Jonathon Taylor

Impact of climate change on the domestic indoor environment and associated health risks in the UK

There is growing evidence that projected climate change has the potential to significantly affect public health. In the UK, much of this impact is likely to arise by amplifying existing risks related to heat exposure, flooding, and chemical and biological contamination in buildings. Identifying the health effects of climate change on the indoor environment, and risks and opportunities related to climate change adaptation and mitigation, can help protect public health. We explored a range of health risks in the domestic indoor environment related to climate change, as well as the potential health benefits and unintended harmful effects of climate change mitigation and adaptation policies in the UK housing sector. We reviewed relevant scientific literature, focusing on housing-related health effects in the UK likely to arise through either direct or indirect mechanisms of climate change or mitigation and adaptation measures in the built environment. We considered the following categories of effect: (i) indoor temperatures, (ii) indoor air quality, (iii) indoor allergens and infections, and (iv) flood damage and water contamination. Climate change may exacerbate health risks and inequalities across these categories and in a variety of ways, if adequate adaptation measures are not taken. Certain changes to the indoor environment can affect indoor air quality or promote the growth and propagation of pathogenic organisms. Measures aimed at reducing greenhouse gas emissions have the potential for ancillary public health benefits including reductions in health burdens related heat and cold, indoor exposure to air pollution derived from outdoor sources, and mould growth. However, increasing airtightness of dwellings in pursuit of energy efficiency could also have negative effects by increasing concentrations of pollutants (such as PM2.5, CO and radon) derived from indoor or ground sources, and biological contamination. These effects can largely be ameliorated by mechanical ventilation with heat recovery (MVHR) and air filtration, where such solution is feasible and when the system is properly installed, operated and maintained. Groups at high risk of these adverse health effects include the elderly (especially those living on their own), individuals with pre-existing illnesses, people living in overcrowded accommodation, and the socioeconomically deprived. A better understanding of how current and emerging building infrastructure design, construction, and materials may affect health in the context of climate change and mitigation and adaptation measures is needed in the UK and other high income countries. Long-term, energy efficient building design interventions, ensuring adequate ventilation, need to be promoted.

The transmission of Mycobacterium tuberculosis in high burden settings

Unacceptable levels of Mycobacterium tuberculosis transmission are noted in high burden settings and a renewed focus on reducing person-to-person transmission in these communities is needed. We review recent developments in the understanding of airborne transmission. We outline approaches to measure transmission in populations and trials and describe the Wells-Riley equation, which is used to estimate transmission risk in indoor spaces. Present research priorities include the identification of effective strategies for tuberculosis infection control, improved understanding of where transmission occurs and the transmissibility of drug-resistant strains, and estimates of the effect of HIV and antiretroviral therapy on transmission dynamics. When research is planned and interventions are designed to interrupt transmission, resource constraints that are common in high burden settings-including shortages of health-care workers-must be considered.

Flood management: prediction of microbial contamination in large-scale floods in urban environments.

With a changing climate and increased urbanisation, the occurrence and the impact of flooding is expected to increase significantly. Floods can bring pathogens into homes and cause lingering damp and microbial growth in buildings, with the level of growth and persistence dependent on the volume and chemical and biological content of the flood water, the properties of the contaminating microbes, and the surrounding environmental conditions, including the restoration time and methods, the heat and moisture transport properties of the envelope design, and the ability of the construction material to sustain the microbial growth. The public health risk will depend on the interaction of these complex processes and the vulnerability and susceptibility of occupants in the affected areas. After the 2007 floods in the UK, the Pitt review noted that there is lack of relevant scientific evidence and consistency with regard to the management and treatment of flooded homes, which not only put the local population at risk but also caused unnecessary delays in the restoration effort. Understanding the drying behaviour of flooded buildings in the UK building stock under different scenarios, and the ability of microbial contaminants to grow, persist, and produce toxins within these buildings can help inform recovery efforts. To contribute to future flood management, this paper proposes the use of building simulations and biological models to predict the risk of microbial contamination in typical UK buildings. We review the state of the art with regard to biological contamination following flooding, relevant building simulation, simulation-linked microbial modelling, and current practical considerations in flood remediation. Using the city of London as an example, a methodology is proposed that uses GIS as a platform to integrate drying models and microbial risk models with the local building stock and flood models. The integrated tool will help local governments, health authorities, insurance companies and residents to better understand, prepare for and manage a large-scale flood in urban environments.

