Assessing children’s exposure to air pollution: Implications for health, and health inequality across communities.

Air pollution is the world’s largest single environmental health risk (World Health Organization, 2014) and in the UK alone is it estimated that over 30,000 people die prematurely due to exposure to outdoor air pollution (Wise, 2018; Lelieveld et al., 2019).  Although air pollution affects everyone, children and pregnant women are among the most vulnerable to the adverse health effects of pollution, with exposure to air pollution linked to the development of asthma, reduced lung function, cardiovascular disease and some cancers (WHO, 2016).  The costs to the NHS of air quality related illnesses between 2017-2025 is estimated to be £5.56 billion (Public Health England, 2018) with the wider economic cost estimated to be £20 billion/year (Royal College of Physicians, 2016).

Pollution levels vary across urban areas, but air quality is typically worse in areas of high economic deprivation (e.g. communities close to busy roads, areas with little greenspace, (Fecht et al., 2015)).  This is particularly important for child health as economically deprived areas often have higher than average numbers of children living in them.

One of the main barriers in assessing the health impacts of air pollution on children is lack of knowledge of the individual’s exposure to pollution.  Traditional approaches to quantifying exposure to air pollution assume that concentrations of air pollutants at the residential address of the study population are representative for overall exposure (Reis et al., 2018).  This is attractive as it allows analysis of the exposure to entire populations, but is clearly unrepresentative in most cases.  One way to address this is to carry out “personal exposure monitoring” in which individual members carry pollution monitors, so their exposure can be tracked accurately (Kaur, Nieuwenhuijsen and Colvile, 2005; Steinle, Reis and Sabel, 2013).  While this is an attractive option, it is much more resource intensive, and for reasons of practicality can only be carried out for limited periods.

In this PhD project the student will investigate children’s exposure to air pollution, initially focusing on personal exposure data, and then investigate methods to upscale this data to groups of children / communities, in order to significantly improve assessment of children’s exposure to air pollution.  The student can then investigate different exposure scenarios (using modelled fields of air pollution), and investigate health inequalities, opportunities for exposure reduction and potential health effects for children across the city.

Study Area

The project will focus on children living in the city of Bradford.  Home to 350,000 people, including 100,000 children, Bradford is an area with high levels of health need, deprivation and a multi-ethnic population (67% White British, 20% Pakistani). It also has some of the highest rates of ill health and inequality in the UK; the area suffers from high mortality from cardiovascular disease under 75 years (102.2 per 100,000), high numbers of low birth weight babies (3.6%), and 22% incidence of wheezing disorders amongst children.  The area also has high levels of air pollution; NO2 levels frequently exceed legal limits, and PM2.5 levels often exceed international recommendations.

Bradford is also home to the largest birth cohort study in the UK: the Born in Bradford study has tracked health, social and economics metrics in a detailed birth cohort study of 12,500 families with >13,500 children born between 2007-2011.  Born in Bradford also provides an infrastructure which provides a research-ready routine-linked administrative health and social care dataset of >500,000 Bradford residents (Connected Health Cities, CHC).  Born in Bradford have already found that up to 33% of childhood asthma cases in Bradford are associated with air pollution (Khreis et al., 2019) and that babies born in areas of high air pollution tend to have reduced birth weight; a common indicator of potential future ill health (Pedersen et al., 2013).  A summary of BiB’s key findings so far can be found here.

To address the high air pollution in the city, Bradford Council plan to introduce a Clean Air Zone (CAZ) to reduce vehicular emissions in the city, and improve air quality across the region.  This intervention is planned for late 2021.  It is expected that within the CAZ pollutant concentrations will be reduced by ~ 25%.  CAZs are an increasingly popular form of pollution control, London is already home to a low emission zone, with further zones planned for the 10 Local Authority Areas in England that were found to exceed legal concentrations of air pollution.   Although the CAZ is expected to significantly reduce pollution within the zone area, little research has been done the effectiveness of CAZs in terms of reducing the people’s exposure to pollution, and identifying and quantifying the subsequent health benefits (NICE, 2017).  The implementation of the CAZ in Bradford, alongside the comprehensive structures for health data, provided by Born in Bradford provides a unique opportunity to investigate exposure to air pollution, behavioural changed and health effects of the intervention.

