|Year : 2017 | Volume
| Issue : 2 | Page : 595-601
Respiratory and auditory disorders in a ceramic manufacturing factory (Queisna City, Menoufia Governorate)
Gaafar M Abdel Rasoul, Safaa Badr, Heba K Allam, Hala M. M. Gabr, Amira M Abdel Monaem
Department of Public Health and Community Medicine, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||01-Nov-2016|
|Date of Acceptance||24-Dec-2016|
|Date of Web Publication||25-Sep-2017|
Amira M Abdel Monaem
Department of Public Health and Community Medicine, Faculty of Medicine, Menoufia University, Shebin Al-Kom, Menoufia, 32511
Source of Support: None, Conflict of Interest: None
The aim of this study was to evaluate respiratory and auditory disorders among workers in a ceramic manufacturing factory and their relationship with workplace environment in the same factory.
The ceramic industry is one of the most hazardous industries to the respiratory system. In addition, disorders due to occupational exposure to noise are possible.
Participants and methods
A cross-sectional, comparative study was carried out on 138 workers in a ceramic manufacturing factory and 138 nonoccupationally exposed participants (control group). An environmental study for total, respirable, and differential dusts and noise was carried out. Spirometric measurements, audiometric assessment, and plain chest radiography were applied.
The mean value of respirable dust level, free crystalline silica concentration, and noise levels were higher than international permissible levels. Ceramic manufacturing factory workers had a higher significant prevalence of respiratory and auditory manifestations as well as deteriorated spirometric measurements, abnormal audiometric assessment, and abnormal radiological findings.
Exposure to free crystalline silica concentrations more than permissible levels results in abnormal spirometric measurements and abnormal radiological findings. Continuous exposure to noise levels more than 90 dBA leads to abnormalities in audiogram in the form of threshold shifting and V-dip depression. Regular use of good-quality personal protective equipment, especially masks and ear muffs, and periodic medical examination are highly recommended.
Keywords: audiometry, ceramic, noise, silicosis, spirometry
|How to cite this article:|
Abdel Rasoul GM, Badr S, Allam HK, Gabr HM, Abdel Monaem AM. Respiratory and auditory disorders in a ceramic manufacturing factory (Queisna City, Menoufia Governorate). Menoufia Med J 2017;30:595-601
|How to cite this URL:|
Abdel Rasoul GM, Badr S, Allam HK, Gabr HM, Abdel Monaem AM. Respiratory and auditory disorders in a ceramic manufacturing factory (Queisna City, Menoufia Governorate). Menoufia Med J [serial online] 2017 [cited 2020 Sep 22];30:595-601. Available from: http://www.mmj.eg.net/text.asp?2017/30/2/595/215470
| Introduction|| |
Workers of the ceramic industry are occupationally exposed to respirable crystalline silica (RCS) derived from ceramic raw materials . The seriousness of health disorders related to RCS exposure is proved by the fatalities and disabling illnesses that keep on occurring after discontinuance of exposure .
Silicosis is the main occupational lung disease caused by inhalation of respirable dust containing crystalline silica . Simple nodular chronic silicosis is the most frequently observed type of silicosis. It results from long-term exposure to low amounts of silica dust that exceed the permissible exposure level. It is recognized radiographically with multiple small nodules ranging from 1 to 10 mm in diameter with upper zone predominance . It may be asymptomatic or may present with exertional dyspnea and cough with sputum production .
There are three requirements for the diagnosis of silicosis. The first is a history of silica exposure sufficient to cause illness. The second is the presence of chest radiography that shows opacity with International Labor Office (ILO) category 1/0 or more consistent with silicosis. The third is the absence of other illnesses that mimic silicosis . Health disorders other than silicosis related to RCS exposure include chronic obstructive pulmonary disease , lung cancer , silica nephrotoxicity , and autoimmune diseases .
Noise emissions occur in several steps of ceramic manufacturing . Noise adversely affects cochlear hair cells through vascular, mechanical, and metabolic changes. Occupational noise-induced hearing loss results from continuous or intermittent exposure to loud noise of moderate intensity ranging from 85 to 130 dBA (A-weighted sound levels are decibel scale readings that have been adjusted to take into account the varying sensitivity of the human ear to different frequencies of sound)  over many years at the workplace .
