Valuing Quiet

An Economic Assessment of U.S. Environmental Noise as a Cardiovascular Health Hazard

      Introduction

      Environmental noise pollution increases the risk for hearing loss, stress, sleep disruption, annoyance, and cardiovascular disease and has other adverse health impacts. Recent (2013) estimates suggest that more than 100 million Americans are exposed to unhealthy levels of noise. Given the pervasive nature and significant health effects of environmental noise pollution, the corresponding economic impacts may be substantial.

      Methods

      This 2014 economic assessment developed a new approach to estimate the impact of environmental noise on the prevalence and cost of key components of hypertension and cardiovascular disease in the U.S. By placing environmental noise in context with comparable environmental pollutants, this approach can inform public health law, planning, and policy. The effects of hypothetical national-scale changes in environmental noise levels on the prevalence and corresponding costs of hypertension and coronary heart disease were estimated, with the caveat that the national-level U.S. noise data our exposure estimates were derived from are >30 years old.

      Results

      The analyses suggested that a 5-dB noise reduction scenario would reduce the prevalence of hypertension by 1.4% and coronary heart disease by 1.8%. The annual economic benefit was estimated at $3.9 billion.

      Conclusions

      These findings suggest significant economic impacts from environmental noise-related cardiovascular disease. Given these initial findings, noise may deserve increased priority and research as an environmental health hazard.

      Introduction

      Environmental noise from road traffic, aircraft, construction and industrial activities, recreational activities, and other sources is a pervasive pollutant associated with a myriad health risks. Noise has detrimental health impacts even at relatively low exposure levels and among people not reporting noise annoyance.
      • Goines L.
      • Hagler L.
      Noise pollution: a modern plague.
      • Willich S.N.
      • Wegscheider K.
      • Stallmann M.
      • Keil T.
      Noise burden and the risk of myocardial infarction.
      Recent estimates indicate that more than 100 million Americans are exposed to levels of environmental noise that put them at risk for hearing loss,
      • Hammer M.S.
      • Swinburn T.K.
      • Neitzel R.L.
      Environmental noise pollution in the United States: developing an effective public health response.
      stress, sleep disruption, annoyance, and cardiovascular disease.
      • Goines L.
      • Hagler L.
      Noise pollution: a modern plague.
      A decrease in an annual equivalent continuous average (LAeq) environmental noise exposure level of 10 decibels (dB) decreases risk of cardiovascular disease by 7%–17%.
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      To put this in context, a decrease in noise levels of this magnitude is about twice the decrease in noise levels that occurred around airports after federal regulations in the 1970s. Cardiovascular disease is the top cause of mortality in the U.S.
      • Heron M.
      Deaths: leading causes for 2010.
      and presents a substantial health-related economic burden. The ubiquitous nature of environmental noise in urban
      • Neitzel R.L.
      • Gershon R.R.M.
      • McAlexander T.P.
      • Magda L.A.
      • Pearson J.M.
      Exposures to transit and other sources of noise among New York City residents.
      and non-urban
      • Flamme G.A.
      • Stephenson M.R.
      • Deiters K.
      • et al.
      Typical noise exposure in daily life.
      areas of the U.S. affects an increasing number of Americans, but research on the economic toll resulting from cardiovascular disease has primarily been conducted in Europe.
      Previous research evaluating the economic impacts of environmental noise has largely focused on transport-related noise and house prices.
      DEFRA
      DEFRA
      • Cohen J.P.
      • Coughlin C.C.
      Changing noise levels and housing prices near the Atlanta airport.
      • Wilhelmsson M.
      The impact of traffic noise on the values of single-family houses.
      This approach is limited because noise levels measured at a residence can differ substantially from individual noise exposures of residents. Also, perceptions of noise hazards, especially at low noise levels, are underestimated, and homebuyers may not fully perceive and value the potential health impacts of noise.
      • Goines L.
      • Hagler L.
      Noise pollution: a modern plague.
      • Willich S.N.
      • Wegscheider K.
      • Stallmann M.
      • Keil T.
      Noise burden and the risk of myocardial infarction.
      Finally, high relocation costs may mask people’s true preferences.
      This assessment seeks to expand upon our understanding of the economic ramifications of environmental noise pollution. We focus on two major categories of cardiovascular disease—coronary heart disease (CHD) and hypertension. A hypothetical noise reduction scenario of 5 dB at a population level is explored, applying published estimates of the relationship between environmental noise and cardiovascular disease, and estimating changes in prevalence and costs of cardiovascular disease. Given the cost of cardiovascular disease in the U.S., even small reductions in cardiovascular disease from reductions in environmental noise could produce significant economic benefits.

