Environmental & Health Impacts

Excerpt from 2021 APHA Policy Statement: Noise as a Public Health Hazard

Summary:

• Decades of scientific evidence show that noise causes or contributes to hearing loss, annoyance, sleep disruption, cardiovascular disease, metabolic disturbances and exacerbation of anxiety and depression.

Leaded Gas Was Phased Out 25 Years Ago. Why Are These Planes Still Using Toxic Fuel?”

Summary:

• Piston engine aircraft are the largest source of lead emissions to air in the US.
• Developments in automobile engines enabled cars to stop using leaded fuel. However, there were no alternatives to piston engines. Thus, piston engines were left out of federal regulation of leaded fuel. 
• Studies show that lead has a detrimental impact on children’s brains and nervous systems. 
• Economically disadvantaged communities are often forced to live in lead-polluted areas due to lower rent prices.

While leaded gasoline was fully phased out in 1996 with the passage of the Clean Air Act, it still fuels a fleet of 170,000 piston-engine airplanes and helicopters. Leaded aviation fuel, or avgas, now makes up “the largest remaining aggregate source of lead emissions to air in the U.S.,” according to the Environmental Protection Agency. The presence of this fuel means the areas near these airports are often inundated with tiny lead particles, according to a 2020 report from the EPA. Lead has been proven to have a detrimental impacton children’s brains and nervous systems.

After 15 years of research, the EPA said it would issue a ruling, known as an “endangerment finding,” in 2018 that would unlock a legal mandate to start driving down leaded aviation fuel. But it has yet to do so. “EPA will follow the science and law in developing any future decisions regarding lead emissions from piston-engine aircraft,” said Enesta Jones, an EPA spokesperson.For now, leaded aviation gas appears to be caught in a bureaucratic limbo: stuck between not meeting the environmental demands of the EPA and the commercial realities of the aviation community. It is the primary viable option for this type of aircraft, as the general aviation community argues it remains critical given the needs of the current fleet.

When the EPA first tackled removing lead emissions from engines, it focused on the biggest polluters: cars. At the time, the automotive industry made up the vast majority of airborne lead, with piston-engine airplanes responsible for only about 5 percent of emissions. Technological advances in auto engines, such as cooling liquid, also made way for a new market for unleaded fuel. But there were no alternatives for piston engines, so they were largely left out of federal regulation. Piston-engine aircraft are now the largest single remaining source of airborne lead, according to a 2016 EPA study. Approximately one-quarter of the piston-engine fleet are estimated to “consume more than half of all avgas,” according to a January report by the National Academy of Sciences (summary provided by Shivani Tripathi).

Why Noise Pollution Is More Dangerous Than We Think

Summary:

• Noise pollution is deadly, be it sirens, car honks, or construction jackhammers.
• Studies show that people living in noisy areas–such as transportation paths–have higher rates of disease. 
• Noise pollution disrupts wildlife as well: ship noise causes dolphins and whales chronic stress, and the sound of busy streets change bird migratory patterns.  

David Owen reports on noise pollution, an intangible phenomenon with serious costs to human health and wildlife (summary provided by Shivani Tripathi).

Why Noise Pollution Is Bad For Your Heart

Summary:

• Noise activates two regions of the brain – the auditory cortex, which deciphers the noise, and the amygdala, which regulates emotional response. Loud noises make the amygdala activate our body’s fight or flight mode, which is a stress response.
• The fight or flight mode releases adrenaline and cortisol. Blood pressure rises, digestion slows, and sugars and fats inundate the bloodstream. 
• This stress response inflames the endothelium, the lining of blood vessels. The “dysfunctional” endothelium interferes with vital processes, potentially leading to high blood pressure, cardiovascular diseases, obesity, and diabetes.

Aircraft noise is the most annoying by far. Münzel had read a 2009 World Health Organization (WHO) report linking noise to heart problems, but evidence at the time was thin. Driven in part by concern for his own health, in 2011 he shifted the focus of his research to learn more. Exposure to loud noise has long been linked with hearing loss. But the ruckus of planes and cars takes a toll beyond the ears. Traffic noise has been flagged as a major physiological stressor, second to air pollution and on roughly equal footing with exposure to second-hand smoke and radon. In the last decade, a growing body of research has linked noise from aircraft and road traffic to a heightened risk for a number of cardiovascular ailments. And scientists are also beginning to pinpoint the mechanisms at play (summary by Shivani Tripathi).

