State of health
‘9 out of 10 people worldwide breathe polluted air’ (World Health Organization1)
Air pollution is considered today as the greatest environmental threat to human health, causing approximately seven million deaths each year2. Exposure to polluted air increases mortality risk to
people from stroke, heart disease, pulmonary disease, lung cancer and respiratory infections3. Our buildings and cities across the world both expose people to indoor air pollution and contribute to the ambient (outdoor) pollution crisis. Both pollution sources have distinct causes across the building lifecycle and must be tackled accordingly to protect human health and wellbeing.
Indoor Air Quality
Studies suggest people spend 90% of their time indoors4. Therefore, exposure to pollutants within the home and other indoor environments can be highly damaging to human health, and worsened in sealed or contained indoor environments with reduced air flow. The primary causes of indoor air pollution that pose risk to human health are as follows:
- Household air pollution from solid fuel combustion: 3.8 million premature deaths are attributed to household air pollution annually5, primarily due to the use of solid fuels and kerosene which creates toxic particulate matter through combustion. Primarily an issue in developing nations, where alternative sources of fuel can be scarce, the World Health Organization estimates that around 3 billion people worldwide lack access to clean or modern energy services for cooking6. Exposure to particulate matter can cause cardiovascular and respiratory disease and strokes7.
- Household air pollution from gas appliances: gas stoves are used worldwide for heating and cooking, and often considered the ‘clean and safe’ upgrade from solid fuel combustion. However, research shows that pollutants released from gas appliances can lead to heightened nitrogen dioxide levels, which can worsen respiratory conditions such as asthma8. Gas is a fossil fuel; combustion of which releases greenhouse gas emissions, worsening climate change.
- Release of harmful gases and chemicals from materials: pollutants released within the indoor environment include volatile organic compounds (VOCs) from building or fit-out materials including paints and varnishes, adhesives and furnishings, and household items such as electronics and cleaning materials. Exposure to these pollutants can be concentrated in an indoor environment, and consequently trigger health issues such as nausea, headaches, respiratory irritation, and allergies9. Organically derived gases, such as radon, can also generate a form of indoor pollution that presents major health risks. Exposure to hazardous chemicals within buildings is further detailed in Principle 6.4 below.
- Biological contaminants: often linked to building quality, infiltration of air through cracks in the building façade (exterior) can cause damp, leading to mould and fungi growth within walls, releasing airborne microbial pollution within indoor air10. This occurs in both hot, humid climates and cold, temperate climates. Research has shown that asthma risk increases by up to 40% when occupants live in homes with mould11.
- Infiltration from outdoors has also been identified as a significant health risk for people within buildings, with studies showing that 65% of our exposure to outdoor air pollution occurs indoors12.
Ambient air pollution
Ambient, or outdoor, air pollution is caused by a range of factors, including transport, agriculture, and waste. The contribution of the built environment across the building and construction lifecycle is substantial and must be mitigated to protect human and environmental health. Causes of ambient air pollution related to the built environment include:
- Manufacturing of building materials: notably the use of highly polluting brick kilns, which contribute to up to 20% of global black carbon emissions, alongside steel and iron production13. 90% of global brick production is concentrated in central Asia, causing direct localised health impacts to local people. Emissions from production are further increased by transportation to global markets11.
- Building construction: 11% of global energy-related carbon emissions are attributed to emissions embodied in the construction process, which further impacts human health through dust creation14. The release of toxic dusts from construction sites (such as silica or hardwood, which are recognised as having carcinogenic properties) creates localised extreme health hazards to construction workers and people living nearby15.
- Operational buildings:
o 28% of global energy-related carbon emissions are attributed to operational buildings,predominantly from energy used for heating, cooling and lighting12. The release of carbon emissions is a core contributor to climate change, explained as a health risk in Principle 6.1.
o Fine particles (PM2.5) are emitted from the combustion of fuels to power our buildings, and for heating or cooking within, as well as from transport emissions16.
o The use of traditional cookstoves, open fires or kerosene lamps for heating, cooking, and lighting within homes in the developing world is responsible for up to 58% of black carbon emissions worldwide17.
Building provides only clean air through the mitigation of air quality risks and incorporation of health-based strategies, whilst maintaining energy efficiency. Air quality should be enhanced at all stages of lifecycle, including construction workers, and protecting health of people within and outside, considering both building occupants and neighbouring people.