Urban social housing resilience to excess summer heat

The potential levels of exposure to indoor overheating in an urban environment are assessed for vulnerable social housing residents. Particular focus is given to the synergistic effects between summertime ventilation behaviour, indoor temperature and air pollutant concentration in relation to energy retrofit and climate change. Three different types of social housing are investigated (1900s’ low-rise, 1950s’ mid-rise and 1960s’ high-rise). The case study dwellings are located in Central London and occupied by vulnerable individuals (elderly and/or people suffering from ill-health or mobility impairment). Indoor temperature monitoring suggests that occupants are already exposed to some degree of overheating; the highest levels of overheating occur in 1960s’ high-rise tower blocks. The thermal and airflow performance simulation of a mid-floor flat in the 1960s’ block under the current and projected future climate indicates that improved natural ventilation strategies may reduce overheating risk to a certain extent, with night cooling and shading being slightly more effective than all-day rapid ventilation. However, their potential may be limited in future due to high external temperatures and the undesired ingress of outdoor pollutants. This highlights the need for the development of combined strategies aiming to achieve both indoor thermal comfort and air quality.

The modifying effect of the building envelope on population exposure to PM2.5 from outdoor sources

A number of studies have estimated population exposure to PM2.5 by examining modeled or measured outdoor PM2.5 levels. However, few have taken into account the mediating effects of building characteristics on the ingress of PM2.5 from outdoor sources and its impact on population exposure in the indoor domestic environment. This study describes how building simulation can be used to determine the indoor concentration of outdoor-sourced pollution for different housing typologies and how the results can be mapped using building stock models and Geographical Information Systems software to demonstrate the modifying effect of dwellings on occupant exposure to PM2.5 across London. Building archetypes broadly representative of those in the Greater London Authority were simulated for pollution infiltration using EnergyPlus. In addition, the influence of occupant behavior on indoor levels of PM2.5 from outdoor sources was examined using a temperature-dependent window-opening scenario. Results demonstrate a range of I/O ratios of PM2.5, with detached and semi-detached dwellings most vulnerable to high levels of infiltration. When the results are mapped, central London shows lower I/O ratios of PM2.5 compared with outer London, an apparent inversion of exposure most likely caused by the prevalence of flats rather than detached or semi-detached properties.

The persistence of flood-borne pathogens on building surfaces under drying conditions.

Previous research into microbial persistence on material surfaces following flooding has produced a wide range of results due to differing experimental conditions, including the temperature and humidity conditions of the experimental material and/or surrounding air. However, investigations to identify and quantify these factors and their links to the hygrothermal properties of building materials and the transient environmental conditions are rarely reported. This paper examines the viability of bacterial species on drying material surfaces that have been saturated with water or synthetic sewage. Escherichia coli and Enterococcus faecalis were inoculated on brick, wood, or plaster and allowed to dry at the conditions intended to mimic the remediation environments commonly found in domestic dwellings following a flood event. The inactivation rates were compared between environmental conditions, water type and the material properties of the surfaces. Significant differences were found in the declines in E. coli according to water type, the surface relative humidity and air relative humidity and between drying rates for sewage floods. Simulations using hygrothermal software were performed to illustrate the wide variation in material drying rates under different scenarios, taking into account material size, wall composition, and ventilation. The significantly differing rates of microbial death on flooded building materials under different drying regimes suggest that building simulation models can be useful tools for predicting the level and duration of microbial contamination in buildings following a flood event. A better understanding of microbial survival on drying surfaces can be used to assess the health risks to occupants in flood affected properties.

