Enough NOx: Rethinking How Cities Tackle Air Pollution
Nitrogen oxides, known as NOx, remain the most common form of human made air pollution. They harm health, damage ecosystems, and lower the quality of life in cities.
Spectrum Blue AS is exploring new ways to reduce NOx directly where people breathe. The focus moves beyond monitoring and regulation toward active removal in urban spaces.
What NOx Is and Why It Matters
NOx mainly includes nitric oxide and nitrogen dioxide. These gases form during high-temperature combustion.
The largest sources include road traffic, shipping, power generation, and industrial activity. In Norway, transport and oil and gas operations dominate emissions. Natural sources exist, such as lightning and wildfires, but human activity produces most NOx in populated areas.
When inhaled, nitrogen dioxide irritates the airways and worsens asthma. Over time, exposure increases the risk of lung disease, heart problems, and early death.
In addition, NOx helps form ground level ozone and fine particles. These pollutants further raise health risks. Acid rain is another outcome, harming crops, buildings, and natural systems.
In cities, NOx often appears as brown smog near busy roads and ports.
Urban Areas Face the Highest Risk
NOx pollution concentrates where traffic and industry cluster. Satellite data and monitoring show clear hotspots in large cities such as London and Delhi.
Levels peak near roads, tunnels, ports, and industrial zones. As a result, city residents face the greatest health burden.
Although regulations have lowered emissions in some regions, NOx remains a stubborn urban problem.
How NOx Is Managed Today
Current strategies focus on three main areas.
First, prevention. This includes electric vehicles and cleaner engines.
Second, regulation. Cities use emission standards and low-emission zones.
Third, monitoring. Air quality tracking helps guide policy, while indoor filtration systems offer limited protection.
However, these methods do little to remove NOx already present in outdoor air. Pedestrians remain exposed.
Why a 20 Percent Reduction Matters
In urban policy, a 20 percent drop in nitrogen dioxide counts as a major success. Evidence from low-emission zones shows such reductions lead to real health benefits.
Cities like Madrid achieved reductions between 14 and 28 percent through traffic restrictions. These changes lowered illness rates and reduced pollution-related deaths.
Therefore, a 20 percent reduction in city centres represents a meaningful improvement.
Using Surfaces to Remove NOx
A newer approach targets NOx directly in the air. Photocatalytic coatings can convert NOx into harmless nitrates when exposed to light.
Traditional versions rely on ultraviolet light. This creates a major limit. UV levels drop with clouds, seasons, and time of day. They disappear entirely in tunnels and shaded streets.
North of the 37th parallel, UV levels are even weaker. Many busy cities fall into this zone.
As a result, standard coatings fail in many of the places with the worst pollution.
Moving Beyond UV With Visible Light
To solve this, Spectrum Blue AS developed a visible light photocatalytic pigment. The work received funding from the EEA and Norway Grants.
The company partnered with BEIA Consult International and HEY’DI AS. Together, they tested the pigment in cement and surface coatings.
The goal was clear. Make NOx removal work under artificial light and shade.
Introducing Q Field Technology
Q field coatings do not need ultraviolet light. They work under visible light instead.
This makes them effective in places such as:
• Indoors
• Tunnels
• Under bridges
• Shaded pavements
Tests showed that Q-coated surfaces reduced NOx even in low light conditions. When applied to pedestrian areas, daily reductions reached around 19 percent. This matches the impact of traffic restrictions.
Real World Impact at Street Level
Lab results suggest that just 100 square metres of coated pavement could remove over six tons of NOx per year at a busy London intersection.
At places like Old Street, this difference could change daily exposure from unhealthy to acceptable levels.
Because the coating works passively, it scales easily and requires little maintenance.
A Practical Toolkit for Cities
Q field allows cities to reduce pollution directly, not only manage it.
Possible uses include:
• Coating tunnel walls and barriers
• Creating NOx traps along highways
• Improving air quality near schools and hospitals
Planning tools also support deployment. Digital models can estimate impact, identify high-risk zones, and support health-focused planning.
Cities and infrastructure owners can now pilot installations, include coatings in construction projects, and track results through independent monitoring.
From Measuring Pollution to Cleaning It
For years, cities focused on tracking NOx. With Q field technology, they can now remove it.
By targeting the hardest-to-reach locations, this approach adds a new layer to urban air quality strategies.
Instead of choosing between regulation and innovation, cities can use both. The result is cleaner air where people live, walk, and work.