      Methods

      Prevalence and Costs of Cardiovascular Disease

      Cardiovascular disease, which includes CHD and hypertension, is pervasive and costly, affecting 27% of Americans (>83 million) and accounting for 15% of healthcare expenditures ($324 billion) in 2010.
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      • Lloyd-Jones D.
      • Adams R.J.
      • Brown T.M.
      • et al.
      Heart disease and stroke statistics—2010 update: a report from the American Heart Association.
      CHD, which includes myocardial infarction, affected 15.4 million Americans in 2010 and cost $96 billion in direct healthcare costs and >$81 billion in lost productivity.
      • Lloyd-Jones D.
      • Adams R.J.
      • Brown T.M.
      • et al.
      Heart disease and stroke statistics—2010 update: a report from the American Heart Association.
      Hypertension affected almost 78 million Americans in 2010
      • Lloyd-Jones D.
      • Adams R.J.
      • Brown T.M.
      • et al.
      Heart disease and stroke statistics—2010 update: a report from the American Heart Association.
      and cost $47.5 billion in treatment.
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      Some individuals are affected by both CHD and hypertension, which we accounted for in these analyses.

      Prevalence of Harmful Noise Exposure

      Environmental impacts of noise are assessed with a sound level meter that measures decibel levels using the A-weighting filter, which approximates the sensitivity of the human ear to certain frequencies. Where localized exposure measurements are unavailable, these levels are estimated using noise exposure models. In 1974, the U.S. Environmental Protection Agency (EPA) recommended an average 24-hour exposure limit of 55 A-weighted dB (dBA) of environmental noise to protect the public from adverse effects on health and welfare in residential areas.
      U.S. Environmental Potection Agency
      This limit is a day–night 24-hour average noise level (LDN), with a 10-dB penalty applied during nighttime hours (11pm–7am) to account for potential sleep disturbance. We based the scenario in this paper on LDN levels.
      U.S. Environmental Potection Agency
      Other nations use different metrics, including the day–evening–night level (LDEN), and the average over the 16 daytime hours (LAeq,16h) of 7am–11pm. For context, 55 dBA is approximately as loud as a microwave oven at 1 to 2 ft, and a 24-hour LDN exposure of 55 dBA could result from 8 hours in a typical large office environment (55 dBA), a 1-hour lunch in a restaurant (60 dBA), a 1-hour commute by automobile (65 dBA), 6 hours doing miscellaneous activities at home (50 dBA), and 8 hours of sleep in a quiet bedroom (40 dBA).
      A 1981 EPA report estimated that 46.2% of the population was exposed to ≥58 dBA LDN from environmental noise, and 13.9% were exposed to ≥65 dBA LDN.
      • Simpson M.
      • Bruce R.
      Though dated (and considerably different from recent WHO guidance),
      WHO
      a 1974 recommendation remains the most current EPA guidance on environmental noise, and the 1981 estimates are the most recent data on exposure above the recommended thresholds. These estimates were produced by applying models of 11 sources of environmental noise to the U.S. population. Among those exposed to ≥58 dBA LDN, traffic or aircraft was the primary source of exposure for the vast majority, though rail, construction, and domestic appliances were also considered.
      • Simpson M.
      • Bruce R.
      We made the conservative assumption that the proportion of the U.S. population exposed to high levels of noise was the same in 2013 as estimated in 1981.
      • Hammer M.S.
      • Swinburn T.K.
      • Neitzel R.L.
      Environmental noise pollution in the United States: developing an effective public health response.
      Assuming zero trend in noise levels is likely a considerably conservative assumption given increasing urbanization in the U.S.
      • Garcia A.
      In 2013, an estimated 46.2% of Americans (145.5 million) were exposed to ≥58 dBA LDN, and 13.9% (43.8 million) were exposed to ≥65 dBA LDN. In sum, high levels of environmental noise exposure (largely from transportation) are extremely common—conservatively, nearly half of all Americans are exposed to environmental noise above the outdated, but most recent, 1974 EPA-recommended level.

