Assessment of the noise annoyance among subway train conductors in Tehran, Iran Mansoureh Hamidi1, Amir Kavousi1, Somayeh Zaheri1, Abolfazl Hamadani1, Roksana Mirkazemi2 Department of Health, Safety and Environment, Shahid Beheshti University of Medical Sciences, 2Hooman Research Collaborators Institute, Tehran, Iran
1
Abstract Subway transportation system is a new phenomenon in Iran. Noise annoyance interferes with the individual’s task performance, and the required alertness in the driving of subway trains. This is the first study conducted to measure the level of noise and noise annoyance among conductors of subway organization in Tehran, Iran. This cross sectional study was conducted among 167 randomly selected train conductors. Information related to noise annoyance was collected by using a self-administered questionnaire. The dosimetry and sound metering was done for the conductors and inside the cabins. There were 41 sound metering measuring samples inside the conductors’ cabin, and there were 12 samples of conductors’ noise exposure. The results of sound level meter showed that the mean Leq was 73.0 dBA ± 8.7 dBA and the dosimetry mean measured Leq was 82.1 dBA ± 6.8 dBA. 80% of conductors were very annoyed/annoyed by noise in their work place. 53.9% of conductors reported that noise affected their work performance and 63.5% reported that noise causes that they lose their concentration. The noise related to movement of train wheels on rail was reported as the worst by 83.2% followed by the noise of brakes (74.3%) and the ventilation noise (71.9%). 56.9% of conductors reported that they are suffering from sleeplessness, 40.1% from tinnitus and 80.2% feeling fatigue and sleepy. The study results showed the high level of noise and noise annoyance among train conductors and the poor health outcome of their exposure to this level of noise. Keywords: Dosimetry, noise annoyance, sound level meter, subway conductor, work performance
Introduction Subway transportation system is a new phenomenon in Iran with around one decade work history. The subway transportation is extended from east to west and north to south of Tehran in four lines, namely line 1, 2, 4 and 5 and transfers around 2 million passengers, daily. Still there is no research on health hazard of this system to the general population or subway conductors. Subway conductors have a very sensitive task that any error or failure in their work can endanger lives of thousands individuals. Media has reported many cases of accidents of passengers in the subway of Tehran; however, there is no Access this article online Quick Response Code:
Website: www.noiseandhealth.org DOI: 10.4103/1463-1741.134918 PubMed ID: ***
177
actual data in this regards. “Speed, Accuracy and Safety” is the motto of subway organization in Iran, which demands maximum alertness and vigilance of its train conductors. The term noise is attributed to any kind of irritating and obtrusive sound.[1] Noise pollution is one of the environmental health hazards. Noise induced stress is a result of inability to ignore, block out or otherwise cope with the unwanted sound, or if it is able to do so, only at a cost.[2] Noise can have negative effects on concentration, productivity, work capacity and increases the risk of accidents[3] and causes annoyance in many people.[4] Noise annoyance is a result of emotional processes related to many factors including personality of individuals and the noise level. The level of noise related disturbances and especially annoyance, varies between individuals, because, although noise is always interpreted in the central nervous system, it generates secondary and tertiary reactions that are not controlled by the brain cortex. The stimulation of these reaction pathways lead to involuntary reflexes, which in chronic exposure creates a give-up feeling, develop by reduced corporal and mental functions and usually causes annoyance as it stimulates the reactions of fear and flight.[5] Noise & Health, May-June 2014, Volume 16:70, 177-182
Hamidi, et al.: Noise annoyance among subway conductors in Tehran, Iran
A very long-term exposure to noise might lead to a reaction of exhaustion or defeat which leads to disturbance in secretion of some hormones such as growth hormone, catecholamine,[6,7] possibly followed by a decrease in function of the immune system and change of mood into apathy and decrease in social contacts.[5] This might be more severe in case of train conductors who have to work alone and in isolation of others. Noise has different effects on mental performance, it mostly deteriorates semantic processing of mental task (involve comparing meanings of a stimulus), while it does not affect, or even facilitates physical processing (require comparing physical characteristics of stimulus).[8] Therefore, noise can have a direct negative effect on performances required in conducting a subway train. Furthermore, it has been shown that intermittent sound is more detrimental to performance, compared with a steady noise of the same level.[9] The noise exposure level is associated with the individuals’ annoyance level. The respective dose-response relations are characterized by a considerable variation due to individual and situational factors.[10] The noise index that is used for measuring the noise exposure level is Leq. Due to the relative simplicity of evaluating Leq from the time history of the noise signal and in the absence of any better predictors, researchers in environmental noise believe that there is some convincing reason for continuing reference to the Leq index among many other related noise rating indices that was proposed by different researchers. However, it is more conservative to consider the level of noise annoyance and sensitivity along with the measuring noise exposure level, when assessing the effects of noise pollution is concerned, because according to some authors, factors like noise sensitivity and attitude toward the noisy situation, account for more variation on annoyance level and related effects than do noise exposure parameters.[5] The right to health imposes a serious responsibility to the public health system to ensure the safety of public transport in each country. Among the direct and most obvious effects of sound on awake subjects, are the negative interference of sound with the individual’s speech communication, concentration ability and consequently the performance of tasks,[5] which lead to the annoyance of the subject and consequently, may interfere with the required alertness and caution while performing tasks like driving behaviors. Therefore, this study was conducted to measure the level of noise and noise annoyance among conductors of subway organization in Tehran, Iran.
