Outdoor Air Pollution and Indoor Air Quality: Why the Air Inside Matters MoreThan Ever
- Innova NanoJet Tech
- Aug 6
- 9 min read
"Air pollution is one of the greatest environmental threats to human health."
– World Health Organisation
A New Pollution Report Highlights a Much Bigger
Global Problem
A recent news report highlighting some of the UK's most polluted neighbourhoods has once again brought air quality into the national spotlight. While the findings are alarming, they also serve as a reminder that this is far more than a British issue.
Outdoor air pollution has become one of the defining public health challenges of our generation. Whether you live in Glasgow, London, Los Angeles, Delhi, Beijing or São Paulo, the quality of the air outside affects millions of people every single day.
According to the World Health Organization (WHO), 99% of the world's population
breathes air that exceeds its recommended air quality guideline limits, making air
pollution one of the largest environmental health risks facing humanity. The combined effects of ambient and household air pollution are associated with approximately 6.7 million premature deaths annually
The recent UK report may have made the headlines, but the reality is that almost every nation is facing the same challenge.
While governments continue investing in cleaner transport, tighter emissions
regulations, renewable energy and better environmental policies, meaningful
improvements take years—often decades—to achieve.
That leaves an important question for all of us.
What can we do today?
The answer begins much closer to home than many people realise.
Why Outdoor Air Pollution and Indoor Air Quality
Are Inseparable
Many people naturally assume that pollution is an outdoor problem.
Unfortunately, buildings do not create an invisible shield against polluted air.
Every time a door opens, a window is cracked open or a ventilation system draws in fresh air, microscopic airborne pollutants can enter our homes, schools, offices, hospitals and workplaces.
These pollutants include:
PM₂.₅ and PM₁₀ particulate matter
Vehicle exhaust emissions
Nitrogen dioxide (NO₂)
Industrial emissions
Outdoor air can enter buildings through infiltration, natural ventilation and mechanical ventilation. Once indoors, these pollutants can remain suspended in the breathing zone, where occupants may be exposed for many hours each day.
This is particularly significant because the US Environmental Protection Agency reports that people in the United States spend about 90% of their time indoors, where indoor conditions can be affected by both indoor activities and outdoor air quality.
In other words...
Outdoor air pollution becomes an indoor air quality problem.
"The world's air doesn't stop at your front door."
The Hidden Health Impacts of Poor Indoor Air Quality
When most people think about air pollution, they immediately think about asthma or breathing difficulties. While these are important concerns, scientific evidence shows that the effects of air pollution can extend far beyond the lungs.
The European Environment Agency describes air pollution as Europe’s greatest environmental health risk, linking exposure to disease, reduced quality of life and preventable deaths.
Long-term exposure to air pollution has been associated with serious respiratory and cardiovascular health effects, including:
Asthma and other respiratory conditions
Chronic obstructive pulmonary disease (COPD)
Cardiovascular disease
Stroke
Reduced lung function
Eye, nose and throat irritation
The health effects can vary according to the pollutant involved, the level and duration of exposure, and an individual’s age and underlying health. Children, older people and those living with existing heart or respiratory conditions may be particularly vulnerable.
One pollutant of particular concern is fine particulate matter, known as PM₂.₅.
PM₂.₅ particles are 2.5 micrometres or smaller—approximately one-thirtieth of the width of an average human hair. Their small size allows them to remain suspended in the air and travel deep into the lungs when inhaled.
Research is also continuing into the possible effects of air pollution on the brain.
Recent studies have identified associations between exposure to air pollution and reduced cognitive performance, although this remains an evolving area of scientific research. Researchers are increasingly examining what this could mean for concentration, learning, reaction time and long-term brain health.
For employers, schools and healthcare providers, indoor air quality should therefore no longer be viewed solely as a building-management or facilities issue.
It is increasingly relevant to health, wellbeing and the quality of the environments in which people live, learn, work and recover.
Recent studies have suggested associations between long-term exposure to fine particulate matter (PM₂.₅) and reduced cognitive performance, prompting researchers to investigate how cleaner air may support concentration, learning and overall brain health.