      Relationship Between Environmental Noise and Cardiovascular Disease

      Potential mechanisms for noise to impact cardiovascular disease are described more fully by Hammer et al.
      • Hammer M.S.
      • Swinburn T.K.
      • Neitzel R.L.
      Environmental noise pollution in the United States: developing an effective public health response.
      and comprehensively in Goines and Hagler.
      • Goines L.
      • Hagler L.
      Noise pollution: a modern plague.
      Briefly, noise is an environmental stressor that impacts sleep, relaxation, and concentration and increases the risk of hypertension and CHD in the long term.
      • Goines L.
      • Hagler L.
      Noise pollution: a modern plague.
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      The impact of noise on cardiovascular disease varies based on the level of noise, duration of exposure, frequency spectrum, source, time of day, and other factors.
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      The exact mechanism(s) by which noise causes cardiovascular disease remains unclear, but appear to be mainly related to sleep, stress, and disruption of neuro-endocrine cycles.
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      Nevertheless, the weight of evidence of the effects of noise on cardiovascular disease (e.g., multiple studies of different types in different populations) is nevertheless substantial, and effect sizes have been shown to be similar across several studies.
      Evaluations of the cardiovascular effects of environmental noise have utilized different noise measures (e.g., transport noise, occupational noise, self-reported noise annoyance) and different cardiovascular disease indicators (e.g., CHD, myocardial infarction, hypertension, stroke). Table 1 provides a summary of findings from a selection of primary studies and meta-analyses.
      Table 1Selected Evidence on the Relationship Between Noise and Cardiovascular Disease
      PublicationSource of dataNoise source(s)Cardiovascular disease metricRelationship and metric(s)
      Babisch (2014)
      • Babisch W.
      Updated exposure-response relationship between road traffic noise and coronary heart diseases: a meta-analysis.
      Meta-analysisRoad trafficVarying indicators of coronary heart disease10 dB LDN increase in noise exposure increases risk of CHD by 8% over a range of 52–77 dBA
      Basner et al. (2013)
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      Literature review
      • Road traffic
      • Air traffic
      • Hypertension
      • IHD
      10 dB LAeq increase of environmental noise increases risk of hypertension or IHD 7%–17%.
      Hansell et al. (2013)
      • Hansell A.L.
      • Blangiardo M.
      • Fortunato L.
      • et al.
      Aircraft noise and cardiovascular disease near Heathrow airport in London: small area study.
      3.6 million residents near Heathrow Airport, United Kingdom
      • Air traffic
      • Daytime and nighttime noise separate
      • Modeled noise exposure
      • Hospital admissions and mortality from:
      • Stroke
      • CHD
      • cardiovascular disease
      Daytime aircraft noise resulted in statistically significant increased risk of hospital admission for stroke (1.24 RR); cardiovascular disease (1.14 RR); and CHD (1.21 RR); RRs were higher for nighttime noise, and similar impacts on mortality; Noise measure: daytime=51–63 dB LAeq, nighttime=50–55 dB LAeq
      Van Kempen and Babisch (2012)
      • Van Kempen E.
      • Babisch W.
      The quantitative relationship between road traffic noise and hypertension: a meta-analysis.
      Meta-analysisRoad trafficHypertension5 dB LAeq,16h increase in noise exposure increases risk of hypertension by 3.4% over a range of 45–75 dBA
      Ndrepepa and Twardella (2012)
      • Ndrepepa A.
      • Twardella D.
      Relationship between noise annoyance from road traffic noise and cardiovascular diseases: a meta-analyses.
      Meta-analysis of 8 studiesSelf-reported annoyance from road traffic
      • Hypertension
      • IHD
      Noise annoyance significantly, positively associated with hypertension (1.16 pooled risk estimate). Noise annoyance significantly, positively associated with IHD (1.07 pooled risk estimate).
      Sørensen et al. (2012)
      • Sørensen M.
      • Andersen Z.J.
      • Nordsborg R.B.
      • et al.
      Road traffic noise and incident myocardial infarction: a prospective cohort study.
      57,053 residents of Copenhagen or Aarhus, Denmark
      • Road traffic
      • Modeled noise exposure
      MI10 dB LDEN residential road traffic noise significantly associated with MI (1.12 incidence rate ratio)
      Gan et al. (2012)
      • Gan W.Q.
      • Davies H.W.
      • Koehoorn M.
      • Brauer M.
      Association of long-term exposure to community noise and traffic-related air pollution with coronary heart disease mortality.
      Residents of Vancouver, Canada
      • Road traffic
      • Modeled noise exposure
      CHD mortality10 dB(A) LDEN elevation in residential noise levels associated with risk of death from CHD (9% increase); other cardiovascular disease indicators also showed positive relationship with noise; stroke death showed positive relationship but not statistically significant
      Gan et al. (2011)
      • Gan W.Q.
      • Davies H.W.
      • Demers P.