The ceramic and antimelting materials industries represents one of the seven major industries in the Egyptian market with a large number of workers ; therefore, our aim was to study health disorders among workers in a ceramic manufacturing factory and the relationship with workplace environment in the same factory as an attempt for proper control and prevention of such disorders.
| Participants and Methods|| |
This study was carried out in a ceramic manufacturing factory (in industrial zone, Queisna City, Menoufia Governorate, Egypt) between June 2015 and October 2016. The industrial processes in this factory include preparation and processing of the ceramic tile body, glaze preparation, glaze application lines, firing, and sorting. A cross-sectional comparative study was designed to evaluate all occupationally exposed male workers (150 workers) from the expected dusty department 'preparation and processing of the ceramic tile body' in the studied factory. The response rate was 95%, with exclusion of seven workers (nonresponders). After application of exclusion criteria, which included workers who had any chronic respiratory, auditory, and liver and kidney diseases before employment in the factory, five workers were excluded. Therefore, the number of studied workers included in this study was 138.
A control group of 138 male individuals were selected from relatives of the exposed individuals, who were never occupationally exposed to similar hazards neither in ceramic-processing factories nor in corresponding works; they were matched with the exposed group for age, residence, education, and income. Participants were interviewed between 7:00 a.m. and 3:00 p.m. Each participant was subjected to questionnaire interviews as well as spirometry and audiometry measurements.
In the questionnaire interviews, detailed descriptive information was collected, including personal characteristics, occupational lifestyles, working positions, working environment, and personal hygiene. Direct observations were also made and recorded to confirm the questionnaire results. In addition, medical history of respiratory, auditory manifestations, heat stroke, heat exhaustion, heat cramps, sterility, cataract, and skin rash as well as past history of diseases (e.g., respiratory, auditory, skin, renal, hepatic disorders, diabetes mellitus, and hypertension as well as skin, chest, or eye allergies) were collected.
Spirometric measurements were performed using the Medical Equipment Europe, PARI Medical Holding GmbH (Starnberg, Germany) Smart Pulmonary Function Test Universal Serial Bus Spirometer to determine forced vital capacity (FVC%), forced expiratory volume at the first second (FEV1%), forced expiratory ratio (FEV1/FVC%), forced expiratory flow during 25–75% of FVC (FEF25–75%), and peak expiratory flow (PEF%). The best value of three technically acceptable maneuvers was recorded and expressed as percentages of predicted values. An automatic comment that represented interpretation was obtained.
Audiometric measurements were carried out using diagnostic audiometer AS67 (Danplex, Spain). Air conduction audiometric examination was performed at different frequencies (250, 500, 1000, 2000, 4000, 6000, and 8000 Hz) for right and left ears separately for both exposed workers and controls. Three measures were taken at 1000 Hz, at the beginning, during, and at the end of the assessment. The mean of intensities of the three measurements at 1000 Hz was taken to assure the compliance of the individual.
Plain, posteroanterior, full-sized (14 × 14 inches) chest radiography was performed for workers with abnormal findings in spirometric measurements. It was performed on six workers/day at the Radiology Department of Menoufia University Hospital. Three radiologists interpreted the radiographic films and compared them with ILO standard films for ILO classification .
For dust analysis, air samples were collected using Heto Personal Dust Sampler (New Delhi, India) which is composed of cyclone loaded with 25-mm cellulose membrane filters and a sampling pump for respirable dust measurements and without cyclone for total dust measurements. The flow rates were 2 L/Min, and sampling periods were ∼8 h/sample. The cyclones were fixed on workers' clothes at the breathing zone, which is the area bordered by the outside of the shoulders and from the midchest to the top of the head. The collected samples were shipped to the analytical laboratory at the National Research Center (Dokki, Cairo) for analysis using spectrophotometry of free silica levels.