Methods This cross-sectional study was conducted to assess the level of noise annoyance among train conductors of Tehran Subway Organization and measure the sound level that they Noise & Health, May-June 2014, Volume 16
are exposed in their work place and the noise level emitted in their cabin during July 2012. Participants Participants were 167 of the train conductors of Tehran Subway Organization, which were selected of the total 835 conductors by simple random sampling. All the subway conductors were males, as no female were recruited as train conductors in Iran. Data collection Information was collected by using a self-administered questionnaire which included demographic, job related and annoyance related information. Job related information included the line of train work, work history, number of working hours and number of hours being in the cabin, extra work and shift work. Level of noise annoyance was measured using information on the level of annoyance by two Likert scales: The first scale was a single question “how much your work place noise annoys you when you are at work” which was scored from 0 to 10 developed by Guoqing et al.[11] and the second question was “In the last 1 year, how much the noise level of your work place annoyed you,” which was scored in a 6 points Likert scale range from 0 (no annoyance) to 5 (very high). Noise sensitivity was measured subjectively by a single question “To what extent do you consider yourself sensitive to noise?” on a Likert scale of 11 points (0 to10). The level of disturbance in their normal life and work function and type of noises that cause the maximum disturbance, noise induced health problems and the timing that creates most disturbance data were collected, too. Most of the questions on the level of noise annoyance, noise sensitivity and health effects of noise was taken exactly from questionnaire developed by “The International Knowledge Center for the Local Environment” in The Netherland (available from: http://rigolett.home.xs4all.nl/ENGELS/ quest/questionnaire.htm). The validity of the questionnaire was tested by using 10 experts’ opinion on the content validity and relevancy of each question, which showed a level of agreement more than 70%, and reliability was measured by Cronbach’s alpha, which showed a reliability level of 0.512 for annoyance, 0.613 for disturbances, 0.668 health impacts and 0.795 for types of noise questions, which showed an acceptable or desirable level of reliability for each subclass of questions.[12,13] Three trained interviewers distributed the questionnaires among conductors during their resting time in a 3 days’ time period. The dosimetry was done for the noise that conductors were exposed and the sound level metering was done inside their cabin (in two points of each cabin). The dosimetry device for the noise that conductors were exposed was a dosimeter 178
Hamidi, et al.: Noise annoyance among subway conductors in Tehran, Iran
model CEL-420 made in UK, which was calibrated before installing to the conductors collars by a calibrator model CEL-282. The sound level meter device for the noise inside conductors’ cabin was a sound level meter model CEL-62X made in UK, which was calibrated before use by a calibrator model CEL-110/2. There were 41 noise measuring samples inside conductors’ cabin, 21 of them were in line 1, 8 in line 4 and 12 in line 5 in seven different cabins of trains and in totally eight different trips. There were 12 samples that measured conductors’ exposure to noise. Thirty two samples (78.0%) were done in motion and 9 (22.0%) in stop status. Twenty three samples (56.1%) were done in head cabins and 18 (43.9%) in rear cabins. Sampling was carried out from 10:30 am to 18:50 pm. Data analysis Statistical Package for Social Sciences version 15.0 for windows (IBM Corporation, New York, United States) was used to analyze the data. The data analysis was performed using descriptive statistics and analytical statistics was performed using Chi-square tests, correlation and t tests. Ethical consideration The study procedures and objectives were explained to the participants. Participants were ensured that the data is kept confidential and only investigators would have access to it and that they would face no disciplinary action for their responses, nor would the data be analyzed on an individual basis. The study participants gave verbal consent to participate in the study.
