Noise pollution, its causes and health implications on residents

Introduction

Noise according to Nwachukwu (2000) is an unpleasant sound. It travels in waves and reaches our ear by means of air vibrations. He said that it is an integral part of our daily life. Alexander (1964) in Nwachukwu work warned that except steps are taken to alleviate it, especially in industry, increasing members of our population could suffer auditory impairment.

Nwajei (2004) posited that noise is a pollution. He said that it is an aspect of pollution that has little or no aspect of pollution that has little or no major consideration until very recently. According to him, modern living has intensified an old problem and that is noise. In the street, in our homes, and on the job, the noise of daily living can be frustrating and harmful to our well being. Every ten years, according to La Place (1987) in Nwajei work said that the intensity of noise in our environment doubles. Noise pollution is emerging as a serious problem and one that demands prompt attention.

Noise is often defined as “unwanted sound” but the definition is subjective because of the fact that one man’s sound may be another man’s noise. Perhaps a better definition of noise is “wrong sound, in the wrong place, at the wrong time” (Park, 2007). Man according to him is living in an increasing noisy environment. He said that the 20^th Century has been described as the “Century of noise”. Noise has become a very important “stress factors” in the environment of man. He further posited that the term noise pollution has been recently coined to signify the vast cacophony of sounds that are being produced in the modern life, leading to health hazards.

Furthermore, he posited that noise has two properties: loudness or intensity and frequency. Loudness or intensity according to him depends on the amplitude of the vibration which initiated the noise. The loudness of noise is measured in decibels (dB). When we say that sound is 60 dB, it means that is 60 dB more intense than the smallest distinguishing noise or the “reference” sound pressure which is understood to be 0.0002 microbar or dynes/cm². A dyne according to him is 1/1,000,000^th of atmospheric pressure. Normal conversation produces a noise of 60-65 dB whispering. 20-30 dB, heavy street traffic, 60-80 dB, and boiler factories, about 100 dB. A daily exposure up to 85 dB is about the unit people can tolerate without substantial damage to their hearing. By his observation, the human ear responds in a non-uniform way to different sound-pressure levels, that is, it respond not to real loudness of a sound, but to the perceived intensity. Secondly, frequency is denoted as Hertz (Hz). One Hz is equal to one wave per sound. The human ear can hear frequencies from about 20 to 20,000 Hz, but this range is reduced with age and other subjective factors. The range of vibrations below 20 Hz are infra-audible, and those above 20,000 Hz are ultra-sonic. Many animals (e.g. dogs) can hear sounds inaudible to the human ear.

Conceptual framework

Nwachukwu (2000) stated that noise is an unpleasant sound. It travels in waves and reaches our ears by means of air vibrations. It is an integral part of our daily life. Alexander (1964) warned that except steps are taken to alleviate it, especially in industries, increasing numbers of our population could suffer auditory impairments. Nwajei (2004) opined that noise is an aspect of pollution that has little or no major consideration, until very recently. According to him modern living has intensified and old problem and that is noise pollution. In the street, in our homes, and on the job, the noise of daily living can be frustrating and harmful to our well-being.

Every ten years, according to Laplace (1987), the intensity of noise in our environment doubles. Noise pollution for Laplace is emerging as a serious problem and one that demands prompt attention. The intensity of noise according to Nwajei is measured in decibels (dB). One decibel is the smallest difference in sound intensity detectable by the human ear, with every ten decibel increase amounting to double in loudness. Common sound range from whisper (20 dB) to rock music (115 dB) to the roar of a jet plane on take off (140 dB or more). Normal conversation tones fall at the middle range of about 60 decibels. Sound below (80 dB) are generally considered safe.

Park (2005) also stated that noise is a health hazard in many industries. The effects of noise are of two ways; (i) Auditory effect which consist of temporary or permanent hearing loss (ii) Non-auditory effects which consist of nervousness, fatigue, interference with communication by speech, decreased efficiency and annoyance. The degree of injury from exposure to noise depends upon a number of factors such as intensity and frequency range, duration of exposure and individual susceptibility.

