Study finds that noise pollution is robbing nearly two decades of healthy hearing from the residents of Delhi and Mumbai

It isn’t news anymore that air pollution is impairing the lungs of Indians, particularly in north Indian cities like Delhi that have to cope with unfavourable meteorology. However, a study across 50 cities in the world finds that noise pollution — from vehicles, power drills, wedding bands, loudspeakers, headphone-use, television and humanity in general — is robbing nearly two decades of healthy hearing from the denizens of Delhi and Mumbai.

Using data gathered from over 2,00,000 participants of their hearing test, the study by Mimi, a German company that works on ways to test hearing and improve music perception, found that 64% of the hearing loss measured in people of a city could be explained by the region’s noise pollution levels.

Variations

The data was gathered by those who used Mimi’s hearing test app, which allows participants to enter their age and gender, and measure their hearing. This is broadly done by playing tones at various frequencies that cover the range of human auditory perception from 20-20,000 Hz. The theory goes that age irreversibly destroys the tiny hair in your inner ear, making it harder to hear high-pitched tones. The older you are, the less the range of frequencies perceived.

There is an international standard on the ideal hearing abilities across age groups and the Mimi researchers determined how far, on average, people’s hearing abilities deviated from what’s ideal for their age. This number, called the ‘Hearing Loss’ (HL), varied from 10 to 20 years and the researchers averaged this based on the number of respondents per city.

Residents of Vienna were found to have the smallest average HL of 12.59 years, meaning that a hypothetical 30-year-old had the hearing of a 42-year-old. Delhi performed the worst with an HL of 19.34, meaning that a 30-year-old Delhiite had the auditory level of a 49-year-old; Mumbai’s is 18.58. Other cities with the highest average HL but trailing Delhi were Istanbul, Cairo and Guangzhou, in that order. Zurich, Switzerland has the least incidence of noise pollution and Guangzhou, China the highest, according to the report.

“While eye and sight checks are routine for most, ear and hearing exams are not,” Dr. Manfred Gross from Charité University Hospital, Berlin, said in a statement, “This is an issue as the earlier hearing loss is detected, the better the chances are for preventing further damage.”

Decibels of discomfort

So far, the study is yet to be published in a scientific journal or peer-reviewed but prior research has established the link between hearing loss and noise levels.

It is estimated, according to a 2015 report commissioned by the European Commission on the impact of noise on health, that 1.3 billion people worldwide suffer from hearing impairment due to noise exposure and that the World Health Organization (WHO) estimates 10% of the global population is currently exposed to noise levels that could lead to hearing impairment. The same body recommends that unprotected exposure to sound levels greater than 100 dB (a firecracker generates about 125 dB) should be limited in duration (four hours) and frequency (four times a year). Additionally, it should never exceed 140 dB in adults and 120 dB in children. India’s Central Pollution Control Board conducts studies of ambient noise in commercial, residential and industrial townships — especially around Diwali — and has found that noise levels in Delhi, Mumbai and Lucknow routinely break the national limit of 75 dB.

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