By: Sean Lennox. MSc. Audiologist

Melamud and Bruhis (1996) investigated the effects of noise exposure greater than 85 dBA on stress levels, fatigue and annoyance, with and without the use of hearing protection devices (HPD). The research population was a group of Israeli textile employees: 22 men and 13 women ranging in age from 27-58. Urinary cortisol levels were monitored at the beginning, middle, and end of each work shift following a week of non-HPD use. The researchers then looked at urinary cortisol amounts after the workers had a week to use HPDs. Urinary cortisol levels have been used in research to measure stress levels as cortisol correlates positively with increased physiological stress. In addition, self report measures of fatigue and irritability were done at the end of the work day following 1 week of noise exposure with and then without HPD use.

The urinary cortisol levels of participants were much lower at the end of the work day for workers in the HPD use condition, following a 1 week exposure of 85dBA TWA, when compared to the non-PD use condition. The urinary cortisol levels with HPD use were found to decrease throughout the day which differed significantly from the non-HPD use condition where cortisol levels increased significantly at the end of the work shift. This study was the first to successfully use cortisol levels to assess the effects of noise on associated stress levels. Fatigue was assessed by using a questionnaire that highlighted the workers perceived tiredness and motivation before heading home at the end of the work day. Fatigue was much lower for the workers after a period of HPD use versus non- HPD use. Irritability, which also measured using a subjective questionnaire after 1 week of HPD use, was found to be significantly lower for the HPD condition. Therefore, the authors concluded that HPD use significantly improved the psychological well-being of these factory workers by reducing the annoyance and heightened physiologic arousal that constant noise exposure caused. In conclusion, these authors recommend HPD use for workers continuously exposed to loud sounds as HPD use not only protects the ability to ear but also lowers physiologic stress levels, fatigue, and general annoyance.

Noise exposure and accident risk

Girard, Picard, Davis, Simard, Laroque, Leroux, and Turcotte, (2011) studied the roles that occupational noise exposure and permanent hearing loss have on the risk of accident event occurrences. This was a retrospective study done by mining previous noise survey data, audiometric evaluations done annually, and accident report records. The independent variables in this study were amount of hearing loss and amount of noise exposure in dBA. The dependent variable was the number of accidents reported to workers compensation, leading to a measure of the probability an accident would occur. The population studied was from all occupational settings monitored by the Quebec (Canada) National Institute of Public Health and the accident report records were found from the Quebec workers compensation board records. The total population included those with normal to severe high frequency sensory neural loss. Additionally this population was separated into two groups: those who worked in settings with noise greater than 90dBA and those who worked in less than 90 dBA. There were a total of 52982 workers included in this study ranging in age from 16 to 64 years of age.

The authors found that the risk of accidents was higher for the workers in higher occupational noise group with a TWA greater than 90dBA. Also, when they looked at hearing loss, those with bilateral average hearing loss greater than 15 dB at 3, 4 and 6 KHz were found to have more accidents reported than normal hearing workers. The risk of accidents odds ratio (OR) for those with moderate hearing loss working in the higher than 90 dBA were found to be higher than moderate hearing loss workers working in less than 90dBA of noise. An interesting interaction was found for those with severe hearing loss where the researchers found that this severe hearing loss population was 2-3 times more likely to have reported an accident when compared to normal hearing workers.

Overall, the authors concluded that there was an increased risk of accidents for workers working in higher noise levels. Higher noise levels interacted positively with permanent hearing loss to increase the risk of accidents in the work place. They suggest that people with severe hearing loss should not work in high noise levels because they would lack the clarity and audibility to attend to security warnings and alarms. For those with hearing impairment, HPDs should allow for audibility of warning signals and loud speech if at all possible. In general the authors agree that hearing loss in high noise work environments is a safety hazard. High occupational noise in general increases accident risk by 1.3 times compared to lower noise levels. The authors conclude that in some instances HPDs can cause accidents especially for those with hearing loss and they prefer the use of engineering controls wherever feasible.

“Noise pollution: effects on sleep and annoyance

Stansfeld and Matheson, (2003) provide a literature review of the effects of community and occupational noise on both physiological and psychological health of humans. They focus on how noise affects sleep, stress, psychosis, annoyance, and pediatric populations. The ability to fall and stay asleep is not permanently affected by intermittent or continuous automobile or airplane traffic noise if we allow time to acclimatize to the noise. At first a noise would inhibit sleep and cause anxiety, but after many exposures to airplane noise or the traffic noise from roads outside, our auditory system is able to filter this non-salient information and its effect becomes minimal. This is true for sounds around 50dB SPL or lower. One study found that electroencephalograms of sleeping participants who lived near a busy airport were not affected by aircraft sounds at or below 80dB SPL. Physiologic measures of heart rate and blood pressure during sleep can be heightened with high traffic noise exposure which leads the authors to conclude that psychological adaptation of noise happens over time; however physiologic blood pressure and heart function do increase with noise exposure even after adaptation.

Focusing on the cardiovascular effects of noise, occupational noise exposure was compared to community noise exposure. Workers exposed at above the known action level were found to have sustained higher blood pressure than workers in lower noise employment. The increased blood pressure was a stable finding intrasubject showing that heightened arousal continues after leaving the factory. Sudden loud sounds have been linked to heart attacks and heart rate fluctuations. In the community, those exposed to loud airport noise have been shown to have poorer heart health indicators (increased heart medication use and hypertension) than people living further from airports. The level of noise that negatively affects heart function may be dose dependent with one study stating that TWA above 55dBA was linked to hypertension risk.

