ENVIRONMENTAL AND LEISURE NOISE POLLUTION  

– A SERIOUS HEALTH HAZARD

Introduction

The perception of sounds in day-to-day life is of major importance for humanity.   Communication through speech, music, television, telephones etc are sounds which human beings cannot live without today.  With urbanisation there appears to be a marked increase in the sounds that human ears are exposed to whether one likes it or not.  Such sounds are termed as noise.  Noise is a disturbance to the human environment that is escalating at such a high rate that it will become a major threat to the quality of human lives. In the past thirty years, noises in all aspects, especially in urban areas, have been increasing rapidly. Slowly and insensibly, we seem to accept noise and the physiological and psychological deterioration that accompanies it as an inevitable part of our lives. Human beings today are resigned to this fact and have developed complacency in regard to this fact.  Hence they do not monitor or object to the sounds that their children are exposed to, be it on their ipods, or the toys that they play with.  Little do they realize that this complacency could affect their offspring’s hearing much earlier in their adult life.   Little heed is paid to government ban on use of air horns by buses and trucks.  Since there is no immediate cause and effect relationship for noise pollution, the problem has been ignored by parents and Governments alike. Our society is now aware that noise can damage hearing. However, short of a threat that disaster would overtake the human race if nothing is done about noise, it is unlikely that many people today would become strongly motivated to do something about the problem. It has been argued that because noise produces no dramatic ill effects, the public has been largely uninterested in its suppression. It may be more to the point to say that the degree of annoyance and discomfort that people will endure is astonishing.

Overexposure to noise has a cumulative effect on the human ear which will be realized only after a number of years.  Researchers working on children with hearing disorders are constantly reminded of the crucial importance of hearing to a child’s development. In the early years, the child cannot learn to speak without special training if one has enough hearing loss to interfere effectively with the hearing of words in context. In this respect, there is a clear need for parents to protect their children’s hearing. If no steps are taken to lessen the effects of noise, we may expect a significant percentage of future generations to become auditory cripples.

Definition of noise:

According to the International Programme on Chemical Safety (WHO 1994), an adverse effect of noise is defined as a change in the morphology and physiology of an organism that results in impairment of functional capacity, or an impairment of capacity to compensate for additional stress, or increases the susceptibility of an organism to the harmful effects of other environmental influences. This definition includes any temporary or long-term lowering of the physical, psychological or social functioning of humans or human organs.  Hearing impairment is typically defined as an increase in the threshold of hearing. Hearing handicap is the disadvantage imposed by hearing impairment sufficient to affect one’s personal efficiency in the activities of daily living. It is usually expressed in terms of understanding conventional speech in common levels of background noise.

In the developing countries, not only occupational noise, but also environmental noise is an increasing risk factor for hearing impairment. In 1995, at the World Health Assembly, it was estimated that there are 120 million persons with disabling hearing difficulties worldwide. It has been shown that men and women are equally at risk of noise-induced hearing impairment.

Effects of noise on the auditory system:

Present knowledge of the physiological effects of noise on the auditory system is based primarily on laboratory studies on animals. After noise exposure, the first morphological changes are usually found in the inner and outer hair cells of the cochlea, where the stereocilia become fused and bent. Every exposure to loud noise destroys some cells, but prolonged exposure damages a larger amount of cells, and ultimately collapses the Organ of Corti, which causes deafness.

Noise-induced hearing impairment occurs predominantly in the high-frequency range of 3000–6000 Hz, the effect being largest at 4000 Hz. With increasing exposure time, noise-induced hearing impairment also occurs at 2000 Hz.

Hearing impairment in young adults and children 12 years and older has been assessed by LAeq on a 24 h time basis, for a variety of environmental and leisure-time exposure patterns.  These include pop music in discotheques and concerts, pop music through headphones, music played by brass bands and symphony orchestras, motorcycling, playing in arcades, using noisy toys, and fireworks.  The results are in agreement with values predicted by the ISO Standard 1999 method on the basis of adjusted time.  Although the characteristics of these exposures are to a certain extent unknown, the details in the publications suggest that LAeq, 24h values of these exposures exceed 70 dB. In contrast, epidemiological studies failed to show hearing damage in populations exposed to an LAeq, 24h of less than 70 dB. The data imply that even a lifetime exposure to environmental and leisure-time noise with an LAeq, 24h of less than 70 dBA would not cause hearing impairment in the large majority of people

Data from animal experiments indicate that children may be more vulnerable in acquiring noise-induced hearing impairment than adults.  At very high instantaneous sound pressure levels, mechanical damage to the ear may occur. Occupational limits are set at peak sound pressure levels of 140 dB. For adults exposed to environmental and leisure-time noise, this same limit is assumed to be valid. In the case of children, however, taking into account their habits while playing with noisy toys, peak sound pressure levels should never exceed 120 dB. Risk for noise-induced hearing impairment may increase when the noise exposure is combined with exposure to vibrations, the use of ototoxic drugs, or some chemicals . In these circumstances, long-term exposure to LAeq,24h of 70 dBA may induce small hearing impairments.  The Occupational Safety and Health Agency (OSHA) has set the danger level at 95 decibels (dB) and above for 4 or more hours per day as likely to induce permanent hearing impairment.

