Noise Pollution

NOISE POLLUTION: AN UNDERAPPRECIATED CULPRIT














Jason Chertoff


Jlc2198


4/8/10


Environmental Health Spring 2010


TA: Simon Lee














Abstract


Although noise has a variety of proven public health consequences and affects millions of people across the globe, it is routinely forgotten and omitted from environmental health exposure discussions. Noise, defined as unwanted sound, has repeatedly been implicated in hearing deficits, endocrine disturbances, hypertension, and cardiovascular morbidity. Review of the literature has shown a direct dose-response relationship between noise exposure and many negative health effects (5). Virkunnen et al showed an association between noise exposure and coronary heart disease, while Jarup et al illustrated an exposure-response relationship between airport and road traffic noise and hypertension (1,2). The EPA, and United States Congress has responded to many of these studies with the proposal of policy innovations, but unfortunately a lack of funding and support has hindered any significant progress in alleviating noises’ adverse public health effects. Further research is needed to investigate the mechanism how noise negatively affects health. In addition, more studies must focus on the effectiveness of interventions at reducing noise exposure. Noise is a burdensome, often overlooked, environmental health exposure that has been implicated as a risk factor for many diseases affecting numerous organ systems. Certainly, more attention and research focused on noise will have enormous public health benefits.


Background


Noise, perceived as an environmental stressor and defined as unwanted sound, has numerous parallels to second-hand smoke in that noise is a burdensome airborne pollutant imposed on us without our consent and oftentimes beyond our control. Exposure to noise of 85-90 dBA may lead to a gradual loss of hearing and an increase in hearing sensitivity, among many other health consequences (5). The 2000 United States Census found that 30% of Americans complained of noise, and of these, 40% said that it was bothersome enough to change their residence. In addition to its detrimental auditory effects, noise has been shown to negatively affect spoken communication, sleep, cardiovascular health, mental health, task performance, and social behavior (3). Appreciating the severity of noise, Congress passed the Noise Control Act in 1972 stating that all Americans are entitled to an environment free from noise that jeopardizes health and wellbeing. Furthermore, the 1990 NIH panel called for more high visibility media campaigns to increase the awareness of noise’s disastrous health effects. As the population continues to rapidly increase, accompanied by escalating industrialization, urbanization, and technological advances, the exposure to noise will increase leading to numerous public health implications (3).


In New York City, and other mass transit subway systems, noise levels exceeding 112 dB have been measured. Human beings respond to these unhealthy exposure levels with a fight or flight stress response. The chronic hormonal, cardiovascular, and nervous adaptations that result from this stress reaction have been proven to cause a variety of detrimental effects on numerous organ systems (1). Stansfeld et al found a direct correlation between occupational noise and hypertension, while Van Kempen et al concluded in a meta-analysis that occupational noise was a significant risk factor for increased systolic blood pressure (3,4). A 1995 meta-analysis of blue collar workers in 21 Israeli industrial plants by Kristal-Boneh et al, illustrated a direct relationship between noise and resting heart rate (6). Melamed et al showed a significant increase in serum lipids along with a positive association between baseline noise exposure and cardiovascular illnesses and death (5). Further supporting the role of noise as an environmental health offender, numerous airport studies in Europe and Asia have shown a direct exposure-response relationship between aircraft noise and hypertension (1).


Although many studies have been invaluable in elucidating noise’s health consequences, two such studies best illustrate the innovative policy implications and advances that diligent environmental health research can provide. In addition, these studies vividly illustrate the gaps in our knowledge of this public health problem and the need for further research and interventions. First, Virkkunen et al, in a prospective study, investigated the relationship between short-term and long-term occupational noise and coronary heart disease in 6005 Finnish industrial workers. It was shown that exposure to noise caused a statistically significant increase in the risk for coronary heart disease, continuing even through retirement. The results of this 2005 study has led to numerous policy discussions and advances in Finland, calling for reduced noise exposure in various industrial workplaces (1). In 2008, the HYENA (Hypertension and Exposure to Noise Near Airports) study by Jarup et al, described the prospective 5-year follow-up of 4,861 people living near six major European airports. Through meticulous research these investigators found a significant dose-response relationship between both airport and road traffic noise, and blood pressure. As a result of this and other airport studies, various policies and laws are either in place or in development to insure reduced noise exposure from aircraft and road traffic (2). In summary, a direct result of sound environmental health research, like the studies published by Virkkunen et al and Jarup et al, are the development and implementation of policies directed at decreasing noise’ burden on the public’s health.


