Laura Bliss is CityLab’s West Coast bureau chief. She also writes MapLab, a biweekly newsletter about maps (subscribe here). Her work has appeared in The New York Times, The Atlantic, Sierra, GOOD, Los Angeles, and elsewhere, including in the book The Future of Transportation.
A worrisome study sheds new light on the health hazards of noise pollution.
The list of concerns around noise pollution is growing longer and wider, as a new study in Occupational and Environmental Medicine reveals an association between exposure to high decibels of road, rail, and air traffic sound and a risk of developing excess fat around the abdomen.
Researchers from Sweden’s Institute of Environmental Medicine conducted a multi-year survey of 5,075 people living in suburban and rural areas around Stockholm, all of whom had been involved in a previous study on diabetes risk factors.
In the new study, participants were asked about their overall lifestyle, physical and psychological health, sleep patterns, and work habits—as well as the level of road, rail, and air traffic sound they regularly heard. The researchers compared these answers to government data on the same noise levels. They found that some 54 percent of participants were exposed on a regular basis to one of the three types of traffic noises at or above 45 decibels—the baseline for what was considered harmful. 15 percent were exposed to two of the traffic noise sources, and 2 percent were exposed to all three. Participants were also given a thorough medical examination.
Controlling for socioeconomic and lifestyle factors, the researchers found a significant association between levels of traffic-noise exposure and the risk of developing fat around the central abdomen for people under the age of 60. Airplane noise was found to be particularly harmful, and there was also a cumulative negative effect from exposure to multiple noise sources: Whereas exposure to one kind of noise source was associated with a 25 percent higher chance of a larger waist, exposure to all three sources nearly doubled that risk.
Why? Noise pollution is an established psychological aggravator. It can trigger increased stress-related hormone production, in turn contributing to excess fat deposition, specifically around the abdomen.
"This may explain why the effects of noise were mainly seen for markers of central obesity, such as waist circumference and waist-hip ratio, rather than for generalised obesity, measured by BMI," the researchers write.
The grumble and roar of planes, trains, and cars can also compromise healthy sleep habits, which can have serious metabolic effects. And a little excess fat around the waist isn’t just a body-image concern: Central obesity is considered the most dangerous form of obesity.
The Swedish study is limited in certain ways, including the fact that household-specific data on noise exposure was a little fuzzy: For example, neither the location of participants’ bedrooms nor the level of wall insulation were taken into account. The researchers also didn’t look into other types of noise pollution.
But the research is still a useful addition to a growing body of knowledge connecting urban noise pollution to serious health hazards. As CityLab reported in April, cardiovascular disease, cognitive impairment, chronic stress, and hearing problems are other associated risks.
One possible solution? A greener city. Not only does glimpsing plant life help mitigate stress, but certain types of green roofs and walls have also been found to reduce road traffic noise by up to 7.5 decibels.