Effect of concurrent exposure to noise and hand-transmitted vibration on auditory and cognitive attention under simulated work with construction tools.

Objectives. This study aimed to investigate the effects of separate and concurrent exposure to occupational noise and hand-transmitted vibration (HTV) on auditory and cognitive attention. Methods. The experimental study was conducted with 40 construction workers who were exposed to noise (A-weighted equivalent sound pressure level of 90 dB) and to HTV (10 m/s2 at 31.5 Hz), and concurrent exposure to both for 30 min under simulated work with vibrating equipment used in construction. Cognitive performance aspects were then evaluated from each individual in two pre-exposure and post-exposure settings for each session. Results. The effect sizes of concurrent exposure (HTV + noise) and separate exposure to noise on auditory attention were very close (effect size = 0.648 and 0.626). The largest changes in the difference of response time in both types of attention (selective and divided attention) were related to the concurrent exposure scenario and then exposure to HTV, respectively. The highest effects for the correct response of selective and divided attention are related to concurrent exposure (HTV + noise) and then noise exposure, respectively. Conclusion. The HTV effect during concurrent exposure is hidden in auditory attention, and noise has the main effects. The divided attention was more affected than the selective attention in the different scenarios.

Effects of wearing medical gowns at different temperatures on the physiological responses of female healthcare workers during the COVID-19 Pandemic.

BACKGROUND: Using medical gowns with high protection against COVID-19 among healthcare workers (HCWs) may limit heat exchange, resulting in physiological challenges. OBJECTIVE: This study aimed to compare the physiological and neurophysiological responses of female HCWs when using two typical medical gowns at different temperatures during the COVID-19 pandemic. METHODS: Twenty healthy female HCWs participated in this study. Participants wore two types of medical gowns: Spunbond gown (SG) and laminate gown (LG). They walked on a treadmill in a controlled climate chamber for 30 minutes at three different temperatures (24, 28, and 32°C). Heart rate (HR), skin surface temperature (ST), clothing surface temperature (CT), ear temperature (ET), blood oxygen percentage (SaO2), galvanic skin response (GSR), and blood pressure were measured before and after walking on a treadmill. The study's results were analyzed using SPSS26. RESULTS: The study found that LG led to an average increase of 0.575°C in CT compared to SG at the same temperatures (P <  0.03). The average HR increased by 6.5 bpm in LG at 28°C compared to SG at a comfortable temperature (P = 0.01). The average ET in SG and GSR in LG at 32°C increased by 0.39°C and 0.25µS, respectively, compared to the comfortable temperature (P <  0.02). CONCLUSION: The study recommends maintaining a comfortable temperature range in hospitals to prevent physiological challenges among HCWs wearing medical gowns with high protection against COVID-19. This is important because using LG, compared to SG, at high temperatures can increase HR, ET, CT, and GSR.

Effect of noise and hand-transmitted vibration exposure on hearing and equilibrium under a simulated work environment with building tools.

BACKGROUND: Construction workers are exposed to hand-transmitted vibration (HTV) and/or noise caused by vibrating hand tools in the work environment. OBJECTIVE: The present study aims to investigate the effects of exposure to HTV and/or noise on workers' hearing loss and body balance. METHODS: Forty construction workers were exposed to HTV (10 m/s2 rms, 31.5 Hz) and/or typical construction noise (90 dBA) in three simulated experiment scenarios with the vibrating hand-held tool for 30 minutes over three days. The hearing loss from 1000 to 6000 Hz and the body balance were determined before and after each exposure scenario. RESULTS: Separate noise exposure at all frequencies except for 1000 Hz could significantly affect hearing threshold levels (p-value<0.05). Separate exposure to HTV cannot lead to a remarkable effect on hearing loss (p-value>0.05); however, it can synergistically increase the effect of noise on hearing loss. Also, the affected frequency range in concurrent exposure has been greater than in separate noise exposure. The separate effects of exposure to HTV and noise on the subjects' body balance were not statistically significant (p-value>0.05); however, these effects became significant in concurrent exposure (p-value<0.05). Based on the estimated effect sizes, noise could synergistically increase the observed effect of HTV on body balance. CONCLUSION: There is a synergistic interaction between HTV and noise on hearing loss and body balance. It seems necessary to pay attention to the risk evaluation of simultaneous exposure to noise and HTV when setting the occupational action limit values.

