Ingenious: UnderstandING the sourcEs, traNsformations and fates of IndOor air pollUtantS

In developed countries such as the UK, we spend 90% of our time indoors with approximately two thirds of this in our homes. Despite this fact, most air pollutant regulation focuses on the outdoor environment. There is increasing evidence that exposure to air pollution causes a range of health effects, but uncertainties on the causal effects of individual pollutants on specific health outcomes still exist partly due to crude exposure metrics. Nearly all studies of health effects to date have used measurements from fixed outdoor air pollution monitoring networks, a procedure that ignores the modification effects of indoor microenvironments where people spend most of their time. There are consequently large uncertainties surrounding human exposure to indoor air pollution, which means we are currently unable to identify the most effective solutions to design, operate and use our homes to minimise our exposure to air pollution within them. In the UK, there are virtually no data to quantify indoor air pollutant emissions, building-to-building variability of these, chemical speciation of indoor pollutants, ingress of outdoor pollution indoors or of indoor generated pollutants outdoors, or the social, economic or lifestyle factors that can lead to elevated pollutant exposures. Without a fundamental understanding of how indoor air pollution is caused, transformed and distributed in UK homes, research aiming to develop behavioural, technical or policy interventions may have little impact, or at worst be counterproductive. For example, energy efficiency measures are broadly designed to make buildings more airtight. However, given that the concentrations of many air pollutants are often higher indoors than outdoors, reducing ventilation rates may increase our exposure to air pollution indoors and to any potentially harmful effects of the resulting pollutant mixture. Further, if interventions are introduced without sufficient consideration of how occupants actually use and behave in a building, they may fail to achieve the desired effect. To understand and improve indoor air quality (IAQ), we must adopt a systems approach that considers both the home and the human. There is a particular paucity of data for the most deprived households in the UK. There is a facile assumption that poorer homes are likely to experience worse IAQ than better off households, although the reality may be considerably more nuanced. Lower quality housing may be leakier than more expensive homes allowing indoor emissions to escape more easily, whilst large, expensive town-houses converted to flats can be badly ventilated following poor retrofitting practices. Differences in cooking practices, smoking rates, internal building materials and the usage of solvent containing products indoors will also be subject to wide variations across populations and hence have differential effects on IAQ and pollutant exposure. In fact, differences in individual behaviour lead to large variations in indoor concentrations of air pollutants even for identical houses, typically driven by the frequency and diversity of personal care product use. The INGENIOUS project will provide a comprehensive understanding of indoor pollution in UK homes, including i) the key sources relevant to the UK ii) the variability between homes in an ethnically diverse urban city, with a focus on deprived areas (using the ongoing Born in Bradford cohort study) iii) the effects of pollutant transformation indoors to generate by-products that may adversely affect health iv) the drivers of behaviours that impact on indoor air pollution (v) recommendations for interventions to improve IAQ that we have co-designed and tested with community members.