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Health

Sound effects

Studies show that chronic noise pollution affects our health, learning and well-being.

By RICK WEISS, Washington Post
Published September 4, 2007

Agrowing body of evidence confirms that the chronic din of construction crews, road projects, jet traffic and those ubiquitous leaf blowers is taking a toll on our health and happiness.

Providing scientific proof of this has not been easy, in part because noise, defined as "unwanted sound," is to a large degree a matter of personal taste and sensitivity. The romantic hears a train whistle differently than the insomniac.

But study after study has found that community noise is interrupting our sleep, interfering with our learning and suppressing our immune systems.

Those leaf blowers, for instance, generate a sound that is only a little less intense than the 85 decibels that the National Institute of Occupational Safety and Health says is physically damaging over a period of hours.

But it is cars, motorcycles, trucks and air traffic that accounts for most of the background noise that disturbs and even sickens people.

More than 40 percent of Americans whose homes have any traffic noise at all classify that noise as "bothersome," according to a 2005 Census Bureau survey.

To research the effect of everyday noise, scientists have taken advantage of situations in which people's exposure to noise changed while other factors remained relatively constant.

In a study of students attending an elementary school near noisy train tracks in New York, for example, researchers showed that by the time the students reached sixth grade, those whose classrooms faced the train were a year behind those whose classrooms were on the quiet side of the building.

After noise-reduction materials were installed in the classrooms and around the tracks, reading scores in the two groups equalized.

Another study, of children whose schools were located near West London's busy Heathrow Airport, found what the study leader termed "a straightforward linear effect from aircraft noise and impairment in reading on standardized tests."

Noise that invades a classroom may make it hard for students to hear the teacher, of course. But blood tests done on children near airports in Munich, Germany, revealed a more insidious biological mechanism through which noise wreaks much of its havoc:

Those children had significantly higher levels of adrenaline and cortisol - the body's so-called stress hormones. They are part of the body's "fight or flight" response that helps a person deal with sudden emergencies.

Blood pressure and heart rate go up in preparation for action. The blood becomes thick with oxygen-toting red blood cells. And the immune system gets suppressed as part of the shift toward fulfilling short-term needs rather than longer-term health.

That response can be lifesaving in an attack, but it is counterproductive when activated chronically. It can corrode the body, eating away at blood vessels and other organs.

As a result of that hormonal activation, children near the Munich airports had significantly higher blood pressure than children in quieter neighborhoods, adding to their risk of having a heart attack or stroke later in life.

Similar impacts have been documented among adults near airports serving Amsterdam and Stockholm.

Even if chronic exposure to noise is unlikely to kill you, it can simmer under the surface and take a toll on your well-being.

Studies have shown that chronic night noise not only leaves you shrouded in a fog of fatigue, irritability and poor concentration, but also activates the stress response as you sleep.

[Last modified September 3, 2007, 20:33:33]