Causes of Air Pollution from the Built Environment
Our buildings and cities across the world are responsible for producing both outdoor and indoor air pollution. Read on for more information about the range of different causes that can impact human health and the natural environment.
Ambient Air Pollution
Ambient, or outdoor, air pollution is caused by a range of factors, including transport, agriculture and waste . However the contribution of the built environment, in both the construction and operational phases, cannot be underestimated.
Causes of outdoor air pollution:
- 39% of global energy-related carbon emissions are attributed to buildings .
- 28% of this is buildings in operation, predominantly for heating, cooling and lighting . Energy use is heavily impacted by the quality of building envelope, with emissions especially substantial in older building stock.
- The additional 11% of carbon emissions are attributed to emissions embodied in the construction process, which has a well-catalogued impact on the environment from waste generation, water use, dust creation and greenhouse gas emissions .
- 1,500 billion bricks are produced each year to construct our buildings – the majority of which are created using polluting kilns . Brick kilns contribute to up to 20% of global black carbon emissions, alongside steel and iron production. 90% of brick production is concentrated in central Asia, with emissions further increased by transportation to global markets .
- Fine particles (PM2.5/PM10) are emitted from the combustion of fuels to power our buildings, as well as from transport emissions mostly concentrated within cities . Sustainable urban planning therefore also has a role in the reduction of air pollution.
- Building construction can be responsible for the release of toxic dusts such as silica or hardwood, which are recognised as having carcinogenic properties .
- Hydroflourocarbons (HFCs), cooling agents commonly found in air-conditioning and refrigeration systems, can be up to 1000 times more potent than carbon dioxide, and are powerful contributors to global warming . The volume of HFCs in the atmosphere is increasing at 8-15% per year due to population growth and urbanisation, and their use is likely to increase as our climate warms . The importance of sustainable development is unparalleled here, with 2.3 billion people across the world expected to soon purchase an air conditioning unit or fridge, and it is likely that choices will be limited to inefficient and highly emitting appliances .
- Residential energy use in the developing world, particularly the use of traditional cookstoves, open fires or kerosene lamps for heating, cooking and lighting within homes, is responsible for up to 58% of black carbon emissions worldwide . Black carbon is an example of a short-lived climate pollutant. Short-lived climate pollutants are powerful climate forcers that remain in the atmosphere for a much shorter period of time than carbon dioxide , however their potential to warm the atmosphere can be between tens and thousands of times greater . The use of these fuels occurs primarily in areas of very low economic development, where over 1 billion people are facing energy poverty and subsistence living . Global sustainable development is clearly a vital instrument in tackling these emissions – “Innovative approaches are needed to address the needs of the 1.3 billion people lacking electricity, while simultaneously transitioning to a decarbonized energy system” – CCAC Secretariat 
Indoor Air Pollution
Pollutants found within all types of buildings can be harmful to people across the world, with nearly 4 million deaths per year attributed to exposure to household air pollutants .
Types of indoor air pollution:
- Emissions from combustion of solid fuels for cooking and heating causes indoor pollution, as well as outdoor. Particulate matter generated from burning wood, coal or other solid fuels causes health consequences such as strokes, pneumonia, lung cancer and heart disease . Cooking appliances in the developed world, including gas-powered systems, can also contribute to poor indoor air quality due to release of gases such as nitrogen oxide .
- Biological contaminants: Air infiltrating through cracks in the building exterior is a recognised cause of damp, leading to mould and fungi growth within walls and buildings, and consequential microbial pollution of indoor air . Research has shown that asthma risk increases by up to 40% when occupants live in homes with mould . Organically derived gases, such as radon, can also generate a form of indoor pollution that presents major health risks .
- Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids, some of which may have adverse health effects, ranging from headaches and nausea to vital organ damage and suspected link to cancer. Concentrations of many VOCs are consistently higher indoors (commonly up to ten times but can reach one thousand times higher) than outdoors . VOCs are emitted by many commonplace products, including paints, sprays, varnishes, cleaning products, air fresheners, building materials and furnishings. Some VOCs in concentration can be perceived as odours by the human nose, which could be pleasant or unpleasant depending on individual preferences. Exposure to unpleasant odours has been scientifically linked to negative mental health impacts .
Causes of indoor air pollution:
- Poor ventilation can cause an accumulation of pollutants inside buildings and can result in carbon dioxide build-up, or accumulation of moisture that can trigger allergens or damp and mould growth.
- Furnishings, including carpets and furniture, often release gases and chemicals that should be cleared from an indoor environment to maintain a healthy indoor environment. Chemicals found in many household items – including flame retardants, pesticides and fragrances – have also been associated with negative health impacts .
- Toxic building materials, such as asbestos, have been common construction materials for decades and causes health issues from exposure to polluted indoor air.
- Occupier activities including cooking or heating with solid fuels, smoking, cleaning or decorating using VOC-releasing products can further contribute to indoor pollutants build-up
- The relationship between outdoor and indoor pollution is not distinct. Outdoor pollution can penetrate into indoor environments through openings and cracks in the building fabric. Given we spend the majority of our time inside (90% according to research ), most of exposure to outdoor air pollution occurs when we’re within buildings .
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