The author is Executive Director of the United Nations Environment Program
Cities offer something for everyone: employment and entertainment opportunities; diversity and density, social benefits as well as social tensions. Yet the world’s largest metropolises – from Bangkok to Barcelona, from Bogotá to Cairo, from Damascus to Delhi, from Karachi to Kolkata and from New York to Nairobi – also present environmental dangers for their inhabitants.
While many of these – including waste, biodiversity loss and global warming – are already well documented, there is another often overlooked environmental threat that is increasingly impacting city dwellers: noise.
Like air pollution, noise pollution is far from being a simple nuisance. In fact, it is increasingly recognized that it has long-term effects on human health. Defined as unwanted, prolonged, high-level sounds, they can seriously impair our physical well-being. This includes chronic discomfort and sleep disturbances, leading to serious heart disease and metabolic disorders such as diabetes, as well as hearing loss and poor mental health.
As cities become more crowded, their soundscapes become a global threat to public health. Acceptable noise levels, as defined by the World Health Organization, are now exceeded in cities around the world. An estimated 90% of New York City transit riders are exposed to levels above the recommended decibel limit. In Ho Chi Minh City, cyclists are exposed to noise levels above 78 dB, which can lead to irreversible hearing loss. In the EU, noise pollution affects one in five citizens and leads to 12,000 premature deaths every year.
In his book, The Death and Life of America’s Big Cities, Jane Jacobs wrote that cities can only offer something to everyone because, and only when, they are created by everyone. This egalitarian ideal is rarely realized today. Cities, especially in low-income countries, are marked by social inequalities and geographic segregation.
Noise pollution particularly affects the very young and the elderly among marginalized communities who tend to live near busy roads and industrial areas rather than near green spaces.
As most of the world urbanizes, cities are becoming an increasingly important ecosystem, not just for humans, but for biodiversity as a whole. Noise pollution is also a threat to animals, altering the communications and behavior of various species, including birds, insects and frogs.
However, research clearly shows that natural sounds, emanating from urban green spaces, can provide various health benefits. In some cases, urban vegetation can absorb acoustic energy and scatter noise. Tree belts, shrubs, green walls and green roofs not only help amplify natural sounds by attracting wildlife, but also enhance the visual landscape of the street. While the ultimate solution to noise pollution is its reduction, rows of trees planted behind highways have been reported to reduce noise levels by up to 12dB in some locations.
Urban planners must consider both the health and environmental risks of noise pollution. Good measures have already been applied in urban areas around the world: from London’s ultra-low emission zone, the “noise radar” in Paris and Berlin’s new cycle paths on wide roads to the Egyptian national plan of noise control and the “tsunami” of 10 billion trees in Pakistan.
Yet there is still much to be done to combat the din in most cities around the world. Noise pollution is not just an inconvenience, but a serious health and environmental problem. Nor is it an inescapable part of city life. In recent years, there has been a great mobilization of resources to combat air pollution, responsible for the premature death of more than 7 million people a year. Cities need a similar campaign against the cacophony that harms people and the planet.