Noise level was measured using Lutron SL-4001 Digital Sound Level Meter (Lutron, Princeton Junction, New Jersey, United States); this was performed at the level of workers' ears, where they usually stood during their regular work. The apparatus was set up on the fast (A) scale. Measurements were obtained twice/year by the Environmental Study and Research Institute, Elsadat City, in response to the factory requisite. Three readings were taken each time, and the mean reading was recorded.
This study was approved by the Menoufia Faculty of Medicine Committee for Medical Research Ethics. All the participants received a clear explanation of the purpose of this study and agreed to participate after signing consent forms. All personal information about the study participants were kept confidential. Approval from the factory management was also obtained.
Statistical analyses of data were conducted with statistical package for the social sciences (SPSS, version 22; SPSS Inc., Chicago, Illinois, USA). Student's t-test was used for comparing means of continuous quantitative parametric variables and Mann–Whitney U-test for nonparametric variables. The χ2-test was used for categorical variables and the Fisher exact test for categorical variables when the expected value was less than 5. Spearman's correlation coefficient (r) was used to measure the association between two quantitative variables. Statistical significance was accepted at P less than 0.05 for results that were two tailed.
| Results|| |
One hundred and thirty-eight male workers of a ceramic manufacturing factory and 138 matched controls were included in this study. The exposed group and controls were matched for age, sex, socioeconomic standard, educational level, residence, and marital status (P < 0.05).
The environmental measurements recorded showed that the mean value of respirable dust was 3.2 ± 0.37 mg/m 3, which is higher than the permissible level of the Egyptian Environmental Law 4 Decree 1095 , and free crystalline silica dust (SiO2) was 54.0 ± 5.3 μg/m 3, which is higher than the permissible level of The Egyptian Environmental Law 4 Decree 1095  and threshold limit value of National Institute for Occupational Safety and Health (NIOSH) . In addition, noise levels had a mean value of 90.3 ± 4.2 dBA, which is higher than the maximal permissible limit of Egyptian Environmental Law 4 Decree 1095  and NIOSH  as shown in [Table 1].
|Table 1: Mean±SD of environmental measurements in the work environment of the exposed group|
Click here to view
The present respiratory manifestations including rhinitis, cough, expectoration, wheezes, dyspnea, chest pain, and chronic bronchitis were significantly more prevalent among exposed individuals (9.4, 24.6, 21.0, 14.5, 15.2, 8.7, and 8%, respectively) compared with controls (2.9, 7.2, 5.1, 5.8, 5.8, 2.2, and 1.4%, respectively) (P < 0.05) [Figure 1].
On comparing workers with work duration of more than 10 years and those with work duration of less than 10 years regarding the respiratory manifestations, there was a significant higher prevalence of rhinitis, expectoration, and dyspnea among workers with work duration of more than 10 years (14.9, 28.4, and 25.7%) than those with work duration of less than 10 years (3.1, 12.5, and 3.1%) (P < 0.05) and a nonsignificant higher prevalence of cough, wheezes, chest pain, chronic bronchitis, and asthma among workers with work duration more than 10 (25.7, 17.6, 10.8, 8.1, and 4.1%) than with work duration less than 10 (23.4, 10.9, 6.2, 7.8, and 1.6%) [Figure 2].
|Figure 2: Respiratory manifestations among the exposed group according to work duration in years.|
Click here to view
Significant deteriorated spirometric measurements were observed in exposed workers than among controls as mean values of FVC%, FEV1%, FEV1/FVC%, FEF25–75%, and PEF% were 73.8 ± 16.5, 78.3 ± 15.6, 82.3 ± 6.5, 77.9 ± 24.6, and 50.7 ± 20.7, respectively, among exposed workers and 89.2 ± 6.04, 89.8 ± 5.9, 87.8 ± 10.8, 83.1 ± 11.3, and 72.9 ± 16.9, respectively, among controls (P < 0.05) [Table 2]. This deterioration was negatively correlated at a significant level with duration of work (in years) for FVC%, FEV1%, FEF25–75%, and PEF% (P < 0.05) [Table 3].