Air Quality Modelling

During the planning phase of the CAZ, Bradford Council commissioned Ricardo Plc to conduct detailed modelling studies to investigate the effect of different potential 5 different CAZ designs on concentrations of nitrogen oxides (NOx), nitrogen dioxide (NO2), sulfur dioxide (SO2) and carbon monoxide (CO) and particulates (PM10 and PM2.5) across the city in (i) present day, (ii) near future and (iii) distant future scenarios.  The gridded model output provides high resolution (between 1 and 3 meters) output for the city of Bradford and surrounding areas.  The RapidAIR model used is an established dispersion model, which has been used extensively for air quality studies (Masey, Hamilton and Beverland, 2018).  The student will use these different scenarios to calculate the exposure of the simulated individuals moving through the city, and in this way calculate the change in exposure of subgroups of the population due to the CAZ.

Personal Exposure Monitoring

To investigate the effect of the CAZ on children’s exposure, Born in Bradford (BiB)and the University of Leeds have designed an extensive schools based personal exposure monitoring campaign in which 120 school children will wear pollution monitors during their normal activities for 3 X 1 month periods.  This experiment will be carried out twice: once in the year before, and again after the year after, the introduction of the Bradford CAZ.  This ambitious project is one of the largest air quality pollution citizen science project ever attempted; and the only one where the focus is on a cohort of children /for which rich health data exists.  BiB will also place static air quality sensors in school playgrounds across Bradford (within, at the edge of, and outside of the CAZ) for the full two-year period.

Figure 1 Trial personal exposure monitoring with pupils in Bradford and Leeds

The data from the personal exposure study done before the CAZ will be used to identify behavioural patterns, e.g. typical distance to school, route taken which can be used to develop a statistical approach to calculate exposure of a population from the modelled data.   It can also be used to investigate periods of peak exposure, and indentify potential behavioural or policy changes that would significantly reduce children’s exposure (e.g. walk through park compared to along road).

 

Objectives

 

The key aim of this study is to develop an approach which will allow us to upscale detailed personal exposure monitoring studies (done before the CAZ) to allow estimation of the exposure of vulnerable sub-groups of the population (initially primary school children).  In initial work, the PhD study the student will analyse the data from the personal exposure monitoring experiment, alongside detailed modelled data from Bradford Council, and data from air quality monitoring site, to address the following broad research questions:

 

  • How does data from the personal exposure monitoring compare to traditional estimates from static data? The student will investigate biases between exposure calculated using the traditional approach (using the air pollution concentration at the home postcode) and the citizen science approach.  This could include analysis of the difference between indoor and outdoor exposure, exposure during travel and sub grid variability and non-linear exposure profiles. This will be done before the implementation of the CAZ (and could potentially be repeated after the CAZ).
  • How can the citizen science data be up-scaled to create representative population estimates? Detailed personal exposure monitoring can only give a snap shot of the exposure of the population, the student will investigate informed methods for scaling up this data to create more comprehensive estimates of the exposure of different subgroups of the population.  This will be done using behavioural data collected by Born in Bradford, census data and model simulations.  The aim is to develop a statistical approach that will enable us to bridge the gap between citizen science and the community / city scales.
  • Investigate the health and economic benefits of the CAZ using the statistical population exposure approach (developed above). Once we have developed a statistical approach to view the movement of Bradford’s children around the city. The approach can be used to estimate a population based change in exposure in Bradford’s children in the different modelled CAZ scenarios.  This would be a new and exciting way to look at the effect of an intervention on local populations, and would supplement field research to evaluate exposure change using citizen science.  The Cost-effectiveness of Air Pollution Reduction model (CAPTOR) model could be used to investigate health and economic benefit.  The student could also make use of the rich dataset held Born in Bradford have data on children obesity, asthma and cognitive development as key ones, geocoded to children’s home address.
  • What are the implications for health inequality in Bradford’s children? The socio-economic data health by Born in Bradford, combined with publicly available data, can be used to investigate the ramifications of the CAZ on health inequality – often the poorest in society live in the most polluted areas, but relatively little research has been done on the extent to which exposure is affected by economic status, and thus the health implications. By focusing in detail on a well characterised population, where extensive health and social data exists, this project can address the scope for reducing health inequality, in Bradford and later across the UK.

 

Potential for High Impact Outcomes

Research into the health impact of air pollution is of extreme importance, this is reflected in recent high profile funding streams from UKRI which have focused on research to identify and quantify the health impacts of air pollution, and developing strategies and interventions to reduce detrimental effects.  This project focuses on one of the key uncertainties in this field – understanding people’s exposure to air pollution.  By developing a method to upscale from individual exposure measurements to population levels assessments this project will greatly increase the impact of individual “personal exposure studies”.  The CASE partnership with Bradford Council, alongside the already developed relationship with Born in Bradford, will provide a direct pathway to impact, and regular meetings with the CASE partner will ensure that research is targeted to be informative to those developing legislation and health interventions.