The science behind helicopter noise

Helicopter Sound: Helicopter noise comes from air passing over rotor blades as they spin. This generates pressure changes which create noisy airflows. ‘Blade slap,’ blade vortex interaction from airflow, is the loudest and most annoying noise for observers. The impulsive vibrations from ‘blade slap’ make listeners perceive helicopters to be almost twice as loud as they actually are. These low frequency vibrations are felt and not always heard.  Read more…

Suggestions for alleviating sound: the Helicopter Association International’s (HAI) 1981 fly neighborly guide suggests a voluntary noise abatement program for communities and helicopter companies. Helicopter operators should conduct community outreach explaining their operations to make people less annoyed. A number of technical developments can also reduce helicopter noise, including: 

• Lower-noise rotor blades
• Hybrid and electric Vertical Takeoff Landing aircraft 
• Ducted rotors, blade shapes, hub phasing, and lower rotor tip speeds to lessen thumping noise

Despite these improvements, public acceptance of helicopters remains low. Other research shows that voluntary agreements are rarely respected and that technological improvements are not implemented (summary provided by Grace Brennan).

Ambient Noise Is “The New Second Hand Smoke”

Like unwanted tobacco smoke, noise doesn’t just bother people but also adversely affects human health and function. 

Transportation noise is particularly concerning considering millions of people face small health effects from exposure. Most experts say data shows a causality of transportation noise exposure and adverse health risks. These risks stem from the “fight or flight” responses triggered in humans from loud noises: chemical changes in our bodies from this stress can cause vascular dysfunctions that lead to disease. 

The only federal U.S. noise regulation comes from the National Institute for Occupational Safety and Health. The NIOSH recommends 85 decibel(dB) equivalent continuous sound pressure level for 8 hours to reduce hearing loss from occupational exposure. The World Health Organization (WHO), however, recommends only 1 hour of exposure per day to 85dB to prevent hearing loss. 

There are no standards for occupational or non-occupational exposure to low-frequency noise, which is produced by helicopters. There are also no federal guidelines for public noise exposure, despite the following threats from varied noise levels:

Noise Level (decibels)	Health effect
30 dB	Sleep disruptions
45 dB	Disturbance of concentration and interference with learning
55 dB	Non-auditory health effects
60 dB	Interference with speech comprehension for hearing impaired
70 dB daily average	Hearing loss

The absence of regulations on ambient noise is a disability rights concern considering people with moderate to severe auditory disorders meet federal disability standards. People with auditory disorders, including hyperacusis, tinnitus, and hearing loss, experience physical pain from noise and can suffer from isolation and depression.

Regulations need to ensure a 70 dB time-weighted average for 24 hours of exposure in occupational and non-occupational settings. This is the only level of evidence-based safe noise exposure (summary by Grace Brennan).

Aircraft and road traffic noise and children’s cognition and health: a cross-national study

Summary:

• In a study of nearly 2844 children from 89 schools, researchers found that aircraft noise could impair cognitive development in children, especially reading comprehension.  
• Schools with high levels of aircraft noise are unhealthy educational environments. 

Our findings indicate that a chronic environmental stressor-aircraft noise-could impair cognitive development in children, specifically reading comprehension. Schools exposed to high levels of aircraft noise are not healthy educational environments (summary by Shivani Tripathi).

American Public Health Association: Environmental Noise Pollution Control

Unwanted and disturbing sound increases the risk for a variety of negative health outcomes such as heart disease, diabetes, hypertension, hearing loss, and sleep disturbance. While current federal and local policy is fragmented, the infrastructure for greater collaboration is available and ready to be utilized to improve public health outcomes. The American Public Health Association should archive the policy statement on noise from 1975 and advocate for the implementation of a federal noise control plan through the United States National Prevention Strategy. Federal leadership in noise monitoring, research, and education will help local governments abate the negative health outcomes associated with environmental noise pollution.

Noise exposure is becoming ‘the new second hand smoke’

“Noise doesn’t just affect hearing, noise activists say. A study by the University of Michigan showed an association with cardiovascular disease and heart attacks, according to Neitzel, who conducted the study. “The consensus is that if we can keep noise below 70 decibels on average, that would eliminate hearing loss,” Neitzel said. “’But the problem is that if noise is more than 50 decibels, there’s an increased risk of heart attack and hypertension,” he said. “Noise at 70 decibels is not safe.’”

