West Midlands Key Health Data 2008/09
CHAPTER SEVEN: ENVIRONMENT AND HEALTH – OUTDOOR AIR POLLUTION
Sharon Walton
Main Body
9: Predictors Of Emergency Department Use At Neighbourhood Level In The West Midlands
7.1 Introduction
“Pollution - the addition of any substance or form of energy (e.g., heat, sound, radioactivity) to the environment at a rate faster than the environment can accommodate it by dispersion, breakdown, recycling, or storage in some harmless form” 1 |
The World Health Organization (WHO) estimates that roughly 2 million deaths a year are from causes directly attributable to indoor or outdoor air pollution2. The WHO recognises that individuals have little control of the air pollutants to which they may be subject2 and therefore measures must be put in place at a global and local level in which to protect individuals.
The ‘Clean Air Act’ of 1956 arose from concerns over smog in London in the 1950s, when in one episode more than 3 times as many people died than would have been expected3. The UK Government has continued to make commitments to improve the countries air quality.
The Department for Environment Food and Rural Affairs (DEFRA) report that daily peak ozone levels and the long-term exposure to particulate matter have the greatest impacts on health4. The adverse health effects of poor air quality can contribute to difficulties in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions. WHO estimate that air quality related deaths could be reduced by 15% if levels of particulate matter (PM10) were reduced from 70 to 20 micrograms per cubic meter. Though outdoor air pollution is thought to have an effect on health, the population spend most of their time indoors.
This chapter will explore some of the potential adverse health effects of outdoor air pollutants and where possible data will be presented for the West Midlands Region.
Since 1993 when DEFRA began making estimates, levels of both PM10 and ozone in the UK have been steadily decreasing4.
7.2 Particulate Matter
Airborne liquid or solid particles from a variety of sources are termed particulate matter. The size of these particulates are important in health terms as it determines which parts of the body they can reach if inhaled. Particulate matter less than 10μg in diameter is referred to as PM10. Levels of PM10 are commonly monitored, as at this size and smaller, the particles have the ability to reach the lower regions of the respiratory tract and can potentially be absorbed into the blood.
In the UK particulate matter pollutants mainly come from car emissions, combustion processes and dust particles thrown up into the air. Coarse particles can cause irritation to the eyes nose and throat5. Smaller particles may get deeper into the lungs and be absorbed into the blood causing lung and other problems.
Particles less than 2.5μg in diameter (PM2.5) come mainly from vehicle exhausts. These smaller particles can penetrate deeper into the lungs and into air spaces involved with gas exchange6.
Both PM10 and PM2.5 are thought to contribute to increases in mortality from respiratory and cardiovascular disease. Increases in SO2 and particulates have been thought to contribute to bronchitis and emphysema incidence5.
To date studies of the association of air pollution and health (mortality and morbidity) have largely focused on areas other that the West Midlands. This chapter explored the distribution of some aspects of air pollution and some respiratory illnesses which might be related to air pollution in the West Midlands.
Map 7.1: Map of annual mean PM10 concentrations in 2008 within LA areas of the West Midlands
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Map 7.1 shows that the areas with the highest PM10 concentration (mean average level) appear to be in the urban areas particularly around the more industrialised areas of Birmingham and the Black Country and Coventry.
The dark blue areas represent the mean average levels of PM10 above 20 micrograms per cubic meter. The areas of Wolverhampton, Dudley, Sandwell, Birmingham and Coventry LA have some small pockets within them that exceed 20µg/m3. Reducing these levels could help reduce mortality2.
Map 7.2 shows the levels of deprivation across the region based on the index of multiple deprivation rankings. Comparing figures 7.1 and 7.2 we can see that areas with higher PM10 concentrations also experience the most deprivation and research by the Environment Agency has produced similar findings7.
Map 7.2: Overall deprivation in the West Midlands (Indices of Deprivation 2007)
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7.3 Nitrogen Oxides
Nitrogen dioxide and nitrous oxides collectively are referred to as nitrogen oxides (NOx). Other pollutants and nitrogen oxides react with other substances found in the air and rapidly breaks down. Its reaction with sunlight can lead to formation of ozone and smog. Concentrations of nitrogen oxides are thought to be higher in areas where there are combustion sources such as coal power plants or heavy traffic. Exposure to nitrogen oxides even at a low level can cause irritation to the eyes, nose and throat.
