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Health effects of noise exposure
Journal of Sound Vibration (1978) 59(l),
HEALTH
65-71
EFFECTS
OF NOISE EXPOSURE
V. J. KRICHAGIN World Health Organization, Regional Ofice for Europe, 8, Scherfgsaej, Copenhagen, Denmark (Received 6 January 1978)
1. INTRODUCTION
Current legislation on limiting community noise is most commonly based on the presence of annoyance reactions among exposed population groups. Behind these reactions lie nonauditory health effects from moderate levels of noise (below 80 dB), which appear to be seen only after long-term, chronic exposures. All degrees of intensity-response relationships based on acute reactions are relatively important when considered in terms of health. This presentation describes some studies designed to detect the influence of communit), noise on the health of chronically exposed population groups. 2. SURVEY
OF EXISTING
RESULTS
AND
STUDIES
WHO has dealt with the health aspects of noise control
on several occasions: in a book by Bell [l], related chiefly to community noise; in a paper from the WHO Regional Office for Europe by Lang and Jensen [2], entitled “Environmental Health Aspects of Noise Research and Noise Control Programme”; in a program, Development of Noise Control [3]; and at a discussion in Brussels in 1976 on the final version of a manual on noise control criteria. Collectively, the publications illustrate that there has been a slow development of attention to health-related problems of community noise. Improvement has been made in the years between 1967 and 1977 in measurement techniques, evaluation and the use ofcertain specific indices and noise pollution levels. In addition. many cities undertook noise level estimations. Sources of noise were registered and legislation developed, mainly in order to protect against hearing damage and prevent social conflict caused by the dissatisfaction of people living near noisy installations, airports and highways. Considerable progress has been made in estimating safety levels for preventing hearing damage. Questionnaires to evaluate the effects of lower levels of community noise have been designed and distributed on a wide scale. The results reveal relatively uniform proportions of people disturbed, annoyed and dissatisfied. Dose-response curves for speech interference and other fairly uncomplicated effects seem to be well established. The existence of non-auditory health effects from noise exposure have been suggested frequently. Bell [I] cited cases of impairment of capillary blood circulation in workers exposed to noise, as well as a high occurrence of neuroses among this group and more cardiac complaints than normal. The WHO noise criteria document in preparation refers to studies of the occurrence in groups exposed to noise of peptic ulcers, hypertension and other disorders not commonly connected with high noise levels. Authorities, says Bell, often comment that “. . . the main auditory effects of noise encountered under industrial conditions do not produce a health problem”. However, industry itself is concerned with the effect of noise on attention and work efficiency and their possible relationship to productivity. While it has been stated that “many employees work under noisy conditions for many years and show no general health changes that can be said to be related 65 0022-460X/78/0708-0065 $01.00/O
8;’1978 Academic Press Inc. (London)
Limited
66
V. J. KRICHAGIN
causally to noise exposure”’ [2], this apparent absence of effect may be the result of many biases in logic. For example, although it may appear that a certain exposed population selected for study has a high health level, this may largely be due to a high rate of labor turnover. Moreover, there are usually no control studies undertaken with exposure studies and no follow-up studies on the health of people after they leave a noisy job. According to Mosskov, Ettema and Zielhuis [4], the interim results of an epidemiological study by Knipschild [5] show a definite correlation between noise exposure load and blood pressure levels (especially diastolic), indicating that noise is indeed a risk factor in hypertension. Their own studies indicated that students showed a decrease of capacity in performance of mental tasks when exposed to aircraft noise and that their diastolic blood pressure was somewhat higher than that of a non-exposed group. Bastonier, Klosterkijtter and Large [6] concluded that auditory stimulation causes arousal of the central and the autonomous nervous system. It is possible to detect and measure arousal reactions by physiological and biochemical methods, It is often stressed that these reactions are not pathological as such, but if repeated frequently under certain conditions, they are undesirable and may become pathogenic. Two effects which must be considered as detrimental to health in the long run are as follows. Sleep disturbances. The time it takes to fall asleep is increased when the noise level is
above 35 dB. Sleep stages are disturbed and there is a loss of deep sleep. Autonomous reactions are caused in sleep by noise levels of 45 dB and above. The awakening effect which occurs at a certain level of noise can hamper the restitution of normal functions expected from sleep (40 to 45 dB awakens sensitive persons; 50 dB awakens babies; 75 dB deprives 75 % of babies of normal sleep). Interferences with relaxation. Throughout the day, man is constantly subjected to fluctuating periods of tension and relaxation which hinder rapid increase of fatigue. This function is affected by noise levels of 50 dB and above. Sick or convalescing people are especially sensitive to this stress. Chronically sick-for example, hypertensive persons-may react more strongly to noise load than healthy persons. Medical doctors are aware that such exposure will eventually have an adverse effect upon the adaptability of physiological functions. Karagodina, Osipov and