Why Everything Is Getting Louder

“Scientists have known for decades that noise—even at the seemingly innocuous volume of car traffic—is bad for us. “Calling noise a nuisance is like calling smog an inconvenience,” former U.S. Surgeon General William Stewart said in 1978. In the years since, numerous studies have only underscored his assertion that noise “must be considered a hazard to the health of people everywhere.” Say you’re trying to fall asleep. You may think you’ve tuned out the grumble of trucks downshifting outside, but your body has not: Your adrenal glands are pumping stress hormones, your blood pressure and heart rate are rising, your digestion is slowing down. Your brain continues to process sounds while you snooze, and your blood pressure spikes in response to clatter as low as 33 decibels—slightly louder than a purring cat.

Experts say your body does not adapt to noise. Large-scale studies show that if the din keeps up—over days, months, years—noise exposure increases your risk of high blood pressure, coronary heart disease, and heart attacks, as well as strokes, diabetes, dementia, and depression. Children suffer not only physically—18 months after a new airport opened in Munich, the blood pressure and stress-hormone levels of neighboring children soared—but also behaviorally and cognitively. A landmark study published in 1975 found that the reading scores of sixth graders whose classroom faced a clattering subway track lagged nearly a year behind those of students in quieter classrooms—a difference that disappeared once soundproofing materials were installed. Noise might also make us mean: A 1969 study suggested that test subjects exposed to noise, even the gentle fuzz of white noise, become more aggressive and more eager to zap fellow subjects with electric shocks.”

Publications on the Mental and Physical Health Effects of Noise, Regulating and Mitigating Noise

Summary:

GrowNYC provides resources (podcasts, books, and articles) on noise pollution. The following article is highlighted (summaries provided by Grace Brennan): 

• Women Whose Noise Complaints Have Been Dismissed Are Asked to Advocate for A Quieter Environment 

“Let me assure you that noise is an irritant that has been intruding on the lives of many people worldwide, causing them stress, a loss of sleep, physical and mental discomfort, and a diminished quality of life.” – Arline L. Bronzaft Ph.D. (GrowNYC board member)Bronzaft is often referred to as the noise lady. She responds to noise complaints from new yorkers, typically women, whose concerns are rarely taken seriously. People have a right to “reasonable quiet” in their apartments, she argues. NYC residents have had success in reducing noise in their environment, and Bronzaft suggests working with your neighbors to contact the EPA about noise concerns. She says to remember the NYC Noise Code in making your demands. Unfortunately, The New York city noise code does not oversee noise from overhead airplanes and helicopters. These complaints are controlled by the Federal Aviation Administration and local airports.

How City Noise is Slowly Killing You

The WHO declared noise pollution as the number-two threat to public health after air pollution. Noise elevates stress levels which are already high across the nation. 

As humans evolved, loud noise correlated with high-stress events. This means that when we hear a siren or the whir of a helicopter, we experience a rise in adrenalin, cortisol, and other stress hormones. Long term noise exposure restructures our brain, can cause tumor development, heart disease, respiratory disorders, and more. Studies have found that we don’t adapt to noise – it consistently makes us less motivated, heightens stress, and zaps our energy. There is currently inadequate or no policy putting research on noise health impacts into action. We need to lessen the din in our environments with government regulation to protect against health threats and improve our quality of life.

Neighborhood Noise and Its Consequences: Special Report #9 (Jan 2006) and #3 (Dec 2004)

These reports show that New York City residents are more bothered by noise and more likely to make a complaint about it than people nationwide. They suffer from the behavioral and emotional consequences of noise exposure (annoyance, helplessness, trouble sleeping or relaxing) more severely. These results are based on a eTownPanel online survey conducted in collaboration with GrowNYC. For each report, about 130 reponses came from New York City residents. 

The 2004 report was released after mayor Bloomberg’s announcement that the City’s Department of Environmental Protection (DEP) had prepared an updated Noise Code, signaling that existing noise legislation was ineffective. The 2006 report followed the 2005 passage of the updated code. 

The 2006 and 2004 report show similar response data. Here are a couple highlights:

• 21% of survey respondents from New York made a noise complaint to a government helpline, whereas only 6 percent of nation-wide respondents did
• When asked, “how often are you bothered by the following sources of noise in your neighborhood?” New Yokers fall between “rarely” or “sometimes” for “airplanes or helicopters”

• Impact of Noise on Health: The Divide between Policy and Science by Arline Bronzaft

In 1976, EPA administrator Russell Train emphasized concerns over air-craft noise: “‘It is time for all to come together, and to come to grips with the problem of aviation noise, and to build, at long last, an air transportation system that is safe, healthy, and quieter.’” Unfortunately, this energy toward noise regulation was short-lived. In 1981, Reagan closed the Environmental Protection Agency’s Office of Noise and Abatement, originally established in 1972. From the 1980s through today, the EPA has ignored the 1972 Noise Control Act, leaving U.S. citizens with “no federal agency to advocate lessening the noise in their communities.” Legislators across the nation have tried without success to restore federal noise regulation.

