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ORIGINAL ARTICLE
Year : 2022 | Volume
: 26
| Issue : 4 | Page : 240-244
Cumulative noise exposure and perceived effects: A comparative study among different occupational groups in Kolkata
Arup Chakraborty1, Arista Lahiri2, Urmila Dasgupta1, Asim Saha3, Salil K Bhattacharya1
1 Department of Community Medicine, Medical College and Hospital, Kolkata, West Bengal, India
2 Community Medicine, Dr. B. C. Roy Multi-Speciality Medical Research Centre, Indian Institute of Technology Kharagpur, West Bengal, India
3 Scientist F, Regional Occupational Health Centre (E), Kolkata, West Bengal, India
Correspondence Address:
Dr. Arup Chakraborty
240, Golpukur Road, P.O-Baruipur, Distt-24Pgs (S) - 700 144, West Bengal
India
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/ijoem.ijoem_51_22
Background: Adverse short-term and long-term health effects following a high level of noise have been established. The current study aims to find the relationship of these effects with an environment-specific level of noise exposure. Materials and Methods: A comparative cross-sectional study was conducted among 50 auto-rickshaw drivers and 51 age-matched service-sector employees. The peak average noise exposure in decibels (dB) was measured. The duration of exposure and response regarding perceptions following noise exposure was assessed through a pre-designed pre-tested semi-structured questionnaire. Results: The mean age of the participants was 42.24 (±13.72) years. Among the auto-rickshaw drivers, 82% perceived stress, 64% had hearing difficulty, and 74% complained of lack of sleep following exposure to a high level of noise. However, the perceptions were comparable among the comparison group and the differences were not statistically significant. The mean average peak level of noise exposure among drivers and their comparison group was 91.64 (±7.37) dB and 91.98 (± 8.06) dB, respectively, but were not different statistically. Around 52.94% of the service-sector respondents and 48% of the drivers were exposed to the lower cumulative noise levels. Those having a higher level of cumulative noise exposure, had a higher odds of feeling irritated (Odds ratio [OR]: 2.182, 95% confidence interval [CI]: 0.845–5.636), feeling stressed (OR: 5.805, 95% CI: 1.552–21.708), having palpitation (OR: 3.694, 95% CI: 1.264–10.793), and lack of sleep (OR: 3.020, 95% CI: 1.006–9.066). Conclusion: Stress and lack of sleep were the most important perceived effects of noise exposure. The exposures to the higher cumulative noise level in specified groups were more important in relation to quantifying perceived symptoms than the average peak noise level.
Keywords: Cumulative exposure, dosimeter, drivers, noise, peak exposure
Noise, an important aspect of the evolution of human civilization, is usually considered in two categories: community noise and occupational noise. Community noise (also called environmental noise, residential noise, or domestic noise) is the noise emitted from all sources except noise in the industrial workplace. Main sources of community noise include road, rail, and air traffic, industries, construction, public work, and the neighborhood. In large cities throughout the world, the general population is increasingly exposed to community noise from different sources, and the health effects of these exposures are considered to be important public health problems.[1]
Noise is the most common occupational risk factor and there are millions of workers (organized as well as unorganized) who are exposed to harmful levels of noise in the workplace. Hearing loss is a well-documented primary biological adverse effect caused by occupational noise exposure.[2] Worldwide, noise-induced hearing impairment is the most prevalent irreversible occupational hazard and it is estimated that 120 million people worldwide have disabling hearing difficulties.[1] In addition, noise exposure activates the sympathetic and endocrine systems, thereby affecting the humoral and metabolic states of human beings. Therefore, noise exposure increases the risk of extra-auditory adverse outcomes such as hypertension and cardiovascular diseases, digestive and behavioral disorders, sleep disturbances, and performance reduction.[2]
In developing countries such as India, not only occupational noise but also environmental noise is an increasing risk factor for hearing impairment.[1] The National Institute of Occupational Safety and Health (NIOSH) establishes recommended exposure limits (RELs) to protect workers against the health effects. It established the REL for occupational noise exposures to be 85 decibels, weighted (dB[A]) as an 8-h time-weighted average. Exposures at or above this level are considered hazardous. NIOSH also specifies a maximum allowable daily noise dose, expressed in percentages. For example, a person continuously exposed to 85 dB (A) over an 8-h work shift will reach 100% of their daily noise dose. For every 3-dB increase in noise level, the allowable exposure time is reduced by half.[3] Measurement of environmental as well as occupational noise considers the frequency content of the sounds, the overall sound pressure levels, and the variation of these levels with time. Because the range of sound pressures that human listeners can detect is very wide, these levels are measured on a logarithmic scale with units of decibels.
