سیامک پورعبدیان

Choosing the suitable hearing protection for workers as part of the Hearing Conservation Program was introduced as a final measure. This study aimed to investigate the absorption and transmission loss of common earmuffs at one third octave band frequencies using the impedance tube method.

An analytical-experimental study was carried out on absorbers of four earmuff models. The transmission loss of the absorbers was measured using the impedance tube by the transfer function method, in accordance with the ISO 10534-2 standard. Data analysis was conducted using the paired-samples t-test and analysis of variance (ANOVA) with SPSS software.

The highest and lowest mean transmission losses measured in absorbers were 27.5 dB and 0.3 dB, respectively. The results showed a significant difference in the mean transmission loss between absorber A and absorbers B, C, and D, as well as between absorber B with absorbers A and D, across all measured frequencies (P < 0.05). Moreover, the results showed a significant difference in all frequencies before and after in absorbers A, B, and C (P < 0.05).

When comparing earmuff absorbers, it is evident that their performance in transmission loss and efficiency varies across different frequencies. In addition, most of the earmuffs examined in the study showed a decrease in transmission loss at low frequencies as the frequency increased. However, above2 kHz, an increasing trend in transmission loss was observed. These results need to be noted when choosing suitable hearing protection for workers in industries.

Using a hearing protection device is one of the ways to control noise pollution in the industry. The purpose of the present study is to evaluate the changes in the sound absorption coefficient of some commonly used earmuffs in laboratory conditions at various sound levels and frequencies.

In this study, four earmuff models, including TASCO2550, AKHAVAN (VENUS-740), 3M optime98, and Parkson ABZ, were prepared. The absorber of the earmuffs was then cut to a diameter of 3 cm and a thickness of 1.2 cm. The absorption coefficient of each sample was measured using an impedance tube and VA-Lab4 software at three sound levels of 75, 85, and 95 dB. Finally, the data were analyzed using SPSS software.

There was no significant difference in the average absorption coefficient between sound levels of 75, 85, and 95 dB. However, in middle and high frequencies, the average absorption coefficient increased. TASCO2550 earmuff absorbent samples showed the highest absorption coefficient at frequencies of 2000-2500 Hz. While AKHVAN (VENUS-740) and 3M optime98 absorbent samples showed the highest average absorption coefficient at the frequency of 4000 Hz. Also, The Parkson ABZ absorbent sample had the highest average absorption coefficient at a frequency of 5000 Hz. In general, The TASCO2550 earmuff absorbent sample showed the highest absorption coefficient, while the 3M optime98 absorbent sample showed the lowest absorption coefficient.

By selecting an earmuff with efficient absorber, we can increase sound absorption rate to achieve the desired results of reducing noise pollution.

The aim of this study was to investigate the level of noise exposure and its relationship with job stress, changes in blood pressure and heart rate among woodworking workshop workers.

In this cross-sectional-analytical-descriptive study, 140 employees of a lumber workshop in Mazandaran province were selected and divided into case and control groups. Demographic information of employees was collected by questionnaire. Systolic and diastolic blood pressure were measured using mercury sphygmomanometer. Heart rate of the case and control groups was measured by Beurer pulse meter. The results were analyzed using SPSS software.

The results of noise measurements showed that the mean noise exposure in workers from 8-hour shifts was 92.11 dB and among non-exposed group was 74.48 dB. The mean systolic and diastolic blood pressure in the control and exposure groups were 124, 126, 80 and 82, respectively. Also, the mean heart rate of the studied groups was 74.9 and 75.83 beats per minute, respectively. There was no significant difference in systolic and diastolic blood pressure and heart rate between the two groups, (p> 0.05).

Based on thefindings, the rate of systolic and diastolic blood pressure, as well as the heart rate and stress levels were higher in the exposed group as compared with the control group; however, the difference between systolic, diastolic blood pressure and heart ratebetween the two groups was not statistically significant. There was a significant difference in stress. It was found to be consistent with the results of some previous studies

The widespread use of cell phones has led to an increase in concern about the effect of radiofrequency radiation on the physiology of the human body. This study was conducted to determine the different reaction temperatures of different brain tissue in exposure to mobile radiofrequency waves.