Health hazards associated with noise overexposure include risk of cardiovascular diseases among older residents, sleep disturbance, hearing loss, and decreased performance. In fact, one alarming 1975 study found that “sixth grade children exposed to passing train noise were nearly a year behind in reading compared to children on a quiet side of the school building.” Sound-deadening acoustic tiles were installed in classroom ceilings, and rubber pads were installed on train tracks. With these soundproofing changes, the learning gap disappeared. It is time to leverage research on noise hazards and for the government to once again regulate noise pollution (summary provided by Grace Brennan).

UK Study of Aviation Noise and Health

There are many human health and well-being concerns from aviation noise exposure.

1. Annoyance: Noise interference causes resentment, discomfort, and displeasure. Annoyance varies with sound level and pitch as well as with social, psychological, or economic factors. 
2. Cognitive impairment: Aircraft noise exposure has a negative effect on reading comprehension, memory, and sustained attention. One study found that children in noisy areas are more likely to give up on difficult tasks.
3. Sleep disturbance: awakenings, arousals in heart rate, and body movements are linked to chronic noise exposure. These disturbances may result in next-day fatigue. 
4. Cardiovascular disease: coronary heart disease, heart attack, and stroke are associated with exposure to high levels of aircraft noise. 

This table shows the number of Quality Adjusted Life Years (QALYs) the average person loses from regular noise exposure. A QALY is a year of life lived in perfect health.  

Figures in each dB column are the number of QALYs lost per person because of the listed health effect. For instance, a person loses 0.1 to 0.2 QALYs from an increased likelihood of developing cardiovascular disease from noise exposure (summary provided by Grace Brennan).

Multilevel modelling of aircraft noise on performance tests in schools around Heathrow Airport London

This extensive study found “chronic exposure to aircraft noise was significantly related to poorer reading and mathematics performance.” Findings were drawn from a sample of about 11,000 children, approximately 11 years old, from 123 schools around Heathrow Airport in London. This study was the first of its kind to consider the additional impact of social class and school characteristics on student performance. Poorer reading and mathematics performance on standardized tests was significantly related to chronic aircraft noise at school. After adjusting for school social class, the association between high noise exposure and poor performance is reduced. This suggests that noise exposure is either a marker or a mediator of how social class impacts student performance. Ultimately, “both noise exposure and social class are interrelated” and both put students at risk (summary provided by Grace Brennan).

Is Noise Pollution the Next Big Public-Health Crisis?

“Acoustical litter” has inspired researchers and noise activists to understand noise patterns in loud environments. The Medusa sensor from Paris non-profit Bruitparif and audio sensors from N.Y.U’s Sounds of New York City (SONYC) project can detect sources of noise pollution. This data provides evidence of noise violation to regulatory bodies. These devices are critical considering the myriad health and environmental threats of noise pollution. People who suffer from overexposure to loud sounds can develop an incurable condition called hyperacusis. They wince at the mere crumpling of a chip bag, and struggle to live or work in our noisy world. Excessive noise can also cause heart disease, high blood pressure, low birth weight, as well as physical, cognitive, and emotional issues from being too distracted or losing sleep. Human-made sounds harm animals too. Road sounds disrupt bird migration patterns, and ocean shipping noises threaten marine creatures’ feeding, mating, and communication habits (summary provided by Grace Brennan).

Environmental News Network – What About Helicopter Emissions?

Calculating helicopter emissions demonstrates their concerning climate impact. For instance, taking a helicopter from the airport to the Chaa Creek eco-resort in Belize uses 3x more fuel than taking a van. Assuming at least one helicopter round-trip every day from the airport to Chaa Creek, the helicopter agency Astrum emits over 140mT GHG per year. This is 96 mT more than vans would emit. Additionally, noise pollution from helicopters impacts birds, locals, and tourists (summary provide by Grace Brennan).

Helicopter Operations: The Environmental Impact And Ground Facilities, Procedures and Operational Standards for the System’s Acceptance

Summary:

• Although the rotorcraft engines of helicopters have “unique flight capabilities,” they create loud, disruptive noise. 
• To mitigate such noise pollution, the exhaust gas and acoustic emissions of rotorcraft engines must be decreased.
• Segmented take-off and landing can also minimize noise (summary by Shivani Tripathi).  