Current Research


Impaired hearing is an increase in the threshold of hearing and is clinically assessed by audiometry. Berglund et al and others have shown that exposure to levels less than 70 dB is safe, regardless of the length of exposure. However, exposure to levels greater than 85 dB and its accompanying sound pressure for longer than 8 hours is potentially dangerous. Exposure to levels greater than 165 dB, even for brief periods, will likely cause cochlear damage (4). The WHO recommends that levels greater than 100 dB should be limited in frequency (four times/year) and duration (4 hours) (5). What is concerning about these guidelines and regulations is that most are oblivious to their existence and ignorant to noise being a health problem. Chung et al showed that only 8% of respondents considered hearing loss a significant problem (3). Even more concerning is that data shows children to be much more vulnerable to the detrimental hearing effects from sound than adults (3). Niskar et al estimated that at least 12.5% of children between the ages of 6-19 in the United States had impaired hearing in one or both ears (3). This hearing loss has proven communication, cognition, academic, speech, and emotional consequences in many of the children affected (3).


In addition to its auditory effects, noise exposure has numerous non-auditory consequences. Noise exposure is one of the leading causes of disturbed sleep. Continuous levels greater than 30 dB has been shown by Stansfeld et al to disturb sleep (3). If this sleep disturbance becomes chronic, the result can be impaired performance, mood disturbances, and other long-term health effects (3). Hobson et al showed that exposure to noise during sleep causes increased body movement, changes in respiration, cardiac arrhythmias, increased resting heart rate, and hypertension. Sleep deprivation has also been linked to accidents, injuries, and death from impaired alertness. Many noise-sleep intervention studies have been published and the consensus is that noise abatement during sleep leads to an increase in REM and slow wave sleep (3). More studies are needed to determine if any long-term health benefits can arise from noise reduction interventions during sleep (3).


Exposure to chronic noise has been linked to mental health disturbances. Numerous population studies have attributed noise pollution to a decrease in self reported well being, to increased use of sleeping pills, and more psychiatric hospital admissions (5). Other community surveys find an increase in headaches, "restless nights", and "being tense and edgy" in locations with high noise exposure (5). Konenci et al showed that exposures greater than 80 dB are associated with an increase in aggressive and selfish behavior (3). An airport study in Japan found a dose-response relationship between noise exposure, "nervousness", and "depressiveness" (3). Current and future research must be focused on noise reduction interventions and their ability to effectively improve mental health outcomes.


Noise exposure is also a proven cause of impaired task performance, especially in children. Children exposed to noise pollution have impaired reading attention, problem solving, memory, and motivation in schools and locations with high exposures (3). When homes or schools are in locations with high noise exposures, such as highways or airports, the result is impaired cognitive and language development, reading attainment, and school performance. According to teachers’ reports, children exposed to noise have worse concentration than students at quieter schools (5). Cohen et al showed that children exposed to noise are less likely to perform well on national standardized tests (3). In a study by Bronzaft and McCarthy, students in a classroom near a railway were compared to controls. The children proximal to the railway showed worse reading scores and an increase in mean reading age (5). Another series of well designed studies investigated schools in close proximity to Heathrow Airport. The 9-10-year-old children near the airport showed impaired attention and reading comprehension when compared to a well matched control group. This study also illustrated a dose-response relationship between noise exposure and math test performance (5). A Munich Airport study studied the cognitive ability of children in three waves; Wave 1 was prior to the closure of a noisy airport, and Waves 2 and 3 were after the closure of this airport and the opening of a new airport. The longitudinal results showed improvements in long-term memory for those children in Waves 2 and 3 (3). These results provided strong evidence suggesting causality between noise exposure and detrimental cognitive effects. Thus, it is obvious that interventions aimed at removing noise exposure to children, has the potential for significant long term benefits.


A review of noise pollution would not be thorough without a description of noise annoyance. It is the most well documented subjective response to noise. Noise annoyance is defined as a feeling of displeasure from the adverse exposure to noise (3). Annoyance will increase when high levels of sound are accompanied by harsh vibrations or low frequency components. Numerous aircraft and traffic studies have shown a dose-response relationship between noise levels and annoyance. It is a person’s perceived lack of control over noise that causes annoyance’s characteristic feelings of anxiety, depression, anger, disappointment, agitation, and dissatisfaction. The lack of control over a noisy environment is seen as intrusive and invasive of one’s privacy. As a result, many experiencing annoyance from noise exposure complain of a worsening in their well being (5). In fact, Bluhm et al showed an indirect correlation between annoyance and quality of life (3). A recurring theme with noise pollution is its preferential effects on children. A study from Munich used a calibrated community measure to illustrate a direct association between noise and annoyance in a series of children. A similar study from London showed a similar relationship, and also showed that little habituation to annoyance occurred in children one year after removal of the exposure (5). It is therefore imperative to investigate the efficacy of annoyance reduction resulting from noise-reduction interventions.


