Noise health effects are the physical and psychological health consequences of regular exposure to consistent elevated sound levels. Noise from traffic, in particular, is considered by the World Health Organization to be one of the worst environmental stressors for humans, second only to air pollution. Elevated workplace or environmental noise can cause hearing impairment, tinnitus, hypertension, ischemic heart disease, annoyance, and sleep disturbance. Changes in the immune system and birth defects have been also attributed to noise exposure. Although age-related health effects (presbycusis) occur naturally with age, in many countries the cumulative impact of noise is sufficient to impair the hearing of a large fraction of the population over the course of a lifetime. Noise exposure has been known to induce noise-induced hearing loss, tinnitus, hypertension, vasoconstriction, and other cardiovascular adverse effects. Chronic noise exposure has been associated with sleep disturbances and increased incidence of diabetes. Adverse cardiovascular effects occur from chronic exposure to noise due to the sympathetic nervous system's inability to habituate. The sympathetic nervous system maintains lighter stages of sleep when the body is exposed to noise, which does not allow blood pressure to follow the normal rise and fall cycle of an undisturbed circadian rhythm. Stress from time spent around elevated noise levels has been linked with increased workplace accident rates, aggression, and other anti-social behaviors. The most significant sources are vehicles, aircraft, prolonged exposure to loud music, and industrial noise. Prolonged exposure to noise at home has been linked to decreased mental health. There are approximately 10,000 deaths per year as a result of noise in the European Union.
Noise-induced hearing loss
Noise-induced hearing loss is a permanent shift in pure-tone thresholds, resulting in sensorineural hearing loss. The severity of a threshold shift is dependent on duration and severity of noise exposure. Noise-induced threshold shifts are seen as a notch on an audiogram from 3000 to 6000 Hz, but most often at 4000 Hz. Exposure to loud noises, either in a single traumatic experience or over time, can damage the auditory system and result in hearing loss and sometimes tinnitus as well. Traumatic noise exposure can happen at work (e.g., loud machinery), at play (e.g., loud sporting events, concerts, recreational activities), and/or by accident (e.g., a backfiring engine). Noise-induced hearing loss is sometimes unilateral and typically causes patients to lose hearing around the frequency of the triggering sound trauma.
Tinnitus Tinnitus is an auditory disorder characterized by the perception of a sound (ringing, chirping, buzzing, etc.) in the ear in the absence of an external sound source. There are two types of tinnitus: subjective and objective. Subjective is the most common and can only be heard "in the head" by the person affected. Objective tinnitus can be heard from those around the affected person and the audiologist can hear it using a stethoscope. Tinnitus can also be categorized by the way it sounds in one's ear, pulsatile tinnitus which is caused by the vascular nature of Glomus tumors and non-pulsatile tinnitus which usually sounds like crickets, the sea and bees. Though the pathophysiology of tinnitus is not known, noise exposure can be a contributing factor; therefore tinnitus can be associated with hearing loss, generated by the cochlea and central nervous system (CNS). High-frequency hearing loss causes a high-pitched tinnitus and low-frequency hearing loss causes a roaring tinnitus. Noise-induced tinnitus can be temporary or permanent depending on the type and amount of noise a person was exposed to.
Cardiovascular effects Noise has been associated with important cardiovascular health problems, particularly hypertension, as it causes an increase in levels of stress hormones and vascular oxidative stress. Noise levels of 50 dB(A) or greater at night may increase the risk of myocardial infarction by chronically elevating cortisol production. Traffic noise has several negative effects, including increased risk for coronary artery disease, with night-time exposure to noise possibly more harmful than day-time exposure. It has also been shown to increase blood pressure in individuals within the surrounding residential areas, with railways causing the greatest cardiovascular effects. Roadway noise levels are sufficient to constrict arterial blood flow and lead to elevated blood pressure. Vasoconstriction can result from elevated adrenaline levels or through medical stress reactions. Long-term exposure to noise is correlated to an increase in cortisol and angiotensin-II levels which are respectively associated with oxidative stress and vascular inflammation. Individuals subject to greater than 80 dB(A) in the workplace are at increased risk of having increased blood pressure. A 2021 systematic review on the effect of occupational exposure to noise on ischemic heart disease (IHD), stroke and hypertension, coordinated by the World Health Organization (WHO) and the International Labour Organization (ILO) located 17 studies that met the inclusion criteria, comprising a total of 534,688 participants (7.47% females) in 11 countries and in three WHO regions (the Americas, Europe, and the Western Pacific). The study found the low quality of evidence the effect of occupational exposure to intense noise (≥85 dBA), compared to occupational exposure below 85 dBA (<85 dBA). They concluded that there is inadequate evidence of harmfulness for the studied outcomes with the exception of the risk of acquiring IHD, which was 29% higher for those exposed to noise in their workplace.
Other physical health effects Traffic noise may also increase the risk of sleep disturbances, stroke, diabetes, and becoming overweight. Noise pollution is an environmental health concern since it is often a risk factor for developing other diseases like tinnitus or impaired speech discrimination.
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