Shishkin [7] have stated that, in the past 10 years, the level of city noise has increased by 10 to 12 dB(A). Certain health effects have proved to be linked with long-term exposure to urban noise at ranges between 40 and 80 dB(A). Based on animal experiments, it is suspected that long-term noise effects can reduce lifespan by 8 to 12 years. In addition, it is indicated that every third person suffering from neurosis and every fifth with mental disorders developed illness as a result of exposure to noise. In populations exposed to urban noise, disorders in the function of the nervous system occur three times more frequently than in unexposed populations and the incidence rate of hypertension is 1.5 times greater. The content of adrenalin substances in the blood of school children exposed to noise levels of 30 and 47 dB(A) were 2.7 and 4.11% respectively. In surroundings with a noise level of 50 to 55 dB(A), the effectiveness of treatment of patients with chronic diseases was reduced 2 to 2.5 times. Although there has been significant progress in the study of effects of noise in the past decade, the studies of actual health effects of chronic exposure to noise on population groups are not as well developed as for such other pollutants as ionizing radiation, certain carcinogenic substances and lead, for which estimations can be made on the probability and character of delayed health impairments. As was pointed out last year at the United Nations Economic Commission for Europe, few of the existing noise studies indicate more than the degree of annoyance or dissatisfaction
HEALTH EFFECTS OF NOISE EXPOSURE
67
caused in selected populations. For this reason, present community noise control legislation is based mainly on psycho-social responses, which are not comprehensive enough to represent health protection goals. Existing manuals on noise control [8, 2, l] contain curves which are relatively well established for : (a) standard levels of outdoor noise in LD, dB(A), L,, dB(A) versus percentage noyed persons (individual annoyance) ; (b) community reaction ; (c) percentage of people disturbed in rest and sleep; (d) percentage of people giving grounds for wanting to move; and (e) proportion of highly annoyed in total number of complaints.
of an..
These curves are usually taken as a background for legislative proposals. For health authorities, discussion always arises as to which level protection measures should be aimed: a level which might be considered as safe for the most sensitioe population group, a level which is apparently tolerablefor the majority of the population [9] (U.S. standard for occupational health), or a level which is clearly acceptable to the majority of the population [9]. It is the responsibility of the government to decide what level of responsibility can be endorsed in legislation, considering economic costs and other factors. In the case of hygiene, it is necessary to know exactly which population groups cannot tolerate accepted noise levels and to make those in government aware of the risks involved. Vermuelen [lo], describing the forthcoming Netherlands Noise Abatement Bill, stated that goals of noise abatement are necessarily linked to maintaining a healthy environment. This implies adherence to three specific rules: (a) law of ergonomics-to provide optimal quality and quantity of human performance; (b) law of hygiene-to remove from the environment factors which may be adverse to health ; and (c) law of eco-social balance-secondary system-linked factors essential in optimum amount in order to avoid unexpected results. Gala et al. [l I] studied a population of 300 000 in Lubljana in 1975 through inquiries carried out by psychology students. As in similar studies, about 60 “/o claimed to be annoyed by motor traffic; 9 to 10 % by the railway; 4 to 5 9; by neighbouring industry and construction work ; 3 to 4 y0 by noise from children at play: and l to 2 “/g by amusement and sport places. The authors did not find wide differences between this analysis and other studies carried out elsewhere. They concluded that effects of noise on health could not be determined by means of questionnaires in general. Health examinations are to be carried out in order to identify differences in the health status of the population groups under study. In December 1976, the ECE Task Force [I21 prepared a comprehensive report on the present situation of noise control studies in Europe. The Task Force’s impression was that there was a sufficient development for practical purposes of most technical problems in measurement methodologies and of interpretation of results for the prediction of cnmmunity reaction (annoyance-disturbance) to different levels and kinds of noise. There i, a genera1 similarity in the principles of legislation and noise abatement technology as well as in requirements for measurement methodologies observed. Different “noise maps” are non available, which describe conditions in city areas and around airports, for example. A methodology for checking noise sources for noise control to aid in the design of buildings and roads has also been developed. On the other hand, the group stated that “relatively little information had been submitted
68
V. J. KRICHAGIN