Understanding and mitigating overheating and indoor PM2.5 risks using coupled temperature and indoor air quality models

Indoor temperature and air quality in dwellings are closely coupled. Differences between the indoor temperature and the temperature outside and in adjoining zones can influence airflow due to the stack effect, whilst changes in ventilation can cause changes in indoor pollution and temperature. This paper demonstrates the relationship between an indoor air pollutant, PM2.5, and temperature in UK domestic building archetypes using the dynamic thermal and contaminant modelling capabilities of EnergyPlus 8.0 under various UK Climate Projections 2009 (UKCP09) scenarios (current, current ‘hot’, 2050 High Emissions and 2050 High Emissions ‘hot’), with both internal and external PM2.5 sources. Results indicate that flats have 0.7–0.8 times as much outdoor PM2.5 infiltrating indoors compared to detached dwellings, but 1.8–2.8 times more PM2.5 from indoor sources. During hot periods, temperature-dependent window opening increases exposure to outdoor PM2.5, meaning that as temperatures rises, dwelling occupants will become exposed to relatively higher levels of outdoor PM2.5 and lower levels of indoor PM2.5 due to the need to increase dwelling ventilation. The practical implications for government and designers and possible policy implications of this research are discussed. Practical applications : This paper demonstrates how an increase in summertime ventilation is necessary in UK homes to reduce overheating risks due to climate change and energy-efficient building retrofits. This, in turn, will lead to a change in the profile of indoor air pollution exposure, with greater exposure to pollution from outdoor sources and reduced exposure to pollution from indoor sources. Roof insulation and trickle vents reduce overheating risk, whilst increased use of mechanical ventilation heat recovery systems in the UK is encouraged, as it offers the co-benefits of cooling through increased ventilation, energy recovery and the potential to reduce indoor pollution levels.

Overheating in English dwellings: comparing modelled and monitored large-scale datasets

ABSTRACT Monitoring and modelling studies of the indoor environment indicate that there are often discrepancies between simulation results and measurements. The availability of large monitoring datasets of domestic buildings allows for more rigorous validation of the performance of building simulation models derived from limited building information, backed by statistical significance tests and goodness-of-fit metrics. These datasets also offer the opportunity to test modelling assumptions. This paper investigates the performance of domestic housing models using EnergyPlus software to predict maximum daily indoor temperatures over the summer of 2011. Monitored maximum daily indoor temperatures from the English Housing Survey’s (EHS) Energy Follow-Up Survey (EFUS) for 823 nationally representative dwellings are compared against predictions made by EnergyPlus simulations. Due to lack of information on the characteristics of individual dwellings, the models struggle to predict maximum temperatures in individual dwellings and performance was worse on days when the outdoor maximum temperatures were high. This research indicates that unknown factors such as building characteristics, occupant behaviour and local environment makes the validation of models for individual dwellings a challenging task. The models did, however, provide an improved estimate of temperature exposure when aggregated over dwellings within a particular region.

Land cover and air pollution are associated with asthma hospitalisations: A cross-sectional study

BACKGROUND There is increasing policy interest in the potential for vegetation in urban areas to mitigate harmful effects of air pollution on respiratory health. We aimed to quantify relationships between tree and green space density and asthma-related hospitalisations, and explore how these varied with exposure to background air pollution concentrations. METHODS Population standardised asthma hospitalisation rates (1997-2012) for 26,455 urban residential areas of England were merged with area-level data on vegetation and background air pollutant concentrations. We fitted negative binomial regression models using maximum likelihood estimation to obtain estimates of asthma-vegetation relationships at different levels of pollutant exposure. RESULTS Green space and gardens were associated with reductions in asthma hospitalisation when pollutant exposures were lower but had no significant association when pollutant exposures were higher. In contrast, tree density was associated with reduced asthma hospitalisation when pollutant exposures were higher but had no significant association when pollutant exposures were lower. CONCLUSIONS We found differential effects of natural environments at high and low background pollutant concentrations. These findings can provide evidence for urban planning decisions which aim to leverage health co-benefits from environmental improvements.

Development of an England-wide indoor overheating and air pollution model using artificial neural networks

With the UK climate projected to warm in future decades, there is an increased research focus on the risks of indoor overheating. Energy-efficient building adaptations may modify a buildings risk of overheating and the infiltration of air pollution from outdoor sources. This paper presents the development of a national model of indoor overheating and air pollution, capable of modelling the existing and future building stocks, along with changes to the climate, outdoor air pollution levels, and occupant behaviour. The model presented is based on a large number of EnergyPlus simulations run in parallel. A metamodelling approach is used to create a model that estimates the indoor overheating and air pollution risks for the English housing stock. The performance of neural networks (NNs) is compared to a support vector regression (SVR) algorithm when forming the metamodel. NNs are shown to give almost a 50% better overall performance than SVR.