Combined Effects of Noise and Hand-transmitted Vibration on Workers' Muscle and Mental Fatigues in a Simulated Construction Operation.

BACKGROUND: The frequent use of hand-held vibrating tools by construction workers exposes them to hand-transmitted vibration (HTV) and noise. This study investigated the effect of combined exposure to HTV and noise on workers' fatigues under simulated work with a typical building destruction tool. METHODS: The repeated measures study was conducted on 40 construction workers exposed to HTV (5 m/s2 rms with frequencies of 31.5, 63, and 125 Hz), HTV (10 m/s2 rms- 31.5 Hz), noise (90 dBA), and concurrent exposure (noise (90 dBA) + HTV (10 m/s2 rms- 31.5 Hz)) with the typical vibrating hand-held tool for 30 minutes. Electromyography signals determined each worker's fatigue level in the Flexor digitorum superficialis (FDS) muscle in two pre- and post-exposure periods. The subjects also filled out the visual analog scale to evaluate mental fatigue severity subjectively. RESULTS: The mean difference of muscle fatigue parameters was significant in all scenarios except for the two scenarios of alone exposure to HTV (5 m/s2 -125 Hz and noise exposure (p-value < 0.05). The mean difference of mental fatigue in all scenarios except for the two scenarios of exposure to HTV (5 m/s2 -125 Hz) and exposure to HTV (5 m/s2 -63 Hz) was significant (p-value < 0.05). The most differences in muscle fatigue parameters (Amplitude = 8.16±5.63, Mean frequency=-4.69±3.78) and mental fatigue (4.97±2.38) were observed in the simultaneous exposure to noise and HTV. CONCLUSION: Noise exposure alone cannot produce remarkable effects on muscle fatigue but can aggravate the effects of vibrations as a consequence of synergistic interaction. However, the role of noise on perceived mental fatigue was more dominant than the HTV. These findings should be considered to adapt the existing exposure limits to actual work conditions.

Staffs' physiological responses to irrelevant background speech and mental workload in open-plan bank office workspaces.

BACKGROUND: Acoustic comfort is one of the most critical challenges in the open-plan workspace. OBJECTIVE: This study was aimed to assess the effect of irrelevant background speech (IBS) and mental workload (MWL) on staffs' physiological parameters in open-plan bank office workspaces. METHODS: In this study, 109 male cashier staff of the banks were randomly selected. The 30-minute equivalent noise level (LAeq) of the participants was measured in three intervals at the beginning (section A), middle (section B), and end of working hours (section C). The heart rate (HR) and heart rate variability (HRV): low frequency (LF), high frequency (HF), and LF/HF of the staff were also recorded in sections A, B, and C. Moreover, staff was asked to rate the MWL using the NASA-Task load. RESULTS: The dominant frequency of the LAeq was 500 Hz, and the LAeq in the frequency range of 250 to 2000 was higher than other frequencies. The LAeq (500 Hz) was 55.82, 69.35, and 69.64 dB(A) in sections A, B, and C, respectively. The results show that the IBS affects staffs' physiological responses so that with increasing in IBS, the HF power decreases. Moreover, with higher MWL, increasing noise exposure, especially IBS, causes more increases in LF power and LF/HF ratio. CONCLUSION: It seems that the IBS can affect physiological responses and increase staff stress in open-plan bank office workspaces. Moreover, the mental workload can intensify these consequences in these working settings.

Analysis of body heat tolerance of workers in a simulated warm environment based on linear mixed model.

