Impact Assessment of Workers on Short Term Exposure within the Recommended Permissible Noise Exposure Limit (85 - 90 dBA) ()
1. Introduction
Occupational noise is considered as one of the most common widespread risk factors, with a strong evidence base linking it to an important health outcome (hearing loss) [1]. It was reported that about 600 million workers worldwide were exposed to occupational noise each year [2].
The Philippines as a developing country started the noise level standardization with the establishment of Occupational Safety and Health Standards in 1978 through the provision of Presidential Decree No. 442 of 1974, which is the Philippine Labor Code [3]. This includes the threshold limit values for noise current known as Permissible Noise Exposure Limit (PNEL) to serve as a baseline for industrial workplaces. PNEL refers to sound pressure that represents conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effects on their ability to hear and understand normal speech [4]. The Department of Labor and Employment (DOLE) under the Occupational Safety and Health Center (OSHC) set PNEL based on the number of hours of exposure. Currently, the PNEL for eight-hour work is 90 dBA. Since then, the PNEL of the Philippines remains at 90 dBA despite the Dec. 06, 2018 implementation of the Republic Act No. 11058 entitled “An Act Strengthening Compliance with Occupational Safety and Health Standards and Providing Penalties for Violations Thereof” [5].
As countries expand, the industry’s noise exposure for workers also increases. Noise exposure in enclosed spaces such as the textile mill and steel plant ranges from 86 to 119 dBA resulted in hearing losses of full-time workers in the Philippines [6]. In addition, noise exposure ranging from 80 to 99 dBA results in to drop in productivity while increasing the issuance of disciplinary actions, absenteeism, and accidents among textile companies [7]. On the other hand, workers assign in an open space such as the traffic enforcers in the streets of Manila were exposed to noise but it does not exceed the current PNEL [8].
Although these studies determine the impact of noise on workers versus productivity and health and safety issues, all of these were conducted in an uncontrolled environment where multiple factors can affect the results. These factors might not only be the noise in the workplace but organizational management, economical factor, socio-psychological or physical factor [9].
Since data for developing countries are scarce, but available evidence suggests that average noise levels are well above the occupational level recommended in many developed nations [10]. These scenarios prompt the researcher to pursue a study regarding the impact of 90-dBA noise level on workers and find out whether 90 dBA would be the safe level for workers. In addition, the researcher would like to check whether lower PNEL at 85 dBA used by other countries such as the United States of America via the National Institute of Occupational Safety and Health (NIOSH) could affect the productivity of workers in an enclosed and controlled workspace.
A study supported by American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) way back 2006 aims to determine whether varying noise exposure level affects worker's productivity. The test was composed of ten workers, five male and five female who were exposed to six different noise conditions while accomplishing different timed examinations inside an enclosed chamber, which resembles a typical office [11].
2. Method
A descriptive study design was used to collect data from the instrument, interviews, test results, and observations. A small business with a total of ten workers was chosen to participate on the study. The participants performed three tests while being exposed to six different noise levels with controlled illumination levels, relative humidity, and temperature. Collection and processing of data Pearson correlation will be, perform for the entire variable to know its relationship to the different noise levels [11].
2.1. Interview
A non-structured and informal interview was performed before the start of the experiment soliciting and noting down the personal information with emphasis on the age, working experience, and company residency of the workers. Orientation was conducted for all ten participants by explaining and describing the purpose and objectives of the study. Speaker was installed inside the room to introduce continuous noise and easily adjust the noise level. Sound Level Meter (SLM) was mounted to verify whether the noise level is maintained inside the booth.
2.2. Abstract and Logic Examination
This examination is composed of abstract and logical image sequences and patterns. There are six different sets of examinations, with 50 items each and it needs to be completed within 60 minutes. Pen, printed questionnaires, and a chair were provided inside the booth, proper sitting positions were not mandated to the workers. They were informed to sit in their most comfortable position. This examination aims to assess the worker’s cognitive skills performance. [12]. It also aimed to verify at which noise level the worker performs the best [11].
2.3. Simple Mathematics Examination
Composed of simple mathematical questions that are all word problems. There were six different sets of tests with 25 items each that should be completed within 30 minutes. Pen, printed questionnaires, and chairs were provided inside the booth, proper sitting positions were not mandated to the workers. They were informed to sit in their most comfortable position. This examination aims to assess the worker's general cognitive skills such as working memory and to verify at which noise level the worker performs the best [12].
2.4. Set-Up Examination
Workers were required to finish ten set-ups within 15 minutes. To pass, the noise meter should be raised 1.2 - 1.5 meters above the floor using a tripod. The noise meter should be “ON” and secured with a cable tie. In addition, this test includes disassembly of the set-up to re-set it up again. An Industrial Hygienist confirms the conformity of each completed set-up and marks it “passed”.