We Can't Control the Air Outside... But We Can Improve the Air Inside
The reality is that none of us can personally reduce motorway traffic, eliminate industrial emissions or change environmental legislation overnight.
Those are long-term challenges requiring governments, industry and society to work together.
However, we can influence the quality of the air inside the spaces where we spend almost all of our lives.
That makes indoor air quality one of the few environmental health challenges where individuals and organisations can take meaningful action immediately.
Whether you manage:
a family home,
a classroom,
a care home,
a hospital ward,
an office,
a hotel,
or a manufacturing facility,
improving indoor air quality is one practical step that can begin today.
"You may not be able to change the air outside today—but you can choose to improve the air you breathe indoors."
Looking Beyond Traditional Air Purification
For decades, indoor air purification has primarily focused on filtration.
HEPA filters, activated carbon filters and mechanical ventilation all have important roles to play within modern buildings and should continue to form part of a comprehensive indoor air quality strategy.
However, different airborne pollutants behave differently.
Dust behaves differently from smoke.
Smoke behaves differently from VOCs.
VOCs behave differently from allergens.
As our understanding of indoor air quality evolves, so too does the technology designed to improve it.
Increasingly, researchers are exploring complementary technologies that work alongside conventional filtration rather than replacing it.
The question is no longer:
"Which technology is best?"
Instead, it has become:
"How can different technologies work together to create healthier indoor environments?"
A Different Approach to Indoor Air Quality
One example of this evolving approach is NanoJet® Technology, the proprietary platform behind AirSancta® Air Purifiers.
Unlike conventional air purifiers that rely solely on continuously drawing air through filters, NanoJet® Technology generates trillions of ultra-fine water droplets, with the vast majority measuring between 10 and 100 nanometres.
These nano-sized droplets disperse throughout the room where they physically interact with airborne pollutants.
As collisions occur, contaminants become encapsulated within the droplets, increasing in size until they naturally settle from the breathing zone.
Unlike traditional filter-based systems, NanoJet® Technology operates using only water during normal air purification.
No disposable filters.
No ongoing carbon media replacement.
No chemical additives.
Rather than operating continuously throughout the day, AirSancta® systems typically complete a treatment cycle in around one minute per 10 m², producing trillions of droplets that continue interacting with airborne pollutants long after the treatment cycle has finished.
This provides a different way of thinking about indoor air purification—one that focuses not only on moving air through a filter but also on physically interacting with airborne contaminants throughout the occupied space.
"The goal isn't simply to move the air. The goal is to improve the quality of the air people actually breathe."
Why This Matters More Than Ever
As governments continue working towards cleaner cities and lower emissions, people still need solutions that can help improve the environments where they spend the vast majority of their lives.
Cleaner indoor air cannot solve global air pollution.
But it can help reduce everyday exposure.
For families, it may provide greater peace of mind.
For schools, it may help create healthier learning environments.
For businesses, it may support employee wellbeing and productivity.
For healthcare providers, it may contribute to healthier indoor environments for patients, visitors and staff.
The journey towards cleaner air does not begin only with governments.
It also begins with the choices we make inside our own buildings.
Looking Ahead
The challenge of outdoor air pollution is unlikely to disappear overnight.
Neither will the need for better indoor air quality.
As scientific understanding continues to grow, we believe the conversation should move beyond simply asking whether air pollution is a problem.
Instead, we should be asking:
What practical steps can we take today while longer-term environmental improvements continue?
At Innova NanoJet Technologies, we believe innovation has an important role to play in answering that question.
Coming Soon: Our Definitive Guide to Outdoor Air Pollution and Indoor Air Quality
This article has been written in response to recent news highlighting the growing challenge of air pollution.
However, it is only the beginning of the conversation.
Our team is currently preparing a comprehensive Knowledge Hub guide exploring:
Outdoor Air Pollution and Indoor Air Quality: The Complete Science
Including:
How outdoor pollution enters indoor environments
PM₂.₅, PM₁₀, VOCs and ultrafine particles explained
The latest global research into health impacts
Air pollution, concentration and cognitive performance
Indoor air quality in homes, schools, workplaces and healthcare settings
The science behind NanoJet® Technology
Practical ways individuals and organisations can improve indoor air quality today
We look forward to sharing this in the coming weeks.