      Exposure to occupational noise and cardiovascular disease in the United States: the National Health and Nutrition Examination Survey 1999-2004.
      6,307 participants in the U.S. NHANES surveySelf-reported occupational noise exposure
      • Angina pectoris
      • CHD
      • Hypertension
      • MI
      Exposure to loud noise in the workplace significantly and positively associated with all cardiovascular disease measures: angina pectoris (2.91 OR); CHD (2.04 OR); hypertension (2.23 OR)
      Babisch and van Kamp (2009)
      • Babisch W.
      • van Kamp I.
      Exposure-response relationship of the association between aircraft noise and the risk of hypertension.
      Meta-analysisAir trafficHypertension10 dBA LDN air traffic noise significantly associated with increase in hypertension (1.13 RR) over the range 45–70 dBA
      Babisch (2008)
      • Babisch W.
      Road traffic noise and cardiovascular risk.
      Meta-analysis of 7 studiesRoad trafficMINoise exposure levels above 60 dBA Lday,16h significantly associated with increased risk of MI; for noise levels above 70 dBA Lday,16h, OR >1.2; no increased risk found at noise levels <60 dBA Lday,16h
      Babisch (2006)
      • Babisch W.
      Transportation noise and cardiovascular risk: updated review and synthesis of the epidemiological studies that indicate that the evidence has increased.
      Literature review/meta-analysis
      • Air traffic
      • Road traffic
      • Rail traffic
      • IHD
      • Hypertension
      Noise exposure levels less than 60 dBA Lday were not associated with increased IHD; 65–70 dBA Lday noise exposure was associated with increased risk of IHD (1.1–1.5 RR); 60–70 dBA Lday noise exposure associated with increased risk of hypertension (1.4–2.1 RR), though earlier studies indicated a less clear relationship
      Willich et al. (2006)
      • Willich S.N.
      • Wegscheider K.
      • Stallmann M.
      • Keil T.
      Noise burden and the risk of myocardial infarction.
      4,115 patients admitted to hospitals in Berlin
      • Self-reported environmental and occupational annoyance
      • Road traffic
      • Rail traffic
      • Modeled noise exposure
      MIEnvironmental noise annoyance slightly significantly positively associated with MI in women, and no association for men; environmental noise associated with increased risk of MI in men (1.46 OR) and women (3.36 OR); occupational noise associated with increased risk of MI in men (1.31 OR) but not in women
      van Kempen and Staatsen (2005)
      • Kempen Eemm Staatsen B
      • van Kamp I.
      Selection and Evaluation of Exposure-Effect Relationships for Health Impact Assessment in the Field of Noise and Health (RIVM Report 630400001/2005).
      Netherlands
      • Air traffic
      • Road traffic
      HypertensionPopulation-attributable risk of 0.06 for noise-induced hypertension (a maximum of 200,000 cases of hypertension in the Netherlands could be attributable to road traffic noise exposure)
      van Kempen et al. (2002)
      • Van Kempen EEMM Kruize H
      • Boshuizen H.C.
      • Ameling C.B.
      • Statsen B.A.M.
      de Hollander AEM. The association between noise exposure and blood pressure and ischemic heart disease: a meta-analysis.
      Meta-analysis of more than 500 studies 1970–1999 in English, German, or Dutch
      • Occupational exposure
      • Road traffic
      • Rail traffic
      Blood pressure5 dBA LAeq occupational noise exposure significantly associated with increased hypertension (1.14 RR); 5 dBA LAeq air traffic noise exposure significantly associated with increased hypertension (1.26 RR) (this based on just one study)
      van Kempen et al. (2002)
      • Van Kempen EEMM Kruize H
      • Boshuizen H.C.
      • Ameling C.B.
      • Statsen B.A.M.
      de Hollander AEM. The association between noise exposure and blood pressure and ischemic heart disease: a meta-analysis.
      Meta-analysis of more than 500 studies 1970–1999 in English, German, or Dutch
      • Road traffic
      • Rail traffic
      IHDCommunity noise positively associated with MI, IHD, angina pectoris, use of cardiovascular medicines, but none of these measures were statistically significant
      Passchier-Vermeer and Passchier (2000)
      • Passchier-Vermeer W.
      • Passchier W.F.
      Noise exposure and public health.
      Literature reviewMainly road traffic, one air traffic study
      • Hypertension
      • IHD
      Sufficient evidence for a noise exposure–related effect above 70 dBA LDN
      CHD, coronary heart disease; IHD, ischemic heart disease; MI, myocardial infarction; NHANES, National Health and Nutrition Examination Survey; RR, relative risk.
      Noise is only one of many factors that impact the risk of CHD,
      • Mozaffarian D.
      • Wilson P.
      • Kannel W.
      Contemporary reviews in cardiovascular medicine: beyond established and novel risk factors—lifestyle risk factors for cardiovascular disease.
      and even taking other lifestyle and environmental factors (such as air quality) into account, a majority of the studies found significant, positive relationships between environmental noise and CVD. As Basner and colleagues
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      summarize, the risk of hypertension or CHD increases by 7%–17% per 10 dB LAeq increased noise exposure.