Strategies across the lifecycle
Tackling ambient air pollution:
- Support the switch to more efficient building material production, particularly around traditional brick firing
- Energy efficient building design (and renovation) to improve the quality of building envelope and consequential energy load for heating and cooling
- Passive design strategies, including energy efficient building fabric, vegetation, and ventilation, can reduce heating or cooling requirement within buildings and maintain comfortable living conditions (see Principle 2.1 for more detail)
- Sustainable urban planning also has a role in the reduction of air pollution, through mitigation of emissions from transport through a low or zero carbon infrastructure networ
- Dust production should be appropriately managed with national and organisational regulation, best practice and policy adherence on site, and other dust-reduction strategies. Off-site, modular construction practices can be preferable due to lower volume and more controlled dust production
- Support the switch to more efficient building material production, particularly around traditional brick firing
- Reduce operational and embodied carbon emissions (see Principle 6.1 for more information)
- Commit to monitoring indoor and outdoor air quality in real-time, to increase awareness and promote data-driven action to mitigate pollution sources and improve public health. Air quality monitoring can be undertaken as part of World Green Building Council’s Plant a Sensor campaign.
Improving indoor air quality:
- Lessen exposure to hazardous chemicals in the indoor environment through conscious product selection and the use of low emission materials, such as low volatile organic compounds (VOCs) emission paints, sealants, adhesives, fixtures, fit-outs, and flooring as well as low- formaldehyde products
- Energy efficient building design and/or renovation to reduce risk of damp or mould build up
- Minimisation of potentially harmful chemicals in building materials (see Principle 6.4 for information)
- Proper filtration of air for forced air systems, particularly in locations susceptible to poor air quality, such as areas susceptible to wildfires
- Removal of harmful materials from existing buildings
- Installing porous materials after ‘wet products’ (adhesives/sealants and paints/coatings) have been given a chance to off-gas, when possible
- Use appropriate ventilation to remove indoor air and toxins to exchange with fresh and clean air into buildings, including designs that maximise cross-flow ventilation. Ventilation can be mechanical, mixed-mode or natural, with energy efficient solutions prioritised.
- Minimise the use of traditional cookstoves through access to clean fuels and technology within buildings, prioritising electric alternatives rather than gas-based
- Phase out fossil fuels, including gas, as an energy source worldwide, prioritising residential
- Ensure localised extraction around gas appliances when used
- Inspect installation, maintenance, and cleaning of filtration and ventilation systems to ensure cleanliness, filter functionality and reduce the potential for mould and bacteria growth
- Commit to monitoring indoor and outdoor air quality in real-time, to increase awareness and promote data-driven action to mitigate pollution sources and improve public health. Air quality monitoring can be undertaken as part of the WorldGBC Plant a Sensor campaign
The World Health Organization (WHO) provides guidance on outdoor air quality, including information of particulate and gaseous pollutants. These outdoor values are also relevant for indoor environments due to close infiltration of pollutants between outdoors and indoors (research suggests an average of 65% of our exposure to outdoor pollution happens indoors4). The WHO Air Quality Guidelines (AQGs) for 24-hour mean concentration limits are18:
• PM2.5 less than 10 μg/m3
• PM10 less than 20 μg/m3
These figures are published as ‘the lowest levels at which total, cardiopulmonary and lung cancer mortality have been shown to increase with more than 95% confidence in response to long-term exposure to PM2.5’19. Interim targets, which reduce mortality risk to a lesser extent than the AQGs, are also available within the WHO Air Quality Guidelines.
There is no simple measure for indoor air quality due to the broad spectrum of parameters that are influenced by external and adjoining environments as well the activities and construction of the internal space. Common factors that contribute to the assessment of indoor air quality are volatile organic chemicals (VOCs) such as formaldehyde, and other gases including carbon dioxide and carbonmonoxide, ozone, nitrogen dioxide water vapour and radon; particulate matter; and biological components including bacteria, fungi (such as mould) and pollen; and ‘odours’. Benchmarks for air quality and ventilation are embedded within country specific standards.
Examples of specific benchmarks or limit values used in international rating tools20,21,22 are as follows:
• Carbon dioxide (CO2): 800ppm
• Carbon monoxide (CO): 9ppm
• Formaldehyde (CH2O): 27 ppb
• TVOC: 500 μg/m3
• Radon (Rn): 0.148 Bq/L [4 pCi/L]
An additional consideration for indoor air quality is humidity, which can heighten susceptibility to microbial airborne pollutants from damp or mould within a building. The American Society of Heating Refrigerating and Air-conditioning Engineers (ASHRAE) sets benchmarks for acceptable ventilation rates to control this risk. See also World Health Organization ‘Guidelines for Indoor Air Quality: Dampness and Mould’;
• ASHRAE Standard 62.1-2016 recommends that relative humidity in occupied spaces be controlled to less than 65% to reduce the likelihood of conditions that can lead to microbial growth
• Humidity levels significantly below 30% are considered less optimum for the respiratory system23. If the relative humidity is below 30%, the air is too dry this can cause irritation of the mucous membranes of the nose and throat, and breathing difficulties in at-risk individuals (e.g., people with asthma). Dry air is also harmful to people with skin or eye conditions24 .
In certain locations, filtration of air is required in addition to ventilation to ensure adequate air quality. MERV ratings of 11 or higher (or HEPA filters) provide air cleaning for pollutants that enter buildings or are recirculated in buildings. Residential homes can be designed to accommodate HEPA filtration.