Air pollution levels may be higher inside your home than outside

People may be exposed to unhealthy levels of airborne pollutants inside their homes, even if the outdoor air quality is good, a new study reveals.  

Researchers at the University of Birmingham used low-cost sensors and innovative techniques over a two-week period to compare particulate matter (PM) in three homes – discovering that pollution levels in each house were higher and more variable than outdoor levels.  

They found significant differences in PM levels between the three houses, with one home exceeding World Health Organisation (WHO) 24-hour PM2.5 limit on nine days - highlighting the importance of monitoring indoor air quality at a household-specific level. 

Published in Scientific Reports, this is the second paper published by McCall MacBain Clean Air Fellows studying on the philanthropically funded Master’s degree in Air Pollution Management and Control at the University of Birmingham.  

Co-author and Clean Air Fellow Catrin Rathbone commented: “Our study shows the need to monitor indoor air pollution, as people can have unhealthy air at home even if outdoor air is good. PM levels varied significantly between homes, indicating that monitoring just one location isn’t enough.” 

The team note that factors such as household location, ventilation, and occupancy patterns influenced particle levels - demonstrating the complexity of indoor air quality.  

Co-author and Clean Air Fellow Owain Rose commented: “With more time spent working from home, understanding the factors that affect air quality within households is increasingly important. The methods we used accurately modelled indoor PM levels, helping to improve exposure estimates at a low cost.” 

Researchers identified five different factors contributing to PM in indoor spaces - two relating to indoor activities, such as increased movement by residents and three linked to external factors such as a nearby restaurant's kitchen vent. They found that larger particles (PM10) tended to settle faster compared to smaller particles (PM1, PM2.5). 

The three households studied are within the Selly Oak area of Birmingham – 4km southwest of the city centre. Each house is occupied by four/five people- all with gas central heating and a gas-fired combined hob and oven. 

Researchers used Non-negative Matrix Factorization (NMF) - a powerful tool for uncovering latent patterns in data - to more accurately model indoor PM levels. Using low-cost sensors enabled them to build a more detailed picture of pollutant levels within the properties. 

Co-author Professor Francis Pope commented: “Our approach is easily scaled due to its low cost and would allow air quality management in homes across Britain and beyond. This could lead to more accurate pollution exposure models and better-informed public health policies.”  

Imogen Martineau from University partners the Clean Air Fund stated: “It has been amazing to see the continuing success of the first Clean Air Fellow cohort. Owain and Catrin have been amazing ambassadors, and it is great to see them continuing their clean air journeys through taking jobs with leading environmental consultancies that specialise in air quality.” 

The University of Birmingham is at the forefront of research on the causes and effects of air pollution upon human health across the United Kingdom and globally. Birmingham has over 100 researchers studying clean air from across its five colleges. The campus also operates state-of-the-art pollution research facilities, which have been commissioned for several seminal air pollution studies. 

ENDS 

For more information, please contact Tony Moran, International Communications Manager, University of Birmingham on +44 (0)782 783 2312 or t.moran@bham.ac.uk. For out-of-hours enquiries, please call +44 (0) 7789 921 165. 

Notes to editor: 

• The University of Birmingham is ranked amongst the world’s top 100 universities institutions. Its work brings people from across the world to Birmingham, including researchers, teachers and more than 8,000 international students from over 150 countries.  

• “Using low-cost sensors to assess common air pollution sources across multiple residences” - Catrin J. Rathbone, Dimitrios Bousiotis, Owain G. Rose, and Francis D. Pope is published in Scientific Reports.