Map 7.3: Map of annual mean NOx concentrations in 2008 within LA areas of the West Midlands
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Map 7.3 shows the annual mean concentrations of NOx. The map highlights the major road networks of the region as having higher levels of pollutants than elsewhere in the region. Again the areas of highest concentrations are the more built up urban areas.
7.4 Ozone
Ozone is a gas that is created in the atmosphere8 by the action of sunlight and the chemical reaction between different primary pollutants. Increases in global emissions have led to a rising trend an in the annual average of background hemispheric ozone concentrations8.
As ozone is very reactive it can cause health problems such as irritations of the eyes, nose and throat. It is thought that at high concentrations ozone can cause cardiovascular respiratory diseases as well as congestion, chest pain and throat inflammation.
The WHO estimates that 21,000 premature deaths are caused each year in Europe from causes attributable to ozone pollution9.
Ozone concentration is linked with levels of Nitrogen Oxides (NOx). However the relationship is complex as higher levels on NOx in urban areas are linked to lower levels of ozone. Several studies however show that over a larger geographical area increases in NOx are related to an increase in ozone. Controls in the UK and Europe of both NOx and Volatile organic compounds (VOC) has helped to lower the intensity of summer ozone episodes8
7.5 Sulphur Dioxide
Sulphur dioxide is a gas released into the atmosphere from the combustion of fossil fuels. It can cause irritation to the airway as it is absorbed in the upper airways. Restriction to the bronchus is common especially in asthmatics6. The health effects in humans of sulphur dioxide pollution presents quickly with symptoms occurring within about 30 minutes of exposure. Due to the difficulty of obtaining data around Sulphur Dioxide for the region no data has been presented.
7.6 Carbon Dioxide Emissions
Carbon dioxide is directly linked to Global Warming. Increases in carbon dioxide lead to increases in air temperature. It is estimated that as little as a one degrees Celsius rise in temperature could lead to 20,000 excess deaths globally10. To tackle excess deaths from rises in temperature we therefore need to reduce carbon dioxide emissions.
Table 7.1: Per capita emissions by Local Authority, 2006
Source: LA CO2 estimates produced by AEA technology on behalf of DEFRA (NI 186) |
The estimated emission from CO2 within the West Midlands shows that North Warwickshire and Bridgnorth produce 10 or more kt CO2 per capita per person per year emissions which are the highest levels within the region and higher than the national average at 7.4 kt CO2 per capita.
7.7 Mortality and Admissions Data
The Committee on the Medical Effects of Air Pollution (COMEAP) research has suggested that there are 8,100 excess deaths per year in Great Britain that may be attributed to PM10 air pollution largely in the elderly or already sick. Some of the excess deaths associated with PM10 may be due to bringing forward of deaths that would have occurred a few days later rather than deaths of healthy individuals11. In this respect, deaths associated with PM10 may be similar to excess winter deaths and deaths ascribed to influenza.
A report by the Department of Health COMEAP suggests that a 10 µg m3 increase in fine particles is associated with a 6% increase in risk of death from all-causes12. This effect is larger than previously thought. The evidence for the effects of long-term exposure to sulphur dioxide, nitrogen dioxide, carbon monoxide and ozone on mortality is also discussed but is felt to be weaker than that regarding particles.
Mortality and hospital admissions data for the West Midlands has been presented for various respiratory diseases. It is not known exactly how many deaths or admissions can be directly attributable to air pollution. Most of the deaths associated with air pollution are due to cardiovascular causes.
Figure 7.1: Directly Age Standardised Mortality rates for Diseases of the Respiratory System (ICD10 J00-J99), by Local Authority, All Ages, 2005-2007 pooled.
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Figure 7.1 shows that the mortality rates from diseases of the respiratory system are highest in Stoke-on-Trent, Sandwell, and Newcastle-under-Lyme. The rural areas of Herefordshire Oswestry, and South Shropshire experience the lowest mortality rates within the region from respiratory diseases.
Figure 7.2: Directly Age Standardised Admission rates for Diseases of the Respiratory System (ICD10 J00-J99), by Local Authority, All Ages, 2005-2007 pooled.
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The admission rate for diseases of the respiratory system was on average 1,500 per 100,000 for males and 1,200 per 100,000 for females. There were roughly 77,000 admissions a year in the region from diseases of the respiratory system.
Figure 7.3: Directly Age Standardised Mortality rates for Chronic Lower Respiratory Disease (ICD10 J40-J47), by Local Authority, All Ages, 2005-2007 pooled.