|Table 2: Mean±SD of spirometric measurements between the exposed group and the control group|
Click here to view
|Table 3: Correlation between duration of work and spirometric measurements of the exposed group|
Click here to view
Regarding auditory manifestations among the studied groups, there was significant higher prevalence of tinnitus and ear ache among exposed workers (23.9 and 15.2%, respectively) than among controls (5.8 and 4.3%, respectively) (P < 0.05). Audiometric findings revealed that 13.8% of exposed workers had hearing impairment, ranging from mild, moderate to severe degree, and 9.4% of exposed workers had V-dip depression, which represented 68.4% of hearing-impaired workers [Table 4].
|Table 4: Numbers and percentage distributions of the exposed group and the control group regarding audiograms findings|
Click here to view
Chest radiography of exposed workers with abnormal spirometric measurements (67 workers) revealed that 50 (74.6%) workers had abnormal radiological findings such as small nodular opacities of different sizes and profusion [N = 33 (66%)], increased bronchovascular markings [N = 38 (76%)], emphysema [N = 10 (20%)], and enlarged hilar lymph node [N = 5 (10%)] [Table 5].
|Table 5: Numbers and percentage distributions of radiological findings among workers with abnormal spiromertry|
Click here to view
| Discussion|| |
In the ceramic industry, numerous health hazards exist including inhalation of airborne particulate matter, especially crystalline silica included in raw materials, and exposure to noise. The present study aimed to assess some health disorders among workers in a ceramic manufacturing factory, Queisna City, Menoufia Governorate, as well as to assess workplace environment in the same factory.
This study included 276 individuals. Among them, 138 were working in the preparation and processing department of the ceramic factory and were occupationally exposed to RCS and noise. The other 138 were selected from among relatives of the studied workers without previous occupational exposure to similar hazards.
In this study, ceramic workers were exposed to respirable dust levels (3.2 ± 0.37 mg/m 3) higher than the permissible levels (3 mg/m 3) of the Egyptian Environmental Law 4 Decree 1095  and free crystalline silica dust (54.0 ± 5.3 μg/m 3) higher than the permissible level of the Egyptian Environmental Law 4 Decree 1095  and threshold limit value of NIOSH  (50 μg/m 3 = 0.05 mg/m 3).
The ceramic industry is considered to be dusty due to the high dust levels in comparison to other levels measured in other ceramics factories for example but not limited to high mean percentage of the free silica (5.2 ± 1.01%) measured in another Egyptian ceramic factory and high mean value of respirable dust level (23.4 mg/m 3) in preparation unit in Iranian ceramic factory ,.
In this study, workers were continuously exposed to noise levels reaching 90.3 ± 4.2 dBA, which are higher than the maximal permissible limit of the Egyptian Environmental Law 4 Decree 1095  of 90 dBA inside the closed work production areas (8 h/shift) and NIOSH  of 85 dBA. Similarly, studies in Iranian ceramic factories reported similar high levels of noise exposure (91.97 ± 4.15 and 92.6 dBA) ,.
The respiratory manifestations were significantly more prevalent among exposed workers than controls (P < 0.05). This may be due to respiratory hazards in the factory environment, including high levels of RCS with added effect of poor ventilation and improper use of personal protective equipment.
These results agree with those reported by Dehghan et al. , who showed that the prevalence of all respiratory complaints (dyspnea, cough, sputum, and wheezing) was significantly higher in production units in tile and ceramic factory workers (13.1, 8.2, 10.2, 4.5, and 8.6%, respectively) than executive employees of the factory (5.9, 6.5, 5.3, 2.3, and 0%, respectively). In addition, Rondon et al.  and Halvani et al.  reported similar results in other ceramic factories. Saad et al.  reported that the prevalence of chronic respiratory symptoms was significantly higher among exposed workers from a ceramic factory than among the control workers.
Duration of exposure is an important determinant of diseases developed due to RCS, and therefore particular attention was paid to compare prevalence of respiratory manifestations among workers with the duration above and below the median, which was 10 years.