Uber Copter Will Be A Disaster For the Environment

Summary

• Transportation is the largest source of greenhouse emissions in the United States.
• Uber Copter is a service in which New Yorkers take a helicopter from Manhattan to JFK airport. The journey expends 88 gallons of gas per hour, whereas an idling car burns about one gallon of gas per hour. 
• Uber Copter is planning on expanding to other cities, enabling unnecessary pollution (summary provided by Shivani Tripathi).

Helicopter Operations: The Environmental Impacts and Ground Facilities (PDF)

NRDC Needless Noise – Negative Impacts of Helicopter Traffic in NYC & Tri-State Region

Summary:

• Summary of the Damages of Helicopter Pollution
  • Helicopters contribute massively to noise pollution in many places, including military bases, urban centers, and the NYC area. 
  • Research indicates that helicopter noise damages human health and learning ability. 
  • Helicopters cause particularly potent noise impacts compared to other forms of transportation due to the blade slap and low-frequency noises, combined with their low altitude. 
  • Helicopters are underregulated. They do not have minimum altitudes at which they can fly, no noise certification, and no regulated flight paths. 
  • Government data on helicopter operations and helicopter engines are severely lacking, preventing an assessment of environmental impact. 
• Federal Recommendations
  • Congress must direct the Federal Aviation Administration (FAA) to establish State 3 noise standards for helicopters and employ tax/market policies to incentivize helicopter owners to use cleaner and quieter Stage 3 helicopters. 
  • Congress should pass bill H.R 729 requiring the FAA to prepare helicopter risk plans for cities with substantial helicopter traffic.
  • The FAA must require heliports to measure helicopter operations data.  
  • The FAA must establish a minimum altitude of 2000 ft at which helicopters can fly. 
  • The Environmental Protection Agency (EPA) should enforce regulatory limits on toxic air emissions from helicopters. 
• Local Recommendations
  • Public officials in the tri-state area should establish financial incentives for helicopter owners to fly quieter, new technology aircraft.
  • Helicopter owners should use noise monitoring systems to measure their acoustic output. Public officials should consider using noise monitoring systems to enforce decibel thresholds.
  • Helicopter owners and operators should measure and publicize helicopter operational data (summary provided by Shivani Tripathi). 

Dutch Helicopter Emmissions Study (Summary PDF)

Summary:

Helicopter emissions exceed those of other forms of transportation. In fact, helicopter emissions are 3 to 5 times higher than emissions of a diesel car (summary provided by Shivani Tripathi). 

CIDNY Testimony – Hearing on Reducing Noise by Sightseeing Helicopters (PDF)

Summary:

• In a testimony to the NYC council, the Center for Independence of the Disabled described how helicopter noise pollution creates social, employment, and financial barriers for individuals with hearing loss. 
• There are nearly 200k New Yorkers who identify as hard of hearing or deaf. 
• Helicopter noise pollution creates unsafe work and living environments for individuals with hearing loss, worsening stress and fatigue levels (summary by Shivani Tripathi). 

Helicopter Urban Noise Study Report to Congress

Summary:

Congress directed the Secretary of Transportation to investigate helicopter noise concerns and propose recommendations for reducing helicopter noise effects. The FAA assessed health threats from helicopter noise as reported by the World Health Organization (WHO). The following threats were corroborated by the FAA:

• Interference with speech communication
• Effects of noise on performance (low-achieving students are more affected)
• Sleep disturbance
• Annoyance

Studies found that the public reacts more negatively to helicopter noise than to louder airplanes. This might be because of helicopter noise characteristics, including high impulsive noise, low-frequency noise, and noise-induced building vibrations. 

The Federal Aviation Administration (FAA) gathered public and helicopter industry concerns from 122 correspondents across the country. Just over 50% of respondents came from New York state. New York City uses more helicopter services than any other city in the world with 150,000 takeoffs and landings at NYC heliports annually. 

There was strong public sentiment against Electronic News Gathering (ENG), sightseeing operations, and cooperative executive flights as they are considered unimportant. Respondents were particularly annoyed by low flight altitude and operations early in the morning and late at night. Respondents stressed the ineffectiveness of voluntary compliance from helicopter companies with community noise agreements.