Enger and Smith (2006) said that noise is unwanted sound. However, noise can be more than just an unpleasant sensation. Research has shown according to them, that exposure to noise can cause physical, as well as mental harm. The loudness of the noise is measured in decibels (dB). Decibel scales are logarithmic rather than linear. Thus, the change from 40 dB (a library) to 80 dB (a dishwasher or garbage disposal) represents a ten-thousand fold in increase in sound loudness.

They further said that frequency or pitch of a sound is also a factor in determining its degree of harm. High pitched sounds are the most annoying. The most common sound pressure scale for high-pitched sounds is the A scale whose units are written “dBA”. Hearing loss begins with prolonged exposure (eight hours or more per day) to 80 to 90 dBA levels of sound pressure. So pressure becomes painful at around 140 dBA and can kill at 180 dBA. Below is table of intensity of noise, its source and the intensity in decibels.

Fig 1: Intensity of sources of noise.

Enger and Smith (2006) further opined that in addition to hearing loss, noise pollution is linked to a variety of other ailments, ranging from nervous tension headaches to neuroses. Research has also shown that noise may cause blood vessel to constrict (which reduces the blood flow to key body parts), disturbs unborn children, and sometimes causes seizures in epileptics.

The United States Environmental Protection Agency has estimated that estimated that noise causes about 40 million US citizens to suffer hearing damage or other mental or physical effects. Park (2006) defined noise as “unwanted sound”, but this definition is subjective because of the fact that one man’s sound may be another man’s noise. Perhaps according to him, a better definition of noise is “wrong sound in the wrong place, at the wrong time”. Man is living in an increasingly noisy environment. The 20^th century has been described as the “century of noise”. Noise has become a very important stress factor in the environment of man. The term “noise pollution” has been recently coined to signify the vast cacophony of sounds that are being produced in the modern life, leading to health hazards.

Sources of noise pollution

Park, (2005) stated that the sources of noise are many and varied. These are automobiles, factories, industries, aircrafts, etc. Noise levels are particularly acute near railway junctions, traffic roundabouts, bus terminuses and airports. Use of pressure horns, recreational noise of loudspeakers with full volume during festivities particularly at night are other sources of noise pollution. The domestic noises from the radios, transistors, television sets – all add to the quantum of noise in daily life.

Nwajei, (2004) opined that noise is a by-product of human activity, and some noise is virtually unavoidable. But the excessive noises most of us hear come from certain common sources. The noise of automobiles, trucks, trains, motorcycles, buses and airplanes is a fairly common nuisance. Many people, especially those who live in cities, become used to the roar of traffic. The sound of motor, engines and construction equipment can be very hazardous.

According to him, our homes fail to provide the quiet environment devoid of noise. Stereos, television sets, air conditioners, and vacuum cleaners are among the household noise makers. The kitchen is likely to be the noisiest room in the house. Even a small device like the food blender or the yam pounder may operate above safe noise levels. Noise from the nearby house may intrude or add to those of nearby homes.

Also, he said that the machinery of many industries is extremely noisy, and many people must work long hours in the environments that have dangerous noise levels. It might be found easier to work or operate some of these noisy equipment at more convenient hours like the nights or break periods. A full understanding of noise pollution has yet to be achieved, but researchers are focussing more attention to this environmental problem as it increases and becomes more annoying and harmful.

Nwachukwu, (2000) gave examples of sources of noise with damaging effects including quarrying industries, airports, engine rooms, grinding mills, music shops, saw mills, etc.

Harmful effects of noise pollution

When noise or sound vibration reaches the eardrum (tympanic membrane) through the air, it causes the eardrum to start vibrating also at the same frequency in the incoming sound waves, (Nwachukwu, 2000). This is called sympathetic vibration. Sound vibration itself is measured in unit called “decibels”.  During ordinary conversation, the eardrum responds to sound frequency of specific value. This is called its hearing threshold. He also said that, unfortunately, the vibration frequency of noise from certain processes in the industry is by far of a much larger number of decibels than the normal hearing threshold in man. So in noisy conditions, the eardrum is forced to vibrate at the same frequency as the incoming noise. Herein lies the danger of noise to hearing, because it cumulatively induces a shift in the hearing threshold of a worker exposed to it.