      Assessment of Economic Impact of Noise-Related Coronary Heart Disease and Hypertension

      Drawing assumptions from the assessments above, the following model estimated the change in prevalence and cost of CHD and hypertension associated with a 5-dB LDN reduction in environmental noise exposure. Table 2 presents key assumptions for this model.
      Table 2Key Assumptions
      VariableAssumptionSource(s)Notes
      U.S. population 2013315,000,000US Census Quickfacts

      U.S. Census Bureau. U.S. Census: State and County QuickFacts. 2013. www.quickfacts.census.gov/qfd/states/00000.html.

      Number of Americans exposed to ≥55 dBA LDN of environmental noise145.5 million (46% of the total population)Application of most recent EPA estimates
      • Simpson M.
      • Bruce R.
      to current population
      The EPA’s 1981 exposure estimates are the most recent and best available information on the proportion of Americans exposed to high levels of environmental noise
      Number of Americans exposed to ≥65 dBA LDN of environmental noise43.8 million (14% of the total population)Application of most recent EPA estimates
      U.S. Environmental Potection Agency
      to current population
      The EPA’s 1981 exposure estimates are the most recent and best available information on the proportion of Americans exposed to high levels of environmental noise
      Relationship between environmental noise exposure and CHD1.04 RR per 5 dBA LDNBabisch (2014)
      • Babisch W.
      Updated exposure-response relationship between road traffic noise and coronary heart diseases: a meta-analysis.
      Babisch estimates 1.08 RR per 10 dBA LDN, and we assume this estimate can be halved for our 5 dB LDN reduction scenario; we also assume that Babisch’s estimates, which are for road noise only, can be applied to all environmental noise, as studies for other sources of environmental noise indicate similar relationships (Table 1)
      Prevalence of CHD, U.S.15.4 millionGo et al. (2013)
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      Figures are for 2010, estimated in 2013; no change assumed for 2013
      Population risk of CHD, U.S.4.89%15.4 million Americans (Go et al. [2013]
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      ) of the 315 million population (U.S. Census

      U.S. Census Bureau. U.S. Census: State and County QuickFacts. 2013. www.quickfacts.census.gov/qfd/states/00000.html.

      )
      Direct cost of CHD, U.S. annual (health care, medications)$96 billionLloyd-Jones et al. (2009)
      • Lloyd-Jones D.
      • Adams R.J.
      • Brown T.M.
      • et al.
      Heart disease and stroke statistics—2010 update: a report from the American Heart Association.
      Figures are for 2009–2010, no change assumed for 2013
      Indirect cost of CHD, U.S. annual (lost productivity due to mortality/morbidity)$81.1 billionLloyd-Jones et al. (2009)
      • Lloyd-Jones D.
      • Adams R.J.
      • Brown T.M.
      • et al.
      Heart disease and stroke statistics—2010 update: a report from the American Heart Association.
      Figures are for 2009–2010, no change assumed for 2013
      Relationship between environmental noise exposure and hypertension1.034 RR per 5 dBA LDNvan Kempen and Babisch (2012)
      • Van Kempen E.
      • Babisch W.
      The quantitative relationship between road traffic noise and hypertension: a meta-analysis.
      We assume that van Kempen and Babisch’s estimated RR of 1.034 per 5 dBA LAeq,16h applies to 5 dB LDN, because these measures are similar and tend to be highly correlated; we also assume that this estimate for road noise only can be applied to all environmental noise, as studies for other sources of environmental noise indicate similar relationships (Table 1)
      Prevalence of hypertension, U.S.77.9 millionGo et al. (2013)
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      Figures are for 2010, estimated in 2013; no change assumed for 2013
      Population risk of hypertension, U.S.24.7%77.9 million Americans (Go et al. [2013]
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      ) of the 315 million population (U.S. Census

      U.S. Census Bureau. U.S. Census: State and County QuickFacts. 2013. www.quickfacts.census.gov/qfd/states/00000.html.

      )
      Direct cost of hypertension, U.S. annual (health care, medications)$47.5 billionGo et al. (2013)
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      Figures are for 2009–2010, no change assumed for 2013
      Indirect cost of hypertension, U.S. annual (lost productivity due to mortality only)$3.5 billionGo et al. (2013)
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      Figures are for 2009–2010, no change assumed for 2013
      CHD, coronary heart disease; EPA, Environmental Protection Agency; RR, relative risk.
      The 5-dB LDN reduction scenario corresponds to established elasticities that estimate how cardiovascular disease prevalence changes in relation to a 5- or 10-dB LDN change in noise exposure (Table 1). A 5-dB reduction in annual LDN appears feasible based on demonstrated and ongoing reductions in aircraft noise following federal regulation,
      • Waitz I.
      • Bernhard R.
      • Hanson C.
      Challenges and promises in mitigating transportation noise.
      and was modeled on similar regulatory approaches for air contaminants, which can include technology-forcing policies. A 5-dB reduction could be achieved through a multi-pronged intervention targeting noise sources that represent the greatest burden of noise exposure in urban areas, including low noise pavement and quiet tire design, traffic calming measures, noise barriers, changes in aircraft flight patterns, adoption of electrical vehicles, incorporation of available noise control technology into industrial and construction equipment, greater use of hearing protection in occupational and public settings, and other approaches.
      National Academy of Engineering
      No single one of these approaches could achieve a 5-dB LDN reduction at a population level, but an integrated strategy employing multiple approaches could do so. The cost would be substantial, but the changes would by necessity be phased in over a long period of time, and would provide ancillary benefits (e.g., improved quality of life and air pollution reduction).
      The 5-dB LDN reduction was applied to the 145.5 million Americans exposed to 58 dBA LDN, which we assumed was a conservative underestimate of those exposed to ≥55 dBA LDN. It was also conservatively assumed that everyone in this group was exposed to the lowest noise level for the group (exactly 55 dBA LDN), even though approximately 43 million in this group were estimated to have exposure levels of >65 dBA LDN.

