Even the low-level but chronic noise of everyday local traffic can cause stress in children and raise blood pressure, heart rates and levels of stress hormones, reports a new study by a Cornell University environmental psychologist and his European co-authors.
"We also found that girls exposed to the traffic noise become less motivated, presumably from the sense of helplessness that can develop from noise they couldn't control," says Gary Evans, an international expert on environmental stress, such as noise, crowding and air pollution.
The study, the first to look at the nonauditory health effects of typical ambient community noise, is published in the Journal of the Acoustical Society of America (Vol. 109, March 2001).
The researchers analyzed data on 115 fourth-graders in Austria with similar family characteristics, such as parent education, parental marital status, housing and family size. Half the children lived in quiet areas – below 50 decibels (dB), the sound level, for example, of a clothes dryer or a quiet office – and half lived in a noisier residential area -- above 60 dB, about the intensity of an average dishwasher or raised voices.
"We found that even low-level noise can be a stressor because it elevates psychophysiological factors, triggers more symptoms of anxiety and nervousness when the children are stressed (by taking a test) and can diminish motivation," says Evans.
Specifically, the researchers found that children in noisier neighborhoods experienced marginally higher resting systolic blood pressure, greater heart rate reactivity to a test (which served as a stressor) and higher overnight cortisol levels, which are signs of modestly elevated physiological stress.
"Anything that increases blood pressure, for example, has negative implications for long-term health effects," says Peter Lercher, M.D., and an epidemiologist at the Institute of Hygiene and Social Medicine at the University of Innsbruck, Austria, and a co-author on the study. Elevated blood pressure in childhood is thought to predict higher blood pressure later in life. Boosts in stress hormones also are of concern because they are linked to adult illnesses, some of which are life-threatening, including high blood pressure, elevated lipids and cholesterol, heart disease and a reduction in the body's supply of disease-fighting immune cells.
The study adds evidence to Evans' previous research showing that noise can have serious health, learning and task-motivation effects in children and adults exposed to chronic noise.
"The findings suggest that children living in noisier areas are subject to stress, which may have serious health implications," the researchers conclude. They intend to monitor the Austrian children and the noise levels to which they are exposed and assess any long-term health effects.
Since the children studied live in small villages and towns in an alpine area with higher traffic noise exposure during the night (night exposure was 2 dB higher than during the day), a direct transfer of the results to other residential neighborhoods is difficult, the researchers point out. A typical urban residential neighborhood in the United States has decibel levels between 55 and 70. Continued exposure to noise above 85 dB causes hearing loss.
Other co-authors of the study are Markus Meis at the Institute for Research into Man-Environment-Relations, University of Oldenburg, Germany; Hartmut Ising at the Federal Environmental Agency, Germany; and Walter W. Kofler at the Institute of Hygiene and Social Medicine, University of Innsbruck.
The study was supported mainly by the Austrian Ministry of Science and Transportation and also, in part, by the Austrian-U.S. Fulbright Commission, the National Institute of Child Health and Human Development, and the College of Human Ecology at Cornell.