Nwachukwu further said that the full impact of noise an individual was studied by Mantysalo and Vuori (1984). They identified two main types of noise, “impulse noise (such as those resulting from explosions or the brief but loud impact of two objects), and “continuous steady-state noise” (like the buzzing of an air conditioner). The researchers carried out a study to compare the hearing effects induced by exposure to impulse noise with those induced to exposure to continuous steady-state noise. The hearing threshold of workers exposed to them was also measured under work conditions. Among other things, they found that intense sound stimulation from any of these two types of noise could raise the hearing threshold. If this rise (or shift) in a worker’s hearing lasts only for a short time, it is called a “noise-induced temporary threshold shift”, (NITTS). But cumulative effects of long period of exposure to high noise level could lead to noise induced permanent threshold shift (NIPTS), causing permanent damage to hearing. It must be stressed that noise does not need to be deafening (or extra loud) to be dangerous. Apart from hearing loss exposure to severe noise, noise could cause decreased efficiency of workers because of disturbed concentration, and/or interference with sleep especially among workers who live very close to their places of work, where the machines may be on throughout the night. Noise also causes changes in cardiovascular blood pressure pulse rate and breathing rate, as well as a decrease in appetite.

Park (2005) classified the effects of noise exposure into two types; auditory and non-auditory.

1. Auditory effects
2. Auditory fatigue: It appears in 90 dB region and greatest at 4000 Hz. It may be associated with size effects such as whistling and buzzing in the ears.
3. Deafness: The most pathological effect is deafness or hearing loss. The victim is generally unaware of it in early stages. The hearing loss results from a specific exposure to noise; the disability disappears after a period of time up to 24 hours following the noise exposure. He said further that most temporary hearing loss occurs in frequency range between 4,000 – 6,000 Hz. Repeated of continuous exposure to noise around 100 decibels may result in a permanent hearing loss; in this, the inner ear damage may vary from minor changes in the ear cell ending to complete destruction of the organs of corti. When this occurs as a result of occupation in industries, it is called “occupational hearing loss”. Exposure to noise above 160 dB may rupture the tympanic membrane and cause permanent loss of hearing.
4. Non-auditory effects: These are;
5. Interference with Speech: Noise interferes with speech communication. In everyday life, the frequencies causing most disturbances to speech are commonly present in noise produces by road and air traffic. For good speech intelligibility, it is considered that the speech sound level must exceed the SIL (speech interference level) by approximately 12 dB.
6. Annoyance: This is primarily a psychological response. Neurotic people are more sensitive to noise than balanced. Workmen exposed to higher intensity of noise in occupational capacities are often irritated, short tempered and impatient, are more likely to resort to agitation and disrupt production.
7. Efficiency: Where mental concentration is to be undertaken, a low level of noise is always desired. Reduction in noise has been found to increase work output.
8. Physiological Changes: A number of temporary physiological changes occur in the human body as a direct result of noise exposure. They are; a rise in blood pressure, a rise in intracranial pressure, an increase in heart rate and breathing and increase in sweating. General symptoms according to him will occur, such as giddiness, nausea and fatigue may also occur. Noise interferes with sleep. Noise is also said to cause visual disturbance. It is said to cause a narrowing of the pupils affect colour perception and reduce night vision. Besides affecting health, noise is also a significant factor in economic losses. The potential cost of noise induced hearing loss to industry is quite great.

Nwajei (2004) posited that noise pollution has harmful effects on both plants and animal. Its affects on human health have risen in more diverse than any other kind of pollution. Effects on human health include;

• Excessive noise causes some degree of hearing loss.
• Immediate symptoms include discomfort, pain and ringing in the air.
• A rise in blood cholesterol and blood pressure.
• Dilation of pupils of the eyes.
• Construction of blood levels and unnatural brainwave rhythm.
• Loss of sleep and relaxation and nervous exhaustion.

Other effects according to him are that studies have shown that noise has some potentially dangerous effects on wildlife, building, property values and the economy. Noise is generally seen as a big problem in educational set up. School children may not learn properly if there are constant distractions by noise from vehicles, dancers, singers and hawkers of food drinks.