Other FAA recommendations were more aggressive. The administration stressed that further social-acoustic research is needed to better assess helicopter noise characteristics and develop an annoyance metric. The FAA found that higher altitude flights reduce helicopter noise. This supports public demands that helicopters fly 1000 ft above the highest obstacle and give a horizontal radius of 2,000 ft. A “keep aircraft high” philosophy should be maintained (summary provided by Grace Brennan).

Green Helicopters

Summary:

• Helicopter rotorcrafts have the ability to take off vertically and hover efficiently. To preserve this ability, new rotorcrafts must be designed to minimize environmental impact while preserving the rotorcraft’s vital functions. 
• To address this issue, Europe’s Clean Sky program designed a Green Rotorcraft Integrated Technology Demonstrator (ITD). The goals include:
  • Reducing CO2 emissions by 20-45% per mission. 
  • Reduce the noise footprint area by 50%. 
  • Ensure that helicopter activity abides by the REACH initiative, which “protects human health and environment from harmful chemical substances.”
• To construct a green helicopter, it is vital to have:
  • Green propulsion systems
  • The reduction of rotorcraft noise through flight path management strategy 
  • The use of conceptual design to evaluate propulsion architectures and vehicle configuration. 

This article provides an overview of ongoing research for greener helicopters through noise, emissions, and hybrid/electric power developments. Currently, gas turbine engines power most helicopters. These  have poor fuel efficiency and release polluting greenhouse gasses (CO₂ and NO_x). NASA researchers are working to develop electric motors that match the power of gas turbines. 

A NASA and Stanford study found that within the next 15-20 years electric lift vehicles might be feasible in the Hopper Bay Area, yet these vehicles did not reduce noise despite traveling at low speeds. Helicopter noise can be limited through design changes and flight path management, yet helicopter companies have not adopted these developments. To implement existing and future research on green helicopters, the Federal Aviation Administration (FAA) could create strict goals for reducing environmental impacts (summary provided by Grace Brennan and Shivani Tripathi).

Guidance on the Determination of Helicopter Emissions

Noise Pollution: A Modern Plague

“Calling noise a nuisance is like calling smog an inconvenience. Noise must be considered a hazard to the health of people everywhere.” -former U.S. Surgeon General William H. Steward (1978)

The World Health Organization (WHO) documents seven categories of noise health effects:  

• Hearing Impairment: can lead to loneliness, depression, and limited job opportunities
• Interference with Spoken Communication: can cause problems with concentration, lack of self-confidence, and decreased working capacity
• Sleep Disturbances: frequent awakenings, a reduction in REM sleep, and increased heart rate can lead to fatigue, depressed mood, and decreased performance.
• Cardiovascular Disturbances: noise can trigger endocrine and nervous system responses that affect the cardiovascular system and pose cardiovascular health risks. 
• Disturbances in Mental Health: noise pollution can “accelerate and intensify the development of latent mental disorders”
• Impaired Task Performance: decreased motivation and feelings of helplessness can be traced back to environmental noise.
• Annoyance: aversion or distress from noise can lead to anger, helplessness, withdrawal, and anxiety 

Low frequency sounds – which are produced by helicopters – pose the most severe health effects, particularly annoyance. “The evidence related to low-frequency noise is sufficiently strong to warrant immediate concern.”

Today’s noise pollution is analogous to the threats of tobacco and environmental pollutants. Children, the elderly, and pregnant women are most vulnerable to noise threats. It is the responsibility of legislators to protect us from noise which can be achieved through reinstituting EPA regulations from the 1970s (summary by Grace Brennan).

Noise As A Public Health Hazard

Sound and effects of low frequency noise

Aircraft are a source of low-frequency and impulsive noise which causes adverse health threats. Annoyance, the most frequently reported effect of this noise, can mean the disturbance of activities, conversation, or sleep. Feelings of helplessness from annoyance can lead to mental health degradation. One study reviewed found that aircraft noise alone contributed to psychiatric hospital admission. Health threats from low-frequency noise can be attributed to its heightened permeability: more energy enters the ear, the body, and other objects. Cardiovascular risks from pervasive low-frequencies include increased heart rate, elevated blood pressure, and circulatory system disruptions. Hormonal changes from stress reactions to prolonged noise exposure can cause decreased immunity and cardiac threats. Sleep is also a major concern: one study found that inhabitants beneath a superhighway facing relentless low-frequency noise and vibrations became chronically insomniac and excessively tired. Given challenges in insulating against low-frequency noise, multiple studies suggest regulating noise at the source before it spreads (summary by Grace Brennan). 

