Building better cities through chemistry

With nearly 70% of the world population projected to live in cities by 2050, Goal 11 aims to make these urban areas inclusive, safe, resilient and sustainable. An understanding of chemistry plays a key role in meeting this global challenge. Goal 11 is a very wide-ranging goal that encompasses aspects of some of the other goals: clean water and sanitation (Goal 6), affordable and clean energy (Goal 7) and responsible consumption and production (Goal 12). These topics are covered in separate articles in this series. This article focuses on the management of urban air pollution and the construction of safe, affordable houses and buildings.

This article is part of the Sustainability in chemistry series, developed to help you integrate the UN’s sustainable development goals into your teaching of chemistry. It supports Goal 11: make cities and human settlements inclusive, safe, resilient and sustainable.

The construction industry uses metals, polymers, ceramics, concrete and glass as its primary building materials. The fundamental properties of these materials, including composite materials, are compared at 11–14 in many chemistry courses. At 14–16, students go on to look in more detail at how metallic and covalent bonding leads to these properties. Novel materials and nanochemistry are also relevant here, as innovative features are built into the design of buildings. Students also study the production of oxides of nitrogen (NO_x) and particulates (eg PM_2.5) as urban pollutants that result from the combustion of the hydrocarbon fuels used in transport and heating.

Put it in context

Students living in urban areas will appreciate first-hand the importance of the issues covered by this goal. However, all students will have encountered relevant issues in the media.

Introduce the topic of urban air pollution by looking at the establishment of congestion pricing zones in many major cities, as well as the controversy caused by car manufacturers installing software to falsify the levels of emitted NO_x. You can highlight existing pollution control measures, such as catalytic converters on vehicles, as well as the plan to phase out internal combustion engines in favour of electric vehicles. Another issue is the increased use of wood burning stoves in city areas leading to higher levels of airborne PM_2.5 particles.

The safety of building materials has also been in the news. The cladding material used on Grenfell Tower was particularly flammable because it is a composite of aluminium and poly(ethene), combining the ability of aluminium to conduct heat, with the low melting temperature of the thermoplastic polymer.

Put it into practice

Make the study of air pollution relevant to your students by using real-time data for a city near to them. Use the downloadable resource (above) to see how you can look up levels of different pollutants across the UK or Republic of Ireland. Students can monitor levels of nitrogen dioxide, as well as particulate matter (PM₁₀ and PM_2.5) over timescales as short as a week or as long as several years. Over the coming years it will be interesting for students to see if the introduction of congestion pricing zones and more hybrid and electric vehicles affect the levels of pollutants.

If you don’t have time to analyse the real-time data, see the resource Assessing air pollution levels, which uses historical data on NO₂ levels for an urban borough in the UK. If your students would like a more global perspective, then the website ourworldindata.org allows you to view air pollution data from 1900 to 2017 globally or by country. You can see how air pollution compares to other risk factors, such as smoking, obesity and alcohol, in causing premature deaths.

Finally, when students are studying nanochemistry at 14–16, there are some excellent examples of applications in buildings. See the articles, Nanotechnology saves bridges and Smart energy homes, for some ideas, and download the starter slide from A whiter shade of paint.