Annoyance is a term describing a psychological state of heightened arousal where a person perceives environmental threat or irritant. Noise has been found to lead to increased annoyance in many studies both in community and occupational health studies. Noise is anxiogenic and can lead to combativeness in the workplace and at home, tension headaches, nausea, and mood swings. In addition, noise can diminish the enjoyment of leisure activities. The psychiatric effects of noise require further investigation as the level of noise at home or at work does not currently correlate with diagnosed psychotic disorders such as depression or anxiety disorders.

Children are similarly affected by noise and the authors state that cognition and motivation are especially affected by ambient noise levels. The auditory effects of noise in children were discussed but these are well understood by audiologists. Focusing on the non-auditory effects of noise, hypertension, catecholamine levels and systolic blood pressure all increased in children following the opening of a nearby Munich airport. Noise has negative effects on the cardiovascular and endocrine function of children and adults alike.

Traffic Noise and Cardiovascular Issues

Babisch, Beule, Schust, Kersten, and Ising, (2005) investigated the association between continuous traffic noise exposure and heart attack risk. This study looked at previous noise exposure for a large group of German heart attack survivors after they were released from hospital. They were asked about previous occupational noise exposure, and their community noise exposure was developed by checking noise survey maps completed for the city of Berlin. The heart attack patient group was matched to a control hospital population of similar age and gender. There were many more males in this study than females and the authors attribute this to the fact that women have a lower incidence of heart disease than men.

Previous noise exposure for each group was broken down into 4 groups based on where the participants lived: <50 (quiet side street), 61-65, 66-70, and > 70 dBA (near highways or airports). In addition, heart attack risk was assessed for those who lived in a particular neighborhood for more than 10 years and as such were more likely to have been affected by the long-term effects of noise exposure. The total number of participants in the heart attack group was 1881 and there were over 2000 matched controls.

The odds ratio of suffering a myocardial infarction (MI) was developed for each noise exposure level group. The authors found that there was a greater likelihood that a male patient that suffered an MI also lived in a nosier neighborhood. This greater chance of suffering a heart attack with prolonged noise exposure was found specifically for men, as women heart attack risk was not significantly affected by any level of noise. For example, the odds ratio for those who were exposed to over 70 dBA TWA on a daily basis was found to be 1.3 greater than men who resided in relative quiet (<50dBA). Women in the same high noise level group over 70 dBA were actually less likely to suffer an MI, which is a finding that the authors were not quite able to explain. Men who lived in the same high level noise address for more than 10 years had almost double the risk (odds ratio= 1.8) of MI when compared to men who lived in quiet.

Overall, the authors stated that this simply extended previous research that tested the hypothesis that prolonged community noise exposure from automobile/ railway/ airplane traffic is strongly and positively associated with MI risk for men only. Women in this particular study were not found to be at increased risk for heart attack even in higher traffic noise neighborhoods.

Blood Pressure and Noise

Chang , Y.Lai, Hsieh, J.S. Lai, Liu, ( 2009) studied how blood pressure of young adults changed in relation to noise exposure over a 24 hour period. Previous studies have found a strong association between high noise exposure and increased blood pressure leading to hypertension.

The authors enlisted 60 university students: 30 males and 30 females, ranging in age from 18 to 32 years of age. Each student was assessed using a self-report questionnaire for other variables that could affect blood pressure differences among participants such as: body mass index (BMI), fitness level, and a family history of hypertension. Each participant wore a remote blood pressure monitor cuff and noise dosimeter set to record 50- 120dBA for a period of 24 hours. Fluctuations in blood pressure which was the dependent variable were recorded every 30 minutes. Blood pressure measurements were related to fluctuations in noise exposure levels measured every 5 minutes. In addition blood pressure fluctuations were compared to previously reported BMI, family history of hypertension and fitness level.

No gender differences were evident with respect to daytime or nighttime noise exposure levels. The average Leq (s) were around 60dBA in the daytime and 50dBA during the nighttime for both gender groups. The authors found that increasing noise level was the strongest predictor of increasing blood pressure for men and women although BMI was also strongly associated for males. More specifically the authors stated that each 5 dB increase in noise exposure level was associated with a significant increase in blood pressure of around 1.4 mmHg for males and around 1.6 mmHg for females.

Unlike the previous study discussed above by Babisch et al, (2003), women were shown to be more affected by noise exposure. More specifically each 5 dB increase in noise was related to a larger increase in blood pressure for women than men. The authors believe that this preponderance of hypertension risk for women in consistent with a myriad of other studies done looking at noise effects on blood pressure for older populations over 35. Overall, this study adds to the growing body of evidence that community noise exposure even below 70dBA can affect the blood pressure of young adults. Prolonged heightened blood pressure can lead to hypertension and cardiovascular disease, so community health officials should consider and prevent environmental noise given this finding.

References

Babisch, Beule, Schust, Kersten, and Ising. (2005).Traffic noise and risk of myocardial infarction. Epidemiology, 16(1), 33-41.

Chang, Lai, Hsieh, Lai, Liu. (2005). Effects of environmental noise exposure on ambulatory blood pressure in young adults. Environmental Research, 109, 900-905.

Girard, Picard, Davis, Simard, Laroque, Leroux, and Turcotte. (2011). Multiple work-related accidents: Tracing the role of hearing status and noise exposure. Journal of Occupational and Environmental Medicine, 66, 319-324.

Melamud and Bruhis. (1996). The effects of chronic industrial noise exposure on urinary cortisol, fatigue, and irritability: A controlled field study. Journal of Occupational and Environmental Medicine, 38(3), 252-256.

Stansfeld and Matheson. (2003). Noise pollution: Non-auditory effects on health. British Medical Bulletin, 68, 243