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The ozone layer protects construction materials from damage caused by too much UV radiation. By protecting the ozone layer, the Montreal Protocol prevents damage to plastics and wood worth almost US$50 billion globally between 1987 and 2060. The Protocol also supports the development of safe, sustainable and affordable refrigeration and air-conditioning that are increasingly required in our cities.

SDG11 aims to ‘Make cities and human settlements inclusive, safe, resilient and sustainable.’ The Montreal Protocol helps to achieve this in several ways, but especially in relation to Target 11.6 ‘reduce the adverse per capita environmental impact of cities’ and Target 11.B ‘increase the number of cities and human settlements adopting and implementing integrated policies and plans towards inclusion, resource efficiency, mitigation and adaptation to climate change.’

There is little doubt that uncontrolled emissions of ozone depleting substances (ODSs) would have threatened the safe and sustainable use of many construction materials. Even now, plastics and wood that are exposed to sunlight are damaged by the UV radiation. UV damage weakens materials and reduces their service life, requiring the use of UV-protectant additives and coatings, and increasing costs.  

Without the Montreal Protocol to control ODSs, run-away ozone depletion would have led to very large increases in UV radiation around the world. The resulting increase in damage to materials would have added costs, either by requiring more frequent replacement or repair, or by the need to use more protectants. For example, The Montreal Protocol and the Green Economy report estimated that, without ozone protection, the global socio-economic cost of increased material damage would have totalled US$30 billion between 1987 and 2060. Note that these figures are based on values in US$ in 1997. 

Research into how UV damages building materials, stimulated by the Montreal Protocol, is now contributing to the development of more sustainable but durable building materials. For example, new, greener UV protectants can help make wood more acceptable as a renewable alternative to plastics. Our improved knowledge of the mechanisms by which UV damages materials is even helping to understand how plastic pollution breaks down in the oceans.  

The Montreal Protocol has also stimulated research into the links between the stratospheric ozone layer and ozone much lower in the atmosphere, or more simply, in the air we all breathe. This research is improving our understanding of air pollution, including ozone itself, which when present low down in the atmosphere is damaging for both crops and human health. Modelling studies indicate that the gradual recovery of stratospheric ozone due to the success of the Montreal Protocol will lead to decreased ground-level ozone as an air pollutant in some urban areas. 

Perhaps the greatest contribution of the Montreal Protocol to making cities and settlements sustainable is through the profound changes in refrigeration and air-conditioning that have resulted from the phase-out of ozone depleting substances (ODSs), as described under SDG7. These changes have enabled major improvements in the efficiency of refrigerators and air-conditioning units, a process that is continuing through the Kigali Amendment. Improved energy efficiency reduces the running costs, and so improves equitable access to air-conditioning and refrigeration. Both are increasing rapidly and expected to be in even greater demand as cities and communities adapt to climate change.