Relationship between air quality and asthma-related emergency hospital admissions in Mexico City 2017-2019.

BACKGROUND: Previous studies found exposure to air pollution leads to exacerbations of asthma in paediatric and adult patients and increases asthma-related emergency hospital admissions (AREHA). METHODS: AREHAs and levels of air pollutants (PM10, PM2.5 and NO2) were obtained from Mexico City for the period 2017-2019. A time-series approach was used to explore the relationship between air pollutants and AREHA. Relative risks of AREHA were estimated using a negative binomial regression in young children (less than 5 years) and adults (greater than 18 years). RESULTS: There was a positive association between AREHA and PM10, PM2.5 and NO2 in adults, which remained after mutual adjustment for these pollutants. The relative risk (RR) of admission in adults increased by 3% (95% CI 1% to 4%) for a 10 µg/m3 increase in PM10, 1% (0.03% to 3%) for a 5 µg/m3 increase in PM2.5 and by 1% (0.06% to 2%) for a 5 µg/m3 increase in NO2. In contrast, in young children, AREHAs were negatively associated with PM10 after adjustment for NO2 (RR 0.97 (0.95 to 0.99) for a 10 µg/m3 and with NO2 after adjustment for PM10 and PM2.5 (RR 0.98 (0.96 to 0.99) and 0.97 (0.96 to 0.99), respectively, for a 5 µg/m3 increase in NO2). AREHAs in children were not associated with PM2.5 after adjustment for NO2. CONCLUSIONS: Ambient air pollution, within the previous week, was associated with emergency hospital admissions for asthma to public hospitals in adults in Mexico City. The relationship in children was less consistent. Further work is needed to explore why differences between adults and children exist to inform appropriate interventions to benefit public health.

Exploring the role of human-following robots in supporting the mobility and wellbeing of older people.

With the ever-pressing challenges of societal ageing, robotic technologies for older people are increasingly portrayed as a solution for better independent living for longer. However, the application of human-following robots for elderly citizens has not yet been considered, and any prospective benefits offered by the technology for active ageing have previously been overlooked. This qualitative research aimed to explore older people's needs and requirements towards the human-following robot through the reflexive thematic analysis of semi-structured interview data from 17 independent older adults, supported by a video-based demonstration of the robot. The results indicate that older people believed that human-following robot has the potential to provide social benefits to an independent older adult by encouraging walking trips and prompting social interaction with others in the community. Practical limitations and cost of the robot are barriers to adoption at present. The findings indicate that there is potential for human-following robots to support active ageing, through increasing opportunities for the social participation of an older adult, but further development of the robot is needed for this potential to be realised.

Driving factors behind the continuous increase of long-term PM2.5-attributable health burden in India using the high-resolution global datasets from 2001 to 2020.

Air pollution is the fourth leading global risk factor, whereas in India air pollution is reported as the highest risk factor with millions of premature deaths every year. Despite implementation of several air pollution control plans, PM2.5 levels over India have not noticeably reduced. PM2.5-associated health burdens in India have increased significantly in past decades. A fine resolution (0·01° × 0·01°) analysis of PM2.5-attribulable premature deaths (rather than the coarse-level analysis) may elucidate the reason for this increase and inform and effective start-of-the-art state-level and national emission control strategies. This study quantified the spatiotemporal dynamics of PM2.5-attributable premature deaths from 2001 to 2020 and applied a decomposition analysis to dissect the contribution of various associated parameters, such as PM2.5 concentration, population distribution and disease-specific baseline death rate. Results show significant spatiotemporal variations of PM2.5 and associated health burden in India. During the study period, population weighted PM2.5 value increased from 46.0 to 59.5 µg/m3 and associated non-communicable death increased around 87.6 %, from 1050 [95 % (CI): 880-1210] thousand to 1970 (95 % CI: 1658-2259) thousand. The states of Uttar Pradesh, Bihar, West Bengal, Maharashtra, Rajasthan, and Madhya Pradesh had the highest PM2.5-attributable deaths. In these states, non-accidental deaths increased from 232.1, 112.7, 81.4, 79.1, 66.3 and 58.5 thousand in 2001 to 424.1, 226.7, 156.2, 154.5, 123.3 and 119.7 thousand in 2020. In per capita population (/105 population), the highest PM2.5-attributable deaths were observed in Delhi, Uttar Pradesh, Bihar, Haryana and Punjab. Throughout the study period, demographic changes outweighed the health burden and were responsible for ~62.8 % increase of PM2.5-related non-accidental deaths across India, whereas the change in PM2.5 concentration influenced only 18.7 %. The change in baseline mortality rate impacts differently for the estimation of disease-specific mortality changes. Our findings suggest more dynamic and comprehensive policies at state-specific level, especially for North India is very indispensable for the overall decrease of PM2.5-related deaths in India.

