Medicosnext
On April 14, 2017, the Government of Nepal instituted a ban on vehicle horns in Kathmandu Valley. A couple of years before this happened, around 2015 or 2016, I remember going to work every day around 10 in the morning. And, as soon as the vehicle would reach Baneswor Chowk, the beeping of the horns would get unbearable. By the time I reached the office, I would have a throbbing headache to help me start my day. And I am far from the only person who cannot bear the presence of loud unnecessary noises.
Noise, in short, is defined as any unwanted sound. What differentiates noise from sound is the listener. Noise is unpleasant, loud, or disruptive to the hearing of the listener. From a physical standpoint, higher decibels of sound have a more pronounced impact on humans, and as such, are more harmful to human health. WHO has categorized any noise above 65 decibels (dB) as noise pollution. When noise exceeds 75 decibels (dB), it can become harmful to humans, and above 120 dB, the noise is painful.
With rapid urbanization and the rise of cities, people are becoming regularly exposed to high levels of unpleasant noise, whether it is from road traffic, construction, industries, or other sources. This regular exposure to elevated sound levels is noise pollution, and it is fast becoming a major issue in cities worldwide when it comes to the health of its inhabitants. According to estimates by the European Environment Agency, more than 72,000 hospital admissions and 16,600 premature deaths are caused by noise pollution every year in Europe alone.
Noise is a stressor for human beings. The most common effect of noise is on the hearing, but it has a lot of unwanted and unpleasant side effects on other systems of the body, as well. Indoor and outdoor environmental noise pollution have been documented as a serious health hazard. Pregnant women, fetuses, newborns, infants, and children are most susceptible to noise-induced health hazards and are in need of most protection.
The most widely known non-auditory effect of noise pollution is stress. Unwanted, uncontrollable, and unpredictable sounds can be annoying to humans, and the human body reacts to this annoyance through a complex set of physiological responses labeled as stress. It has been well established that noise pollution can cause stress. According to a study done on male street vendors in Brazil, vendors exposed to higher levels of noise (70.2 to 76.6 dB) than recommended by WHO standard showed higher cortisol levels in their saliva samples.
Noise and noise-induced stress affects various systems in a human body, including the nervous, endocrine, and circulatory systems. Physiological responses to noise-induced stress can include rise in blood pressure, excessive secretion of certain hormones, a change in heart rhythm, or a slowing down of digestion. Prolonged exposure to noise and its accompanying stress can cause permanent ailments in the circulatory, cardiovascular, or gastrointestinal systems.
Looking at the current data from the European Environment Agency, environmental noise contributes to 48,000 new cases of ischemic heart disease, and subsequently, 12,000 premature deaths every year. Furthermore, it is estimated that 22 million people suffer chronic high annoyance and 6.5 million people suffer chronic high sleep disturbance due to noise pollution.
Noise severely affects our sleep. WHO recommends less than 30 dB in the bedroom for a good night’s sleep. A 2000 study by Passchier-Vermeer and Passchier noted that noise pollution or noise disturbances at night can lead to changing sleep patterns and increased awakenings, and it also showed an effect on heart rate. Noise-induced sleep loss can also affect work performance, make one less attentive, and more accident prone. A 2018 study done on students in Bulgaria also showed that higher residential noise level was associated with higher annoyance, and subsequently, with lower restorative quality of the environment, as well as lower physical activity.
Children are particularly susceptible to the negative impacts of noise pollution. Studies have shown that behavioral problems in children are related to noise. Similarly, noise had negative impacts on cognitive development of infants. It also reduced attention span and increased recovery time after mild stress. A study done by Evans and Lepore in 1993 concluded that residential noise delays the early cognitive development in children. In the classroom setting, chronic exposure to noise was associated with poorer reading. The study also showed that children with lower aptitude were apparently more susceptible to the harmful impact of noise.
Noise pollution has an impact on mental health, as well. In 2017, a multilevel analysis of noise pollution in Beijing on the mental health of the people was conducted. It showed that higher noise pollution was significantly associated with worse mental health. While studying the distribution of the noise pollution, the researchers also found that proximity to the main road (hence more exposure to traffic noise) also contributed to variations in self-reported mental disorders.
Other studies have shown that annoyance caused by noise affects the complexity of brain activities and EEG signals. This may cause psychological problems like reduced attention, and it can also affect the function of individuals and their cardiovascular condition.
According to various studies conducted between 2014 and 2018, noise annoyance was most consistently associated with depression and anxiety. The studies suggested that noise annoyance was related to stress and increased suicide ideation. Two studies conducted in 2018 and 2020 by Min and Min, and Diaz, respectively, also discovered an association between cases of suicide and noisier neighborhoods.
With the rise of cities and increasing urbanization, it is expected that noise pollution may become an even greater challenge on human health. Studies have shown that noise pollution affects inhabitants of megacities worldwide. The social costs of traffic noise in the 22 member states of the European Union was calculated to be more than €40 billion per year. According to the report by the European Environment Agency, about 100 million people are exposed to road traffic noise above 55 dB in European Union countries. Worldwide, the number reaches 200 million.
As cities grow and expand, the population living in the cities, as well as sources of noise pollution in cities (road traffic, construction, etc.), are expected to increase. According to United Nations estimates, more than 55% of the world population lives in cities, and by 2050, it is projected that more than two-thirds of people in the world will live in cities. Living in increasingly denser cities means higher exposure to noise pollution and higher health impacts of noise pollution. So, it is imperative that cities take a stand to reduce noise pollution for the health and well-being of its inhabitants.