This was an experimental study. The cow's brain tissue was examined in a chamber at three depths of 2,12 and 22 mm and at a distance of 4 mm and 4 in the cell phone from the tissue for 15 min of the radiofrequency radiation of the mobile phone during exposure and after the exposure was discontinued. . Luteron thermometer was used to measure tissue temperature.

During the exposure to the brain tissue at a distance of 4 mm from the mobile phone, the temperature increase at 22 mm depth was more than the depths of 2 and 12 mm, so that the tissue temperature at 2, 12 and 22 mm depths was 29 ° C 0 /, 0.3 / 0 and 0/37 respectively. Also, the temperature of the brain tissue at 4 cm intervals was greater than the other depths with increasing tissue depth. An increase in tissue temperature was also associated with increased brain tissue depth after exposure to mobile phones. The temperature of the depth of 22 mm of texture increased during exposure to higher temperatures.
 

Mobile radiofrequency waves not only increased the temperature of the tissue at all depths of the brain but at higher depths (22 mm), brain tissue was higher than the temperature of mobile radiofrequency waves.

Noise is one of the most common stress-inducing factors in a workplace and can cause many detrimental effects. Regarding this, the present study was conducted to investigate the effects of exposure time to noise and sound pressure level on mental fatigue and release of noradrenaline in the human body under lab situations. This study was conduced on 10 students of Isfahan University of Medical Sciences, Isfahan, Iran, during 4 consecutive days. The subjects were exposed to the noise levels of 85 and 90 dB on the first (0.5 h)/second (1 h) and third (0.5 h)/fourth (1 h) days, respectively. They solved 20 mathematic questions before and after exposure to noise every day, and then marked their fatigue severity on a visual analog scale. In addition, blood samples were collected before and after exposure to noise. The data were analyzed in SPSS software (verion 20). The noradrenaline level estimated after 0.5 h exposure to 90 dB was significantly different with the level obtained after 1 h exposure to the same sound level (P=0.037). However, no significant difference was observed for other exposure durations. Furthermore, the mental fatigue degrees evalauted before exposure to the sound pressure levels of 85 and 90 dB were significanty different form those measured after exposure to these pressure levels in all situations. As the findings indicated, the elongation of time exposure to noise led to the elevation of mental fatigue; however, it resulted in no change in the level of noradrenaline. Furthermore, the rise of noise level from 85 to 90 dB did not lead to the elevation of mental fatigue and noradrenaline release. Consequently, it seems that increased exposure time to noise is more important in causing mental fatigue than the sound pressure level in a short period of time.

Considering the great advances and extensive use of cell phones and its effects on the human communications and interactions, investigation of potential negative effects of cell phones on the user's health is necessary. The aim of this study was to determine the effect of the distance between cell phones and brain tissue on the temperature of the central and gray matters of the brain, because of the heat generated by radiofrequency waves.
This was an experimental study. Cow brain tissue was analyzed in a compartment with three depths of 2 mm, 12 mm and 22 mm, and at the distances of 4 mm and 4 cm from a cell phone, for 15 minutes. Lutron thermometer was used to measure the tissue temperature. Data analysis performed by using Lutron and MATLAB software packages.
Temperature increase was more at the distance of 4 mm and in the depths of 2, 12, and 22 mm compared to that at the distance of 4 cm. Also temperature increase after removal of the confrontation was more than the baseline temperature at both distances which was higher at the distance of 4 mm.
Decreased distance between brain tissue and cell phone can increase the tissue temperature. Increasing the cell phone distance from the brain tissue can result in slower trend in temperature increase and decreased collective temperature after discontinuing the confrontation.

Earplug as one of the protective equipment of the auditory system has different function at different frequencies. Thus, in this study, by simulating a model of human ear canal, protective effectiveness of earplug in sound attenuation was checked at different frequencies and different lengths of the ear canal.
In this cross-sectional descriptive-analytical study, in one side of the simulated ear canal, a microphone was used as the sound receiver, and earplug was embedded in the other end of the ear canal. After playing the pink noise through the speaker, the insertion loss (IL) of earplug at one octave frequency and at different lengths of placement of earplug in simulated ear canal (12.8, 17.5, 25.5, and 31.1 mm) was examined and the results were recorded using Labview software.
Findings: The result of insertion loss of earplug at one octave frequencies showed that in comparison with other distances, the insertion loss of earplug at 25.5 mm in low frequencies (below 500 Hz) was higher, and at this distance, the frequency at 4000 Hz reached the highest rate.
The highest rate of insertion loss was achieved for low frequencies at 25.5 mm. The average length of the human ear canal is 2.5 cm; so, in human hearing system, the highest levels of environmental sound attenuation are at the this distance. Due to the maximum insertion loss of earplug at this distance and at 4000 Hz, producing protective device from absorbent substance for this frequency is suggested.