on non-auditory physiological effects of noise. There appeared to be relatively little recent worthwhile information on effects of noise on animals”. There is still confusion, unfortunately, between the annoyance effect of noise-largely a sociological factor-and the actual health effects. Engineers often wish to imply simple doseresponse relationships between environmental pollutants and physiological responses and are not always completely aware of the complexity of the slow biological reaction of species to changed environments. Biologists are often intrigued by the various indices suggested by acousticians for noise exposure descriptions, but sometimes forget or are unable to properly consider the basic underlying philosophy. “An ideal approach to establish criteria for environmental noise levels,” say Vaniv and von Gierke [13], “in terms of their effects on long-term public health and welfare would be to start by establishing the cumulative noise dose which an individual, or a population, may sustain over a lifetime, irrespective ofwhere or under what situation this exposureis received”. This misunderstanding of the case is typical. It is a concept in no way applicable to noise exposure. Such concepts are valid only when the active agent inflicts cumulative and irreparable damage to health. In the case of noise, the dose-approach may be applied only if one wishes to calculate the exposure within a very narrow intensity range. Because each intensity level produces a different effect, comparison between different intensity ranges are difficult. Efforts to arouse the receptor organs act not through total amount of energy but through intensity-i.e., energy density per unit of time combined with frequency characteristics. Especially in ranges of low intensity, sounds are necessary elements of normal environments and serve a practical purpose. Logically, this intensity should not be added but rather deducted from the noise dose. There is no reason, however, to dispute all noise measurements in L,, or LDN.For practical purposes, when used for uniform noise sources and conditions, these measurements can produce comparable data valid for evaluation purposes. This is true, however, only within narrow margins of applicability and they should not be regarded as seriously based on physiological, and especially biological, backgrounds. They represent characteristics of the environment which may be related more to immediate human responses than to health problems. Many investigators have fixed the great differences in adaptation potential among individuals to the same noise levels. It is evident that the adaptation of the receptor organs in human beings (to light, sound, temperature, odors, taste) is an inherent feature developed through evolution; the mechanism for such adaptation is well “constructed”, but not unlimited. Sound is a necessary condition of life. Certain noise levels create a normal living environment, adaptation to which is maintained without stress. Noise of a certain level thus becomes a background element, something which adds to an individual’s general well-being. These background levels might vary depending upon many factors of individual circumstances. Only unwanted sound (by character or by level) may create unnecessary stress which might be considered as a burden to the general adaptation capabilities of the organism, reducing its general resistance in the perpetual balance with the living environment. A noisy environment is a biologically unnatural environment. It is a change in circumstances which requires human beings to develop some tolerance. When these changes are beyond normal homeostasis, permanent stress occurs and adaptation through disease and evolutionary selection is probable. The purpose, then, of finding criteria for limiting community noise is to determine the limits of homeostasis among both normal and sensitive population groups. Experience gained from studying biological effects of environmental pollution brings us to the general conclusion that one can discover hazardous health effects of pollutants even below levels of direct pathological and sometimes apparently physiological effects. For example, air pollution by SO, (which is not a natural component of air and cannot be compared with
HEALTH
EFFECTS
OF NOISE EXPOSURE
69
noise) produces harmful effects on humans in values much lower than the threshold of odor. It has been established that correlation between active concentrations of this agent, 100 times below the threshold of odor, increases hospital admission rates of patients suffering from chronic lung disease [ 141.This effect is now seriously considered in setting limits and standards. The same is true at present for delayed effects from air pollution by such agents as lead, asbestos particles in the air and certain dusts. According to this analogy, one may expect that between 80 and 85 dB(A)-now accepted as the minimum borderline of hearing damage-and 30 and 35 dB(A)-an average background noise level of modern urban environments-there are several thresholds giving rise to harmful effects which might be discovered by means of properly organized epidemiological studies. At the International Symposium on Recent Advances in the Assessment of the Health Effects of Environmental Pollution, Rylander stated [ 151that the degree of annoyance itself may be interpreted as strain and stress which interferes with human well-being. The latter is a component of the WHO definition of health, but it is not, by any means, only well-being which is impaired under noise exposure. Certainly, a highly annoyed person is one who is under permanent psychosomatic stress. He is also constantly in the process of adapting to the denial of normal rest and relaxation, which is manifested in chronic fatigue, a decrease in working capacity and a reduction of his biological adaptability to other environmental hazards. As in the case of SO, pollution, it was discovered that not only lung but also cardiac and other diseases increased in exposed populations. Thus, noise-induced stress may not necessarily manifest itself only in hearing damage or fatigue. Data from the Erisman Hygiene Institute in Moscow suggests that changes in general morbidity and its character in populations living in noisy areas of big cities can definitely be correlated with noise levels [12]. The approach cited above shows that, in the case of protection against noise, conclusions cannot be drawn from reactions of the majority of the population. Health authorities are concerned also with minority groups which cannot tolerate certain levels of noise. It is considered that the following risk groups deserve