Frequently Asked Questions About Outdoor Air Pollution and Indoor Air Quality
How does outdoor air pollution affect indoor air quality?
Outdoor pollutants can enter buildings through open windows and doors, ventilation systems, air intakes, structural gaps and cracks. Once indoors, fine particles, smoke and other pollutants may remain in the air and combine with pollution generated inside the building.
What is PM2.5?
PM2.5 refers to fine particulate matter measuring 2.5 micrometres or less in diameter. These particles can be produced by sources such as traffic, combustion, industrial activity, wildfires and urban fires, and they can enter indoor environments from outside.
Can an air purifier solve outdoor air pollution?
No indoor air-quality system can solve the wider causes of outdoor pollution. However, appropriate air purification, ventilation, source control and building-management measures may help reduce exposure within individual indoor environments.
What can organisations do to improve indoor air quality?
Organisations can begin by assessing pollutant sources, maintaining ventilation systems, monitoring indoor conditions, reducing avoidable indoor emissions and considering appropriate air-purification technologies. The most suitable approach will depend on the building, its occupants and the pollutants involved.
Final Thoughts
Outdoor air pollution is one of the greatest environmental challenges of our time.
Improving it will require governments, scientists, industry and communities working together over many years.
But while we wait for cleaner skies, we do not have to wait to improve the air inside the places where we spend most of our lives.
Every healthier classroom.
Every cleaner office.
Every more comfortable hospital ward.
Every family home.
They all contribute towards the same goal.
Because while we may not be able to solve global air pollution overnight...
Together, we can make the places where we live, learn, work and recover healthier places to breathe.
References and Further Reading
Mirror, 2026. Most polluted neighbourhoods in UK revealed – see how yours fares, 27 July 2026. The news report that prompted this article.
World Health Organization, 2024. Ambient (outdoor) air pollution.
Provides global figures on exposure to outdoor air pollution, premature deaths and associated respiratory and cardiovascular diseases.
World Health Organization, 2026. WHO Ambient Air Quality Database – Version 8.0.
Compiles ground-level measurements of nitrogen dioxide, PM₁₀ and PM₂.₅ from cities and towns around the world.
World Health Organization, 2021. WHO global air quality guidelines: particulate matter, ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.
Sets out the WHO’s evidence-based air-quality guideline levels and reviews the health effects associated with major air pollutants.
United States Environmental Protection Agency. Indoor Air Quality.
Provides information on indoor-air pollutants, vulnerable groups and measures including source control, ventilation and filtration. It also reports that people spend approximately 90% of their time indoors.
United States Environmental Protection Agency. How does outdoor air enter a building?.
Explains how outdoor air enters buildings through natural ventilation, infiltration and mechanical ventilation.
United States Environmental Protection Agency. Particulate Matter (PM) Basics.
Defines PM₁₀ and PM₂.₅ and explains the relative size of fine particles compared with a human hair.
United States Environmental Protection Agency. Health and Environmental Effects of Particulate Matter.
Summarises the respiratory and cardiovascular health effects associated with exposure to particle pollution.
United States Environmental Protection Agency. Wildfires and Indoor Air Quality.
Explains how outdoor wildfire smoke and fine particles can enter homes and affect indoor air quality.
European Environment Agency, 2025. How air pollution affects our health.
Describes air pollution as Europe’s largest environmental health risk and outlines its links with stroke, COPD, asthma, respiratory infections and other diseases.
National Institute of Environmental Health Sciences. Indoor Air Quality.
Reviews potential health effects associated with short- and long-term exposure to indoor air pollution, including respiratory disease, heart disease and cognitive effects.
Engleitner, H., Suárez Pinilla, M., Rossor, M. et al., 2026. Topological modelling of urban air pollution and cognition. npj Digital Public Health, 1, Article 7.
An observational UK Biobank study examining geographical associations between urban air pollution and cognitive performance.
All online sources accessed 5 August 2026
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