Analysing the effect of gender on the human-machine interaction in level 3 automated vehicles.

The emergence of the level 3 automated vehicles (L3 AVs) can enable drivers to be completely disengaged from driving and safely perform other non-driving related tasks, but sometimes their takeover of control of the vehicle is required. The takeover of control is an important human-machine interaction in L3 AVs. However, little research has focused on investigating the effect of gender on takeover performance. In order to fill this research gap, a driving simulator study with 76 drivers (33 females and 43 males) was conducted. The participants took over control from L3 AVs, and the timing and quality of takeover were measured. The results show that although there was no significant difference in most of the measurements adopted to quantify takeover performance between female and male. Gender did affect takeover performance slightly, with women exhibited slightly better performance than men. Compared to men, women exhibited a smaller percentage of hasty takeovers and slightly faster reaction times as well as slightly more stable operation of the steering wheel. The findings highlight that it is important for both genders to recognise they can use and interact with L3 AVs well, and more hands-on experience and teaching sessions could be provided to deepen their understanding of L3 AVs. The design of the car interiors of L3 AVs should also take into account gender differences in the preferences of users for different non-driving related tasks.

Analysis of fine particulates from fuel burning in a reconstructed building at Çatalhöyük World Heritage Site, Turkey: assessing air pollution in prehistoric settled communities.

The use of wood, dung and other biomass fuels can be traced back to early prehistory. While the study of prehistoric fuel use and its environmental impacts is well established, there has been little investigation of the health impacts this would have had, particularly in the Neolithic period, when people went from living in relatively small groups, to living in dense settlements. The UNESCO World Heritage Site of Çatalhöyük, Turkey, is one of the earliest large 'pre-urban' settlements in the world. In 2017, a series of experiments were conducted to measure fine particulate (PM2.5) concentrations during typical fuel burning activities, using wood and dung fuel. The results indicate that emissions from both fuels surpassed the WHO and EU standard limits for indoor air quality, with dung fuel being the highest contributor for PM2.5 pollution inside the house, producing maximum values > 150,000 µg m-3. Maximum levels from wood burning were 36,000 µg m-3. Average values over a 2-3 h period were 13-60,000 µg m-3 for dung and 10-45,000 µg m-3 for wood. The structure of the house, lack of ventilation and design of the oven and hearth influenced the air quality inside the house. These observations have implications for understanding the relationship between health and the built environment in the past.

Unprecedented reduction in air pollution and corresponding short-term premature mortality associated with COVID-19 lockdown in Delhi, India.

Countries around the world introduced strict restrictions on movement and activities known as 'lockdowns' to restrict the spread of the novel coronavirus disease (COVID-19) from the end of 2019. A sudden improvement in air quality was observed globally as a result of these lockdowns. To provide insight into the changes in air pollution levels in response to the COVID-19 restrictions we have compared surface air quality data in Delhi during four phases of lockdown and the first phase of the restriction easing period (25 March to 30 June 2020) with data from a baseline period (2018-2019). Simultaneously, short-term exposure of PM2.5 and O3 attributed premature mortality were calculated to understand the health benefit of the change in air quality. Ground-level observations in Delhi showed that concentrations of PM10, PM2.5 and NO2 dropped substantially in 2020 during the overall study period compared with the same period in previous years, with average reductions of ~49%, ~39%, and ~39%, respectively. An overall lower reduction in O3 of ~19% was observed for Delhi. A slight increase in O3 was found in Delhi's industrial and traffic regions. The highest peak of the diurnal variation decreased substantially for all the pollutants at every phase. The decrease in PM2.5 and O3 concentrations in 2020, prevented 904 total premature deaths, a 60% improvement when compared to the figures for 2018-2019. The restrictions on human activities during the lockdown have reduced anthropogenic emissions and subsequently improved air quality and human health in one of the most polluted cities in the world.Implications: I am submitting herewith the manuscript entitled "Unprecedented Reduction in Air Pollution and Corresponding Short-term Premature Mortality Associated with COVID-19 Forced Confinement in Delhi, India" for potential publishing in your journal.The novelty of this research lies in: (1) we utilized ground-level air quality data in Delhi during four phases of lockdown and the first phase of unlocking period (25th March to 30th June) for 2020 as well as data from the baseline period (2018-2019) to provide an early insight into the changes in air pollution levels in response to the COVID-19 pandemic, (2) Chatarize the change of diurnal variation of the pollutants and (3) we assess the health risk due to PM2.5 and O3. Results from ground-level observations in Delhi showed that concentrations of PM10, PM2.5 and NO2 substantially dropped in 2020 during the overall study period compared to the similar period in previous years, with an average reduction of ~49%, ~39%, and ~39%, respectively. In the case of O3, the overall reduction was observed as ~19% in Delhi, while a slight increase was found in industrial and traffic regions. And consequently, the highest peak of the diurnal variation decreased substantially for all the pollutants. The health impact assessment of the changes in air quality indicated that 904 short-term premature deaths (~60%) were prevented due to the decline in PM2.5 and O3 concentrations in the study period. The restrictions on human activities during the lockdown have reduced the anthropogenic emissions and subsequently improved air quality and human health in one of the most polluted cities in the world.