special protection : (a) healthy people with intense living style, effectively working at the boundary of human capability, who have an acute requirement for limited but complete relaxation and sleeping time; (b) healthy people who are required to work with constant concentration of attention; according to Setchenov’s theory of concurrence of arousal areas in the cortex of the brain, side effect stimulators create additional areas of arousal which inhibit the main arousal area (dominanta); (c) fairly healthy people with constitutional partial deficiency in adaptation to stress (neurotics, etc.); (d) chronically sick people with reduced adaptability, including added impairment from degenerative diseases ; (e) children in certain stages of growth who are sensitive and vulnerable to stressors and whose proportional growth and development may be impaired. Noisy areas in cities are, of course, not evenly distributed. There is a constant turnover of population which self-selects towards groups tolerant of noise. This can dramatically decrease the number of hypersensitive and sensitive subjects from the risk groups mentioned above within noisy areas. Because man has a sensitive receptor organ for noise, his behavioral reaction of avoidance is rather obvious. This is not true for such hidden hazards as change of salt content in drinking water or exposure to microwave energy, which create annoyance but cannot be detected. In this case, knowledge and proper education are essential to avoid the undesirable agent and the danger is commonly underestimated, as in smoking habits. In the case of noise, however,
70
V. J.KRICHAGIN
there may be an overestimation of danger in connection with some side-effects (i.e., social benefits offered to exposed populations). In considering whether community noise can produce a negative effect upon the health of a population, there is still a major gap between laboratory studies of direct biological effects and the delayed effects of long-term stress induced by a noisy environment. There is no doubt that the creation of permanent stress from noise pollution in densely populated areas constitutes a social danger comparable to that of such well documented hazards as carcinogenic dusts, lead, carbon monoxide and other air pollutants. It might be a prioripostulated that among the many causes of permanent nervous stress, noise is one of the most widely influential factors. Bell [l] refers to several experiments on animals which deal primarily with noise of intense levels, with registration of acute or delayed effects. The effect of chronic exposure to moderate levels of noise, similar to community noise, is not as well described; it is difficult to determine what levels of noise might be classified as moderate to animals. This difficulty may be overcome through special planning of experiments aimed at creating stress in higher nervous functions. The ECE Task Force [ 121 presented excellent analyses of the present situation in research on noise control. According to the Task Force, half of the work has been on noise physics and the remainder on the sociological influence of community noise (analysis of questionnaires). Only marginal research efforts have been concentrated on basic medical effects. In summary, it may be concluded that it is necessary to strengthen co-ordination in research aimed at evaluating real dangers of community noise to the health of the exposed population. Programs must be formulated for this purpose.
REFERENCES 1. A. BELL 1966 WHO Public Health Paper No. 30, Geneva. Noise: an occupational hazard and public nuisance. 2. J. LANG and G. JENSEN1970 WHO EURO 2631, Copenhagen. Environmental health aspects of noise research and noise control programme. 3. ANON 1971 WHO EURO 3901. Development of noise control programme. 4. J. MOSSKOV,J. H. ET~EMAand R. I. ZIELHUIS1976 Proceedings of the AICB International Congress on Noise Abatement, Budapest, September 1976, III, 203-206. Experimentelle Untersuchung tiber Fluglarmwirkungen. See p. 203. 5. P. KNIPSCHILD 1976 Dissertation, Cozonel Laboratorium, University of Amsterdam. Medishe gerolgen van vliegtu iglawaai. 6. H. BASTONIER,W. KLOSTERK~TTERand I. LARGE 1975 CEC book in series: Environment and Quality of Life, EUR 5398e, Luxembourg. Damage and annoyance caused by noise. 7. I. KARAGODINA,G. OSIPOVand I. SHISHKIN1972 Noise Control in Cities. Moscow Medicina: Boxba & Shumon V. Gorodach. 8. U.S. Environmental Protection Agency Dot. No. 550/g-73402, Washington, D.C. 1973 Public health and welfare criteria for noise. 9. K. OESER1976 Proceedings of the AICB International Congress on Noise Abatement, Budapest, September 1976, III, 61-64. Notwendigkeit, Moglichkeiten und brenzen des Burgernegagements bei der Larrnbekampfung bzw. dem Ruheschutz. 10. C. A. VERMUELEN1976 Proceedings of the AICB International Congress on Noise Abatement, Budapest, September 1976, III, 53-58. The coming Dutch noise abatement bill. See p. 55. 11. D. GALA and D. ALEKSANDER1976 Proceedings of the AZCB International Congress on Noise Abatement, Budapest, September 1976, III, 151-154. Community for protection of the environment of Slovenia. See p. 151. 12. 1976 (10 December) ECE Task Force on Noise, Geneva. National approaches to community noise problems.
HEALTH
EFFECTS
OF
NOISE EXPOSURE
71
13. S. L. YANIVand H. E. VON GIERKE 1974 Proceedings of the ItiternationaL Symposium on Recenr Advances in the Assessment of the Health Eflects of Environmental Pollution, Paris, 24-28, June 1974, 1263-1276. Method for the identification of environmental noise levels requisite to protect
public health and welfare. 14. B. PRINZ 1977 WHO Regional Publications EURO Series No. 1, Copenhagen. Manual on urban air quality management : ambient air quality standards and their application. 15. R. RYLANDER1974 Proceedings of the International Symposium on Recent Advances in the Assessment of the Health Effects of Environmental Pollution, Paris, 24-28 June 1974.