Environmental Noise and the Cardiovascular System

It is now well-known that noise causes heart diseases including:

• Hypertension
• Coronary artery disease
• Heart failure
• Metabolic disorders

These diseases come from indirect pathways beginning with noise-induced sleep disturbance, annoyance, chronic stress, and other severe disturbances which translate into molecular changes and imbalances in the body. Given the extensive human and animal research on the health threats of noise, these authors propose that “noise induces a stress response, characterized by activation of the sympathetic system and increased levels of catecholamines, cortisone, and angiotensin-II” which ultimately leads to vascular damage. Traffic noise, including aircraft, creates the most noise pollution

Aircraft noise, when studied in comparison to white noise of the same sound pressure, was uniquely associated with:

• increased blood pressure
• circulatory system dysfunction
• increased stress markers

Large population-based studies show that aircraft noise was associated with higher stroke mortality. The authors conclude that “legislation to reduce noise is important for public health.” Air transport should be significantly curtailed with nighttime and daytime restrictions (summary by Grace Brennan).  

WHO Guidelines for Community Noise

This foundational WHO study on community noise insists on “practical action to limit and control the exposure to environment noise.” Community noise is emitted from “road, rail, and air traffic, industries, construction and public work, and the neighborhood.” The myriad health threats associated with this noise include but are not limited to cardiovascular effects, sleep disturbance, and annoyance. Aviation noise poses some of the most severe health threats: one referenced study found that school children in the Los Angeles area were deficient in reading and problem solving following exposure to aircraft noise. The uncontrollability of noise is more critical than its intensity. Adaptation strategies for dealing with aircraft noise, such as tuning out or ignoring noise, present new health problems including increased stress hormone levels and elevated blood pressure. The longer the exposure to aircraft noise, the greater the damage to student reading skills and motivation. Findings of heightened annoyance toward aircraft noise might be attributed to the added fear of aircraft crashes. Helicopters present the additional threat of low frequency noise – a type of noise that demands immediate concern, according to the WHO. Low frequency noise exacerbates health threats and disturbs rest at low sound pressure levels. The WHO thus recommends 5 dB lower noise safety parameters for low frequency noise. 

Even if scientific proof of public health endangerment is lacking, action should be taken to reduce noise at its source to the lowest level possible. We do not totally understand the complex links between noise characteristics and human effects, and there is currently no model for assessing total annoyance from combinations of environmental noise sources. Given these concerns, the WHO outlines three principles for noise management (summary by Grace Brennan): 

• The precautionary principle: “In all cases, noise should be reduced to the lowest level achievable in a particular situation. When there is a reasonable possibility that public health will be damaged, action should be taken to protect public health without awaiting full scientific proof.”
• The polluter pays principle: “The full costs associated with noise pollution (including monitoring, management, lowering levels and supervision) should be met by those responsible for the source of noise.”
• The prevention principle: “Action should be taken where possible to reduce noise at the source. Land-use planning should be guided by an environmental health impact assessment that considers noise as well as other pollutants.” 

Reduced Aircraft Noise Pollution During COVID-19 Lockdown Is Beneficial to Public 

Aircraft noise is an important environmental health risk factor and public health threat. Noise induces psychosocial stressors that can cause increased stress hormones, blood pressure, and heart rate which create cardiovascular risks. The COVID 19 lockdown led to a reduction in noise exposure that was found to decrease noise annoyance and blood pressure. These study results suggest that “even short-term reductions in aircraft noise levels, as experienced during the COVID-19 lockdown, may have the potential to reverse the unfavorable noise-induced cardiovascular effects, highlighting the importance of environmental noise limits.” Aircraft noise exposure is thus an important determinant of public cardiovascular health (summary by Grace Brennan).  

Residential exposure to aircraft noise and hospital admissions for cardiovascular diseases: multi-airport retrospective study

This study of 6 million older people (≧65 years) residing near airports found a statistically significant increase in hospital admission rates for cardiovascular disease with increased exposure to aircraft noise. Zipcodes with 10dB higher noise exposure had a 3.5% higher cardiovascular hospital admission rate after controlling for other characteristics including age, sex, race as well as zipcode socioeconmic status, air pollution, and roadway density (summary by Grace Brennan). 