Control of noise pollution

Nwajei (2004) stated that unlike some other environmental pollutants, noise pollution can be eliminated through existing technology. Many sound dampening devices and techniques are available, including sound and vibration-absorbing material for motors and engines, sound proofing materials for building construction and baffles and exhaust silencer for power generators. Sometimes enactment of noise control ordinances can save situation.

Nwachukwu (2004) stated the harmful effects of noise could be prevented by;

1. Wearing ear-muffs or ear-plugs
2. Reduction of noise at its source (using silencers, for example).
3. Isolation of noisy operation, at reasonable distances away from the centre of activity of most workers.
4. Reduction of friction by adequate lubrication of parts of machines or other devices.

Insel and Roth (2001) also said that one can avoid noise pollution by;

• Wear ear protectors when working around noisy machinery.
• When listening to music on a headset with a volume range of 1 – 10, keep the volume no louder than 4; your headset is too loud if you are unable to hear people around you speaking in a normal tome of voice.
• Avoid loud music, do not sit or stand near speakers or amplifier at a rock concert, and do not play car radio or stereo so high that you cannot hear the traffic.
• Avoid exposure to painfully loud sounds, and avoid repeated exposure to any sounds above so 80 decibels.

Park (2005) on his part said that a variety of approach as may be needed to control noise. These include;

1. Careful planning of cities: In planning cities, the following measures should to reduce noise;
2. Division of the city into zones with separation of areas concerned with industry and transport.
3. The separation of residential areas from the main streets by means of wide green belt. House fronts should lie not less than 15 metres from the road and the intervening space should be thickly planted with trees and bushes.
4. Widening of main streets to reduce the level of noise penetration into dwellings.
5. Control of vehicles: Heavy vehicles should not be routed into narrow streets. Vehicular traffic on residential street should be reduced. Indiscriminate blowing of the horn and use of pressure horn should be prohibited.
6. To improve acoustic insulation of building: From the acoustic standpoint, the best arrangement is construction of detached buildings rather than single large building or one that is continuous. Installation that produce noise or disturb the occupants within dwellings should be prohibited. Buildings should be sound-proof where necessary.
7. Industries and railways: Control of noise at source is possible in industries. Special areas must be earmarked outside residential areas for industries, for railways, marshalling yards and similar installations. When these demands cannot be met, protective green belts must be laid down between the installations and residential areas.
8. Protection of exposed persons: Hearing protection is recommended for everyone or workers who are consistently exposed to noise louder than 85 decibels in the frequency bands above 150 Hz. Workers must be regularly rotated from noisy areas to comparatively quiet parts of the factories. Periodic audiogram check-ups and use of ear-plugs, ear-muffs are also essential as the situation demands.
9. Legislation: Many states have adopted legislation providing for controls which are applicable to a wide variety of sources. Workers have the right to claim compensation if they have suffered a loss of ability to understand speech.
10. Education: No noise abatement programme can succeed without people’s participation. Therefore, their education through all available media is needed to highlight the importance of noise as a community hazard.

References

Dougherty, J.D. (1966). Noise Engineering, Journal of Medicine, pp 755-757.

Insel, P.M. and Roth, W.T. (9^th Ed.). Core Concepts in Health, Boston, McGraw-Hill Companies.

Koenigsberger, O.H. (1973). Manual of Tropical Housing and Building, Part 1. Climate Design, Bombay, Orient Longman.

La Place, John (1987) Health (5^th ed.) London, Prentice Hall International

Nwachukwu, A. E. (2000). Industrial and Occupational Health and Safety, Abuja, Totan Publishers Limited.

Nwajei, S.D. (2004). Health Education for Colleges, Universities and Practitioners. Lagos, Functional Publishing Company.

Park, K. (2005) Preventive and Social Medicine, Jabolpur, India, M/s Banasidas Bhanot, Publishers

The Nose Advisory Council (1971). Neighbourhood Noise; Report of the Working Group on Noise Abatement Act, HMSO, London.

W.H.O. (1966). Noise, An Occupational Hazard and Public Nuisance. Public Health Paper 30.