HEALTH
65-71
EFFECTS
OF NOISE EXPOSURE
V. J. KRICHAGIN World Health Organization, Regional Ofice for Europe, 8, Scherfgsaej, Copenhagen, Denmark (Received 6 January 1978)
1. INTRODUCTION
Current legislation on limiting community noise is most commonly based on the presence of annoyance reactions among exposed population groups. Behind these reactions lie nonauditory health effects from moderate levels of noise (below 80 dB), which appear to be seen only after long-term, chronic exposures. All degrees of intensity-response relationships based on acute reactions are relatively important when considered in terms of health. This presentation describes some studies designed to detect the influence of communit), noise on the health of chronically exposed population groups. 2. SURVEY
OF EXISTING
RESULTS
AND
STUDIES
WHO has dealt with the health aspects of noise control
on several occasions: in a book by Bell [l], related chiefly to community noise; in a paper from the WHO Regional Office for Europe by Lang and Jensen [2], entitled “Environmental Health Aspects of Noise Research and Noise Control Programme”; in a program, Development of Noise Control [3]; and at a discussion in Brussels in 1976 on the final version of a manual on noise control criteria. Collectively, the publications illustrate that there has been a slow development of attention to health-related problems of community noise. Improvement has been made in the years between 1967 and 1977 in measurement techniques, evaluation and the use ofcertain specific indices and noise pollution levels. In addition. many cities undertook noise level estimations. Sources of noise were registered and legislation developed, mainly in order to protect against hearing damage and prevent social conflict caused by the dissatisfaction of people living near noisy installations, airports and highways. Considerable progress has been made in estimating safety levels for preventing hearing damage. Questionnaires to evaluate the effects of lower levels of community noise have been designed and distributed on a wide scale. The results reveal relatively uniform proportions of people disturbed, annoyed and dissatisfied. Dose-response curves for speech interference and other fairly uncomplicated effects seem to be well established. The existence of non-auditory health effects from noise exposure have been suggested frequently. Bell [I] cited cases of impairment of capillary blood circulation in workers exposed to noise, as well as a high occurrence of neuroses among this group and more cardiac complaints than normal. The WHO noise criteria document in preparation refers to studies of the occurrence in groups exposed to noise of peptic ulcers, hypertension and other disorders not commonly connected with high noise levels. Authorities, says Bell, often comment that “. . . the main auditory effects of noise encountered under industrial conditions do not produce a health problem”. However, industry itself is concerned with the effect of noise on attention and work efficiency and their possible relationship to productivity. While it has been stated that “many employees work under noisy conditions for many years and show no general health changes that can be said to be related 65 0022-460X/78/0708-0065 $01.00/O
8;’1978 Academic Press Inc. (London)
Limited
66
V. J. KRICHAGIN
causally to noise exposure”’ [2], this apparent absence of effect may be the result of many biases in logic. For example, although it may appear that a certain exposed population selected for study has a high health level, this may largely be due to a high rate of labor turnover. Moreover, there are usually no control studies undertaken with exposure studies and no follow-up studies on the health of people after they leave a noisy job. According to Mosskov, Ettema and Zielhuis [4], the interim results of an epidemiological study by Knipschild [5] show a definite correlation between noise exposure load and blood pressure levels (especially diastolic), indicating that noise is indeed a risk factor in hypertension. Their own studies indicated that students showed a decrease of capacity in performance of mental tasks when exposed to aircraft noise and that their diastolic blood pressure was somewhat higher than that of a non-exposed group. Bastonier, Klosterkijtter and Large [6] concluded that auditory stimulation causes arousal of the central and the autonomous nervous system. It is possible to detect and measure arousal reactions by physiological and biochemical methods, It is often stressed that these reactions are not pathological as such, but if repeated frequently under certain conditions, they are undesirable and may become pathogenic. Two effects which must be considered as detrimental to health in the long run are as follows. Sleep disturbances. The time it takes to fall asleep is increased when the noise level is
above 35 dB. Sleep stages are disturbed and there is a loss of deep sleep. Autonomous reactions are caused in sleep by noise levels of 45 dB and above. The awakening effect which occurs at a certain level of noise can hamper the restitution of normal functions expected from sleep (40 to 45 dB awakens sensitive persons; 50 dB awakens babies; 75 dB deprives 75 % of babies of normal sleep). Interferences with relaxation. Throughout the day, man is constantly subjected to fluctuating periods of tension and relaxation which hinder rapid increase of fatigue. This function is affected by noise levels of 50 dB and above. Sick or convalescing people are especially sensitive to this stress. Chronically sick-for example, hypertensive persons-may react more strongly to noise load than healthy persons. Medical doctors are aware that such exposure will eventually have an adverse effect upon the adaptability of physiological functions. Karagodina, Osipov and Shishkin [7] have stated that, in the past 10 years, the level of city noise has increased by 10 to 12 dB(A). Certain health