Short-term effects of air pollution on daily asthma-related emergency department visits in an industrial city.

BACKGROUND: Epidemiological studies from Europe and North America have provided evidence that exposure to air pollution can aggravate symptoms in asthmatic patients. METHODS: Daily number of AEDv, air pollution levels (PM10, PM2.5, SO2, NO2 and CO) and meteorological variables was obtained from Jubail Industrial City, Saudi Arabia, for the period of 2007-11. Data were analyzed using a time-series approach. Relative risks (RRs) were estimated using Poisson regression. RESULTS: The associations between AEDv and PM10, PM2.5, SO2 and NO2 remained positive and statistically significant after mutual adjustment in the multi-pollutant model.The RR of AEDv increased by 5.4, 4.4, 3.4 and 2.2% per an inter-quartile range increase in SO2 (2.0 ppb), PM2.5 (36 µg/m3), NO2 (7.6 ppb) and PM10 (140 µg/m3), respectively. No significant associations between AEDv and CO were found. CONCLUSIONS: Current levels of ambient air pollution are associated with AEDv in this industrial setting in the Middle East. Greater awareness of environmental health protection and the implementation of effective measures to improve the quality of air in such settings would be beneficial to public health.

Continuous increases of surface ozone and associated premature mortality growth in China during 2015-2019.

Ambient ozone (O3) pollution has become a big issue in China. Recent studies have linked long- and short-term O3 exposure to several public health risks. In this study, we (1) characterize the long-term and short-term O3-attributed health metric in China from 2015 to 2019; (2) estimate the surface O3 trends; and (3) quantify the long-term and short-term health impacts (i.e. all-cause, cardiovascular and respiratory mortality) in 350 urban Chinese cities. In these 5-years, the national annual average of daily maximum 8 h average (AVGDMA8) O3 concentrations and warm-season (April-September) 4th highest daily maximum 8 h average (4DMA8) O3 concentrations increased from 74.0 ± 15.5 µg/m3 (mean ± standard deviation) to 82.3 ± 12.0 µg/m3 and 167 ± 37.0 µg/m3 to 174 ± 30.0 µg/m3 respectively. During this period, the DMA8 O3 concentration increased by 1.9 ± 3.3 µg/m3/yr across China, with over 70% of the monitoring sites showing a positive upward trend and 19.4% with trends >5 µg/m3/yr. The estimated long-term all-cause, cardiovascular and respiratory premature mortalities attributable to AVGDMA8 O3 exposure in 350 Chinese cities were 181,000 (95% CI: 91,500-352,000), 112,000 (95% CI: 38,100-214,000) and 33,800 (95% CI: 0-71,400) in 2019, showing increases of 52.5%, 52.9% and 54.6% respectively compared to 2015 levels. Similarly, short-term all-cause, cardiovascular and respiratory premature mortalities attributed to ambient 4DMA8 O3 exposure were 156,000 (95% CI: 85,300-227,000), 73,500 (95% CI: 27,500-119,000) and 28,600 (95% CI: 14,500-42,800) in 2019, increases of 19.6%, 19.8% and 21.2% respectively compared to 2015. The results of this study are important in ascertaining the effectiveness of recent emission control measures and to identify the areas that require urgent attention.