      Model 1: Coronary Heart Disease

      The meta-analysis of Babisch et al.
      • Basner M.
      • Babisch W.
      • Davis A.
      • et al.
      Auditory and non-auditory effects of noise on health.
      on the relationship between road noise and CHD associated a 10-dB LDN increase in road traffic noise with an 8% increase in CHD. This measure is on the conservative side of the elasticities in Table 1. This effect size was selected because it covers all CHD, a more comprehensive measure than studies evaluating smaller categories of cardiovascular disease, such as myocardial infarction. The effect size is similar to the relationship between noise and CHD mortality found in Gan and colleagues
      • Gan W.Q.
      • Davies H.W.
      • Koehoorn M.
      • Brauer M.
      Association of long-term exposure to community noise and traffic-related air pollution with coronary heart disease mortality.
      and the relationship between noise and hypertension found in van Kempen and Babisch.
      • Van Kempen E.
      • Babisch W.
      The quantitative relationship between road traffic noise and hypertension: a meta-analysis.
      This measure is also similar to or more conservative than that found in studies using different measures of noise (e.g., aircraft, rail, occupational, self-reported). The measure was halved to 4% as an estimate of the increase in CHD risk associated with a 5-dB LDN increase in environmental noise, to correspond with our hypothetical exposure reduction scenario.
      By assigning the elevated relative risk (RR) of CHD of 1.04 to the 145.5 million Americans exposed to ≥55 dBA LDN, the rate of CHD for those in the exposed group and those unexposed (Ru) was calculated using Equation 1:
      CHDc=(Pu×Ru)+(Pe×RRe×Ru)
      (1)


      where CHDc is the current number of cases of CHD (15.4 million, Table 2), Pu is the population unexposed to high noise (169.5 million), Ru is the risk of CHD among Pu, Pe is the population exposed to ≥55 dBA LDN (145.5 million), and RRe is the RR of CHD among Pe (1.04). Solving Equation 1, the rate of CHD for those unexposed (Ru) is 4.8%, and for those exposed (1.04*Ru) is 4.99%.
      In the assumed noise reduction scenario, the Pe group experienced a 5-dB LDN reduction in noise exposure to 50 dBA LDN, and the risk of CHD among this group reduced from 4.99% to 4.8%. The estimated number of cases of CHD in the exposure reduction scenario (CHDr) was calculated using Equation 2:
      CHDr=(Pu×Ru)+(Pe×Ru)
      (2)


      where all variables are defined as in Equation 1.

      Model 2: Hypertension

      The meta-analysis of road traffic and hypertension conducted by Van Kempen and Babisch
      • Van Kempen E.
      • Babisch W.
      The quantitative relationship between road traffic noise and hypertension: a meta-analysis.
      estimated a RR of 1.034 for each additional 5 dB LAeq,16h of road noise exposure over a range of 45–75 dBA. This standard was applied to estimate the effect of environmental noise on hypertension in the U.S. Again, it was conservatively assumed that the 140 million Americans exposed to ≥55 dBA LDN were exposed at exactly 55 dBA LDN. We also assumed that a 5-dB change in LAeq,16h is equivalent to a 5-dB change in LDN in our hypothetical exposure reduction scenario, as these measures are slightly different, but tend to be highly correlated.
      • Babisch W.
      Updated exposure-response relationship between road traffic noise and coronary heart diseases: a meta-analysis.
      The estimated RR of 1.034 per 5 dB LAeq,16h of noise exposure is conservative compared with other estimates in Table 1, namely Babisch and van Kamp,
      • Babisch W.
      • van Kamp I.
      Exposure-response relationship of the association between aircraft noise and the risk of hypertension.
      which estimated an RR of hypertension of 1.13 per 10 dB LDN, and Babisch,
      • Babisch W.
      Transportation noise and cardiovascular risk: updated review and synthesis of the epidemiological studies that indicate that the evidence has increased.
      which estimated an RR of hypertension of 1.4–2.1 per 10 dB increase in noise between 6am and 10pm (the Lday metric, nearly identical to the LAeq,16h).
      Repeating the methodology from Model 1, the risks for hypertension among the exposed and unexposed population were calculated. The rate of hypertension for those unexposed (Ru) was 24.3%, and that for those exposed (1.034 × Ru) was 25.2% (Equation 1).
      In the assumed noise reduction scenario, the noise-exposed group experienced a 5-dB LDN reduction in noise exposure to 50 dBA LDN, and the risk of hypertension among this group reduced from 25.2% to 24.3% (Equation 2). Estimates of the number of hypertension cases in this scenario were generated.