Training

The student will be supervised by an interdisciplinary team comprising Dr Kirsty Pringle, Dr Jim McQuaid and Dr Rosie McEachan. Due to the multiple disciplines represented by the project team, there is a wide variety of opportunities for training in advanced techniques.  This includes: (i) modelling of air pollution, (ii) statistical modelling of the behaviour of a population, (iii) collection and analysis of environmental data (iv) mixed methods research that incorporates quantitative and qualitative social science approaches, (v) epidemiological data analysis of large datasets.

Co-supervision will involve regular meetings between all supervisors and key partners at Bradford Council (Sally Jones). The student will also spend one or more extended stays at Born in Bradford, working alongside health researchers on tasks specific to the project.

The successful PhD student will have access to a broad spectrum of training workshops put on by the faculty of the Environment that include an extensive range of training workshops in numerical modelling, scientific data analysis, through to managing your degree and to preparing for your viva.

Case Partner

The proposal has been agreed as a CASE project with Bradford Council providing extra funding additional to the NERC student stipend. The project builds on recent collaborations between the University of Leeds, Born in Bradford and Bradford Council.  Born in Bradford will provide access to data, expert advice on qualitative research done with community groups in the city, and the infrastructure to utilise and interpret this data. Bradford Council will share their experience in city scale modelling, including modelling of the health and economic impacts of different emissions scenarios.

Student Profile

This multidisciplinary project could attract a student from a wide range of background, and there is scope to tailor the project to the student’s interests.  Whatever their background, the student should have a strong interest in atmospheric science, population geography, development of statistical tools and interdisciplinary, impactful research.   We would welcome applicants from any scientific background (including chemistry, physics, geography and environmental science).  The student will develop skills in statistics and programming, so any previous experience in these fields would be advantageous.  An interest in public engagement and co-developed research would also be advantageous, as would experience of working with community groups.

References

Fecht, D. et al. (2015) ‘Associations between air pollution and socioeconomic characteristics, ethnicity and age profile of neighbourhoods in England and the Netherlands’, Environmental Pollution. Elsevier Ltd, 198, pp. 201–210. doi: 10.1016/j.envpol.2014.12.014.

Kaur, S., Nieuwenhuijsen, M. and Colvile, R. (2005) ‘Personal exposure of street canyon intersection users to PM2.5, ultrafine particle counts and carbon monoxide in Central London, UK’, Atmospheric Environment, 39(20), pp. 3629–3641. doi: 10.1016/j.atmosenv.2005.02.046.

Khreis, H. et al. (2019) ‘Traffic-related air pollution and the local burden of childhood asthma in Bradford, UK’, International Journal of Transportation Science and Technology. Elsevier BV, 8(2), pp. 116–128. doi: 10.1016/j.ijtst.2018.07.003.

Lelieveld, J. et al. (2019) ‘Cardiovascular disease burden from ambient air pollution in Europe reassessed using novel hazard ratio functions’, European Heart Journal. Oxford University Press, 40(20), pp. 1590–1596. doi: 10.1093/eurheartj/ehz135.

NICE (2017) ‘Overview | Air pollution: outdoor air quality and health’. NICE.

Pedersen, M. et al. (2013) ‘Ambient air pollution and low birthweight: a European cohort study (ESCAPE).’, The Lancet. Respiratory medicine, 1(9), pp. 695–704. doi: 10.1016/S2213-2600(13)70192-9.

Public Health England (2018) Estimation of costs to the NHS and social care due to the health impacts of air pollution: summary report About Public Health England. Available at: www.facebook.com/PublicHealthEngland (Accessed: 23 September 2019).

Reis, S. et al. (2018) ‘The influence of residential and workday population mobility on exposure to air pollution in the UK’. doi: 10.1016/j.envint.2018.10.005.

Royal College of Physicians (2016) Every breath we take: the lifelong impact of air pollution | RCP London. Available at: https://www.rcplondon.ac.uk/projects/outputs/every-breath-we-take-lifelong-impact-air-pollution (Accessed: 23 September 2019).

Steinle, S., Reis, S. and Sabel, C. E. (2013) ‘Quantifying human exposure to air pollution-Moving from static monitoring to spatio-temporally resolved personal exposure assessment’, Science of the Total Environment, pp. 184–193. doi: 10.1016/j.scitotenv.2012.10.098.

‘WHO | Ambient air pollution: A global assessment of exposure and burden of disease’ (2016) WHO. World Health Organization.

Wise, J. (2018) ‘Air pollution may claim 36 000 lives a year in UK’, BMJ (Clinical research ed.). NLM (Medline), 362, p. k3632. doi: 10.1136/bmj.k3632.