The sound levels of most noises vary with time. The sum of the total energy over some time gives a level equivalent to the average sound energy over that period. Thus, “LAeq, T” is the energy average equivalent level of the A-weighted sound over a period T. LAeq, T should be used to measure continuing sounds, such as road traffic noise. However, measures of individual events such as the maximum noise level (LAmax), or the weighted sound exposure level (SEL), should also be obtained in addition to LAeq, T, when there are distinct events to the noise. Currently, the recommended practice is to assume that the equal energy principle is approximately valid for most types of noise and that a simple LAeq, T measure will indicate the expected effects of the noise reasonably well. When the noise consists of a small number of discrete events, the A-weighted maximum level (LAmax) is a better indicator of the disturbance to sleep and other activities.[1]
In this background, the present study was conducted to look at the relationship between certain perceived health effects with the environment-specific level of cumulative noise exposure in an urban slum in Kolkata city. For this purpose, based on accessibility, two occupational groups were chosen as a proxy for the differing levels of noise exposure—auto-rickshaw drivers and service sector employees. Auto-rickshaw drivers are usually exposed to the noise of road traffic for a longer duration by virtue of their engagement throughout the day on the road. In contrast, the service sector employees used to get exposed much lesser time to noise mostly during their transit to the office. However, in both the groups the peak level exposure to noise may be the same. Therefore, a valid comparison could be obtained to ascertain the relationship between health effects and environment-specific noise levels.
Materials and MethodStudy design and participants
A comparative cross-sectional study was conducted among randomly chosen 50 auto-rickshaw drivers and 51 age-matched service-sector employees in an urban slum area of Kolkata between January 2019 and February 2020. Subjects who gave consent to become part of the study were included. The auto-rickshaw drivers were recruited from dedicated auto-rickshaw depots identified through snowball sampling. Then from the friends and relatives of the selected auto-rickshaw drivers, maintaining the inclusion criteria, the age-matched control group was selected. People who had been already diagnosed with ear diseases, psychiatric illnesses, or any other chronic diseases were excluded from the study.
Data collection and measurements
Data collection in the study comprised two components, first a questionnaire-based survey and a second, measurement of the exposure to the noise level. A pre-designed pre-tested questionnaire was administered among the selected participants, enquiring about the basic socio-demographic details, duration of exposure, and perceptions following high levels of noise exposure. The questionnaire was developed following sequential brainstorming sessions and expert judgment by three experts from the fields of occupational health, public health, and otorhinolaryngology. Then, it was pre-tested on a group of seven individuals who were excluded from the final study. Following pre-testing, the questionnaire was finalized and used in the study. The participants were enquired about their experience of “feeling irritated,” “headache,” “feeling of stress,” “palpitation,” “currently unable to hear properly,” and “lack of sleep” following noise exposure.
The average noise exposure in decibels (dB) was measured with the help of a noise dosimeter (VLIKE LCD Digital Audio Decibel Meter Sound Level Meter), which is considered the most accurate instrument for measuring personalized noise exposure and also can be used in different environmental settings for the relevant measurements.[4]The meter provided continuous readings, which with relatively constant background noise yielded a floating average. It has a weighted measurement mode considered as a simulation of the hearing characteristics of the human ear.[5] Based on the floating average, a mean peak level of noise was noted. The mean peak level of noise was the major exposure variable.
Statistical analysis
The data were entered into a spreadsheet software and were subsequently analyzed in STATA 14.2 (StataCorp., College Station, Texas, USA). The different self-reported symptoms were tabulated among auto-rickshaw drivers and service-sector employees. A Chi-square test with continuity correction was used to test for any statistical significance of each symptom/experience among the two occupational groups. Both the duration of noise exposure and the mean peak noise exposure were separately tested for statistical difference between the two groups being studied using an unpaired t-test. To understand the noise exposure, a new variable was generated, “cumulative noise exposure.” This was calculated by multiplying the duration of exposure to noise (as reported by the respondents) and the mean peak level of noise exposure (as measured by the noise dosimeter in dB). The cut-off of cumulative noise exposure was calculated based on the mean cumulative exposure of respective groups. Those who had a cumulative noise exposure above the mean level were considered the high exposure group and the others as the low exposure group. Association of occupational groups with exposure groups as identified were tested with the help of the Chi-square test with continuity correction. Finally, in a similar manner, the association of various perceived health effects in relation to respective groups based cut off on their cumulative noise exposure, that is, high or low cumulative exposure, was tested.
Ethical considerations
The current study is a part of a larger study, which was approved by the Institutional Ethics Committee. Written informed consent was obtained from the participants before administering the study tools.
ResultsBackground information
The mean age of the participants was 42.24 (±13.72) years. Overall, 68.32% were from joint family backgrounds and are currently not married. Also, 38.61% were educated at least up to the secondary level. Although among the auto-rickshaw drivers 32.00% were in the lowest income quartile, this was 17.65% among the comparison group.
Felt effects of exposure to noise
[Table 1] shows the distribution of study subjects based on their response to certain perceived effects among both groups. The majority of the participants perceived stress (81.19%) followed by lack of sleep (76.24%) when exposed to noise. The perceived effects were not statistically different between the two study groups.