      Sensitivity Analyses

      Three analyses were performed: (1) ±20% the number of Americans exposed to high levels of noise; (2) ±20% RR; and (3) ±20% direct and indirect costs assumed for CHD and hypertension. Reductions in healthcare costs were estimated in proportion with reductions in prevalence of CHD and hypertension.

      Results

      In the CHD model, the reduced exposure scenario (CHDr) reduced CHD cases by 279,000 (1.8%), from 15.4 cases to 14.8 million cases (Table 3, Model 1). A corresponding 1.8% reduction in CHD costs would equate to annual savings of 1.8% of direct healthcare costs ($1.7 billion) and in 1.8% of indirect costs ($1.5 billion) from lost productivity.
      Table 3Model Results
      ModelCurrent situation5-dB reduction scenario estimateDifference (current – reduction scenario)
      Model 1: coronary heart disease
       Number of people exposed ≥55 dBA LDN145.5 million0–145.5 million
       Number of affected individuals15.4 million15.1 million–279,000
       Population risk (%)4.894.80–0.09
       Annual cost, direct ($)96 billion94.3 billion–1.7 billion
       Annual cost, indirect ($)81.1 billion79.6 billion–1.5 billion
      Model 2: hypertension
       Number of people exposed ≥ 55 dBA LDN145.5 million0–145.5 million
       Number of affected individuals77.9 million76.7 million–1.2 million
       Population risk (%)24.724.3–0.4
       Annual cost, direct ($)47.5 billion46.8 billion–684 million
       Annual cost, indirect ($)3.5 billion3.4 billion–50 million
      Note: Data sources and assumptions for “Current situation” explained in Table 2.
      The 5-dB LDN scenario reduced hypertension cases by 1.2 million (1.4%), from 77.9 million to 76.7 million (Table 3, Model 2). The associated 1.4% annual cost reduction equaled $684 million in direct healthcare costs and $50 million in indirect costs.
      Table 4 provides a summary of the results of three sensitivity analyses. Because of the simplicity of the model, adjustments in each of three tests by 20% had similar impacts on the outcomes in terms of reduction in costs (roughly 20% reduction or increase in the overall outcome) and reduction of prevalence (roughly 20% reduction or increase).
      Table 4Sensitivity Analyses
      ModelReduction in prevalence% reduction in prevalenceReduction in direct and indirect costs (USD billions)% reduction in direct and indirect costs
      Model 1: coronary heart disease
       Central estimate279,0001.83.21.8
       +20%: U.S. population in the noise-exposed group334,0002.23.82.2
       –20%: U.S. population in the noise-exposed group224,0001.52.51.5
       +20%: risk ratio associated with exposed group334,0002.23.82.2
       –20%: risk ratio associated with exposed group224,0001.52.51.5
       +20%: direct and indirect costs279,0001.83.91.8
       –20%: direct and indirect costs279,0001.82.61.8
      Model 2: hypertension
       Central estimate1.2 million1.40.71.4
       +20%: U.S. population in the noise-exposed group1.4 million1.70.91.7
       –20%: U.S. population in the noise-exposed group967,0001.20.61.2
       +20%: risk ratio associated with exposed group1.4 million1.70.91.7
       –20%: risk ratio associated with exposed group967,0001.20.61.2
       +20%: direct and indirect costs1.2 million1.40.91.4
       –20%: direct and indirect costs1.2 million1.40.61.4

      Discussion

      This exploratory analysis evaluates the impact of environmental noise on two key components of cardiovascular health—CHD and hypertension. The results from Models 1 and 2 suggest that a 5-dB LDN reduction in environmental noise would reduce hypertension cases by 1.2 million and CHD cases by 279,000. The associated cost savings equal $2.4 billion annually in healthcare costs and $1.5 billion annually in productivity gains. Together, the estimated economic impact of the reduction scenario is more than $3.9 billion annually.
      This analysis underestimates the impact of environmental noise on cardiovascular disease in a number of ways. Impacts on only two significant components of cardiovascular disease, CHD and hypertension, have been estimated, and these account for less than half of the costs associated with cardiovascular disease.
      • Go A.S.
      • Mozaffarian D.
      • Roger V.L.
      • et al.
      Heart disease and stroke statistics—2013 update: a report from the American Heart Association.
      • Lloyd-Jones D.
      • Adams R.J.
      • Brown T.M.
      • et al.
      Heart disease and stroke statistics—2010 update: a report from the American Heart Association.
      With further research, the estimates could be applied to all cardiovascular disease, and the cost savings would likely be considerably larger.
      These analyses represent the effect of noise exposure, and we believe that we have excluded confounding effects to the greatest extent possible. Many of the studies described in Table 1 account for demographic factors, other medical conditions, and other environmental factors (such as air quality) to attempt to isolate the impact of noise exposure on cardiovascular disease.
      The threshold for the noise-exposed group was ≥55 dBA LDN, though there is evidence in the literature that there may be important impacts at even lower levels of noise exposure.
      WHO
      Also, in the noise-exposed group, it was assumed that all individuals were exposed only at the minimal level for the group: 55 dBA LDN.
      Estimates for wider impacts, such as quality of life, were not included here, but would increase the benefit. For example, recent United Kingdom government guidance estimates that a decrease in environmental noise from 60 to 55 dBA LAeq,18hr is worth £13 ($22) in quality of life from reduced myocardial infarction per noise-reduced household.
      DEFRA
      Furthermore, these estimates are only illustrative of a portion of noise-related cardiovascular impacts, including only environmental noise exposure. Occupational noise exposure also has significant (and perhaps greater) cardiovascular impacts.
      • Gan W.Q.
      • Davies H.W.
      • Demers P.
      Exposure to occupational noise and cardiovascular disease in the United States: the National Health and Nutrition Examination Survey 1999-2004.
      • Davies H.W.
      • Teschke K.
      • Kennedy S.M.
      • Hodgson M.R.
      • Hertzman C.
      • Demers P.A.
      Occupational exposure to noise and mortality from acute myocardial infarction.
      Crude sensitivity analyses illustrate the impacts of changes in key model assumptions. Adjustments in each of the sensitivity tests by 20% have similar impacts on reduction in costs and prevalence (roughly 20% reduction or increase, except for reduction in cost, which has no impact on prevalence).