Prevalence, risk factors and clinical correlates of COPD in a rural setting in Tanzania.

Chronic obstructive pulmonary disease (COPD) causes substantial burden of disease in developed countries, but there are limited data from Africa. We aimed to estimate the prevalence of COPD in Tanzania and identify the risk factors associated with it.This was a cross-sectional descriptive survey involving adults aged ≥35 years. We collected data on symptoms and risk factors using the Burden of Obstructive Lung Diseases questionnaire. Spirometry was performed and COPD diagnosed based on post-bronchodilator forced expiratory volume in 1 s/forced vital capacity <70%. We also measured indoor and outdoor carbon monoxide (CO) levels.A total of 869 participants (49.1% females) completed the questionnaires. Of these, 57.1% completed post-bronchodilator spirometry. Of the 25.2% ever-smokers, only 5.4% were current smokers. COPD prevalence was estimated at 17.5% (21.7% in males and 12.9% in females). COPD was associated with a history of cough, phlegm production and wheezing. 51.7% of COPD patients reported cough and 85% had mild to moderate airway limitation. Females had a higher rate of exacerbation. Pulmonary tuberculosis (TB) was reported in 10% of patients. Only 1.7% of patients who were diagnosed as COPD had ever received any medication, with only one female COPD patient having received an inhaler. 99.5% of the population used biomass fuels for cooking. The majority of households had CO levels up to 20 ppm.The prevalence of COPD in Tanzania is high, with a peak at a relatively young age and a preponderance in males. A history of TB, cigarette smoking and male sex are important risk factors. Indoor air pollution coupled with use of biomass fuel for cooking and heating may be an important risk factor for developing COPD in rural Tanzania. However, these factors need to be studied further.

Understanding active school travel through the Behavioural Ecological Model.

Active school travel (AST) is an important source of physical activity for children and a conceptual understanding of AST is necessary to inform promotion efforts. The aim of this article is to provide a conceptual analysis of AST. All currently identified AST formulations include intra-individual variables which are often recommended as intervention targets. However, existing literature lacks clarity on precisely how these intra-individual variables might shape specific AST interventions. Moreover, evaluative studies of AST interventions typically fail to specify an underpinning theory or model. To address this limitation, the Behavioural Ecological Model (BEM), not previously addressed in AST, is presented to guide this area of research. Based on specific examples, we draw attention to the role of potential antecedents and potential reinforcers of AST, as well as potential reinforcers of motorised travel. Antecedents and reinforcers may help to explain choices of school travel mode, and to inform and increase intervention options to promote AST. Consistent with the BEM, the provision of more immediate consequences, such as fun and material prizes, is an evidence-based strategy for increasing AST which is likely to be low-cost and easier to deliver than alternative interventions. This approach to the study of AST is expected to contribute to similar analyses in this and other areas of behaviour change research, and to a more useful discussion and treatment of theoretical and conceptual behavioural models.

Feasibility of an incentive scheme to promote active travel to school: a pilot cluster randomised trial.

BACKGROUND: In Great Britain, 19% of trips to primary school within 1 mile, and 62% within 1-2 miles, are by car. Active travel to school (ATS) offers a potential source of moderate-to-vigorous physical activity (MVPA). This study tested the feasibility of an intervention to promote ATS in 9-10 year olds and associated trial procedures. METHODS: A parallel cluster randomised pilot trial was conducted over 9 weeks in two schools from a low-income area in northeast England. Measures included daily parental ATS reports (optionally by SMS) and child ATS reports, as well as accelerometry (ActiGraph GT3X+). At baseline, all children were asked to wear the accelerometer for the same week; in the post-randomisation phase, small subsamples were monitored each week. In the 2 weeks when a child wore the accelerometer, parents also reported the start and finish times of the journey to school. The intervention consisted of a lottery-based incentive scheme; every ATS day reported by the parent, whether by paper or SMS, corresponded to one ticket entered into a weekly £5 voucher draw. Before each draw session, the researcher prepared the tickets and placed them into an opaque bag, from which one was randomly picked by the teacher at the draw session. RESULTS: Four schools replied positively (3.3%, N = 123) and 29 participants were recruited in the two schools selected (33.0%, N = 88). Participant retention was 93.1%. Most materials were returned on time: accelerometers (81.9%), parental reports (82.1%) and child reports (97.9%). Draw sessions lasted on average 15.9 min (IQR 10-20) and overall session attendance was 94.5%. Parent-child report agreement regarding ATS was moderate (k = 0.53, CI 95% 0.45; 0.60). Differences in minutes of accelerometer-assessed MVPA between parent-reported ATS and non-ATS trips were assessed during two timeframes: during the journey to school based on the times reported by the parent (U = 390.5, p < 0.05, 2.46 (n = 99) vs 0.76 (n = 13)) and in the hour before classes (U = 665.5, p < 0.05, 4.99 (n = 104) vs 2.55 (n = 19)). Differences in MVPA minutes between child-reported ATS and non-ATS trips were also significant for each of the timeframes considered (U = 596.5, p < 0.05, 2.40 (n = 128) vs 0.81 (n = 15) and U = 955.0, p < 0.05, 4.99 (n = 146) vs 2.59 (n = 20), respectively). CONCLUSIONS: Data suggest the feasibility of an ATS incentive scheme and of most trial procedures. School recruitment stood out as requiring further piloting. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02282631. Registered 5th September 2014.