Results Part 1: Results of dosimetry and sound level metering The results of sound level meter inside the cabin showed that the mean maximum sound pressure level (SPL) was 84.0 ± 5.6 dBA (range 72.9-98.3 dBA), the mean minimum SPL was 65.4 ± 3.6 dBA (range 57.6-73.3 dBA) and the mean Leq was 73.0 dBA ± 8.7 dBA (range 63.8-80.7 dBA). The mean noise dose that conductors were exposed to was 130-150% of the standard allowed noise dose and the mean time weighting average (8 h) exposure was 50.70 ± 17.70 dBA of the standard allowed noise dose. The mean measured Leq was 82.1 dBA ± 6.8 dBA (range 75.2-98.1 dBA), the mean maximum SPL was 101.3 dBA ± 11.4 dBA (range 89.2-128.7 dBA), the mean SPL average was 65.9 dBA ± 32.8 dBA (range 0.0-88.6 dBA) and the mean SPL peak was 126.1 ± 7.3 (range 114.6-142.9 dBA). Part 2: Noise annoyance assessment results Demographic and job related information [Table 1]. shows the demographic characteristics of subway conductors. All the conductors were males in the age group of 179
Table 1: Demographic and work related characteristics of train conductors (n = 167) Demographic Number (%) characteristics Marital status Married 52 (31.1) Single 113 (67.7) Others 1 (0.6) Number of children One child 40 (24.0) Two children 5 (3.0) More than two 1 (0.6) children NA 121 (72.5) Educational level Bachelor 55 (33.5) College 95 (56.9) Diploma 14 (8.5) Mean (SD) Age 29.3 (3.2)
Work related characteristics Line of work Line 1 Line 2 Line 4 Line 5 Shift work Yes No Extra work
1
Abstract Subway transportation system is a new phenomenon in Iran. Noise annoyance interferes with the individual’s task performance, and the required alertness in the driving of subway trains. This is the first study conducted to measure the level of noise and noise annoyance among conductors of subway organization in Tehran, Iran. This cross sectional study was conducted among 167 randomly selected train conductors. Information related to noise annoyance was collected by using a self-administered questionnaire. The dosimetry and sound metering was done for the conductors and inside the cabins. There were 41 sound metering measuring samples inside the conductors’ cabin, and there were 12 samples of conductors’ noise exposure. The results of sound level meter showed that the mean Leq was 73.0 dBA ± 8.7 dBA and the dosimetry mean measured Leq was 82.1 dBA ± 6.8 dBA. 80% of conductors were very annoyed/annoyed by noise in their work place. 53.9% of conductors reported that noise affected their work performance and 63.5% reported that noise causes that they lose their concentration. The noise related to movement of train wheels on rail was reported as the worst by 83.2% followed by the noise of brakes (74.3%) and the ventilation noise (71.9%). 56.9% of conductors reported that they are suffering from sleeplessness, 40.1% from tinnitus and 80.2% feeling fatigue and sleepy. The study results showed the high level of noise and noise annoyance among train conductors and the poor health outcome of their exposure to this level of noise. Keywords: Dosimetry, noise annoyance, sound level meter, subway conductor, work performance
Introduction Subway transportation system is a new phenomenon in Iran with around one decade work history. The subway transportation is extended from east to west and north to south of Tehran in four lines, namely line 1, 2, 4 and 5 and transfers around 2 million passengers, daily. Still there is no research on health hazard of this system to the general population or subway conductors. Subway conductors have a very sensitive task that any error or failure in their work can endanger lives of thousands individuals. Media has reported many cases of accidents of passengers in the subway of Tehran; however, there is no Access this article online Quick Response Code:
Website: www.noiseandhealth.org DOI: 10.4103/1463-1741.134918 PubMed ID: ***
177