2.5. Health and Safety Data
Data were collected on any health and safety issues observed by the Industrial Hygienist or reported by the participants while performing the test within the prescribed time.
2.6. Controlled Environment
The isolation booth can be adjusted to six controlled noise levels from 85 dBA, 86 dBA, 87 dBA, 88 dBA, 89 dBA, and 90 dBA adjusted using the portable speakers. Illumination is set at 250 lux, while the thermostat is set at 24 degrees Celsius indoor environmental temperature and relative humidity at 45%. These variables were verified via calibrated tools such as room noise meter, lux meter, room thermometer, and hygrometer. The method assesses exposure at two noise levels (85 - 90 and >90 dB (A)), and by occupational category and economic subsector [1].
2.7. Recording of Data
The laboratory Industrial Hygienist performs the collection, checking, and verification of data from the test questionnaires, participant profile, scheduling, observations, environmental conditions, and interview of the workers.
2.8. Data Analysis
Data were analyzed using SPSS version 26 for descriptive statistics and Pearson correlation while complicated graphs and charts were created in Microsoft Excel version 2016.
3. Results
Presented below are the test results of each worker for the three examinations conducted to assess the impact of noise level on the performance of the workers.
Table 1 shows that employees exposed at 85 dBA has a mean score of 72% correct answers for abstract and logic while it goes down to 59% when employees are exposed at 86 dBA, a mean score of 57% for 87 dBA, 52% for 88 dBA, 42% for 89 dBA and 39% for 90 dBA.
As presented above, Table 2 shows that when employees are exposed to 85 dBA while answering simple mathematics problems a mean score of 72% was gained while it goes down to 81% when employees are exposed at 86 dBA, a mean score of 74% for 87 dBA, 73% for 88 dBA, 66% for 89 dBA and 64% for 90 dBA.
Foregoing in Table 3 shows that when employees are exposed to 85 dBA while doing set-up, a mean score of 81% was gained while it goes down to 77% when employees are exposed at 86 dBA, a mean score of 76% for 87 dBA, 73% for 88 dBA, 69% for 89 dBA and 67% for 90 dBA.
Aforementioned in Table 4, accidents and health issues occur nineteen times in total with seven related to health and 12 for safety (accidents) while inside the isolation booth.
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Table 1. Abstract and logic percentage test results.
*Values in percentage (%).
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Table 2. Simple mathematics percentage test results.
*Values in percentage (%).
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Table 3. Actual set-up productivity percentage results.
*Values in percentage (%).
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Table 4. Health and safety summary results.
*Issues are tallied per total number.
4. Discussion
Figure 1 test result shows no direct relationship to the age of the workers since all workers of the same age such as SP1 and SP3 at age 28 rank first and lasts which is nine places away from one another. SP5 and SP6 at age 34 rank eighth and third with five ranking difference from one another, SP9, and SP10 at age 39 ranks second and fifth, which is three places away from one another as per the rankings. All the personnel of the same age has different means, which fluctuate the results up and down which results in an unpredictable bar graph. As for the years of experience (represented by the brown line) when correlated with the examination results. It was identified that there is no clear pattern of whether personnel with longer experience performs better than the less experienced ones or vice versa, as SP1 having two-year experience received a mean of 74.33 which ranks first as the best performer while SP9 which has nine years of experience receives 62.33 and ranked as a second-highest score. Since they rank first and second, this gives the experience correlation a fluctuating or unpredicted result. In addition, SP1 and SP6 with two years’ experience, which is the most inexperienced among the group, rank first and third respectively while SP10 with the
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Figure 1. Abstract & logic productivity correlated to age, experience and mean.
most experience at ten years ranks fifth which is located in the middle of the group. This gives an unpredictable result for the sampled group.
Figure 2 test results show no direct relationship to the age of the workers though SP9 and SP10 at age 39 rank eighth and seventh respectively, SP1 and SP3 at age 28 rank second and ninth respectively which are seven places away from one another, while SP5 and SP6 at age 34 rank tenth and third which are seven places away from one another also. This resulted in an unpredictable bar graph. As for the experience correlated with the examination results, it is identifiable that there is no clear pattern of whether personnel with longer experience performs better than the fewer experience ones or vice versa. SP1 and SP6 with two years’ experience, which is the most inexperienced among the group, ranks second and tenth respectively while SP10 with the most experience at ten years ranks seventh. This gives an unpredictable result for the sampled group.
Figure 3 results show no direct relationship to the age of the workers since all workers of the same age, such as SP1 and SP3 at age 28, ranks second and third which is one place away from one another; SP5 and SP6 at age 34 rank first and fifth with four places away from one another and SP9 and SP10 at age 39 ranks tenth and seventh with three places away from one another as per the rankings. All the personnel of the same age has different means, which fluctuate the results up and down which results in an unpredictable bar graph.