Water and electrolytes are essential to maintain the health and performance in hot occupational environments. The aim of this study was to determine the effect of different drinks on indices HSSI, PESI and PSI under laboratory conditions.
This clinical trial study was conducted on 13 male students in hot and dry laboratory conditions, (40 ° C, humidity 30%). In 3 steps within 2 hours of interferences, water, the combination of water and lemon, and lemon juice in the amount of 400 cc for 4 times was given to the participants. Every 10 minutes from the beginning of exposure to the heat index, Heat Strain Score Index (HSSI), Perceptual Strain Index (PESI), Physiological Strain Index (PSI), heart rate and oral temperature were measured. Analysis of variance with repeated observations and post hoc test was used to analyze the data.
The results showed that the index of HSSI (P= Drinking leads to keeping and maintaining normal conditions in participants. Compared with water and the combination of water and lemon, lemon juice drink has the greatest impact in reducing the average scores in all three indicators.

Water and electrolytes can maintain thermal balance of the body at encounter to heat. The purpose of the present study was to determine the effect of different drinks on changes in physiological indexes in laboratory conditions.
This clinical trial study was conducted on 13 male students under hot and dry Laboratory condition (40 ° C, humidity 30%). People in 3 steps within 2 hours ate the interferences water, lemonade and lemon juice in the amount of 400 cc at 4 times. . Every 10 minutes, heart rate, oral temperature and skin temperature were measured. At the end of encounter, urine samples were taken to determine the temperature and turbidity, as well as the sweat was calculated.Repeated Measures ANOVA and LSD(Least significant difference) was used to analyze the data.
The results showed that the average temperature of the urine (p=0.155), turbidity of urine (p=0.171), heart rate during activity (p=0.345) and severity sweating (p=0.988) no significant difference but mean heart rate in the third minute from every 10 minutes rest (p=0.04), oral temperature (p=0.007) and skin temperature (p=0.005) were significantly different.
The effect of lemon juice compared to water lemonade and water was major to reduce physiological heat strain.

In addition to the adverse effects of noise in the auditory system, non-auditory effects can be regarded as factors which cause physiological harassment, discomfort and also disorder in cognitive functions. The present study aimed at determining cognitive function after exposuring to different levels of sound pressure level in a clinical trial study.
This study was clinical trial type (before and after clinical trial). In order to evaluate the effects of noise (65, 75 and 85 dB) on cognitive function, 12 students (6 males and 6 females) of Isfahan Medical Science University students between the ages 22 and 27 with BMI 20-25kg/m were studied. To analyze data, the statistical pair-T test was used and ANOVA (P=0.05) was run.
Applying sound pressure level of 65 dB in comparison with prior applying of 65 dB sound pressure level led to average increase in chosen reaction times colors (P=0.041) and sounds (P=0.038) were significant. Also, by increasing the sound pressure level of 65 dB to 75 and then 85 dB reaction time average increase was significant (001/0> P).
Accordingly, the 75 and 85 dB sound pressure level of 65 dB sound pressure range cannot be considered within safe limits for non-auditory effects according to its impact on cognitive function. Besides, this issue in jobs that expose people to high sound leads to disorder in cognitive function (reaction time, attention, etc.) causing the risk which must be taken into consideration.

Nursing، is one the stressful professions. The stressful factors in this job have affected nurses in a serious way. The purpose of the present study was to identify causes of job stress in nurses working in emergency wards. In this analytical study، 84 female nurses of emergency wards were selected by stratified sampling، and female clerks of hospitals by quota sampling (42 individuals in each group). The data collection tool was the Persian short version of generic job stress questionnaire of the National Institute for Occupational Safety and Health (NIOSH). After collecting information، data were analyzed using Student’s t-test، ANOVA، and Pearson correlation tests. For all tests، P = 0. 05 was considered as the level of significance. The mean score of job stress was 97. 30 ± 9. 29 and 91. 85 ± 10. 91 in nurses and clerks، respectively (P = 0. 01). The results show a significant difference between the two groups with regard to the scores obtained for workload (P = 0. 005)، role control (P = 0. 02)، and social support (P = 0. 004). Nurses working in emergency wards are exposed to more stressing factors. Moreover، work load، role control، and social support are of great importance in determination of job stress in nurses working in emergency wards.