Tools and toys of recreation appear to be the source of toxic noise causing hearing impairment among young adults and children today.  Youngsters are pounding their ears with high amplified car stereos, i-pods, discotheque music and rock concerts.  H.E.A.R., or “Hearing Educators and Awareness for Rockers,” an organization started in 1988 by rock and roll musician Kathy Peck and physician Dr. F.Gordon in San Francisco, has a special appeal for students. Peck’s motivation to start the organization came from having her own hearing damaged from repeated exposure to excessively loud music. This happened as a result of her work as a bass player and singer for the San Francisco punk band, “The Contractions”. H.E.A.R. is dedicated to educating the public regarding the awareness of hearing damage. They provide public service announcements in mainstream media and earplugs to those attending concerts.  Musician Pete Townsend of the rock group “The Who” is a leading supporter of H.E.A.R. A passage in a feature article from the House Ear Institute Internet site states: In 1987, an article in the Los Angeles Times told the world of Pete Townsend’s battle with tinnitus and his hearing loss. In the last line of the article, Townsend said that the saddest circumstance of his hearing loss was not being able to hear his children speak to him. The high frequencies, where children’s voices are pitched, are usually the first to be affected by noise-induced hearing loss. Other areas of recreation can also be of concern.  The movies Armageddon and Saving Private Ryan had sound tracks that reached 118 decibels. A study from the mid 1990s found that 80 percent of the health clubs and fitness spas surveyed cranked up the music in group exercise classes from 105 to 110 decibels, and a few exceeded 120 decibels.  Some toys were testing as loud as 135 decibels with a sound meter. Among them was a Playskool clock that registers 79 decibels at adult arm’s length but 125 decibels at close range.

Usually noise-induced hearing impairment is accompanied by an abnormal loudness perception which is known as loudness recruitment. With a considerable loss of auditory sensitivity, some sounds may be perceived as distorted (paracusis). Another sensory effect that results from noise exposure is tinnitus (ringing in the ears). Commonly, tinnitus is referred to as sounds that are emitted by the inner ear itself (physiological tinnitus). Tinnitus is a common and often disturbing accompaniment of occupational hearing impairment and has become a risk for teenagers attending pop concerts and discotheques   Noise-induced tinnitus may be temporary, lasting up to 24 hours after exposure, or may have a more permanent character, such as after prolonged occupational noise exposure.

The main social consequence of hearing impairment is an inability to understand speech in daily living conditions, which is considered a severe social handicap. Even small values of hearing impairment (10 dB averaged over 2000 and 4000 Hz, and over both ears) may have an effect on the understanding of speech. When the hearing impairment exceeds 30 dB (2000 and 4000 Hz in both ears) a social hearing handicap is noticeable.

Regulations for occupational noise exposure exist almost worldwide and exposures to occupational noise are to a certain extent under control.  On the other hand, environmental noise exposures due to a number of noisy activities, especially those during leisure-time activities of children and young adults, have scarcely been regulated.  Given both the increasing number of noisy activities and the increasing exposure duration, such as loud music in cars and the use of i-pods, regulatory activities in this field are to be encouraged. 

According to a WHO report to the UN Conference on Environment, “Of all environmental problems, noise is the easiest to control". In most of the developed countries specific legislations have been made and scientific methods for investigation of noise pollution exist. As present, there is no specific and detailed legislation to control noise pollution in India.   Hence there is an urgent need for the Central Government of India to get a legislation passed for the control of noise pollution.  Masses are still ignorant of the grave effects of the noise pollution.  People should be educated through radio, TV, and newspapers about noise pollution.  Manufacturers of household devises and toys need to be regulated regarding permissible noise levels of their gadgets.

If we don’t wake up and take matters of environmental noise pollution seriously, it might be too late to save future generations from the irreversible effects of noise induced hearing loss.  Hearing loss among the younger population has far reaching ramifications.  Effects of hearing impairment range from a child’s language acquisition delay to an adult’s inability to hear and communicate effectively.  We have to take environmental noise seriously before it is too late.  Let’s sit up and do something about it.