effects have proved to be linked with long-term exposure to urban noise at ranges between 40 and 80 dB(A). Based on animal experiments, it is suspected that long-term noise effects can reduce lifespan by 8 to 12 years. In addition, it is indicated that every third person suffering from neurosis and every fifth with mental disorders developed illness as a result of exposure to noise. In populations exposed to urban noise, disorders in the function of the nervous system occur three times more frequently than in unexposed populations and the incidence rate of hypertension is 1.5 times greater. The content of adrenalin substances in the blood of school children exposed to noise levels of 30 and 47 dB(A) were 2.7 and 4.11% respectively. In surroundings with a noise level of 50 to 55 dB(A), the effectiveness of treatment of patients with chronic diseases was reduced 2 to 2.5 times. Although there has been significant progress in the study of effects of noise in the past decade, the studies of actual health effects of chronic exposure to noise on population groups are not as well developed as for such other pollutants as ionizing radiation, certain carcinogenic substances and lead, for which estimations can be made on the probability and character of delayed health impairments. As was pointed out last year at the United Nations Economic Commission for Europe, few of the existing noise studies indicate more than the degree of annoyance or dissatisfaction
HEALTH EFFECTS OF NOISE EXPOSURE
67
caused in selected populations. For this reason, present community noise control legislation is based mainly on psycho-social responses, which are not comprehensive enough to represent health protection goals. Existing manuals on noise control [8, 2, l] contain curves which are relatively well established for : (a) standard levels of outdoor noise in LD, dB(A), L,, dB(A) versus percentage noyed persons (individual annoyance) ; (b) community reaction ; (c) percentage of people disturbed in rest and sleep; (d) percentage of people giving grounds for wanting to move; and (e) proportion of highly annoyed in total number of complaints.
of an..
These curves are usually taken as a background for legislative proposals. For health authorities, discussion always arises as to which level protection measures should be aimed: a level which might be considered as safe for the most sensitioe population group, a level which is apparently tolerablefor the majority of the population [9] (U.S. standard for occupational health), or a level which is clearly acceptable to the majority of the population [9]. It is the responsibility of the government to decide what level of responsibility can be endorsed in legislation, considering economic costs and other factors. In the case of hygiene, it is necessary to know exactly which population groups cannot tolerate accepted noise levels and to make those in government aware of the risks involved. Vermuelen [lo], describing the forthcoming Netherlands Noise Abatement Bill, stated that goals of noise abatement are necessarily linked to maintaining a healthy environment. This implies adherence to three specific rules: (a) law of ergonomics-to provide optimal quality and quantity of human performance; (b) law of hygiene-to remove from the environment factors which may be adverse to health ; and (c) law of eco-social balance-secondary system-linked factors essential in optimum amount in order to avoid unexpected results. Gala et al. [l I] studied a population of 300 000 in Lubljana in 1975 through inquiries carried out by psychology students. As in similar studies, about 60 “/o claimed to be annoyed by motor traffic; 9 to 10 % by the railway; 4 to 5 9; by neighbouring industry and construction work ; 3 to 4 y0 by noise from children at play: and l to 2 “/g by amusement and sport places. The authors did not find wide differences between this analysis and other studies carried out elsewhere. They concluded that effects of noise on health could not be determined by means of questionnaires in general. Health examinations are to be carried out in order to identify differences in the health status of the population groups under study. In December 1976, the ECE Task Force [I21 prepared a comprehensive report on the present situation of noise control studies in Europe. The Task Force’s impression was that there was a sufficient development for practical purposes of most technical problems in measurement methodologies and of interpretation of results for the prediction of cnmmunity reaction (annoyance-disturbance) to different levels and kinds of noise. There i, a genera1 similarity in the principles of legislation and noise abatement technology as well as in requirements for measurement methodologies observed. Different “noise maps” are non available, which describe conditions in city areas and around airports, for example. A methodology for checking noise sources for noise control to aid in the design of buildings and roads has also been developed. On the other hand, the group stated that “relatively little information had been submitted
68
V. J. KRICHAGIN
