Indoor pollution twice as high in Bradford’s most deprived households

After 4.5 years of a wide range of research activities, the INGENIOUS project has finally come to an end. The scheme was one of the most comprehensive studies to try and better understand air pollution in UK homes.

INGENIOUS stands for UnderstandING the sourcEs, traNsformations and fates of IndOor air pollUtantS.

The project aimed to:

• undertake the first comprehensive mapping exercise of the main sources, transformations and fate of air pollutants in typical UK residences
• identify inequalities in exposure and the consequent impacts on health amongst diverse populations
• identify the physical, social and behavioural factors that control pollutant distribution;
• co-design novel, scalable interventions to improve air quality and health

One of the BiB families (photo: Ian Beesley, of the Born in Bradford team)

To achieve all of these aims, we assembled an interdisciplinary team, which combined expertise in air pollution measurements and modelling, behavioural science, social science, health science and citizen science. The project was led by the University of York, and also involved the Universities of Manchester, Cambridge and Sheffield, the Born in Bradford Team (Bradford Teaching Hospitals NHS Foundation Trust) and the Stockholm Environment Instrument at York. We also had 8 project partners (Ricardo, WSP, Tincture, Reckitt, Immaterial, Homelink and NCAS (National Centre for Atmospheric Science)), who provided essential input to the research activities, attending progress meetings and contributing to research outputs. Together there were more than 40 team members working on the project in some capacity.

The INGENIOUS study built on the extensive, long-standing birth cohort study, ‘Born in Bradford (BiB)¹, which follows the health and wellbeing of over 12,500 families in Bradford. Women were recruited in pregnancy between 2007-2011; the families cover a range of social groups with fifty percent of mothers in the cohort of South Asian origin, and over half of all of the BiB families are living within the fifth most deprived areas of England and Wales (figure 1). All of the parents in the cohort are of working age, with one-third of families living in rented accommodation, and one-third of households with more than 5 occupants². The BiB team have followed this cohort extensively  over the years, and have access to routine primary and secondary health care records for the families, as well as education data and other routinely-linked data³. The BiB team has unprecedented access to families in Bradford, which significantly aided recruitment of families willing to have their indoor air quality sampled for the INGENIOUS project.

To achieve the project aims, we carried out a range of activities⁴. Our first workpackage (WP1) involved studies in experimental chambers at York, where we measured emissions from cooking and cleaning experiments. We measured emissions rates for 6 main meals (vegetarian and meat versions of chilli, stir-fry and curry) and additional information on heating oil and spices^5,6. Use of air-friers and fresh versus frozen ingredients was also investigated, as well as 20 different cleaning products, with a focus on anti-bacterial surface cleaners. We also investigated emissions from 13 homecare products, including plug-in diffusers, mist diffusers, bakoor, incense and scented candles

WP2 focused on measurements in occupied homes in Bradford between March 2023 and April 2024. Each home was sampled for about 2 weeks using a low-cost sensor, with residents also asked to keep a diary to note any activities that might lead to indoor air pollution (such as cooking and cleaning). We monitored 3 rooms in each house: the kitchen, the lounge and a bedroom, and measured carbon dioxide (CO₂) and fine particulate matter (PM2.5) concentrations, as well as temperature and relative humidity. In a subset of homes, we also installed research grade instrumentation (which was bigger and noisier) for 3 days to collect additional data.

WP3 involved driving a mobile laboratory around York and Bradford (figure 3), to try and understand whether emissions from activities indoors could be detected in outdoor urban areas. In particular, we were interested to understand whether emissions from restaurants, beauty salons, or auto-repair garages could impact outdoor air quality.

WP4 involved providing further insights from the measurements using state-of-the-art models, whilst WP5 looked at links between indoor air pollutants and health effects. WP6 aimed to design and test interventions to improve indoor air quality and WP7 focused on dissemination activities that ran throughout the project. You can read more about the experimental design and some of our preliminary findings in our recent overview paper⁴.

We have already found some interesting results, although we expect many more to come as we continue to analyse the data in more detail. Key findings so far are that:

• Peak daily PM₅ concentrations regularly exceeded WHO guidelines by more than a factor of 10 in the Bradford homes we sampled, and were driven by cooking activities^4,7
• The most deprived families in our sampled homes experienced indoor PM2.5 concentrations that were twice as high as those experienced by the least deprived families⁷
• Cooking and air freshener/diffuser were found to generate very high indoor concentrations of VOCs in our chamber experiments, hundreds of ppbs in some cases, and far greater than those typically experienced outdoors^5,6
• Carbon dioxide concentrations are often elevated in bedrooms at nighttime owing to poor ventilation (door closed, window closed)⁴
• Peak indoor concentrations were driven by internal activities (e.g. cooking) rather than the influence of outdoor air pollution. The latter only became important for indoor air quality in the absence of indoor activities
• There is a wide variability in air pollutant concentrations between households, highlighting the importance of understanding occupant behaviour
• Our mobile measurements showed that outdoor butanone and acetone concentrations showed robust associations with auto repair garages and beauty salons respectively⁸.

Although it wasn’t a focus of our study, we also found strong evidence that a portion of our sampled households were living in fuel poverty. As well as low internal temperatures in some houses, 7% of our households reported that they were never, or rarely, able to keep their house warm in winter. In fact, the INGENIOUS project has provided critical insights into winter underheating, fuel poverty, and the high rates of mould growth in homes across Bradford, reinforcing the need to address these challenges in line with key governmental priorities, particularly in the context of the UK’s ageing building stock, rising fuel costs, widening social inequalities, and the growing impacts of climate change.

Key facts and findings from the INGENIOUS project are summarised in our Insight document.

Acknowledgements: We would like to acknowledge funding for the INGENIOUS project from NERC through the following grant numbers: NE/W001993/1, NE/W002019/1, NE/W002159/1, NE/W002248/1 and NE/W002256/1. Born in Bradford is only possible because of the enthusiasm and commitment of the participating children and their parents. We are grateful to all participants, health professionals, schools and researchers who have made Born in Bradford happen.

References

1. The BiB Breathes project, n.d., ISRCTN – ISRCTN67530835: Born in Bradford Breathes: evaluating the health, air quality and economic impact of a city wide intervention to improve air quality.
2. Cohort Profile Update: Born in Bradford https://academic.oup.com/ije/article/53/2/dyae037/7637702?login=false
3. Connected Bradford: a Whole System Data Linkage Accelerator.
4. The INGENIOUS project: towards understanding air pollution in homes – Environmental Science: Processes & Impacts (RSC Publishing)
5. Chemical fingerprints of cooking emissions and their impact on indoor air quality – Environmental Science: Processes & Impacts (RSC Publishing)
6. Fingerprinting the emissions of volatile organic compounds emitted from the cooking of oils, herbs, and spices – Environmental Science: Processes & Impacts (RSC Publishing)
7. Inequalities and indoor air pollution: a prospective observational study of particulate matter (PM2.5) levels in 309 UK homes from the Born in Bradford cohort study | BMC Public Health
8. Toward Linking Indoor Commercial Source Emissions to Outdoor Volatile Organic Compounds Using Mobile Measurements | ACS ES&T Air