actual data in this regards. “Speed, Accuracy and Safety” is the motto of subway organization in Iran, which demands maximum alertness and vigilance of its train conductors. The term noise is attributed to any kind of irritating and obtrusive sound.[1] Noise pollution is one of the environmental health hazards. Noise induced stress is a result of inability to ignore, block out or otherwise cope with the unwanted sound, or if it is able to do so, only at a cost.[2] Noise can have negative effects on concentration, productivity, work capacity and increases the risk of accidents[3] and causes annoyance in many people.[4] Noise annoyance is a result of emotional processes related to many factors including personality of individuals and the noise level. The level of noise related disturbances and especially annoyance, varies between individuals, because, although noise is always interpreted in the central nervous system, it generates secondary and tertiary reactions that are not controlled by the brain cortex. The stimulation of these reaction pathways lead to involuntary reflexes, which in chronic exposure creates a give-up feeling, develop by reduced corporal and mental functions and usually causes annoyance as it stimulates the reactions of fear and flight.[5] Noise & Health, May-June 2014, Volume 16:70, 177-182
Hamidi, et al.: Noise annoyance among subway conductors in Tehran, Iran
A very long-term exposure to noise might lead to a reaction of exhaustion or defeat which leads to disturbance in secretion of some hormones such as growth hormone, catecholamine,[6,7] possibly followed by a decrease in function of the immune system and change of mood into apathy and decrease in social contacts.[5] This might be more severe in case of train conductors who have to work alone and in isolation of others. Noise has different effects on mental performance, it mostly deteriorates semantic processing of mental task (involve comparing meanings of a stimulus), while it does not affect, or even facilitates physical processing (require comparing physical characteristics of stimulus).[8] Therefore, noise can have a direct negative effect on performances required in conducting a subway train. Furthermore, it has been shown that intermittent sound is more detrimental to performance, compared with a steady noise of the same level.[9] The noise exposure level is associated with the individuals’ annoyance level. The respective dose-response relations are characterized by a considerable variation due to individual and situational factors.[10] The noise index that is used for measuring the noise exposure level is Leq. Due to the relative simplicity of evaluating Leq from the time history of the noise signal and in the absence of any better predictors, researchers in environmental noise believe that there is some convincing reason for continuing reference to the Leq index among many other related noise rating indices that was proposed by different researchers. However, it is more conservative to consider the level of noise annoyance and sensitivity along with the measuring noise exposure level, when assessing the effects of noise pollution is concerned, because according to some authors, factors like noise sensitivity and attitude toward the noisy situation, account for more variation on annoyance level and related effects than do noise exposure parameters.[5] The right to health imposes a serious responsibility to the public health system to ensure the safety of public transport in each country. Among the direct and most obvious effects of sound on awake subjects, are the negative interference of sound with the individual’s speech communication, concentration ability and consequently the performance of tasks,[5] which lead to the annoyance of the subject and consequently, may interfere with the required alertness and caution while performing tasks like driving behaviors. Therefore, this study was conducted to measure the level of noise and noise annoyance among conductors of subway organization in Tehran, Iran.