on non-auditory physiological effects of noise. There appeared to be relatively little recent worthwhile information on effects of noise on animals”. There is still confusion, unfortunately, between the annoyance effect of noise-largely a sociological factor-and the actual health effects. Engineers often wish to imply simple doseresponse relationships between environmental pollutants and physiological responses and are not always completely aware of the complexity of the slow biological reaction of species to changed environments. Biologists are often intrigued by the various indices suggested by acousticians for noise exposure descriptions, but sometimes forget or are unable to properly consider the basic underlying philosophy. “An ideal approach to establish criteria for environmental noise levels,” say Vaniv and von Gierke [13], “in terms of their effects on long-term public health and welfare would be to start by establishing the cumulative noise dose which an individual, or a population, may sustain over a lifetime, irrespective ofwhere or under what situation this exposureis received”. This misunderstanding of the case is typical. It is a concept in no way applicable to noise exposure. Such concepts are valid only when the active agent inflicts cumulative and irreparable damage to health. In the case of noise, the dose-approach may be applied only if one wishes to calculate the exposure within a very narrow intensity range. Because each intensity level produces a different effect, comparison between different intensity ranges are difficult. Efforts to arouse the receptor organs act not through total amount of energy but through intensity-i.e., energy density per unit of time combined with frequency characteristics. Especially in ranges of low intensity, sounds are necessary elements of normal environments and serve a practical purpose. Logically, this intensity should not be added but rather deducted from the noise dose. There is no reason, however, to dispute all noise measurements in L,, or LDN.For practical purposes, when used for uniform noise sources and conditions, these measurements can produce comparable data valid for evaluation purposes. This is true, however, only within narrow margins of applicability and they should not be regarded as seriously based on physiological, and especially biological, backgrounds. They represent characteristics of the environment which may be related more to immediate human responses than to health problems. Many investigators have fixed the great differences in adaptation potential among individuals to the same noise levels. It is evident that the adaptation of the receptor organs in human beings (to light, sound, temperature, odors, taste) is an inherent feature developed through evolution; the mechanism for such adaptation is well “constructed”, but not unlimited. Sound is a necessary condition of life. Certain noise levels create a normal living environment, adaptation to which is maintained without stress. Noise of a certain level thus becomes a background element, something which adds to an individual’s general well-being. These background levels might vary depending upon many factors of individual circumstances. Only unwanted sound (by character or by level) may create unnecessary stress which might be considered as a burden to the general adaptation capabilities of the organism, reducing its general resistance in the perpetual balance with the living environment. A noisy environment is a biologically unnatural environment. It is a change in circumstances which requires human beings to develop some tolerance. When these changes are beyond normal homeostasis, permanent stress occurs and adaptation through disease and evolutionary selection is probable. The purpose, then, of finding criteria for limiting community noise is to determine the limits of homeostasis among both normal and sensitive population groups. Experience gained from studying biological effects of environmental pollution brings us to the general conclusion that one can discover hazardous health effects of pollutants even below levels of direct pathological and sometimes apparently physiological effects. For example, air pollution by SO, (which is not a natural component of air and cannot be compared with
HEALTH
EFFECTS
OF NOISE EXPOSURE
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noise) produces harmful effects on humans in values much lower than the threshold of odor. It has been established that correlation between active concentrations of this agent, 100 times below the threshold of odor, increases hospital admission rates of patients suffering from chronic lung disease [ 141.This effect is now seriously considered in setting limits and standards. The same is true at present for delayed effects from air pollution by such agents as lead, asbestos particles in the air and certain dusts. According to this analogy, one may expect that between 80 and 85 dB(A)-now accepted as the minimum borderline of hearing damage-and 30 and 35 dB(A)-an average background noise level of modern urban environments-there are several thresholds giving rise to harmful effects which might be discovered by means of properly organized epidemiological studies. At the International Symposium on Recent Advances in the Assessment of the Health Effects of Environmental Pollution, Rylander stated [ 151that the degree of annoyance itself may be interpreted as strain and stress which interferes with human well-being. The latter is a component of the WHO definition of health, but it is not, by any means, only well-being which is impaired under noise exposure. Certainly, a highly annoyed person is one who is under permanent psychosomatic stress. He is also constantly in the process of adapting to the denial of normal rest and relaxation, which is manifested in chronic fatigue, a decrease in working capacity and a reduction of his biological adaptability to other environmental hazards. As in the case of SO, pollution, it was discovered that not only lung but also cardiac and other diseases increased in exposed populations. Thus, noise-induced stress may not necessarily manifest itself only in hearing damage or fatigue. Data from the Erisman Hygiene Institute in Moscow suggests that changes in general morbidity and its character in populations living in noisy areas of big cities can definitely be correlated with noise levels [12]. The approach cited above shows that, in the case of protection against noise, conclusions cannot be drawn from reactions of the majority of the population. Health authorities are concerned also with minority groups which cannot tolerate certain levels of noise. It is considered that the following risk groups deserve special protection : (a) healthy people with intense living