London's air improved again in 2025 on paper — roadside nitrogen dioxide has fallen since the ULEZ expanded to cover all boroughs. But two things haven't changed: fine-particle PM2.5 still regularly exceeds World Health Organisation guideline levels, and a large share of outdoor pollution ends up inside our homes.
PM2.5 is the pollutant that matters most for health, and it's only loosely affected by ULEZ because much of it comes from tyre and brake wear, wood burning and sources beyond the city. On a still day it pools at street level and seeps indoors through vents and gaps.
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Shop the UK store → See all kitsThe hotspots
- Euston Road / Marylebone Road — persistently among the UK's worst NO2.
- Inner-city arterials — the A10, A11/A12, South Circular.
- Winter wood-burning — a growing PM2.5 source in residential areas.
What it means for your home
Outdoor improvements are slow and partial; indoor air is something you control today. A high-airflow purifier holds indoor PM2.5 well below outdoor levels, especially overnight. Check your local readings on the London Air Quality Network before airing rooms on calm, sunny days.
Frequently asked questions
Has London's air actually got better?
Roadside NO2 has fallen with ULEZ, but PM2.5 still breaches WHO guidelines across much of the city. The health-critical pollutant hasn't improved as much as headline NO2 figures suggest.
Can I control indoor air even if outdoor air is bad?
Yes — a purifier keeps indoor PM2.5 well below outdoor levels, which is where you spend most of your time.