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Long lasting diseases of the airways and lung structures are referred to as chronic respiratory diseases. These include chronic obstructive pulmonary disease (COPD) and asthma which have also been presented individually in figures 7.5-7.7 to give a more informative picture.
The average mortality rate for the region from Chronic Lower Respiratory Disease is 38.8 per 100,000 for males and 25 per 100,000 for females. Stoke-on-Trent LA has the highest rates of mortality, probably an historic artefact of the industrial revolution.
Figure 7.4: Directly Age Standardised Admission rates for Chronic Lower Respiratory Disease (ICD10 J40-J47), by Local Authority, All Ages, 2005-2007 pooled.
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There are over 19,000 admissions from Chronic Lower Respiratory Disease each year. The rates are highest in males for Sandwell LA (491 per 100,000) and for Females in Birmingham LA (425 per 100,000). These rates are 3 to 4 times that of the lowest rates within the region.
Other pollutants which may be carcinogenic are emitted by individual processes though these are strictly controlled by licensing operations. In the 1950s studies were carried out that proved a link between smoking and lung cancers. Several other studies have since been carried out trying to establish a link between air quality and lung cancer. A review of the evidence done in 200013 concluded it was difficult to quantify the exact causal effect due to so many other factors that could not be easily controlled for.
Figure 7.5: Directly Age Standardised Mortality rates for Chronic Obstructive Pulmonary Disease (ICD10 J40, J41, J42, J43, J44), by Local Authority, All Ages, 2005-2007 pooled.
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In the West Midlands there are over 2000 deaths each year from COPD. Figure 7.3 shows the death rate from COPD varies across the West Midlands region. Stoke-on-Trent LA has the highest death rate for males within the region of 55.8 per 100,000. The highest death rate amongst females was in Coventry with 32.1 per 100,000.
Figure 7.6: Directly Age Standardised Admission rates for Chronic Obstructive Pulmonary Disease (ICD10 J40, J41, J42, J43, J44), by Local Authority, All Ages, 2005-2007 pooled.
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There are over 11,000 admissions to hospital a year from COPD in the West Midlands. Sandwell has the highest rate, other urban areas such as Stoke-on-Trent, Birmingham and Walsall also have high rates for both males and females.
Figure 7.7: Directly Age Standardised Admission rates for Asthma (ICD10 J45 - J46), by Local Authority, All Ages, 2005-2007 pooled.
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Death rates from Asthma remain low, however there are over 7,500 admissions to hospital from Asthma each year in the West Midlands. It is important to remember however that most episodes of asthma do not lead to a hospital admission.
Rates again appear highest in the more urban industrial areas of the region with the more rural areas having a lower than average admission rate for the region. The admission rates range from 52-226.7 per 100,000 population.
Figure 7.8: Directly Age Standardised Mortality rates for Lung Cancer (ICD10 C33-C34), by Local Authority, All Ages, 2005-2007 pooled.
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Death rates from Lung Cancer are again highest in Stoke-on-Trent LA followed by Cannock Chase and Sandwell LAs. Rates are lowest in the more rural areas of Oswestry, Herefordshire and Stratford-upon-Avon.
Figure 7.9: Directly Age Standardised Admission rates for Lung Cancer (ICD10 C33-C34), by Local Authority, All Ages, 2005-2007 pooled.
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Lung Cancer admission rates for the West Midlands are on average for males 108 per 100,000 and for females 64 per 100,000. Stoke-on-Trent, Sandwell and Walsall experience the highest admissions rates within the region and Redditch, Bromsgrove and North Warwickshire the lowest.
7.8 Conclusion
Studies in the UK, Europe and elsewhere clearly show an association of air pollution and health. In the West Midlands air pollution and poor respiratory health tend to be found in similar places. However these places also have other characteristics in common such as high deprivation scores and perhaps smoking so it does not necessarily follow that air pollution causes the ill health. None the less there is a strong health argument for reducing air pollution.
Appendix 1 – Data definitions used to pull off Mortality and HES data
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Hospital Episode Statistics
Hospital admissions data was filtered on finished in year admissions, ungrossed, total episodes.
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Acknowledgements:
George Fowajuh and Dr John Kemm
For more information please contact Sarafina
Cotterill
© Public Health, Epidemiology and Biostatistics Unit, School of Health and Population Sciences, University of Birmingham