Deaf defining: today's noise pollution solutions

Better Nutrition, August, 2003 by Michael Downey

One little-known--and invisible--health risk has already affected 100 million Americans: partial hearing loss as a result of society's rising levels of noise. In the past, most victims of this ailment were adults, many of whom worked in factories or other noisy environments. Today, however, the risk has spread to children and young adults--and has become a common occupational and environmental hazard.

Up to 30 million Americans are exposed to dangerous sound levels in the workplace on a regular basis, reports the US National Institutes of Health (NIH). And many others also pursue noisy recreational activities.

Ear-itation

Sixty million Americans own firearms, and many use them without adequate hearing protection, according to a 1995 study in the Archives of Otolaryngology--Head and Neck Surgery. Then, there are chain saws, power tools, amplified music, traffic, sirens, snowmobiles, wave runners and motorcycles.

We're not just talking about jet engine mechanics or rock stars. In fact, experts say that hearing loss and permanent ringing in the ears is being reported at younger and younger ages. Even children's toys can produce sounds capable of causing permanent hearing damage, according to research published in 1997 in the International Journal of Pediatric Otorhinolaryngology. As many as half of today's children now have some noise-caused hearing loss. The first-ever nationwide survey of children's hearing, published in the April 1998 edition of The Journal of the American Medical Association, showed that children have suffered hearing loss in both low and high frequencies. And hearing loss in children is often mistaken for other disorders--mental retardation, mental illness, brain damage or learning disorders.

Of the more than 28 million Americans with hearing impairment, about 10 million have hearing loss caused by excessive noise exposure, according to the NIH. Some ear pollution sources are obvious, but many hazards aren't. And once you lose your hearing, or some portion of it, it never comes back.

Can You Hear Me Now?

Both intensity and duration of noise exposure determine the potential for damage. Even sounds perceived as comfortably loud can be risky.

We actually hear with our brains, not our ears. First, sound waves--literally, waves of compressed air molecules--enter the ear and cause tiny hair cells to brush against a membrane. The membrane, in turn, sends electrical impulses to the brain, which interprets the impulses as the phenomenon we call sound.

Those extremely delicate hair cells can be damaged--either by a single blast or by a prolonged, lesser exposure to noise. Hair cells sometimes rebuild over 48 hours--the normal period of temporary hearing loss.

However, the August 22, 2002 issue of Nature reports that permanent loss can occur when damage is so severe that it overwhelms the ear's self-repair mechanism.

Standards for hearing health are very misleading. Sound pressure against the ears is measured in decibels (db) on a scale that is logarithmic. That means each increase of 10 db represents a ten-fold increase in noise intensity. In other words, a small sound increase from 90 to 100 db means 10 times the pressure against those delicate hair cells.

That 10 db shift is approximately the difference between running a lawnmower (90 db) and using a chain saw (110 db). Switching between these two common tools results in more than 10 times the noise intensity (see "Earmark These Numbers," below).

Know Noise

What can be done about noise-induced hearing loss? Actually, some vitamins may hold a partial answer. The results of research published in the March 1999 edition of The American Journal of Clinical Nutrition found lower vitamin [B.sub.12] and folate levels in hearing-impaired, older women. Also, people with high cholesterol levels have greater hearing loss as they age.

And a study published in the 1999 edition of Life Sciences and Biotechnology Update found corticosteroids administered one hour after noise exposure protect some hair cells from damage. This research, however, doesn't constitute a causal link and may only apply to age-related hearing loss.

Another theory suggests that excess noise could be harming delicate hair cells through free oxygen radicals. Antioxidants--such as vitamins A, C and E--might help reduce this risk. Fruits and vegetables are rich sources of these vitamins.

Regardless, your best defense is earplugs or headphones with a noise reduction rating (NRR) of 29-32. Custom-fitted earplugs are best, but foam rubber or wax plugs can also work. Protect your children by turning down the volume on stereos and TVs. Use one appliance at a time, and turn it off as soon as possible. And do you really have to buy toys that squeak, ring or play music?

Most municipalities also have laws to deal with hearing hazards such as car alarms, loud music and construction noise. Use them. Report violations.

Like air pollution, noise pollution is a public health problem--one we can prevent with sound reasoning.

Earmark These
Numbers

Prolonged exposure to sounds averaging
85 decibels (db)--or even
short blasts of louder noises--can
contribute to hearing problems.

Noise                        Decibels (db)
whisper                              30-40
refrigerator hum                        40
talking                             50-100
normal conversation                     60
television, average volume              68
vacuum cleaner,
  6 feet away                        73-81
office din                           79-85
city traffic                            80
stove fan                               84
dishwasher                              88
lawnmower                               90
busy kitchen noise                  90-100
rock concert, chain
  saw, diesel train &
  stereo headphones                110-120
motorcycles &
  firecrackers                     120-140
jet takeoff                            140
gunshots                           140-170