The purpose of the present study was to compare salivary immunoglobulin A (SIgA) levels of female nurses working in emergency wards with those of female hospital clerks. In this descriptive-analytical study, 42 female nurses in emergency wards and 42 female clerks of hospitals were selected. SIgA levels were determined using enzyme-linked immunosorbent assay (ELISA). The collected data was analyzed using t-test, analysis of variance (ANOVA) and Pearson's correlation coefficient. The levels of SIgA in nurses and clerks were 338.04 ± 380.93 and 706 ± 354.70, respectively (P < 0.001). SIgA levels had significant differences between 20-29 year-old and 30-39 year-old members of the two groups (P = 0.001 and P = 0.02, respectively). Moreover, SIgA levels were significantly different between nurses and clerks with different working experience. The results of the current study confirmed that working in stressful emergency environments has a significant relationship with decreased SIgA level. These findings may suggest SIgA as a biomarker of psychological stress.

A lot of research has been done on the post-traumatic stress, but few studies have investigated the effect of chronic stress disorders on physical and psychological health. This study investigated the combined interactive effects of chronic stress disorders and mental disorders on somatoform disorders reporting among employees at Isfahan Steel Company. In this correlational study, 189 employees in Isfahan Steel Company wwere selected according to the stratified random sampling method and completed demographic characteristics, chronic stress disorders of Cohen, Karmark, and Mermelstein, and mental disorders and somatoform disorders of Barling, Loughlin, and Kelloway questionnaires in 2011. Data were analyzed using Pearson correlation coefficient and hierarchical regression. Results showed significant internal correlations among chronic stress disorders, mental disorders, and somatoform disorders (p<0.01). In addition, by controlling for demographic variables, the results of hierarchical regression analysis showed the interactive effect of chronic stress disorders and mental disorders on reporting somatoform disorders to be significant (p<0.05). This study showed that chronic stress disorders have a positive relationship with reporting somatoform disorders both in experiencing and not experiencing psychological disorders; however, this relationship was stronger when employees in addition to chronic stress disorders experienced psychological disorders.

Technology- related tools, including computers and video display terminals (VDTs), are rapidly expanding as a result of the quick growth of technology itself. Investigation on the complaints of VDT users reported visual discomfort. This study aimed to design an appropriate tool to assess visual fatigue of VDT users. This cross-sectional study was performed on 248 VDT users in different professions during 2011. After reading books, articles, and similar questionnaires, question banks were provided and an initial questionnaire was developed. Validity and reliability of the questionnaire were evaluated by Cronbach's alpha coefficient and content validity index (CVI). A theoretical model based on four categories of symptoms of visual fatigue, extracted from previous studies, was designed. AMOS software was used to assess the validity of its constructs using confirmatory factor analysis and fitted parameters. Using the SPSS18, internal correlation coefficients of the domains were calculated. In order to investigate the reliability and grade the final scores of the questionnaire, visual fatigue was simultaneously assessed by the questionnaire and the VFM-90.1 device and the results were compared. In addition, cutting points were determined by the ROC curve. A minimum CVI of 0.75, reliability coefficient of 0.755, model fit indices of RMSEA = 0.026, GFI = 0.96 and AGFI = 0.92 were found. The correlation between the results measured with a questionnaire and VFM-90.1 was -0.87 and the cut-off points were calculated as 0.65, 2.36 and 3.88. Four main domains of the questionnaire, including eye strain (4 questions), visual impairment (5 questions), surface-related impairments of the eye (3 questions) and problems outside the eye (3 questions), were approved. The questionnaire contained 15 questions to assess visual fatigue. It had excellent reliability and validity. Therefore, VDT users can easily assess their extent and level of visual fatigue by this relatively short and simple questionnaire.