Investigating the traffic-related environmental impacts of hydraulic-fracturing (fracking) operations.

Hydraulic fracturing (fracking) has been used extensively in the US and Canada since the 1950s and offers the potential for significant new sources of oil and gas supply. Numerous other countries around the world (including the UK, Germany, China, South Africa, Australia and Argentina) are now giving serious consideration to sanctioning the technique to provide additional security over the future supply of domestic energy. However, relatively high population densities in many countries and the potential negative environmental impacts that may be associated with fracking operations has stimulated controversy and significant public debate regarding if and where fracking should be permitted. Road traffic generated by fracking operations is one possible source of environmental impact whose significance has, until now, been largely neglected in the available literature. This paper therefore presents a scoping-level environmental assessment for individual and groups of fracking sites using a newly-created Traffic Impacts Model (TIM). The model produces estimates of the traffic-related impacts of fracking on greenhouse gas emissions, local air quality emissions, noise and road pavement wear, using a range of hypothetical fracking scenarios to quantify changes in impacts against baseline levels. Results suggest that the local impacts of a single well pad may be short duration but large magnitude. That is, whilst single digit percentile increases in emissions of CO2, NOx and PM are estimated for the period from start of construction to pad completion (potentially several months or years), excess emissions of NOx on individual days of peak activity can reach 30% over baseline. Likewise, excess noise emissions appear negligible (<1dBA) when normalised over the completion period, but may be considerable (+3.4dBA) in particular hours, especially in night-time periods. Larger, regional scale modelling of pad development scenarios over a multi-decade time horizon give modest CO2 emissions that vary between 2.5 and 160.4kT, dependent on the number of wells, and individual well fracking water and flowback waste requirements. The TIM model is designed to be adaptable to any geographic area where the required input data are available (such as fleet characteristics, road type and quality), and we suggest could be deployed as a tool to help reach more informed decisions regarding where and how fracking might take place taking into account the likely scale of traffic-related environmental impacts.

Systems scale assessment of the sustainability implications of emerging green initiatives.

This paper demonstrates a systems framework for assessment of environmental impacts from 'green initiatives', through a case study of meso-scale, anthropogenic-biogenic interactions. The following cross-sectoral green initiatives, combining the emerging trends in the North East region of the United Kingdom, have been considered - increasing the vegetation cover; decarbonising road transport; decentralising energy production through biomass plants. Two future scenarios are assessed - Baseline_2020 (projected emissions from realisation of policy instruments); Aggressive_2020 (additional emissions from realisation of green initiatives). Resulting trends from the Aggressive_2020 scenario suggest an increase in emissions of pollutant precursors, including biogenic volatile organic compounds and nitrogen dioxide over the base case by up to 20% and 5% respectively. This has implications for enhanced daytime ozone and secondary aerosols formation by up to 15% and over 5% respectively. Associated land cover changes show marginal decrease of ambient temperature but modest reductions in ammonia and ambient particulates.

A novel approach for investigating the trends in nitrogen dioxide levels in UK cities.

