Urban Heat Islands and their Associated Impacts on Health

Towns and cities generally exhibit higher temperatures than rural areas for a number of reasons, including the effect that urban materials have on the natural balance of incoming and outgoing energy at the surface level, the shape and geometry of buildings, and the impact of anthropogenic heating. This localized heating means that towns and cities are often described as urban heat islands (UHIs). Urbanized areas modify local temperatures, but also other meteorological variables such as wind speed and direction and rainfall patterns. The magnitude of the UHI for a given town or city tends to scale with the size of population, although smaller towns of just thousands of inhabitants can have an appreciable UHI effect. The UHI “intensity” (the difference in temperature between a city center and a rural reference point outside the city) is on the order of a few degrees Celsius on average, but can peak at as much as 10°C in larger cities, given the right conditions. UHIs tend to be enhanced during heatwaves, when there is lots of sunshine and a lack of wind to provide ventilation and disperse the warm air. The UHI is most pronounced at night, when rural areas tend to be cooler than cities and urban materials radiate the energy they have stored during the day into the local atmosphere. As well as affecting local weather patterns and interacting with local air pollution, the UHI can directly affect health through heat exposure, which can exacerbate minor illnesses, affect occupational performance, or increase the risk of hospitalization and even death. Urban populations can face serious risks to health during heatwaves whereby the heat associated with the UHI contributes additional warming. Heat-related health risks are likely to increase in future against a background of climate change and increasing urbanization throughout much of the world. However, there are ways to reduce urban temperatures and avoid some of the health impacts of the UHI through behavioral changes, modification of buildings, or by urban scale interventions. It is important to understand the physical properties of the UHI and its impact on health to evaluate the potential for interventions to reduce heat-related impacts

Potential health impacts from sulphur dioxide and sulphate exposure in the UK resulting from an Icelandic effusive volcanic eruption

Ash, gases and particles emitted from volcanic eruptions cause disruption to air transport, but also have negative impacts on respiratory and cardiovascular health. Exposure to sulphur dioxide (SO2) and sulphate (SO4) aerosols increases the risk of mortality, and respiratory and cardiovascular hospital admissions. Ash and gases can be transported over large distances and are a potential public health risk. In 2014–15, the Bárðarbunga fissure eruption at Holuhraun, Iceland was associated with high emissions of SO2 and SO4, detected at UK monitoring stations. We estimated the potential impacts on the UK population from SO2 and SO4 associated with a hypothetical large fissure eruption in Iceland for mortality and emergency hospital admissions. To simulate the effects of different weather conditions, we used an ensemble of 80 runs from an atmospheric dispersion model to simulate SO2 and SO4 concentrations on a background of varying meteorology. We weighted the simulated exposure data by population, and quantified the potential health impacts that may result in the UK over a 6-week period following the start of an eruption. We found in the majority of cases, the expected number of deaths resulting from SO2 over a 6-week period total fewer than ~100 for each model run, and for SO4, in the majority of cases, the number totals fewer than ~200. However, the 6-week simulated period with the highest SO2 was associated with 313 deaths, and the period with the highest SO4 was associated with 826 deaths. The single 6-week period relating to the highest combined SO2 and SO4 was associated with 925 deaths. Over a 5-month extended exposure period, upper estimates are for 3350 deaths, 4030 emergency cardiovascular and 6493 emergency respiratory hospitalizations. These figures represent a worst-case scenario and can inform health protection planning for effusive volcanic eruptions which may affect the UK in the future

Climate change effects on human health: projections of temperature-related mortality for the UK during the 2020s, 2050s and 2080s