Methods This cross-sectional study was conducted to assess the level of noise annoyance among train conductors of Tehran Subway Organization and measure the sound level that they Noise & Health, May-June 2014, Volume 16
are exposed in their work place and the noise level emitted in their cabin during July 2012. Participants Participants were 167 of the train conductors of Tehran Subway Organization, which were selected of the total 835 conductors by simple random sampling. All the subway conductors were males, as no female were recruited as train conductors in Iran. Data collection Information was collected by using a self-administered questionnaire which included demographic, job related and annoyance related information. Job related information included the line of train work, work history, number of working hours and number of hours being in the cabin, extra work and shift work. Level of noise annoyance was measured using information on the level of annoyance by two Likert scales: The first scale was a single question “how much your work place noise annoys you when you are at work” which was scored from 0 to 10 developed by Guoqing et al.[11] and the second question was “In the last 1 year, how much the noise level of your work place annoyed you,” which was scored in a 6 points Likert scale range from 0 (no annoyance) to 5 (very high). Noise sensitivity was measured subjectively by a single question “To what extent do you consider yourself sensitive to noise?” on a Likert scale of 11 points (0 to10). The level of disturbance in their normal life and work function and type of noises that cause the maximum disturbance, noise induced health problems and the timing that creates most disturbance data were collected, too. Most of the questions on the level of noise annoyance, noise sensitivity and health effects of noise was taken exactly from questionnaire developed by “The International Knowledge Center for the Local Environment” in The Netherland (available from: http://rigolett.home.xs4all.nl/ENGELS/ quest/questionnaire.htm). The validity of the questionnaire was tested by using 10 experts’ opinion on the content validity and relevancy of each question, which showed a level of agreement more than 70%, and reliability was measured by Cronbach’s alpha, which showed a reliability level of 0.512 for annoyance, 0.613 for disturbances, 0.668 health impacts and 0.795 for types of noise questions, which showed an acceptable or desirable level of reliability for each subclass of questions.[12,13] Three trained interviewers distributed the questionnaires among conductors during their resting time in a 3 days’ time period. The dosimetry was done for the noise that conductors were exposed and the sound level metering was done inside their cabin (in two points of each cabin). The dosimetry device for the noise that conductors were exposed was a dosimeter 178
Hamidi, et al.: Noise annoyance among subway conductors in Tehran, Iran
model CEL-420 made in UK, which was calibrated before installing to the conductors collars by a calibrator model CEL-282. The sound level meter device for the noise inside conductors’ cabin was a sound level meter model CEL-62X made in UK, which was calibrated before use by a calibrator model CEL-110/2. There were 41 noise measuring samples inside conductors’ cabin, 21 of them were in line 1, 8 in line 4 and 12 in line 5 in seven different cabins of trains and in totally eight different trips. There were 12 samples that measured conductors’ exposure to noise. Thirty two samples (78.0%) were done in motion and 9 (22.0%) in stop status. Twenty three samples (56.1%) were done in head cabins and 18 (43.9%) in rear cabins. Sampling was carried out from 10:30 am to 18:50 pm. Data analysis Statistical Package for Social Sciences version 15.0 for windows (IBM Corporation, New York, United States) was used to analyze the data. The data analysis was performed using descriptive statistics and analytical statistics was performed using Chi-square tests, correlation and t tests. Ethical consideration The study procedures and objectives were explained to the participants. Participants were ensured that the data is kept confidential and only investigators would have access to it and that they would face no disciplinary action for their responses, nor would the data be analyzed on an individual basis. The study participants gave verbal consent to participate in the study.
Results Part 1: Results of dosimetry and sound level metering The results of sound level meter inside the cabin showed that the mean maximum sound pressure level (SPL) was 84.0 ± 5.6 dBA (range 72.9-98.3 dBA), the mean minimum SPL was 65.4 ± 3.6 dBA (range 57.6-73.3 dBA) and the mean Leq was 73.0 dBA ± 8.7 dBA (range 63.8-80.7 dBA). The mean noise dose that conductors were exposed to was 130-150% of the standard allowed noise dose and the mean time weighting average (8 h) exposure was 50.70 ± 17.70 dBA of the standard allowed noise dose. The mean measured Leq was 82.1 dBA ± 6.8 dBA (range 75.2-98.1 dBA), the mean maximum SPL was 101.3 dBA ± 11.4 dBA (range 89.2-128.7 dBA), the mean SPL average was 65.9 dBA ± 32.8 dBA (range 0.0-88.6 dBA) and the mean SPL peak was 126.1 ± 7.3 (range 114.6-142.9 dBA). Part 2: Noise annoyance assessment results Demographic and job related information [Table 1]. shows the demographic characteristics of subway conductors. All the conductors were males in the age group of 179
Table 1: Demographic and work related characteristics of train conductors (n = 167) Demographic Number (%) characteristics Marital status Married 52 (31.1) Single 113 (67.7) Others 1 (0.6) Number of children One child 40 (24.0) Two children 5 (3.0) More than two 1 (0.6) children NA 121 (72.5) Educational level Bachelor 55 (33.5) College 95 (56.9) Diploma 14 (8.5) Mean (SD) Age 29.3 (3.2)
Work related characteristics Line of work Line 1 Line 2 Line 4 Line 5 Shift work Yes No Extra work