Likewise, experience correlated with the examination results; it is identifiable that there is no clear pattern whether personnel with longer experience performs better than the less experienced ones or vice versa. SP1 and SP6 with two years' experience, which is the most inexperienced among the group, rank second and fifth respectively. In addition, SP5 and SP7, which have six years of experience, rank first and seventh respectively, that is six places apart from one another, while SP10 with the most experience at ten years ranks seventh. This gives an unpredictable result for the sampled group.
Figure 4 shows Health and Safety issues raise are back ached and stress that was noted for four participants of the ages 28, 30, 34, and 35 respectively (all
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Figure 2. Simple mathematics correlated to age, experience and mean.
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Figure 3. Actual set-up correlated to age, experience and mean.
male) during the after-exposure examination. On the other hand, a falling object, such as a pen, tape measure, and tripod was noted as the source of safety issues.
Figure 5 shows that female examination results are higher than males for simple mathematics and actual noise measurement. As such, male examination results are higher for the abstract and logic examination. Although this result has a non-proportioned number of male and female participants, having eight males and two females.
Figure 6 reveals that as the noise level increases from 85 dBA to 90 dBA, the three mean scores of the samples decrease. Hence, the increasing noise level serves as a hindrance that affects the test results of the workers. Notably, the simple mathematics output has the highest results while the actual set-up output results have the lowest outcome.
Three tests were conducted for 10 employees to find the highest productivity level, lowest incident rates, and minimal possible health stress or issues when
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Figure 5. Gender performance comparison.
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Figure 6. Mean of test scores vs noise levels.
they are exposed to 85, 86, 87, 88, 89, and 90 dBA for 1.75 hours in total. These tests challenged the current 90 dBA standard set by the Philippine government under DOLE-OSHC. In the abstract and logic examination, it is evident that 85 dBA produced the highest results in an average of all the ten participants with a 72% score output. Nevertheless, 8/10 got the highest result in the said noise level exposure. Two participants had managed to perform their best on higher noise exposure. This test also shows that 80% of participants can identify photos and shapes differences including sequential order of patterns with 60% precision. For the simple mathematics examination, 90% secured the highest score while exposed to 85 dBA noise. This means that 9/10 workers can perform rational thinking for solving mathematical word problems. As noise increases the scores on the exam dropped from 87% to 64%. The test determines the efficiency of an actual setup, which provides accurate productivity for the test. And based on the results, taking into consideration the noise exposure, 100% performed at their best within the 85 dBA exposure.
An additional observation was also taken into consideration such as health and safety issues; this is minimal for the test as the room is small while the required movements are few to cause accidents. However, the summary of the Health and Safety observation also resulted in higher disturbance to the examinees during higher noise exposure.
Aforementioned in Table 5, the Pearson correlation results for noise levels correlated with the dependent variables. Results show that the Noise Level has a moderate negative Pearson correlation with Abstract and Logic examination at −0.571 and is significant at 0.000. This reveals that the participant’s mental workload and visual or auditory attention is significantly reduced when exposed to the higher noise level [13].
While Noise level correlated with the Simple Mathematics examination has moderate negative Pearson correlation at −0.475 and is significant at 0.000. This means that a high background noise level (≥85 dBA) negatively affects the performance of workers when it comes to their mathematics skills and comprehension [14].
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Table 5. Pearson correlation for noise level & dependent variables.
**Correlation is significant at the 0.01 level (2-tailed).
Noise Level correlated with Practical Assembly or Set-up has a high negative Pearson correlation at −0.646 and is significant at 0.000. This implies that noise has an inversely proportional relationship with workers' productivity of set-up assembly wherein, the higher the noise level the lower the number of qualified assemblies completed [15].
In addition, Noise Level correlated with Health Issues has a moderate positive Pearson correlation at 0.410 and is significant at 0.001. This means that workers exposed to higher noise levels (≥85 dBA) may develop health issues [16], although further study needs to be conducted to identify what are the health issues that may occur.
Lastly, Noise Level correlated with Safety Issues (accidents) has a negligible positive Pearson correlation at 0.133 and is not significant at 0.310.
5. Conclusion
This study found out that there is a significant correlational impact between the tested noise levels (85 - 90 dBA) within a short-term exposure versus the ability of workers to identify visual patterns, comprehend and solve simple mathematics problems, and complete an assembly or set-up. Wherein, workers performance decrease as noise level increase. Subsequently, safety or the occurrence of accident was not significant however, noise level has also affected the workers’ health as issues were raised during the test but further study needs to be perform to investigate whether noise affect the health of workers and what health issue arise within the short term exposure.
Acknowledgements
A heartfelt thanks to the best advisers, namely, Engr. Rene Rubio and Engr. Carol Jazmine Dizon demonstrates their expertise in guiding the proponent concerning technical, grammar, and statistical aspects of the study. These persons are the key to drafting and finalizing the study.