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Medical School Hot Topic: Air Quality & The Environment
Air pollution is the contamination of the air we breathe - be it indoors or outdoors. It may be due to a variety of sectors or polluters.
We should be especially aware of the role of Particulate matter (PM). PM can have an adverse effect on health at low concentrations, and there is no evidence of a threshold below which no adverse effects might occur. Health effects may be short term or long term, and should be seen as a concern across the world, rather than just in developing countries. Some PM is emitted directly from a source - like a construction site or smokestack - whereas most form in the atmosphere as a result of reactions between emitted chemicals like nitrogen oxides and sulphur dioxide.
Small particulate matter is the most harmful to our health, with ozone, nitrogen oxides and sulphur oxides being of particular concern as they are precursors to secondary particulate matter in the atmosphere, exposure to which can cause ischaemic heart disease and stroke, COPD, lower respiratory infections and lung cancer. PM is composed of sulphates, nitrates, carbons and mineral dusts. Fine PM, known as PM 2.5 accounts for most health effects due to air pollution.
Where does air pollution come from?
Air pollution stems from a variety of sources. Human made air pollution is primarily driven by vehicles, fuel oils and natural gas, coal fuelled power plants, chemical production and manufacturing and industry by-products.
TRAP - traffic related air pollution - comes from motor vehicle emissions and is perhaps the most easily recognised form of air pollution. It contains a mixture of ozone, carbon, nitrogen oxides, sulphur oxides, organic compounds and fine particulate matter.
Ozone is labelled as smog when at ground level, and created by cars, boilers, refineries etc - through the reaction of pollutants in the presence of sunlight.
Noxious gases - including carbon dioxide, carbon monoxide, nitrogen oxides and sulphur oxides stem from both motor vehicle emissions and industrial processes.
Volatile organic compounds - VOCs - vaporize around room temperature. They may be released by paints, pesticides, furnishings or glue.
Polycyclic aromatic hydrocarbons (PAH) contain carbon and hydrogen, and many are carcinogenic. They are released from combustion engines and industrial processes. They may be found in particulate matter.
Nature itself may release methane from decomposing organic matter, or hazardous substances from wildfires and volcanic eruptions.
Air Pollution in Europe
Emissions of the principal air pollutants have been declining in Europe, although a large part of the population still suffers from exposure that is higher than the World Health Organisation’s guidance. The principal sectors that contribute to air pollution in Europe are agriculture, energy, transport, industrial, commercial and the waste sectors. Tobacco smoke is also thought to be an important source.
The agricultural sector emits 94% of ammonia, 54% of methane and is the third most significant source of PM emissions. The sector is yet to instigate viable measures to reduce its emissions. The energy sector is responsible for the largest release of sulphur oxides and certain heavy metals.
Health Effects of Particulate Matter
The smallest particles - those under 10 micrometres, especially Fine PM - are most able to penetrate deep into the lungs or even enter the bloodstream. An overview list of problems linked to particle pollution exposure includes: premature death in those with heart or lung disease, myocardial ischaemia, irregular heartbeat, aggravated asthma, decreased lung function, airway irritation, COPD, and difficulty breathing. Those with existing heart or lung disease are most likely to be affected by particle pollution.
Around 3% of cardiopulmonary deaths and 5% of lung cancer deaths are attributable to PM across the globe, with this figure being in the region of 1-3% and 2-5% in the EU. In 2010, ambient air pollution of PM 2.5 accounted for more than 3 million deaths, and 3% of global disability adjusted life years.
- What do you know about the role of air pollution in human health?
- What do you know about different types of air pollution?
- What type of air pollution is thought to be the most dangerous to our health?
- What health problems are typically brought about through particulate matter?
- What sectors contribute the most to air pollution across the world?
- Why are the smallest particles the most damaging to human health?
- How can we combat air pollution?
Interview Questions & Example Answers
What do you know about the role of air pollution in human health?
I understand that air pollution can be very damaging to our health. Particulate matter - known as PM - is the primary cause of human pathology from air pollution, and the smaller particles are the most damaging.
Fine PM - the smallest of all, those less than 2.5 micrometres - are able to enter deep into the lungs and even into our bloodstream, causing heart and lung problems, like asthma, lung cancer, COPD or ischaemic heart disease.
Around 5% of lung cancer deaths worldwide are attributable to PM, and around 3% of cardiopulmonary deaths.
What do you know about different types of air pollution?
Air pollution comes from a range of sources. Our motor vehicles release traffic related air pollution, a mixture of ozone, carbon, nitrogen oxides, sulphur oxides, organic compounds and fine PM. Volatile organic compounds - VOCs - may be released from paints, pesticides and furnishings. Ozone is released by refineries, cars, boilers and industry. Nature itself releases pollution - methane from decomposing organic matter and hazardous gases from wildfires and volcanoes.
Particulate matter is primarily formed from the reaction of emitted chemicals within the atmosphere, but may also be produced directly from a pollution source like a smoke stack.
What type of air pollution is thought to be the most dangerous to our health?
The most dangerous type of air pollution is small particulate matter. Small particulate matter may be formed from the interaction of ozone, nitrogen oxides, and sulphur oxides, or may be released directly. It is the primary cause, amongst air pollution, of ischaemic heart disease and stroke, COPD, LRTIs and lung cancer. Fine PM - known as PM 2.5 - is the most damaging form of particulate matter.
What health problems are typically brought about through particulate matter?
Particulate matter causes premature death in those with heart or lung disease, myocardial ischaemia, and an irregular heartbeat. It also causes aggravation of asthma, chronic obstructive pulmonary disease, and difficulty breathing. It may exacerbate existing heart or lung disease.
What sectors contribute the most to air pollution across the world?
In order to answer this question I must focus on specific areas and a specific type of air pollution, and I will therefore choose to focus on particulate matter - specifically PM 2.5. 25% of PM worldwide was created by traffic, 15% by industrial activities including the generation of power, 20% was generated by domestic fuel burning, 18% from natural dust, and 22% from unspecified human activities.
If we look at different areas, we will find relatively similar results - traffic for example contributed to 37% of PM 2.5 in India, 34% in Southern Asia, and 35% in Southwestern Europe.
Why are the smallest particles the most damaging to human health?
The smallest particles are the most damaging as their small size allows them to travel deep into the respiratory tract and into the lungs. This means that they will cause both short-term effects like the irritation of your nose and throat, coughing or sneezing, and long-term effects like asthma, COPD or lung cancer.
Additionally, fine particle pollution can cause cardiovascular disease through accelerated atherosclerosis, an alteration in cardiac autonomic function, and pulmonary and systemic inflammation.
How can we combat air pollution?
There are many steps that we can all take to reduce air pollution. We should carpool or use public transportation as far as is possible or use bikes or walk to work. We should ensure that our cars are properly serviced, with their tyres properly inflated. We should look to use environmentally safe paints and cleaning products.
We might choose a new way of commuting or a new route, act to combine trips to the shops or errands, and act to conserve electricity. This might involve using less heating or AC, reducing the number of showers we take, and ensuring that we turn off lights and power around the house when it is not being used.