Background The most direct way in which climate change is expected to affect public health relates to changes in mortality rates associated with exposure to ambient temperature. Many countries worldwide experience annual heat-related and cold-related deaths associated with current weather patterns. Future changes in climate may alter such risks. Estimates of the likely future health impacts of such changes are needed to inform public health policy on climate change in the UK and elsewhere. Methods Time-series regression analysis was used to characterise current temperature-mortality relationships by region and age group. These were then applied to the local climate and population projections to estimate temperature-related deaths for the UK by the 2020s, 2050s and 2080s. Greater variability in future temperatures as well as changes in mean levels was modelled. Results A significantly raised risk of heat-related and cold-related mortality was observed in all regions. The elderly were most at risk. In the absence of any adaptation of the population, heat-related deaths would be expected to rise by around 257% by the 2050s from a current annual baseline of around 2000 deaths, and cold-related mortality would decline by 2% from a baseline of around 41 000 deaths. The cold burden remained higher than the heat burden in all periods. The increased number of future temperature-related deaths was partly driven by projected population growth and ageing. Conclusions Health protection from hot weather will become increasingly necessary, and measures to reduce cold impacts will also remain important in the UK. The demographic changes expected this century mean that the health protection of the elderly will be vital

The winter urban heat island: Impacts on cold-related mortality in a highly urbanized European region for present and future climate.

Exposure to heat has a range of potential negative impacts on human health; hot weather may exacerbate cardiovascular and respiratory illness or lead to heat stroke and death. Urban populations are at increased risk due to the Urban Heat Island (UHI) effect (higher urban temperatures compared with rural ones). This has led to extensive investigation of the summertime UHI and its effects, whereas far less research focuses on the wintertime UHI. Exposure to low temperature also leads to a range of illnesses, and in fact, in the UK, annual cold-related mortality outweighs heat-related mortality. It is not clearly understood to what extent the wintertime UHI may protect against cold related mortality. In this study we quantify the UHI intensity in wintertime for a heavily urbanized UK region (West Midlands, including Birmingham) using a regional weather model, and for the first time, use a health impact assessment (HIA) to estimate the associated impact on cold-related mortality. We show that the population-weighted mean winter UHI intensity was +2.3 °C in Birmingham city center, and comparable with that of summer. Our results suggest a potential protective effect of the wintertime UHI, equivalent to 266 cold-related deaths avoided (~15% of total cold-related mortality over ~11 weeks). When including the impacts of climate change, our results suggest that the number of heat-related deaths associated with the summer UHI will increase from 96 (in 2006) to 221 in the 2080s, based on the RCP8.5 emissions pathway. The protective effect of the wintertime UHI is projected to increase only slightly from 266 cold-related deaths avoided in 2009 to 280 avoided in the 2080s. The different effects of the UHI in winter and summer should be considered when assessing interventions in the built environment for reducing summer urban heat, and our results suggest that the future burden of temperature-related mortality associated with the UHI is likely to increase in summer relative to winter

Comparing temperature-related mortality impacts of cool roofs in winter and summer in a highly urbanized European region for present and future climate

Human health can be negatively impacted by hot or cold weather, which often exacerbates respiratory or cardiovascular conditions and increases the risk of mortality. Urban populations are at particular increased risk of effects from heat due to the Urban Heat Island (UHI) effect (higher urban temperatures compared with rural ones). This has led to extensive investigation of the summertime UHI, its impacts on health, and also the consideration of interventions such as reflective 'cool' roofs to help reduce summertime overheating effects. However, interventions aimed at limiting summer heat are rarely evaluated for their effects in wintertime, and thus their overall annual net impact on temperature-related health effects are poorly understood. In this study we use a regional weather model to simulate the winter 2009/10 period for an urbanized region of the UK (Birmingham and the West Midlands), and use a health impact assessment to estimate the impact of reflective 'cool' roofs (an intervention usually aimed at reducing the UHI in summer) on cold-related mortality in winter. Cool roofs have been shown to be effective at reducing maximum temperatures during summertime. In contrast to the summer, we find that cool roofs have a minimal effect on ambient air temperatures in winter. Although the UHI in summertime can increase heat-related mortality, the wintertime UHI can have benefits to health, through avoided cold-related mortality. Our results highlight the potential annual net health benefits of implementing cool roofs to reduce temperature-related mortality in summer, without reducing the protective UHI effect in winter. Further, we suggest that benefits of cool roofs may increase in future, with a doubling of the number of heat-related deaths avoided by the 2080s (RCP8.5) compared to summer 2006, and with insignificant changes in the impact of cool-roofs on cold-related mortality. These results further support reflective 'cool' roof implementation strategies as effective interventions to protect health, both today and in future