style, effectively working at the boundary of human capability, who have an acute requirement for limited but complete relaxation and sleeping time; (b) healthy people who are required to work with constant concentration of attention; according to Setchenov’s theory of concurrence of arousal areas in the cortex of the brain, side effect stimulators create additional areas of arousal which inhibit the main arousal area (dominanta); (c) fairly healthy people with constitutional partial deficiency in adaptation to stress (neurotics, etc.); (d) chronically sick people with reduced adaptability, including added impairment from degenerative diseases ; (e) children in certain stages of growth who are sensitive and vulnerable to stressors and whose proportional growth and development may be impaired. Noisy areas in cities are, of course, not evenly distributed. There is a constant turnover of population which self-selects towards groups tolerant of noise. This can dramatically decrease the number of hypersensitive and sensitive subjects from the risk groups mentioned above within noisy areas. Because man has a sensitive receptor organ for noise, his behavioral reaction of avoidance is rather obvious. This is not true for such hidden hazards as change of salt content in drinking water or exposure to microwave energy, which create annoyance but cannot be detected. In this case, knowledge and proper education are essential to avoid the undesirable agent and the danger is commonly underestimated, as in smoking habits. In the case of noise, however,
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there may be an overestimation of danger in connection with some side-effects (i.e., social benefits offered to exposed populations). In considering whether community noise can produce a negative effect upon the health of a population, there is still a major gap between laboratory studies of direct biological effects and the delayed effects of long-term stress induced by a noisy environment. There is no doubt that the creation of permanent stress from noise pollution in densely populated areas constitutes a social danger comparable to that of such well documented hazards as carcinogenic dusts, lead, carbon monoxide and other air pollutants. It might be a prioripostulated that among the many causes of permanent nervous stress, noise is one of the most widely influential factors. Bell [l] refers to several experiments on animals which deal primarily with noise of intense levels, with registration of acute or delayed effects. The effect of chronic exposure to moderate levels of noise, similar to community noise, is not as well described; it is difficult to determine what levels of noise might be classified as moderate to animals. This difficulty may be overcome through special planning of experiments aimed at creating stress in higher nervous functions. The ECE Task Force [ 121 presented excellent analyses of the present situation in research on noise control. According to the Task Force, half of the work has been on noise physics and the remainder on the sociological influence of community noise (analysis of questionnaires). Only marginal research efforts have been concentrated on basic medical effects. In summary, it may be concluded that it is necessary to strengthen co-ordination in research aimed at evaluating real dangers of community noise to the health of the exposed population. Programs must be formulated for this purpose.
REFERENCES 1. A. BELL 1966 WHO Public Health Paper No. 30, Geneva. Noise: an occupational hazard and public nuisance. 2. J. LANG and G. JENSEN1970 WHO EURO 2631, Copenhagen. Environmental health aspects of noise research and noise control programme. 3. ANON 1971 WHO EURO 3901. Development of noise control programme. 4. J. MOSSKOV,J. H. ET~EMAand R. I. ZIELHUIS1976 Proceedings of the AICB International Congress on Noise Abatement, Budapest, September 1976, III, 203-206. Experimentelle Untersuchung tiber Fluglarmwirkungen. See p. 203. 5. P. KNIPSCHILD 1976 Dissertation, Cozonel Laboratorium, University of Amsterdam. Medishe gerolgen van vliegtu iglawaai. 6. H. BASTONIER,W. KLOSTERK~TTERand I. LARGE 1975 CEC book in series: Environment and Quality of Life, EUR 5398e, Luxembourg. Damage and annoyance caused by noise. 7. I. KARAGODINA,G. OSIPOVand I. SHISHKIN1972 Noise Control in Cities. Moscow Medicina: Boxba & Shumon V. Gorodach. 8. U.S. Environmental Protection Agency Dot. No. 550/g-73402, Washington, D.C. 1973 Public health and welfare criteria for noise. 9. K. OESER1976 Proceedings of the AICB International Congress on Noise Abatement, Budapest, September 1976, III, 61-64. Notwendigkeit, Moglichkeiten und brenzen des Burgernegagements bei der Larrnbekampfung bzw. dem Ruheschutz. 10. C. A. VERMUELEN1976 Proceedings of the AICB International Congress on Noise Abatement, Budapest, September 1976, III, 53-58. The coming Dutch noise abatement bill. See p. 55. 11. D. GALA and D. ALEKSANDER1976 Proceedings of the AZCB International Congress on Noise Abatement, Budapest, September 1976, III, 151-154. Community for protection of the environment of Slovenia. See p. 151. 12. 1976 (10 December) ECE Task Force on Noise, Geneva. National approaches to community noise problems.
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13. S. L. YANIVand H. E. VON GIERKE 1974 Proceedings of the ItiternationaL Symposium on Recenr Advances in the Assessment of the Health Eflects of Environmental Pollution, Paris, 24-28, June 1974, 1263-1276. Method for the identification of environmental noise levels requisite to protect
public health and welfare. 14. B. PRINZ 1977 WHO Regional Publications EURO Series No. 1, Copenhagen. Manual on urban air quality management : ambient air quality standards and their application. 15. R. RYLANDER1974 Proceedings of the International Symposium on Recent Advances in the Assessment of the Health Effects of Environmental Pollution, Paris, 24-28 June 1974.