Systemic inequalities driving exposure to high indoor air pollution

The study, conducted by researchers at UCL, said the biggest contributing factors in this are the quality of housing and the characteristics of the surrounding environment, taking location and levels of outdoor air pollution into account – factors beyond occupants’ control.

For the study, the researchers used available data and models, assembling evidence to examine five factors explaining why lower socio-economic groups may be exposed to higher levels of indoor air pollution in their homes, focusing on London and the pollutants PM2.5, NOx, and CO. The researchers selected such pollutants to analyse because they are primarily produced by combustion processes, such as cooking or burning fuel, and are therefore found in most households.

Factors of the study included housing location and ambient outdoor levels of pollution, housing characteristics including ventilation properties and internal sources of pollution, occupant behaviours, time spent indoors, and underlying health conditions. They also focused on pollutants in London because housing there isn’t typically representative of the rest of the country, with a higher proportion of renters and flats as dwellings.

The team used a systems approach highlighting interactions and links between factors to show how they lead to systemic exposure inequalities, with lower-income households having limited opportunities to improve their indoor air quality.

“This research highlights that exposure to indoor air pollution can lead to health inequalities depending on socio-economic status,” said lead author of the study Lauren Ferguson. “Differences in housing quality and characteristics of the surrounding areas mean low-income households are likely to bear a disproportionate risk of elevated exposure to indoor air pollution.”

Ferguson, a PhD candidate at UCL Energy Institute and UCL Institute for Environmental Design & Engineering, added: “Poor-quality housing can lead to several negative health effects and is, therefore, an area which should be targeted in order to address the growing health inequalities gap in the UK.”

Air pollution exposure is the greatest environmental health threat in the UK, experts have said, with long-term exposures estimated to cause 28,000-36,000 premature deaths a year. Experts have also associated it with health problems such as respiratory and cardiovascular complications, birth defects, childhood asthma cases, and sudden infant deaths. The study also suggests it can link to adult depression, but there is yet to be more research on this.

Low socioeconomic status (SES) groups are more likely to live in higher-density flats and smaller dwellings and areas of London with higher levels of air pollution, the researchers said. While high-density dwellings often have lower ventilation levels, which can prevent some outdoor air pollution from getting in, this does not offset living in an area of high outdoor pollution. Dwellings with low levels of ventilation prevent indoor air pollution from activities including cooking and smoking from escaping and are more vulnerable to local pollution from neighbours’ cooking or smoking.

The researchers added that low SES groups are more likely to spend less time outdoors, because of a variety of factors including higher levels of unemployment, fewer after-school clubs, and little access to green spaces. This raises their susceptibility to developing health conditions from increased exposure to indoor air pollution.

They are also at a higher risk of experiencing underlying health conditions, material deprivation, and psychological stress, making them more susceptible to air pollution. Material deprivation includes lack of access to healthcare, poor diet – which is strongly linked to income class – and lack of physical activity, which is linked to spending more time indoors.

Recently, researchers at Edinburgh University published a study that suggested exposure to air pollution in childhood is linked to a decline in thinking skills in later life.