Background and aimsNegative job stress puts harmful effects on physical and psychological health of workers. However, the effects of stress can be mediated by other variables. This study examines the relationship between job stress, work pressure and the rate of reported incidents. Methodsstatistical research community included all workers of Isfahan Steel Company in the winter 1388 that among them, 189 individuals were selected as sample using stratified random sampling method (from the list of workers per sector) and they responded to questionnaires including 10 questions of job stress, 4 questions of work pressure and 22 questions of the rate of reported incidents. Data were analyzed using Pearson correlation coefficients and hierarchical regression.ResultsResults showed that there was a significant internal correlation among study variables (job stress, work pressure and the rate of reported incidents) (p<0.05). In addition, regression analysis showed that job stress on the rate of incidents reported directly and indirectly through perception of job pressure was effective (p<0.05). Similarly, in the inverse mediation analysis, job stress mediated relationship between work pressure and the rate of reported incidents (p<0.05).ConclusionReducing job stress by changing workers’ perceptions of work pressure can lower the rate of reported incidents and also the reduction of work pressure perception by improving job stress can be effective in incidence of occupational accidents.

Millions of occupational accidents and disease cases are reported from work places annually causing considerable human and financial damages. Safety training is globally considered the best strategy to mitigate these damages. In this project a safety attitude questionnaire was used to obtain the required information. The questionnaire contained items about 13 relevant variables: job conscientiousness, fatalism, leadership, safety consciousness, role overload, work pressure, job safety perception, supervisor safety perception, coworker safety perception, management safety perception, safety program and policies perception, interpersonal conflicts at work, and job involvement. A total of 204 individuals (101 in the control and 103 in the experiment group) in the Isfahan Steel Company completed the safety attitude questionnaire. This was followed by a 4-hour safety training course attended by the experimental group. After 30 days both the experimental and control group completed the questionnaire again. Descriptive statistics and covariate analysis were used the compare the data between the 2 groups. Safety training in the workplace influenced positively the general attitude of the personnel towards safety issues. Further analysis of the data revealed that the training affected statistically significantly only safety consciousness, leadership, and management safety perception. Assessment of safety attitude in the workplace and its dimensions can be used to identify those areas of safety training that need more attention and a better design.

Workers working in car painting workshops are exposed to different contaminants including isocyanates. One of the most important sequelae of this exposure is occupational asthma. The aim of this study was to identify alterations in peak expiratory flow test in the workers working in the car painting workshops. This was a cross-sectional descriptive study. 43 workers were selected randomly from the car painting workplaces in Isfahan. The peak expiratory flow of the workers was measured by means of a peak flow meter set at the beginning and at the end of the work shift, for one week. The mean percentage of alterations in peak expiratory flow was 6.91% on the first day and 8.11% on the last day of week. The mean percentage of alternation of peak expiratory flow of the workers were 11.2±1.8 and 7.9±1.9 an the day of exposure to the contaminants after painting, and also one day after exposure respectively, which was indicative of pathological changes in the lungs of the workers, as shown by standard tests of pulmonary function. 72% of the workers after exposure to the contaminants showed alternation of more than 10% in the peak expiratory flow. This study showed there is high risk of occupational asthma and other lung diseases in the workers working in car painting workshops and peak flow meter test can be useful for assessment of pulmonary disorders

The concept of perceived organizational support (POS) has received considerable attention in the literature. However, little attention has been paid to this construct within safety field of study. This study is designed to fill the void in our knowledge about the relationship between perceived organizational support and safety. This study is based on three premises: (1) Perceived organizational support for safety (POSS) is associated with safety-related events, (2) providing safety training increases workers’ perception of organizational support. A sample of employees working in a large manufacturing firm, Isfahan Steel Company, completed the survey questionnaire. The questionnaire included perceived organizational support for safety and safety-related events measures. Data were analyzed using ANCOVA and correlation analyses. Results provided support for the research hypotheses. Findings suggest that improving employees’ perception of organizational support decreases safety-related events which in turn can reduce the frequency of accidents, injuries, and fatalities in the organizations.

Driving is a usual job with many occupational complications. Occupational hearing loss in track driver is not an unusual occupational problem. We studied the relation of occupational hearing loss and long term noise exposure in track drivers. This descriptive study was done among track driver population in Kashani and Al-Zahra hospitals in Isfahan. Taking medical history and physical examination were done by an expert otolarygologist and then, eudiometry was done. The data were analyzed by paired-t and variance regression tests via SPSS11.5 software. In 384 track drivers, hearing threshold in left ear was more than hearing threshold in right ear (P < 0.001). In this study, such as the other studies, a relation between persistent noise and hearing loss was observed. In track drivers, persistent noise can cause occupational hearing loss and their left ears are more susceptible than the rights in risk.

