Diesel taxis in London (Image by Flickr user Lars Ploughmann, used under CC license)
The air pollution caused by vehicle emissions has been linked to numerous health issues, something that's caused many world cities to work to reduce the number of carbon-emitting cars on their roads.
But a new study from the U.K. indicates that large volumes of cars moving through an area can cause additional problems for nearby residents.
The study found a possible link between prolonged exposure to traffic noise and reduced life expectancy, as well as an increased risk of stroke.
Research was led by the London School of Hygiene & Tropical Medicine, in partnership with King's College London and Imperial College London.
For this study, researchers analyzed data from 8.6 million people living in different areas of London between 2003 and 2010.
Researchers compared levels of road traffic noise in different postal codes, and made separate notations for day and night, with daytime considered 7:00 a.m. to 11:00 p.m. and nighttime the remaining 12 hours.
New Delhi traffic, by Flickr user denisbin (Used under CC License)
In areas where average traffic noise was higher than 60 decibels, deaths were found to be 4 percent higher than in areas where the average was less than 55 dB.
These deaths were mostly linked to "heart or circulatory disease."
Researchers claim this could be due to increased blood pressure, sleep problems, and stress from the noise.
Traffic in Atlanta, Georgia during rush hour (via Wikimedia)
Night traffic noise was also linked to a 5-percent increase in stroke risk, but only for the elderly.
In London, an estimated 1.6 million people are exposed to daytime traffic noise levels above 55 dB--which the World Health Organization defines as a "level of community noise that causes health problems."
However, the study's authors note that the results only look at area trends, and are not predictive of the risk to individuals.
They do not account for individuals who may already have an elevated risk of stroke or heart problems.