaner, more sustainable operations.”

Councillor John Savage, Cabinet Member for Environment and Net Zero, welcomed the achievement and highlighted the role of residents and partners in driving change. He said: “I am delighted that Southampton is set to exit the Government’s Nitrogen Dioxide Programme after years of hard work by the council, our partners and local people who have understood the need to switch to greener and healthier modes of transport when they can.

“This work has underscored our missions for a greener and healthier city with long term benefits for residents and we will continue to champion activities and initiatives that support local people to thrive.”

Despite the planned exit from the programme, the council stressed that its commitment to improving air quality will continue. Future work will include delivering the Air Quality Action Plan 2023–2028, expanding public engagement on issues such as woodburning, schools and healthcare, and maintaining public reporting through an online citywide air quality map.

The authority also plans to continue enforcing smoke control areas, investing in electric vehicle infrastructure, working with port operators to reduce shipping-related emissions and introducing future zero-emission buses through the Bus Service Improvement Plan. Further improvements to cycling, walking, public transport and the wider road network are also planned.

An exit plan from the Nitrogen Dioxide Programme is due to be considered by the council’s Cabinet on 24 March 2026.