The aim of this study was to evaluate the relation of intensity of low back discomfort with two factors that contribute to low back pain -Ergonomics risk factors and psychosocial factors- most seen in emergency unit nurses. This cross-sectional survey was conducted on 120 emergency unit nurses in Isfehan. For daily assessment of psychosocial and Ergonomics factors and intensity of Low back discomfort, questionnaires such as: Job Content, Ergonomics hazards and Nordic questionnaire were used respectively. Nurses were questioned during a 5-week period, at the end of each shift work. Using Spearman, Mann-Whitney and Kolmogorov-Smirnove test, the final results were analyzed with SPSS software18/PASW. There was significant relationship between work demand, job content, social support and intensity of low back discomfort (P-value<0.05). But there was not any link between intensity of Low Back discomfort and decision latitude. Also there was significant relationship between Intensity of low back discomfort and Ergonomics risk factors. This study showed that intensity of low back discomfort will increase with decreasing social support and increasing work demand, Job Content and Ergonomics factors. So, to decrease work related low back discomfort, psychosocial factors should be attended in addition to Ergonomics factors.

Introduction & The aim of this study was to evaluate the relation of intensity of low back discomfort with two factors that contribute to low back pain-Ergonomics risk factorsand psychosocial factors- most seen in emergency unit nurses. This cross-sectional survey was conducted on 120 emergency unit nurses in Isfahan. For daily assessment of psychosocial and Ergonomics factors and intensity of Low back discomfort, questionnaires such as: Job Content, Ergonomics hazards and Nordic questionnaire were used respectively. Nurses were questioned during a 5-week period, at the end of each shift work. Using Spearman, Mann-Whitney and Kolmogorov-Smirnove test, the final results were analyzed with SPSS software18/PASW.There was significant relationship between work demand, job content, social support, Ergonomics risk factors and intensity of low back discomfort (P-value<0.05). But there was not any link between intensity of Low Back discomfort and decision latitude.This study showed that intensity of low back discomfort will increase with decreasing social support and increasing work demand, Job Content, Ergonomics factors, manual patient handling and repetitiveness, standing continuously more than 30 minutes). So, to decrease work related low back discomfort, psychosocial factors should be attended in addition to Ergonomics factors.

BackgroundThis paper aims to study the emergency reactions training in employee's safety consciousness regarding the importance of safety trainings and careful planning in order to prevent and minimize disasters.MethodsThe research methodology involved the study of 50 employees of Esfahan Steel Company by stratified random sampling in 2009. Control and experimental groups were selected and evaluated in pretest and posttest after one month. The data was surveyed by using of SPSS, covariance and safety survey of Munteanu.FindingsBased on the test score, emergency reactions training boosted the employee's safety consciousness compared with the meaningful relation of pretest and posttest scores. (p<0/05)ConclusionThe results show that emergency reactions training improve the employee's safety consciousness.

This study investigated different causes of bladder cancer. We followed two chief objectives first to identify high-risk occupations in Isfahan and second to re-inspect occupations that were in relation with bladder cancer. In this cross control study, 300 bladder cancer cases and 500 hospital controls were interviewed. The cases and controls were matched for age and sex; and demographic information, occupational history and exposure history to the chemical compounds such as aromatic amines were collected. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated by unconditional logistic regression for each occupation. After grouping job titles based on international standard classification of occupations (ISCO-08), there was a significant association for increased risk of bladder cancer among truck and bus drivers (OR=11.3), farmers (OR=6.04), Metal industry workers(OR=6), domestic housewives (OR=5.9), and construction workers (OR=3.8),. There was no significant relation ship between bladder cancer in workers and textile, paint, rubber, print, leather and shoe. Truck and bus drivers, farmers, metal industry workers, domestic wives, and construction workers demonstrated a major association between occupation and elevated risk of bladder cancer. The findings of this investigation should be tested in the future studies, in particular since exposures to agents such as cutting fluids or aromatic amines in metal industry workers and farmers.