Workers' heat tolerance plays a crucial role in maintaining their health and performance in hot environments. This study aimed to empirically analyze the body heat tolerance of workers under a simulated warm environment. Twenty healthy male workers from the typical light metal industry (age: 23.15±2.45 years) were participated in the experimental study. Workers were exposed to two thermal environments (Ta = 22°C, RH = 35%, and Ta = 35°C, RH = 35%) in a simulated moderate workload in a climate-controlled room. The maximal aerobic capacity (VO2 max) and body fat mass of workers were determined. The heat tolerance indicators were determined based on heart rate (HR) and ear temperature (ET) before and after each experiment. A linear mixed model was employed to analyze body heat tolerance indicators using the SPSS statistical package. All physiological responses significantly increased in the warm air condition compared to the thermoneutral condition. The HR and ET increased by an average of 14 bpm and 0.75°C, respectively (p<0.05). The mixed model could accurately predict heat tolerance indicators (r = 0.95 and r = 0.97) so that the VO2 max and body fat mass were identified as the main individual influential factors. The VO2 max showed significant correlation with urinary specific gravity (r = -0.55, p<0.05), HR (r = -0.59, p<0.05), and ET (r = -0.57, p<0.05) in warm environment. The model confirmed that physical fitness is critical in increasing heat tolerance in warm environments. It can be a helpful screening tool for properly selecting workers in occupational medical examinations for working in warm air conditions. It is proposed that workers' regular exercise and lifestyle modifications can strengthen their heat tolerance.

The simultaneous exposure to heat and whole-body vibration on some motor skill functions of city taxi drivers.

BACKGROUND: Driving requires sensory-motor abilities in unpredictable and complex driving scenarios. This experimental study aimed to investigate the combined effects of exposure to whole-body vibration and heat on motor skill functions of city taxi drivers. METHODS: This study was conducted using a driving simulator on 30 male taxi drivers. The drivers were exposed to five exposure conditions set by a single or combined exposure of two air temperatures (24 and 30 °C) and two vibration levels (0.5, 1 m/s2). Motor skill functions, including body balance, hand grip strength, and perceived fatigue, were measured using a force plate, dynamometer, and Borg CR-10 questionnaire. RESULTS: The separate exposure to heat did not modify balance and hand grip strength, but its combined exposure to vibration affected balance and grip strength. The effect sizes of heat, vibration, and heat + vibration on balance were respectively 0.003, 0.23, and 0.441. Vibration exposure made the most significant mean differences in hand grip strength compared with the other scenarios. The separate effect of heat on drivers' perceived fatigue was comparable to vibration. The combined exposure to heat and vibration aggravated the perceived fatigue associated with exposure to heat and vibration alone. CONCLUSION: Vibration mainly affects the driver's postural equilibrium, handgrip strength, and fatigue. The heat exposure alone did not have any remarkable effects on the balance responses and handgrip strength; however, it significantly increased the drivers' perceived fatigue. Exposure to heat can aggravate the effects of vibration on motor skills with a synergistic interaction.

Body physiological responses of city bus drivers subjected to noise and vibration exposure in working environment.

Background: The city bus drivers have critical roles in public transport and are occupationally exposed to different environmental stressors. This study aimed to investigate body physiological responses of city bus drivers subjected to noise and vibration exposure while crossing city routes. Methods: This cross-sectional study was conducted on 103 city bus drivers working in the governmental transportation system in Hamadan city. The subjects' exposures to noise and body vibration were measured during driving activities. Their blood pressure (BP), as well as heart rate (HR), were measured before and after driving. Multivariate regressions (MLR) were employed to analyze the effect size of the stimulus on body physiological responses using SPSS 22. Results: Exposure levels to noise, whole-body vibration (WBV), and hand-arm vibration among drivers were 79.50 ± 3.51dB, 0.620 ± 0.159 m/s2, and 0.438 ± 0.064 m/s2, respectively which were lower than the exposure limits. Heart rate as main physiological response before and after driving were 74.22 ± 4.11 and 79.23 ± 8.59 bpm, respectively. The developed MLR models statistically showed that noise exposure could only affect the HR (ß = 0.193 and p < 0.001); while WBV exposure affected both BP (ß = 0.360 and p < 0.001) and HR (ß = 0.367 and p = 0.020). The statistical analysis represented that exposure to noise and vibration in the presence of other possible covariates have significant effects on body physiological responses. Conclusion: The study empirically confirmed the possibility of body physiological changes influenced by physical stimulus during real driving activities. It is highly recommended that occupational health surveillance should continuously be implemented to maintain and promote the safety and health of drivers throughout their careers.

Prediction of occupational exposure limits for noise-induced non-auditory effects.