Federal Aviation Administration (FAA) Neighborhood Environmental Survey (February 2021)

Aircraft noise is found significantly more annoying than other types of transportation noise. This FAA finding is based on data from 10,000 residents living near 20 airports. Residents were asked via mailed questionnaires if different environmental concerns bother, disturb, or annoy them; “Noise from aircraft” was one of these 13 concerns. Airports selected hosted around 100 jet operations per day. Of the ~10,000 survey respondents, 69% experienced 50-60 dB noise exposure, 28% experienced 60-70 dB, and 3% experienced 70+ dB. When compared to the current standard on transportation noise exposure-annoyance relationships, these survey results show “a substantial increase in the percentage of people who are highly annoyed by aircraft noise over the entire range of aircraft noise levels.” A voluntary follow-up phone survey, including 2,000 of these 10,000 respondents, revealed that residents are “startled,” “frightened,” or “awakened,” by aircraft at home. 

The Schultz curve (left) is the current accepted standard for describing transportation noise exposure-annoyance relationships. The curve is based on outdated data from the 1970s that was last reviewed in 1992. On the right is the new national curve on aircraft noise exposure and annoyance relationships based on data from this study (summary by Grace Brennan). 

Residential exposure to aircraft noise and hospital admissions for cardiovascular diseases: multi-airport retrospective study

This study of 6 million older people (≥ 65 years) living near 89 airports in the United States found that as aircraft noise increased, so did hospital admissions for cardiovascular disease. Of the over 2000 zip codes included in the study, those with 10 dB higher noise exposure had a 3.5% higher cardiovascular hospital admission rate. This is the first study of its kind to include a large study population across multiple airports to estimate the links between aircraft noise exposure and hospital admission for cardiovascular problems. Furthermore, these findings remained after controlling for air pollution, socioeconomic status, demographic data, and roadway proximity variables. Aircraft noise pollution alone causes serious cardiovascular disease threatening elderly populations and burdening our healthcare systems (summary by Grace Brennan). 

A neurobiological mechanism linking transportation noise to cardiovascular disease in humans 

It is well known that chronic noise exposure causes cardiovascular disease (CVD). This recent 2019 study investigated the biologic pathway of noise exposure to CVD. Researchers tested for stress-induced amygdalar metabolic activity, arterial inflammation, and risk for major adverse cardiovascular disease events (MACE) in 498 adults experiencing varying levels of transportation noise. Results showed that higher noise exposure generated heightened amygdala metabolic activity and increased arterial inflammation while increasing risks of MACE after adjusting for confounding variables. The figure below traces the biologic pathway of noise exposure to CVD in the human body. These findings highlight how noise exposure is an “independent and clinically under-recognized CVD risk factor” severely impacting “individuals otherwise presumed to have low CVD risk.” The study authors suggest regulations to reduce transportation noise. They also highlight the environmental injustice of noise exposure: those with MACE were typically of lower socioeconomic status and suffered greater exposure to noise and air pollution (summary by Grace Brennan). 

Crucial role for Nox2 and sleep deprivation in aircraft noise-induced vascular and cerebral oxidative stress, inflammation, and gene regulation

This study is the first of its kind to demonstrate that aircraft noise exposure during sleep times leads to cardiovascular diseases and cognitive impairment. More specifically, aircraft noise causes endothelial dysfunction, raises blood pressure, disrupts circadian clocks and stress hormone levels, and heightens cerebral and oxidative stress. This was discovered through exposing mice to aircraft noise around the clock during sleep and awake phases for days at a time. Ultimately, researchers determined that noise from aircraft causes annoyance (a type of mental stress) which creates pathophysiological damage and increased cardiovascular events and disease. Cardiovascular risks are not the only health threat of aircraft noise. Chronic exposure also causes cognitive impairment in children and mental diseases in adults (summary by Grace Brennan).

Noise and cardiovascular risk: nighttime aircraft noise acutely triggers cardiovascular death

Nighttime aircraft noise can trigger acute cardiovascular mortality. This calls for a complete ban on nighttime flights. Just one night of aircraft noise exposure can cause an individual to suffer endothelial dysfunction, increased stress hormone levels, and deteriorated sleep quality. These short term effects might eventually lead to death. ~3% of cardiovascular nighttime deaths can be attributed to aircraft noise. Researchers used high precision modeling with radar records of each flight between 2000 and 2015 to show that aircraft noise is a fatal trigger of cardiovascular mortality (summary by Grace Brennan). 

Noise and cardiovascular risk: nighttime aircraft noise acutely triggers cardiovascular death

WHO recommendations for safe aircraft noise levels. According to the hearing health foundation, 40 DB is the sound of a refrigerator humming while 60 DB is the level of a normal conversation (summary by Grace Brennan).