In addition to having auditory, behavioral, and mental consequences, noise causes significant health concerns in other organ systems such as the cardiovascular and endocrine systems. Noise is perceived as a stressor, and the body reacts with its appropriate endocrine response. However, when this stressor is not removed, stress hormones become chronically elevated leading to a variety of pathologies (5). Numerous studies have shown increased cortisol, norepinephrine, and epinephrine in those that are chronically exposed to noise (3). Brandenberger et al showed that workers wearing noise protection had decreased catecholamine levels (3). Chronically elevated levels of these stress hormones often cause adverse changes in cholesterol, triglyceride, and blood glucose levels. These pathologic changes, along with an increase in blood pressure, can have significant effects on cardiovascular health (5). Therefore, any attempt at reducing noise has the potential to improve cardiovascular outcomes.


An overwhelming amount of research has been devoted to noise’s role as a risk factor for cardiovascular disease. Most agree that acute exposure to levels greater than 80-85 dB and chronic exposure to levels greater than 65 dB can cause an increase in blood viscosity, vasoconstriction, heart rate, and blood pressure (3). These changes, each proven risk factors for atherosclerosis and coronary heart disease, are excellent illustrations of noise’s danger to overall cardiovascular health. Furthermore, children do not seem to be immune from these effects as seen by elevations in blood pressure and stress hormones (5).


There is a wealth of studies that confirm noise’s negative effects on cardiovascular health. A case-control study in 1994 by Fogari et al showed an increased systolic blood pressure in those chronically exposed to noise (3). A cross-sectional study by Zhao et al showed dose-response relationships between noise, systolic blood pressure, and diastolic blood pressure (3). Furthermore, Kristal-Boneh et al showed that the intensity of noise was related to the resting heart rate in women (6). An airport study in Amsterdam showed noise exposure to be directly correlated with more treatment for hypertension and more cardiovascular drug use. Another airport study, conducted in Los Angeles, showed chronic noise exposure to be directly related to an increase in both systolic and diastolic blood pressure (5). It is extremely important to realize that although most of these cited studies illustrate noise having only a minor effect on cardiovascular health, noise remains an important public health problem because of the abundance of people that are at risk and exposed.


There are two landmark studies that have been chosen in this review because of their ability to illustrate how environmental health research can lead to changes in policy. The first study is entitled, "Long-term Effect of Occupational Noise on the Risk of Coronary Heart Disease", by Virkkunen et al. This Finnish study’s, published in 2005, main aim was to investigate the short- and long- term effects of occupational exposure to continuous and impulse noise on the risk of coronary heart disease (CHD). This nested prospective cohort study of 6,005 participants consisted of two phases, short-term and long-term, which were 9 and 18 years of follow-up, respectively. The investigators used systolic blood pressure and serum lipid levels as proxies for coronary artery disease. For the short-term phase, those workers exposed to continuous occupational noise levels > 85 dB had a RR=1.45 (p<0.01) for having a CHD event. Those exposed to impulse noise during the short-term follow-up did not show any statistically significant increase in CHD risk. For the long-term phase, those workers exposed to continuous occupational noise levels > 85 dB had a RR=1.48 (p<0.01) for having a CHD event. Those exposed to impulse noise during the short-term follow-up had a RR=1.34 (p<0.01) for having a CHD event. To further delineate the possible causal role between noise and CHD, the researchers were able to illustrate a clear dose response relationship, such that the amount of noise exposure (intensity, frequency, and duration) was directly related to the risk of CHD. What is commendable about these highly suggestive results is that the investigators meticulously controlled for most confounding variables such as age, systolic blood pressure, serum cholesterol, smoking status, BMI, and labor type (white vs. blue collar). Perhaps, the most interesting finding in this study is that when the follow-up was limited to start when participants reached 60 years, the corresponding risks were 1.89 for continuous noise and 1.53 for impulse noise, each being statistically significant. Since most workers in Finland are retired by age 60, this data suggests that the occupational noise’s risk for CHD events persists, even after the exposure is removed. Thus, it appears that the exposure to occupational noise, whether continuous or impulse noise, may cause irreversible damage to one’s cardiovascular health. In response to this data deeming noise a significant environmental health culprit, Finland has responded with numerous policy and law deliberations aimed at reducing noise exposure in the industrial workplace (1). Therefore, Virkkunen et al is an excellent example of how environmental health research can have beneficial public health implications.