There is a recent trend to place more emphasis on noise non-auditory effects. Despite its implications on health, there is a lack of recommendations for noise in occupational settings. This study aimed to present occupational exposure limits for noise-induced non-auditory effects in healthy males using empirical exposure-response regression models based on the data of laboratory and field considering the effective variables. To this end, the equivalent noise level was measured and recorded in four working settings including closed offices, open-plan offices, control rooms, and industrial workplaces during a normal working day. They were 65, 68, 73, and 80dB(A), respectively. In the laboratory, 31 healthy males were exposed to five noise conditions (four noisy conditions and one quiet) during 8 h and they were asked to perform the cognitive tests. In the field phase, 124 healthy males were also examined from four working settings in their workstations for 8 h. The psychophysiological parameters of the participants were recorded in both lab and field. The results indicated variations in mental responses at levels above 55dBA, and psychophysiological variations at levels above 70dB(A) in both phases. The findings also showed that the developed regression models could plausibly predict the noise-induced psychophysiological responses during exposure to noise levels; thus, they can be presented the likely exposure limits. Based on the results of the models, the levels <55dB(A) are likelihood of the acoustic comfort limit, and the levels ranged from 55 to 65dB(A) are the acoustic safe limits. The acoustic caution limit is the likelihood of the levels ranged from 65 to 75dB(A). The levels ranged from 75 to 80dB(A) are likely the action levels or control limits, and the occupational exposure limit are the probability of levels> 80dB(A).

Ergonomic risk factors and musculoskeletal disorders in bank staff: an interventional follow-up study in Iran.

BACKGROUND: Long-term use of computer in a static mode may cause musculoskeletal disorders (MSDs) in bank staff. Considering the high number of bank employees in different countries, such as Iran, the risk factors of these disorders should be investigated in order to implement interventions required to reduce the risk factors. This study aimed to examine the risk factors of MSDs using the Rapid Office Strain Assessment (ROSA) method and to perform an ergonomic intervention program with banking staff in Iran. METHODS: This interventional study was conducted on 277 bank employees in Iran. Subjects were randomly divided into three groups, including a control group (without any intervention), an educational intervention (EI) group, and a group receiving both educational and physical intervention (EPI). Before and after the intervention, the ROSA method and Nordic questionnaire were used to assess the risk factors of MSDs in office jobs and to investigate the prevalence of MSDs. Data were collected 2 weeks before and 9 months following the intervention. RESULTS: Before the intervention, the mean score of ROSA at workstations of all groups was above five with high risk. Nine months after the start of the intervention, there was a significant decrease in the mean ROSA score and its components in the two groups that received the intervention, which was statistically significant (P < 0.001). The results of the study of the prevalence of MSDs in the employees-before the intervention-indicate that the highest prevalence of MSDs in the control group was in areas of the neck (67.1%), back (64.4%), and lower back (63%). In the EI group, the highest prevalence of MSDs was in the neck (65.2%), lower back (61.6%), and back (60.7%) areas. In the EPI group, the discomfort areas were the neck (68.5%), shoulders (66.3%), and lower back (60.9%). Nine months after the intervention, there was a significant decrease in the prevalence of MSDs in the neck, shoulders, and lumbar regions of staff who received the intervention (P < 0.05). CONCLUSION: Nine months after performing the interventions, there was a relative improvement in workstations and prevalence of MSDs in various areas within the bodies of the bank staff. This study showed that using the ROSA method is appropriate for assessing the risk factors of office work and that it can identify deficiencies in workstations. These defects can be addressed by designing and implementing an EI program together with physical interventions according to the components of the ROSA method.

Effect of warm/cool white lights on visual perception and mood in warm/cool color environments.

Color and light are two ambient attributes for interior spaces that can be used in the design and modification of workspaces. The visual and psychological effects of color and light of each have been studied separately and widely. The aim of this study was to investigate the simultaneous effects of warm/cool white light on visual perception and mood in a simulated colored workspace. Thirty-three healthy male participants were recruited. They were asked to judge the visual perception and mood of three types of workspace that were designed by colors of white, red, blue, and lights of a cool and warm white in the random six sessions. The participants have experienced higher levels of tension, anger, depression, anxiety and lower levels of visual comfort, attractiveness, brightness and calmness of environment in the red condition than to white in both state of light. The blue wall reduced brightness and increased attractiveness of environment compared to white wall. Cool white light reduced the warmth of color and increased brightness in all three color environments compared to warm light. The preference for cool or warm light depends on the color of the environment's indoor surface. It seems that the combination of the white color and warm light or the blue color with cool light has a more favorable effect on visual perception and people's mood in workplaces.