The comparison showed a significant higher prevalence of rhinitis, expectoration, and dyspnea among workers with work duration more than 10 years (14.9, 28.4, and 25.7%) than those with work duration less than 10 years (3.1, 12.5, and 3.1%) (P < 0.05), and the prevalence of cough, wheezes, chest pain, chronic bronchitis, and asthma was nonsignificantly higher among workers with work duration more than 10 years (25.7, 17.6, 10.8, 8.1, and 4.1%) than among workers with work duration less than 10 years (23.4, 10.9, 6.2, 7.8, and 1.6%) (P < 0.05).
These results agree with those reported by Halvani et al.  who showed a significant relationship between years of employment and respiratory symptoms. Prevalences of lower respiratory, upper respiratory, and chronic obstructive symptoms were 79, 83, and 81%, respectively, among workers with more than 12 years of exposure, compared with 6, 3.5, and 8.2%, respectively, among workers with eight to 12 years of exposure, 9, 3.5, and 5.4%, respectively, among workers with 4–8 years of exposure, and 6, 10, and 5.4%, respectively, among workers with 1–4 years of exposure . Therefore, it is obvious that work duration affects the development of respiratory manifestations.
On comparing exposed workers and controls regarding spirometric measurements, there were significant lower mean values of FVC%, FEV1%, FEV1/FVC%, FEF25–75%, and PEF% among exposed workers (73.8 ± 16.5, 78.3 ± 15.6, 82.3 ± 6.5, 77.9 ± 24.6 and 50.7 ± 20.7, respectively) than among controls (89.2 ± 6.04, 89.8 ± 5.9, 87.8 ± 10.8, 83.1 ± 11.3 and 72.9 ± 16.9, respectively) (P < 0.05).
The FVC% and FEV1% mean values (73.8 ± 16.5 and 78.3 ± 15.6) were lower than the American Thoracic Society (ATS)  fifth percentile lower limit of normal, which is 80% of predicted for FVC and FEV1. Other spirometric readings in exposed workers were still within the normal values, but they were significantly lower than the mean values in controls (P < 0.05). Abnormal spirometric measurements suggested occurrence of lung pathology following RCS exposure, which could take an obstructive pattern due to chronic bronchitis and emphysema, restrictive pattern due to silicosis, or a combined pattern.
These results are consistent with those reported by Dehghan et al.  as a significant decrease in FVC%, FEV1%, FEV1/FVC%, FEF25–75%, and PEF% between the exposed group (88.07 ± 1144, 87.17 ± 11.80, 91.75 ± 6.46, 82.79 ± 12.40 and 80.08 ± 17.45, respectively) than between controls (92.10 ± 12.52, 92.03 ± 12.34, 97.56 ± 5.63, 86.82 ± 20.79 and 83.85 ± 20.36, respectively) was observed.
Again, effect of work duration was studied, but this time on spirometric measurements. There was a significant negative correlation between work duration and spirometric measurements (P < 0.001). In a 2-year follow-up study in five tile and ceramics factories, it was observed that FVC significantly decreased by 245 ml (P = 0.003) after 1 year and by 431 ml (P = 0.002) after 2 years . Al-Batanony et al.  also reported a significant negative correlation between duration of employment and FVC% and FEV1% in a glue factory.
This study has also considered the consequences of noise exposure. It was reported that exposed workers experienced a significantly higher prevalence of tinnitus and ear ache (23.9 and 15.2%, respectively) than controls (5.8 and 4.3%, respectively) (P < 0.05). High prevalence of auditory manifestations was reported as a consequence of exposure to high noise levels by Ahmed et al.  who showed that 10% of the total exposed participants to noise levels greater than or equal to 85 dB claimed to have tinnitus, compared with none among the nonexposed. Similar results were obtained by Abdel-Rasoul et al.  who reported significant increased prevalence of tinnitus among workers in an iron and steel factory exposed to noise levels greater than 90 dBA.
Audiometric findings revealed that 13.8% of exposed workers had hearing impairment that ranged from mild, moderate to severe degree and 9.4% of exposed workers had V-dip depression, which represented 68.4% of hearing-impaired workers. This could be explained by high levels of noise exposure and improper use of hearing-protective equipment by workers in this factory.
