• Only 20% of monitored days (227 out of 1109 days) were below the World Health Organisation 24-hour PM2.5 exposure health guideline of 15 μg/m³.

• Highest PM2.5 exposure was monitored at Blantyre, Malawi (median 41.8 µg/m³).

• Factors for higher PM2.5 exposure: presence of smokers at home, use of coal or wood for cooking, and kerosene lamps for lighting.

• Lower PM2.5 exposures found for children who attended schools with paved grounds compared to those with grounds covered with loose dirt.

Research overview

Dyson engineers worked in conjunction with Children’s Air Pollution Profiles in Africa (CAPPA) , arm of the Achieving Control of Asthma in Children in Africa study led by Queen Mary University London (QMUL) and Imperial College London to understand personal air quality exposure across six African cities. The Dyson air quality monitoring backpacks was at the heart of this endeavour; the backpack was carried by 297 urban school children aged between 12 and 15 years. with asthma between 21^st June and 26^th November, 2021. Data was collected from each participating child in Ghana, Malawi, Nigeria, South Africa, Tanzania, Uganda and Zimbabwe, making it the largest study of its kind.

Each Dyson air quality monitoring backpack features on-board sensors, a battery pack and GPS, allowing data to be collected on the go and matched to location. Re-working existing sensing technology used in Dyson air purifiers, engineers designed the portable air monitoring device, engineering it to be smaller, lighter, and more portable, whilst still accurately capturing PM2.5, PM10 and VOCs and NO₂ exposure.

In Africa, air pollution ranks as the second-largest health risk, contributing to 1.1 million annual deaths¹, with children suffering from asthma being notably susceptible. Despite this, and like much of the world, the region lacks sufficient air pollution exposure data, as prior studies predominantly focused on rural areas and household air pollution, leaving uncertainties about urban exposure magnitudes and sources.

Key Findings

The Dyson air quality monitoring backpacks were used during weekdays (Monday 10am to Friday 10am) to monitor the children’s PM2.5 exposure at one second intervals. Mean daily exposure values were then calculated for each child, providing an overview of their overall exposure on that specific day. 

Only 20% of monitored days adhered to the World Health Organisation short term PM2.5 exposure guideline of 15 μg/m³. Exposure levels varied across cities, with Blantyre, Malawi recording the highest exposure (median 41.8 µg/m³), and Durban, South Africa (16.0 µg/m³) reporting the lowest . Exposure patterns also varied, with some cities demonstrating higher exposures at school (Kumasi, Lagos, Moshi), while others demonstrated higher exposures at home and during commuting (Blantyre, Durban, Harare).

Determinants for higher PM2.5 exposure included the presence of smokers at home, the use of coal or wood for cooking, and kerosene lamps for lighting. Lower exposures were associated with schools with paved ground compared to schools covered with loose dirt likely due to the decreased level of dust. The study’s recommendations highlight the necessity for effective changes, including providing paving in school grounds, promoting clean fuel for cooking and lighting in homes, and discouraging smoking within homes.

Future implications

This study’s findings provide valuable insights for mitigating PM2.5 exposure in urban areas of sub-Saharan Africa, especially amongst children with respiratory conditions such as asthma. Whilst overarching air quality improvement policies remain essential, the use of Dyson air quality monitoring backpacks has allowed pinpointing specific microenvironments with higher exposure levels.

This precision allows for targeted interventions, emphasising the importance of addressing issues in places such as schools, where elevated exposure is linked to dust released from unpaved grounds. The research stresses the necessity for focused strategies, in contrast to generic air pollution reduction policies, to effectively diminish children's daily exposure to PM2.5. 

Read the full research paper here