Human cognitive functions and psycho-physiological responses under low thermal conditions in a simulated office environment.

BACKGROUND: In office environments, thermal comfort is one of the most significant factor affecting employees' performance. OBJECTIVE: This study aimed to determine the effects of exposure to low air temperatures on human cognitive performance, physiological responses, and thermal perceptions during mental work. METHODS: Twenty-four volunteers with an age range of 18-30 years participated in this study. The subjects were exposed to four different air temperatures (10, 14, 18, and 22°C) in a climate chamber based on a within-subject design. The n-back, CPT, and PVT tests were employed to evaluate some basic aspects of cognitive performance. Body physiological responses and the subjective thermal comfort were also measured. RESULTS: When the thermal condition deviated from relatively neutral temperature, the subjects' cognitive responses significantly disturbed (P < 0.05), such that the response accuracy was more affected by reduction of air temperature. The blood pressures and heart rate, galvanic skin response, and respiration rate increased as the air temperature decreased (P < 0.05), such that the galvanic skin response as a stress indicator was more affected. In the test configurations, as a result of decrease in air temperature of 1°C, the finger and body skin temperatures reduced to 0.74°C and 0.25°C, respectively. CONCLUSIONS: The findings confirmed that low thermal condition can considerably affect cognitive performance and physiological responses during some office work tasks. The subjects' thermal comfort votes proposed that air temperature lower than 14 °C can be intolerable for employees during routine mental work. It is suggested that personalized conditioning systems should be used to provide individual thermal comfort in moderate cold air conditions.

Effects of Light on Attention and Reaction Time: A Systematic Review.

BACKGROUND: Accuracy, speed, efficiency, and applicability of activities in the workplace are among the most important effective factors on people's productivity, which is in turn affected by environmental factors, such as light. Therefore, the present research aimed to review the studies performed about the effects of light on attention and reaction time. METHODS: This review study systematically searched articles from 2000-2019 in databases of Google Scholar, ISC, SID, Magiran, Web of Science, Science Direct, PubMed, and Scopus using keywords of light, lighting, attention, and reaction time. The titles and abstracts of articles containing relevant results over the past 20 years were extracted. Thereafter, they were categorized and analyzed according to the title, author name, publication year, study method, study type, and evaluation results. RESULTS: Based on the results, the light with shorter wavelengths, higher intensity, and higher color temperature led to suppressed melatonin, higher consciousness, less somnolence, increased attention, and faster reaction time. Simultaneous exposure to harmful levels of environmental factors affects cognitive and physiological parameters, acting independently with a separate mechanism or synergistically with a similar mechanism. The best light in the regulation of psychological, biological, and cognitive processes is bright daylight in the morning with a short wavelength, high intensity, and more lasting effects. CONCLUSION: As evidenced by the obtained results,  light is a powerful modulator of non-visual performance in cognitive tasks. The wavelength, color temperature, and light intensity modulate brain responses to cognitive tasks, including attention and reaction time. Therefore, these parameters, along with personal and environmental factors, should be considered in designing and using light.

The effect of hearing protection devices on speech intelligibility of Persian employees.

OBJECTIVE: This study aimed to investigate the effect of hearing protection devices (HPDs) on speech intelligibility in Persian work environments. Three current earmuffs and three earplugs and one of the prototypes of molded earplug were tested on 15 male subjects which were randomly selected. The noise reduction of HPDs was measured based on the Real Ear Attenuation at Threshold (REAT) method. Speech intelligibility during using HPDs was determined based on the speech discrimination score (SDS) at two signal to noise (S/N) ratios (0 and + 5). Data were analyzed using SPSS 22. RESULTS: The actual to nominal noise reduction rating values were from 47 to 84% for HPDs. At two S/N ratios, no significant differences were observed in speech intelligibility using HPDs (p > 0.05). At S/N ratio = 0, the speech intelligibility descriptively has been only improved by using common earmuffs up to 9.07%. There was a significant difference up to 21.27% in speech intelligibility for proposed molded earplugs at S/N ratio = 0 (p < 0.05). Increasing the HPDs' noise attenuation values led to an increase in speech interference (p < 0.05). The HPDs with the minimum required noise attenuation while maintaining acceptable speech intelligibility should be worn by employees exposed to medium noise levels.