Forces between electric charges in motion: Rutherford scattering, circular Keplerian orbits, action-at-a-distance and Newton's third law in relativistic classical electrodynamics

Standard formulae of classical electromagnetism for the forces between electric charges in motion derived from retarded potentials are compared with those obtained from a recently developed relativistic classical electrodynamic theory with an instantaneous inter-charge force. Problems discussed include small angle Rutherford scattering, Jackson's recent `torque paradox' and circular Keplerian orbits. Results consistent with special relativity are obtained only with an instantaneous interaction. The impossiblity of stable circular motion with retarded fields in either classical electromagnetism or Newtonian gravitation is demonstrated.Comment: 26 pages, 5 figures. QED and special relativity forbid retarded electromagnetic forces. See also physics/0501130. V2 has typos corrected, minor text modifications and updated references. V3 has further typos removed and added text and reference

Multiple air pollutants and their health impacts for both present-day and future scenarios

The adverse health impacts of air pollution, both short-term and long-term, have been widely studied in recent years; however there are a number of uncertainties to consider when carrying out health impact assessments. Health effects attributable to exposure to air pollutants are typically estimated using measured or modelled pollutant concentrations which vary both temporally and spatially. The goal of this thesis is to perform health impact assessments using modelled pollutant concentrations for present-day and future. The specific aims are: (i) to study the influence of model horizontal resolution on simulated concentrations of ozone (O3) and particulate matter less than 2.5 μm in diameter (PM2.5) for Europe and the implications for health impact assessments associated with long-term exposure (ii) to model air pollutant concentrations during two air pollution episodes in July 2006 together with the corresponding short-term health impact in the UK (iii) to estimate potential future health burdens associated with long-term pollutant exposure under future UK emission changes for 2050 in the UK. First, the impact of model horizontal resolution on simulated concentrations of O3 and PM2.5, and on the associated long-term health impacts over Europe is examined, using the HadGEM3–UKCA (UK Chemistry and Aerosol) chemistry– climate model to simulate pollutant concentrations at a coarse (~140 km) and a finer (~50 km) horizontal resolution. The attributable fraction (AF) of total mortality due to long-term exposure to warm season daily maximum 8-hr running mean (MDA8) O3 and annual-mean PM2.5 concentrations is then estimated for each European country using pollutant concentrations simulated at each resolution. Results highlight seasonal variations in simulated O3 and PM2.5 differences between the two model resolutions in Europe. Simulated O3 concentrations averaged for Europe at the coarse resolution are higher in winter and spring (~10 and ~6 %, respectively) but lower in summer and autumn (~-1 and ~-4 %, respectively) compared to the finer resolution results. These differences may be partly explained by differences in nitrogen dioxide (NO2) concentrations simulated at the two resolutions. Compared to O3, the opposite seasonality in simulated PM2.5 differences between the two resolutions is found. In winter and spring, simulated PM2.5 concentrations are lower at the coarse compared to the finer resolution (~-8 and ~-6 % averaged for Europe, respectively) but higher in summer and autumn (~29 and ~8 %, respectively). Differences in simulated PM2.5 levels are largely related to differences in convective rainfall and boundary layer height between the two resolutions for all seasons. These differences between the two resolutions exhibit clear spatial patterns for both pollutants that vary by season, and exert a strong influence on country to country variations in the estimated AF of mortality for the two resolutions. Results demonstrate that health impact assessments calculated using modelled pollutant concentrations, are sensitive to a change in model resolution with differences in AF of mortality between the countries ranging between ~-5% and ~+3%. Under climate change, the risk of extreme weather events, such as heatwaves, is likely to increase. Thus the UK health burden associated with short-term exposure to MDA8 O3 and daily mean PM2.5 is examined during two five-day air pollution episodes during a well-known heatwave period in July 2006 (1st - 5th July and 18th – 22nd July) using the UK Met Office air quality model (AQUM) at 12 km horizontal resolution. Both episodes are found to be driven by anticyclonic conditions (mean sea-level pressures ~1020hPa over the UK) with light easterly and south easterly winds and high temperatures that aided pollution build up in the UK. The estimated total mortality burden associated with short-term exposure to O3 is similar during the each episode with about 70 daily deaths brought forward summed across the UK. The estimated health burden associated with short-term exposure to daily mean PM2.5 concentrations differs between the first and second episode resulting in about 43 and 36 daily deaths brought forward, respectively. The attributable fraction of all-cause (excluding external) mortality for both pollutants differs between UK regions and ranges between 1.6% to 5.2% depending on the pollution levels in each episode; the overall total estimated health burdens are highest in regions with higher population totals. Results show that during these episodes, short-term exposure to MDA8 O3 and daily mean PM2.5 is between 36- 38% and 39-56% higher, respectively, than if the pollution levels represented typical seasonal-mean concentrations. Finally, emission scenarios for the UK following three Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCPs); RCP2.6, RCP6.0 and RCP8.5 are used to simulate future concentrations of O3, NO2 and PM2.5 for 2050 relative to 2000 using the AQUM air quality model at 12km resolution. The present-day and future AF of mortality associated with long-term exposure to annual mean MDA8 O3, NO2 and PM2.5 and the corresponding mortality burdens are estimated for each region in the UK. For all three RCPs, simulated annual mean MDA8 O3 concentrations in 2050 are estimated to increase compared to 2000, due to decreases in nitrogen oxides (NOx) emissions reducing titration of O3 by NO, and to increases in methane (CH4) levels across all of the UK. In contrast, annual mean NO2 concentrations decrease everywhere. This highlights that the whole of the UK is simulated to be in a NOx-saturated chemical environment. PM2.5 concentrations decrease under all RCPs for the 2050s mostly driven by decreases in NOx and sulphur dioxide (SO2) emissions affecting secondary inorganic aerosols concentrations. For all pollutants the largest changes are estimated under RCP8.5 while the smallest changes are estimated for RCP6.0 in 2050 as compared to present-day. Consequently, these two RCPs represent the high and low end of the AF and mortality burden difference range relative to present-day for all three pollutants. For all UK regions and all three RCPs, the AF of mortality associated with long-term exposure to O3 is estimated to increase in 2050 while the AF associated with long-term exposure to NO2 and PM2.5 is estimated to decrease as a result of higher and lower projected pollutant concentrations, respectively. Differences in the UK-wide mortality burden attributable to long-term exposure to annual mean MDA8 O3 across the RCPs range from +2,529 to +5,396 additional attributable deaths in 2050 compared to 2000. Long-term exposure to annual mean NO2 and PM2.5 differences in health burdens are between - 9,418 and -15,782 and from - 4,524 to -9,481 avoided attributable deaths in 2050 relative to present-day, respectively. These mortality burdens are also sensitive to future population projections. These results demonstrate that long-term health impact assessments estimated using modelled pollutant concentrations, are sensitive to a change in model resolution across Europe, especially in southern and eastern Europe. In addition, air pollution episodes are shown to have the potential to cause substantial short-term impacts on public health in the UK. Finally the sensitivity of future MDA8 O3-, NO2- and PM2.5-attributable health burdens in the UK to future emission scenarios as well as population projections is highlighted with implications for informing future emissions control strategies for the UK

Angular momentum effects in weak gravitational fields

It is shown that, contrary to what is normally expected, it is possible to have angular momentum effects on the geometry of space time at the laboratory scale, much bigger than the purely Newtonian effects. This is due to the fact that the ratio between the angular momentum of a body and its mass, expressed as a length, is easily greater than the mass itself, again expressed as a length.Comment: LATEX, 8 page

Rotation of electromagnetic fields and the nature of optical angular momentum

The association of spin and orbital angular momenta of light with its polarization and helical phase fronts is now well established. The problems in linking this with electromagnetic theory, as expressed in Maxwell's equations, are rather less well known. We present a simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields and discuss some of the remaining challenges. Crucial to our investigation is the duplex symmetry between the electric and magnetic fields