      Limitations

      As a result of the paucity of current noise exposure estimates in the U.S., a number of assumptions were made in extrapolating from the 1981 EPA noise exposure estimates.
      • Simpson M.
      • Bruce R.
      Notably, assuming zero trend in noise levels is likely a conservative assumption, especially given increasing urbanization in the U.S.
      • Garcia A.
      Another limitation of the analysis is that noise exposure metrics are often drawn from transportation research. Transportation is believed to be the primary source of environmental noise, and although different sources of noise can have different impacts on the listener, there is enough similarity in the documented cardiovascular disease/noise dose–response relationships that we elected to apply this transportation noise effect size to noise from any environmental source.
      The use of LDN here is warranted given the demonstrated relationship between LDN and annoyance.
      • Babisch W.
      • van Kamp I.
      Exposure-response relationship of the association between aircraft noise and the risk of hypertension.
      However, if a non–stress mediated pathway exists between noise exposure and cardiovascular disease, then the estimates presented here should be modified. Similarly, individual-level exposure variability due to recreational activities, occupational noise, listening to music, or other sources was not considered, and these activities may substantially increase noise exposure.
      • Neitzel R.L.
      • Gershon R.R.M.
      • McAlexander T.P.
      • Magda L.A.
      • Pearson J.M.
      Exposures to transit and other sources of noise among New York City residents.
      • Neitzel R.
      • Seixas N.
      • Goldman B.
      • Daniell W.
      Contributions of non-occupational activities to total noise exposure of construction workers.

      Conclusions

      This study estimates that reducing environmental noise by 5 dB LDN would reduce hypertension cases by an estimated 1.2 million (1.4%) and CHD cases by 279,000 (1.8%). The associated cost savings and productivity gains are estimated to exceed $3.9 billion annually, demonstrating that environmental noise has significant economic ramifications.
      This analysis is an important first step in estimating the economic and social costs of environmental noise exposure. Adding the benefits of reduced cardiovascular disease to cost–benefit analyses of proposed noise mitigation policies and investments (such as low-noise pavement, noise barriers, and active noise control) could appropriately enhance the economic valuation of these strategies, as the scale of the impacts estimated here make modest mitigation seem economically promising. This analysis also demonstrates that environmental noise exposures warrant further research and consideration in context with other environmental health priorities. Environmental noise exposure is a preventable risk factor for cardiovascular disease that is closely tied to community planning and government regulation, rather than personal risk factors, such as smoking, stress, and diet.
      • Mozaffarian D.
      • Wilson P.
      • Kannel W.
      Contemporary reviews in cardiovascular medicine: beyond established and novel risk factors—lifestyle risk factors for cardiovascular disease.
      • Perk J.
      • Hambraeus K.
      • Burell G.
      • Carlsson R.
      • Johansson P.
      • Lisspers J.
      Study of Patient Information after percutaneous Coronary Intervention (SPICI): should prevention programmes become more effective?.
      Evidence is gathering on other non-auditory health impacts of noise, such as annoyance, sleep deprivation, childhood learning disruption, stress, and mental health,
      • Goines L.
      • Hagler L.
      Noise pollution: a modern plague.
      and future estimates can address these impacts.

      Acknowledgments

      We gratefully acknowledge the assistance of Utibe Effiong, MD, MPH in preparing this manuscript and the University of Michigan Risk Science Center (UMRSC) for support of this work. The UMRSC did not have a role in the study design; collection, analysis, and interpretation of data; writing the report; or the decision to submit the report for publication.
      No financial disclosures were reported by the authors of this paper.

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