Combined effects of noise and air temperature on human neurophysiological responses in a simulated indoor environment.

The aim of the present study was to evaluate the combined effects of noise and air temperature on the human body neurophysiological responses. This study was conducted on 35 male students, who were exposed to four different air temperatures (18 °C, 22 °C, 26 °C, and 30 °C) and two noise levels (55 dBA and 75 dBA) in eight sessions in a simulated indoor environment. The mean values of accuracy and time of response to stimuli in N-back test as well as neurophysiological responses were measured. In the studied experiment configurations, with increasing air temperature and noise, the working memory and neurophysiological responses were disturbed. The results indicated the significant effect of noise on working memory, as compared with that of air temperature. The effects of air temperature on heart rate, respiratory rate as well as theta and alpha bands were more significant than the impact of noise. The combined effects of noise and air temperature were more significant than the influence of each of them alone. In the presence of high noise levels, the increase in air temperature did not worsen the response accuracy. However, in the presence of high noise level, the rise in air temperature aggravated the mean value of neurophysiological responses. Overall, noise has a greater effect on working memory, while the air temperature can disturb neurophysiological responses in a more profound way.

The impact of indoor air temperature on the executive functions of human brain and the physiological responses of body.

Background: This study aimed to investigate the effect size (ES) of air temperature on the executive functions of human brain and body physiological responses. Methods: In this empirical study, the participants included 35 male students who were exposed to 4 air temperature conditions of 18°C, 22°C, 26°C and 30°C in 4 separate sessions in an air conditioning chamber. The participants were simultaneously asked to take part in the N-back test. The accuracy, electrocardiogram (ECG) signals and the respiration rate were recorded to determine the effect of air temperature. Results: Compared to moderate air temperatures (22°C), high (30°C) and low (18°C) air temperatures had a much more profound effect on changes in heart beat rate, the accuracy of brain executive functions and the response time to stimuli. There were statistically significant differences in the accuracy by different workload levels and various air temperature conditions(P<0.05). Although the heart beat rate index, the ratio between low frequency and high frequency (LF/HF), and the respiratory rate were more profoundly affected by the higher and lower air temperatures than moderate air temperatures (P<0.05), this effect was not statistically significant, which may be due to significant reduction in the standard deviation of normal-to normal intervals (SNND) and the root of mean squared difference between adjacent normal heart beat (N-N) intervals (RMSSD) (P>0.05). Conclusion: The results confirmed that the unfavorable air temperatures may considerably affect the physiological responses and the cognitive functions among indoor employees.Therefore, providing them with thermal comfort may improve their performance within indoor environments.

The Effects of Noise on Human Cognitive Performance and Thermal Perception under Different Air Temperatures.

BACKGROUND: Environmental factors are interrelated, and human comfort is a complex state that is under the influence of all these factors perceived by a person. We aimed to investigate the effects of noise on human cognitive performance and thermal perception under different air temperatures. STUDY DESIGN: An experimental study. METHODS: This study was conducted on 24 volunteers (12 males and 12 females) aged 18-30 yr old. All the experiments were carried out in a climate chamber located in Hamadan University of Medical Sciences in 2018. The subjects were exposed to ten different conditions set by a combination of three different air temperatures (14, 18, and 22 °C), three different noise levels (55, 65 and 75 dBA), and one irrelevant speech level in the climate chamber. The n-back, CPT, and PVT tests were employed to evaluate different aspects of cognitive performance. Thermal comfort and thermal sensation were measured with subjective questionnaires. RESULTS: With increasing noise under different air temperatures, working memory (P=0.001), sustained attention (P=0.001), and simple reaction time (P=0.001) were significantly disturbed. The combined effects of noise and low air temperature on working memory, sustained attention, and reaction time were higher than the effect of each of them individually. As compared with air temperature, noise has a larger effect on working memory, sustained attention, and reaction time in the test configurations. CONCLUSION: The cognitive performance effects from noise has one veto power over these effects from low air temperature. Speech sound had more negative effects on subjects' cognitive functions than the typical noise caused by office equipment. The subjective thermal perceptions were also influenced by noise at lower air temperatures.