Table 1: Distribution of study subjects based on their response to certain perceived effectsNoise exposure
[Figure 1] shows the mean of the peak level of noise exposure among auto drivers and their comparison group, which was 91.64 (±7.37) dB and 91.98 (± 8.06) dB, respectively, though no statistically significant difference was observed. The distribution of study subjects based on the type of cumulative exposure to noise is depicted in [Table 2]. Cut off of cumulative noise exposure was calculated based on the mean cumulative exposure of respective groups. The result shows there were no significant statistical differences between the two groups in terms of high and low cumulative noise exposure. It was observed that amongst auto-drivers, average exposure to noise was 7.88 h (± 1.08 h), much higher than that among service sector employees, who had a mean duration of noise exposure of 2.04 h (± 1.03 h).
Figure 1: Comparison of mean peak levels of noise (dB) exposure among the study groups
Table 2: Distribution of study subjects based on the type of cumulative exposure to noiseEffect of cumulative noise exposure
Finally, the association of various perceived health effects in relation to respective group-based cut off on their cumulative noise exposure was obtained [Table 3]. It was noted that auto-drivers exposed to a higher level of noise as compared to the service sector employees, had a statistically significantly higher proportion of felt effects such as palpitation, lack of sleep, and stress.
Table 3: Association of various perceived health effects with cumulative noise exposure in different study groups Discussions In the European countries, about 40% of the population are exposed to road traffic noise with an equivalent sound pressure level exceeding 55 dB(A) during daytime and 20% are exposed to levels exceeding 65 dB(A). Taking all exposure to transportation noise together, about half of the European Union citizens are estimated to live in zones, which do not ensure acoustical comfort to residents. More than 30% are exposed at night to equivalent sound pressure levels exceeding 55 dB(A), which are disturbing to sleep. The noise pollution problem is also severe in cities of developing countries and caused mainly by traffic. Data collected alongside densely traveled roads were found to have equivalent sound pressure levels for 24 h of 75 to 80 dB(A).[1] In Brazil, the impact of noise was observed among the drivers and nurses posted in the mobile support units of two private urgency and emergency services. The most-reported auditory symptoms were tinnitus, intolerance to intense sounds, and ear plenitude. The most-reported nonauditory symptoms were irritability, headache, talking difficulties in noisy environments, and sleep alterations.[6] The present study revealed that urban slum dwellers of Kolkata having different occupations such as service sector employees as well as auto-rickshaw drivers were on averagely exposed to more than 90 dB sound level, which was much higher than that reported by other study findings. The self-reported perceive complaints were the highest for feeling stressed and the lowest for having palpitation. The other complaints were lack of sleep, hearing problem, irritation, and headache as per their proportion from high to low.
A study conducted in rural Australia, to compare hearing levels of individuals regularly exposed to noise in their workplace to self-reported hearing loss found that the perceptions of workplace noise tended to be more positive if people felt they had hearing problems.[7]The present study did not find any difference in perceived hearing loss among people who had higher exposure to noise due to their occupation. Though this study did not quantify the noise-induced hearing loss, it has been planned to conduct audiometry on the subjects during the course and the data will be disseminated elsewhere.
A study reported around 58% of hearing difficulty among specific occupational groups are due to noise exposure in the US.[8] In the present study, we found the overall proportion of perceived hearing difficulty was more than 60%. The finding is quite similar to the study conducted in the US. Though this is quite alarming and may be due to the fact that our study subjects belonged to specific occupational groups such as drivers and by virtue of their profession their cumulative noise exposure was much higher than general people or other professional groups. In Sao Paolo, Brazil similar study shows the prevalence of hearing loss among drivers was 22%.[9]
Though the present study did not explore the entire gamut of cardiovascular ailments among the studied occupational groups in relation to noise exposure, the perceived palpitation among the study subjects was quite high (27%). Though in comparison to other complaints it is the lowest perceived one. In the US, the prevalence of hypertension and high cholesterol among the specific occupational groups due to noise exposure were 14 and 9%, respectively.[8]Another study conducted at the University of Kentucky observed that the current noise-exposed participants had slightly increased diastolic blood pressure; however, previously exposed participants had bilateral high-frequency hearing loss, heart rate, and the prevalence of hypertension.[10]
ConclusionThe exposures to the higher cumulative noise levels in specified groups were more important in relation to quantifying perceived symptoms than the average peak noise level. The baseline exposure to noise appears more important in developing symptoms related to noise exposure in occupational groups. Measurement of baseline noise exposure in different occupational settings with a mean noise-based cut-off can help to play a role to take preventive measures among the people engaged in various occupations.
Declaration of patient consent
Informed consent was obtained from all the subjects regarding sharing of their clinical information for academic purposes only. Due efforts were made to conceal their identity.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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