These obtained results are broadly consistent with what was observed by Mostaghaci et al.  in a 2-year follow-up study in a tile and ceramic factory. A standard threshold shift was observed in 2.34 and 8.83% of participants in the first and second years of follow-up in the right ear and in 3.96 and 11.35% of participants in the first and second years of follow-up in the left ear. Hearing loss was significantly higher and most commonly seen at 4000 Hz in workers exposed to noise levels ranging from 75 to 92 dBA .
Similar results of abnormal conventional audiometric findings were observed in 29% of workers in a ceramic and tile factory, and the most frequently affected frequencies were 4000 and 6000 Hz in a similar study .
On studying chest radiological findings among exposed workers with abnormal spirometric measurements, 50 (74.6%) out of 67 workers had abnormal radiological findings such as small nodular opacities of different sizes and profusion [N = 33 (66%)], increased bronchovascular markings [N = 38 (76%)], emphysema [N = 10 (20%)], and enlarged hilar lymph node [N = 5 (10%)]. These radiological findings were concurrent with the effects of RCS on the respiratory system, including silicosis.
These results agree with those revealed by Aziz et al.  who reported that 66.6% of workers exposed to free silica (>5%) had statistically significant prevalent abnormal chest radiography findings in the form of small fine fibronodular changes, increased bronchovascular markings, and hyperinflated chest in comparison with 44.3% of workers exposed to free silica (<5%). The increased bronchovascular markings were reported in 7.0% of exposed workers and 2.5% of controls .
In present study, the small nodular opacities were mainly of P size (97.0%) and then q (3%), with profusion of 1/1 (66.7%) and 1/0 (33.3%). This result is in agreement with those revealed by Fahmy et al. , who recorded that the chest radiography of 27 silicotic workers was mainly of P size (66.7%) and then q (33.3%), with profusion of 1/1 (59.3%), 1/2 (25.9%), and 2/2 (14.8%). In addition, Abdel-Rasoul et al. , in a study on glass industry workers, reported that small nodular opacities are mainly of P size (73.33%) and then q (26.67%), with profusion of 1/1 (73.33%), 2/2 (6.67%), and 2/3 (20.0%).
| Conclusion|| |
From the outcome of the present study, it is possible to conclude that exposure to high levels of RCS in the ceramic industry adversely affects the respiratory system of workers, which appears in the form of abnormal spirometric measurements and abnormal radiological findings. Continuous exposure to noise levels more than 90 dBA leads to abnormalities in audiogram in the form of threshold shifting and V-dip depression. Adequate engineering control, ventilation, and periodic medical examination are required for proper control of such conditions.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Broaddus V, Mason R, Ernst J, King T, Lazarus S, Murray J, et al.Murray & Nadel's textbook of respiratory medicine
. Vol. 6. Saunders/Elsevier, USA: Elsevier Saunders 2016:p. 73.
Kim I, Kim W, Lee K, Lee S, Park K, Choi J, et al.
Imaging of occupational lung disease. Radiographics 2001; 21:1371–1391.
Schwarz M, King T Interstitial lung disease: the health effects of silica and coal dust exposures
. Vol. 5. USA: People Medical Publishing House (PMPH); 2010:pp. 515–6.
Meijer E, Kromhout H, Heederik A. Respiratory effects of exposure to low levels of concrete dust containing crystalline silica. Am J Ind Med 2001; 40:133–140.
International Agency for the Research on Cancer (IARC). A review of human carcinogens: arsenic, metals, fibers and dusts. IARC Monogr Eval Carcinog Risks Hum. 2012; 100C: 355–397.
Ghahramani N. Silica nephropathy: review. Int J Occup Environ Health 2010; 1:108–115.
Brown J, Archer A, Pfau J, Holian A. Silica accelerated systemic autoimmune disease in lupus-prone New Zealand mixed mice. Clin Exp Immunol 2003; 131:415–421.