This paper investigates the variations in levels of nitrogen dioxide, NO2, monitored over the decade 2001-2010, in Newcastle-upon-Tyne (UK) city centre, to develop fundamental understanding of the periods of persistence of levels of NO2 greater than 40 µg m(-3) (~21 ppb) defined as air pollution event duration. The appropriateness of the hazard theory as a mechanism to understand failure rate of the duration of poor air pollution events was explored. The results revealed two types of air quality events. The longer duration air quality events (between 24 and 68 h) were associated with the "extreme-weather" conditions and were responsible for a small number of extremely long air pollution duration events. These created bias in the results and therefore the analysis was restricted specifically to the 'normal-weather' related air pollution event durations, conforming to a geometric distribution. This novel approach shows promise as a mechanism to monitor and investigate year on year trends observed in air quality data.

Estimation of age-related vulnerability to air pollution: assessment of respiratory health at local scale.

This paper demonstrates association of short-term variation in pollution and health outcomes within the same geographical area for a typical urban setting in the northern part of the UK from time series analysis. It utilises publicly available datasets for regulated air pollutants (PM10, NO2, SO2, CO and O3), meteorology and respiratory hospital admissions (and mortality) between April 2002 and December 2005 to estimate the respiratory health effect of pollution exposure, mainly in the elderly. Our results show that PM10 and O3 are positively associated with respiratory hospital admissions in the elderly, specifically in the age group 70-79. CO effects seem to be concentrated on the most elderly age group (80+) whereas NO2 seems to have the opposite age-related effect, with lower effects on the more elderly.

Air flow and concentration fields at urban road intersections for improved understanding of personal exposure.

This paper reviews the state of knowledge on modelling air flow and concentration fields at road intersections. The first part covers the available literature from the past two decades on experimental (both field and wind tunnel) and modelling activities in order to provide insight into the physical basis of flow behaviour at a typical cross-street intersection. This is followed by a review of associated investigations of the impact of traffic-generated localised turbulence on the concentration fields due to emissions from vehicles. There is a discussion on the role of adequate characterisation of vehicle-induced turbulence in making predictions using hybrid models, combining the merits of conventional approaches with information obtained from more detailed modelling. This concludes that, despite advancements in computational techniques, there are crucial knowledge gaps affecting the parameterisations used in current models for individual exposure. This is specifically relevant to the growing impetus on walking and cycling activities on urban roads in the context of current drives for sustainable transport and healthy living. Due to inherently longer travel times involved during such trips, compared to automotive transport, pedestrians and cyclists are subjected to higher levels of exposure to emissions. Current modelling tools seem to under-predict this exposure because of limitations in their design and in the empirical parameters employed.

Investigating the relationship between air pollution, health and social deprivation in Leeds, UK.

This study examines the relationship between air pollution, social deprivation and health in the city of Leeds, UK under a baseline and three distance-based road user charging (RUC) scenarios set at 2 pence, 10 pence and 20 pence/km. Through application of a series of linked models of traffic, emission and pollutant dispersion, air quality was modelled in response to RUC scenarios. The pollutant modelled were NO(2), PM(10), CO, benzene and 1,3-butadiene, though results of NO(2) are used in this study. The RUC scenarios were compared with the 'base' scenario, all set for the year 2005. The RUC initiatives result in the differences in ambient concentrations of NO(2). The study correlates NO(2) concentrations with derived indices of social deprivation and health. The study concludes that positive but weak relationship exists between air quality and social deprivation, and indicates that deprived population groups are disproportionately exposed to higher NO(2) levels. The relationship between air quality and health status of the population is weak. There is a strong relationship between social deprivation and health status of the population. The study concludes that RUC scenarios result in reducing disparity between affluent and deprived populations.

An empirical study of estimating vehicle emissions under cordon and distance based road user charging in Leeds, UK.

This paper presents the impact of road user charging (RUC) on vehicle emissions through application of traffic assignment and pollutant emission models. It presents results of an analysis of five RUC schemes on vehicle emissions in Leeds, UK for 2005. The schemes were: a 3 pound sterling inner ring road cordon charge; a double cordon with a 2 pound sterling inner ring road and a 1 pound sterling outer ring road charge; and distance charges of 2, 10 and 20 p/km levied for travel within the outer cordon. Schemes were compared to a no charge option and results presented here. Emissions are significantly reduced within the inner cordon, whilst beyond the cordon, localised increases and decreases occur. The double cordon exhibits a similar but less marked pattern. Distance charging reduces city-wide emissions by 10% under a 2 p/km charge, 42-49% under a 10 p/km charge and 52-59% under a 20 p/km charge. The higher distance charges reduce emissions within the charge zone, and are also associated with elevated emissions outside the zone, but to a lesser extent than that observed for cordon charging.