Clean Air


Condition for an Ecocity

The city maintains a level of air quality that is conducive to good health within buildings, the city’s air shed, and atmosphere.

Justification: breathe, both inside and outside. Overall conditions for healthy biodiversity and healthy life on this planet are conditional upon the maintenance of a healthy atmosphere.

Suggested Headline Indicator

Quality of indoor and outdoor air and quantity of greenhouse gas emissions

The IES calls for clean air at three scales: i) in buildings, ii) the city’s air shed, and iii) the atmosphere. Most people spend a portion of every day in some form of shelter. Whether it is a natural enclosure (like a cave), a one-room shelter, or a multi-story building, the air we breathe affects our health. Natural ventilation usually provides the best solution from an environmental perspective because it avoids the need for electrical and mechanical equipment that increase demand for energy and materials.

Of course, what we do inside also affects the air. Cooking, cleaning, and off- gassing of fabrics and paints can contribute to poor indoor air quality. For example, using toxic chemicals or burning charcoal or wood in a poorly ventilated area can negatively impact health. Ensuring clean air in buildings is, therefore, about what we build, how we build, and what we do in buildings – be they big or small.

If the air outside is polluted, however, then a naturally ventilated shelter cannot provide healthy indoor air. Clean air in the city is critical. Urban air pollution comes from a variety of sources, most notably the combustion of fossil fuels. Cities that are automobile-dependent tend to have poor urban air quality. Buildings can also contribute to local air pollution if they are being heated by wood, coal, oil or to a lesser extent natural gas, or if these products are used in activities such as cooking. Clean burning technologies can help reduce theimpacts substantially. But it isn’t just buildings and transportation that affect a city’s air quality. Where the city is located also plays a role. This larger context is the city’s air shed.

An air shed is an area defined by the natural movement of air within a region. Air flow is affected by prevailing wind patterns. Topography (e.g., mountain ranges) and other geographic features such as large open bodies of water or savannah, seasonal changes in temperature, and even localized weather events such as a warm sunny day, can all affect air flow in the air shed. For example, cities located within valleys are often subject to the build-up of emissions that create a brown haze on hot sunny days. This can be caused by a thermal inversion – where a mass of cold air sits above the air shed, trapping the warmer air and all of the contaminants below. To ensure clean air in the city’s air shed, ecocities support the principles of: a) Access by Proximity, b) Clean and Renewable Energy, and c) Responsible Use of Resources and Materials.

Moving beyond the city’s air shed, the largest scale of concern is the atmosphere. Ozone depleting substances and an imbalance in greenhouse gases can jeopardize both human health and all life on the planet. The atmosphere is the relatively thin layer of gases that surround the Earth and enable life to thrive by shielding out harmful ultraviolet rays from the sun while simultaneously retaining a certain amount of thermal radiation to keep the planet warm. This is an essential feature of GAIA (Lovelock 1972), earth’s self-regulating systems that maintain the conditions necessary for life. Global conventions, such as the Montreal Protocol and the Kyoto Protocol aim to regulate human activities that jeopardize the health of the atmosphere.

However, more action is needed. Scientists call for an 80% reduction in greenhouse gas emissions to stabilize the insulating function of our atmosphere and avoid disruptive impacts such as rising sea-levels from thermal expansion of the oceans as they warm coupled with melting glaciers. Fortunately, ecocities can help reduce greenhouse gas emissions through the very same principles that support clean air in the city’s air shed. Yes, what is good for the air shed is also good for the atmosphere: a) Access by Proximity, b) Clean and Renewable Energy, and c) Responsible Use of Resources and Materials.

J. E. Lovelock (1972). Gaia as seen through the atmosphere, Atmospheric Environment 6 (8), pp. 579-580.

Suggested Ecocity Level 1 Benchmark

Total per capita greenhouse gas emissions at or below 1.5 tCO2e/ca/yr

Climate stabilization studies indicate that at a global population of 7.3 billion, per capita emissions of no more than 2 tonnes per year meet the global sequestration threshold. A target of not more than 1.5 tCO2e per capita has been identified as the per capita target for a one-planet city (Moore 2015; 2013). However, it should be noted that even a lower target of 1 tonne per person per year may be inadequate to achieve climate stability, let alone reverse climate changes already underway. It is possible to reach 1 tonne per person per year even in a high consuming society, e.g. North America, for someone fully committed to solar, car-free living. A consumption-based approach to emissions inventorying (vs a territorial approach) provides a more comprehensive, and therefore, more accurate reflection of the emissions associated with an urban resident’s lifestyle.