Pierre R, Maguire D. The impact of a-weighting sound pressure level measurements during the evaluation of noise exposure. Paper presented at Noise-Con 04. The 2004 National Conference on Noise Control Engineering; Baltimore, MD; 2004. Available at: http://storeycountywindfarms.org/ref3_Impact_Sound_Pressure.pdf
. [Accessed 2013 Nov 20].
Mackie J. Current Occupational and Environmental Medicine, Occupational Medicine. Vol 58. NY, USA: McGraw Hill Medical; 2008. p. 77.
Ministry of Enviornment Egyptian Environmental Affairs Agency. Egyptian Environmental Law 4 Decree 1095. Official Gazette No. 199; 2011. pp. 77–81 (for noise) and pp. 110–112 (for dust).
National Institute for Occupational Safety and Health (NIOSH). Health effects of occupational exposure to respirable crystalline silica
. Washington, USA: Department of Health and Human Services; 2002. pp. 75–96.
NIOSH. Recommendations for a noise standard
. [Chapter 1]. Washington, USA: NIOSH; 1998. pp. 1–4. publication no. 98–126.
Aziz H, Ahmed S, Saleh I. Respiratory hazards among Egyptian ceramics workers. Researcher 2010; 2:65-73.
Dehghan F, Mohammadi S, Sadeghi Z, Attarchi M. Respiratory complaints and spirometric parameters in tile and ceramic factory workers. Tanaffos 2009; 8:19–25.
Mehrparvar M, Mirmohammadi S, Davari M, Mostaghaci M, Mollasadeghi A, Bahaloo M, et al.
Conventional audiometry, extended high-frequency audiometry, and DPOAE for early diagnosis of NIHL. Iran Red Crescent Med J 2014; 16:e9628.
Mostaghaci M, Mirmohammadi S, Mehrparvar A, Bahaloo M, Mollasadeghi A, Davari M. Effect of workplace noise on hearing ability in tile and ceramic industry workers in Iran: a 2-year follow-up study. Scientific World J 2013; 2013:923731.
Rondon E, Silva R, Botelho C. Respiratory symptoms as health status indicators in workers at ceramics manufacturing facilities. J Bras Pneumol 2011; 37:36–45.
Halvani G, Zare M, Halvani A, Barkhordari A. Evaluation and comparison of respiratory symptoms and lung capacities in tile and ceramic factory workers of Yazd. Arh Hig Toksikol 2008; 59:197–204.
Saad A, Awad A-H, Aziz H. Assessment of respiratory health problems due to exposure to airborne fungi in ceramics industry. Egypt J Occup Med 2006; 30:193–216.
American Thoracic Society (ATS). Official American Thoracic society technical standards: spirometry in the occupational setting. Am J Respir Crit Care Med 2013; 189:984–994.
Mehrparvar A, Mirmohammadi S, Mostaghaci M, Davari M, Hashemi S. A 2-year follow-up of spirometric parameters in workers of a tile and ceramic industry, Yazd, Southeastern Iran. Int J Occup Environ Med 2013; 4:73–79.
Al-Batanony M, Abdel-Rasoul G, Abu Salem M, Al-Ahmar I, Al-Badry A. Cohort study on respiratory and neurological disorders among workers in a Bone Glue Factory in Egypt. Int J Occup Environ Med 2012; 3:84–91.
Ahmed H, Dennis J, Badran J, Ismail M, Ballal S, Ashoor A, et al.
Occupational noise exposure and hearing loss of workers in two plants in Eastern Saudi Arabia. Ann Occup Hyg 2001; 45:371–380.
Abdel-Rasoul G, Mahrous O, Abou-Salem M, Al-Batanony M, Allam H. Auditory and respiratory health disorders among workers in an iron and steel factory. Zagazig J Occup Health Saf 2009; 2:1–10.
Fahmy F, Abdel-Hamid M, Abbas F, El-Gazzar R. Renal Affection and Some Oxidative Stress Biomarkers among Workers Exposed to Silica Dust. Egypt J Occup Med 2011; 35:1–21.
Abdel-Rasoul G, Al-Batanony M, Abu-Salem M, Taha A, Unis F. Some health disorders among workers in a Glass Factory. Occup Med Health Aff 2013; 1:106.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]