Another important study illustrating environmental health research’s crucial role in transforming public health policy is entitled, "Hypertension and Exposure to Noise Near Airports: the HYENA Study", by Jarup et al. This European airport study’s main objective was to assess the relationships between noise exposure from airports and road traffic and the risk of hypertension. For those exposed to nighttime aircraft noise, the OR=1.141 (p=0.031) for hypertension. For those exposed to road traffic noise, the OR=1.097 (p=0.031) for hypertension. Although these odds ratios are small in magnitude, their statistical significance suggests the potential for a large public health advances since many people are exposed to aircraft and road traffic noise and are potentially at risk for hypertension. In response to these results, numerous policy deliberations are considering preventive measures to reduce road traffic noise and nighttime noise from aircrafts (2).


Conclusion


Much research illustrates the harmful role that environmental noise exposure has on the public’s health. It has been shown repeatedly that exposure to high intensity sounds for prolonged periods have potential auditory and non-auditory consequences. Auditory effects such as tinnitus and hearing loss can have many public health consequences, especially in children. Children exposed to noise have proven difficulties in educational attainment, social development, emotional maturation, and mood stability. These effects on American children can have many implications as they mature into adulthood. To decipher the magnitude of detriment that these effects will have in adulthood requires further research and there is an urgent need for prospective cohort studies to follow these children into maturity and investigate specific social and biological health outcomes. For example, the cohort of children in the Bronzaft and McCarthy study could be followed into adulthood and compared to a well matched control group for social outcomes such as unemployment rate, poverty, or violent crimes. This group could also be followed for biological outcomes such as hypertension, hypercholesterolemia, or diabetes. These innovative cohort studies would emphasize to policymakers the importance of intervening to reduce noise as early as possible, especially during childhood.


Another area open to further research is the need to expand on the CHD study by Virkkunen et al. In the literature, many studies link noise to coronary heart disease risk factors like hypertension, and hypercholesterolemia. However, no studies in this literature review can directly link noise to coronary heart disease. The study by Virkkunen et al showed an increase in CHD risk factors, and extrapolated this to mean that the CHD risk also increased. Although it would be extremely costly, a cardiac catheterization study, the gold standard for diagnosing CHD, would provide the most effective and convincing outcome measure. Assuming cohort studies such as these illustrated pathologic changes with cardiac catheterization from noise exposure, few would argue against noise reduction policies.


Another knowledge gap in this environmental health arena concerns the effectiveness of noise reduction interventions. Past and current research has been invaluable in elucidating noise’s dangerous role in health. However, this information might appear moot and theoretical, if interventions to reduce noise and improve health were not successful. To clarify, it is certainly important to know that prolonged noise exposure can lead to educational delays in children, or hypertension in adults. Even more pertinent, however, would be studies that could illustrate the reversal or stabilization of educational delays or hypertension as a direct result of noise reduction interventions. This would add further support for noise’s causal role in negative health outcomes, and would afford policymakers the information needed to impose interventions. Since so many people are exposed to noise, children and adults, an intervention proven to be effective at reducing noise and at improving health would undoubtedly have an enormous public health benefit.


The world’s population, industrialization, and urbanization continue to rise. As a result, the public is being exposed to sound levels of higher and longer intensities than ever before. These noise exposures have numerous public health consequences as illustrated from vast amounts of research. Children forced to endure prolonged noise exposures have proven deficiencies in educational attainment, and the development of healthy social skills. Adults exposed to noise succumb to hypertension, hypercholesterolemia, and other risk factors for coronary heart disease. Since so much of the population is exposed to noise, especially with the globe’s escalating levels of industrialization, most would consider noise to be an enormous public health burden in 2010. Further research must be conducted to provide policymakers the ability to implement noise reduction interventions. The successful implementation of these interventions will surely lead to massive public health benefits.

















References


1. Virkkunen, H et al. "Long-term Effect of Occupational Noise on the Risk of Coronary Heart Disease" Scand J Work Environmental Health 2005;31(4):291-299.


2. Jarup, L et al. "Hypertension and Exposure to Noise Near Airports: The HYENA Study" Environmental Health Perspectives 2008;16(3):329-333.


3. Stansfeld, SA et al. "Noise Pollution: Non-Auditory Effects on Health" 2003;68:243-257.


4. Van Kempen, EEMM et al. "The Association Between Noise Exposure and Blood Pressure and Ischemic Heart Disease: A Meta Analysis" Environmental Health Perspectives 2002;110:307-317.


5. Goines, L et al. "Noise Pollution: A Modern Plague" Medscape Today 2007.


6. Kristal-Boneh, E et al. "Acute Noise Exposure on Blood Pressure and Heart Rate among Industrial Employees: The CORDIS Study." Archives of EnvironmentalHealth, 50(4):298-304.