Effects of light intervention on alertness and mental performance during the post-lunch dip: a multi-measure study.

Disrupting sleepiness and fatigue during the post-lunch dip by environmental factors may result in a decrease in human errors and accidents, and enhance job performance. Recent studies have shown that both red white light as well as blue white light can have a positive effect on human alertness and mental functioning. In the present study, the light intervention was evaluated for its effectiveness on alleviating the post-lunch dip. Twenty healthy volunteers experienced 117 min of four light conditions preceded by a 13-min initial dim light while performing a continuous performance test (CPT) and undergoing recording of the electroencephalogram (EEG): blue-enriched white light (12,000 K, 500 lx, BWL), red saturated white light (2,700 K, 500 lx, RWL), normal white light (4,000 K, 500 lx, NWL), and dim light (<5 lx, DL) conditions. Other outcome measures were subjective sleepiness, mood, and performance tests (working memory, divided attention, and inhibitory capacity). We found that exposure to both BWL and RWL conditions decreased the lower alpha-band power compared to the NWL and DL conditions. No significant differences were observed in subjective sleepiness and mental performance during sustained attention, working memory, and inhibitory capacity tasks between NWL, RWL, and BWL conditions. The present findings suggest that both RWL and BWL, compared to NWL condition, can improve the physiological correlates of alertness in EEG measurements. However, these changes did not translate to improvements in task performance and subjective alertness.

The combined effects of occupational exposure to noise and other risk factors - a systematic review.

PURPOSE: Noise-induced health effects exacerbate by many other risk factors. This systematic review aims at shedding light on the combined effects of co-exposure to occupational noise and other factors. MATERIAL AND METHODS: A literature search in Web of Science, Scopus, PubMed, Science Direct, and Google Scholar, with appropriate keywords on combined effects of occupational noise, and co-exposure to noise and other factors, revealed 7928 articles which were screened by two researchers. A total of 775 articles were reviewed in full text. We found 149 articles that were relevant and had sufficient quality for analysis. RESULTS: We identified 16 risk factors that exacerbate occupational noise-induced health effects. These factors were classified into four groups: chemical (carbon monoxide (CO), solvents, heavy metals, and other chemicals), physical (lighting, heat, vibration, and cold), personal (age, gender, genetics, smoking, medication, contextual diseases) and occupational (workload and shift work). Hearing loss, hypertension, reduced performance, and cardiovascular strains, are the most important risk factors combined effects due to concurrent exposure to noise and other risk factors. CONCLUSION: Evidences of combined effects of solvents, vibration, heavy metals, CO, smoking, chemicals, aging, heat, and shiftwork were respectively stronger than for other factors. Most of the studies have investigated only the combined effects of risk factors on hearing, and the evidence for non-auditory effects is still limited, and more studies are warranted. Therefore, in the Hearing Conservation Programs, besides noise, aggravating factors of noise effects should also be taken into account.

Non-Image Forming Effects of Light on Brainwaves, Autonomic Nervous Activity, Fatigue, and Performance.

Fatigue and sleepiness are one of the main causes of human errors and accidents in the workplace. The empirical evidence has approved that, in addition to stimulating the visual system, light elicits brain responses, which affect physiological and neurobehavioral human functions, known as the non-image forming (NIF) effects of light. As recent evidences have shown the positive effects of red or low correlated color temperature white light on alertness and performance, we investigated whether exposure to 2564 K light could improve subjective and objective measures of alertness and performance compared with 7343 K, 3730 K, and dim light (DL) conditions during the daytime. Twenty two healthy participants were exposed to the light while they were performing a sustained attention task and their electroencephalogram (EEG) and electrocardiogram (ECG) were recorded. Both 2564 K and 7343 K conditions significantly reduced EEG alpha-power compared with the DL and 3730 K conditions. Moreover, the 2564 K, 7343 K, and 3730 K conditions significantly reduced subjective fatigue, sleepiness and increased heart rate and performance compared with the DL condition. Furthermore, the effects of light conditions on alertness and performance varied over the day so that more effective responses were observed during the afternoon hours. These findings suggest that light interventions can be applied to improve daytime performance.