Hematotoxicity induced by simultaneous exposure to noise and toluene in New Zealand white rabbits: Synergistic and antagonistic effects.

Exposure to numerous pollutants is prevalent in workplaces. Examination of combined exposure to different harmful physical factors and chemicals has offered new insights into toxicology in recent years. This study aimed to investigate the hematological alterations caused by exposure to noise and toluene. Twenty-four New Zealand white rabbits were exposed to 1000 ± 50 ppm toluene and/or 100 ± 5 dB noise for 14 consecutive days. Exposure to noise and toluene changed a number of parameters of white blood cells (WBC), red blood cells (RBC), and platelets on different days after the exposure. Simultaneous exposure to noise and toluene increased WBC, and exposure to noise and toluene alone decreased RBC. Exposure to noise and toluene alone increased basophile, monocyte, and neutrophil counts. The coefficient of variation of red blood cell distribution width (RDW-CV) and the standard deviation of red blood cell distribution width (RDW-SD) significantly increased after co-exposure to noise and toluene. Platelet levels increased in the noise-exposed and the co-exposed groups and decreased in the toluene-exposed group. Furthermore, co-exposure to noise and toluene induced dissimilar synergistic and antagonistic effects on the hematological indices. According to the results of this study, simultaneous exposure to toluene and noise can aggravate some hematotoxic effects compared to exposure to noise or toluene alone. The results also demonstrated the vital role of the modulatory mechanisms of the body in controlling the detrimental effects of stressors.

Hepatotoxic effects caused by simultaneous exposure to noise and toluene in New Zealand white rabbits: a biochemical and histopathological study.

The aim of this experimental study was to investigate hepatotoxicity effects of noise and toluene, and in particular, to study hepatotoxicity effects of simultaneous exposure to noise and toluene by histopathological and biochemical experiments. To experiment hepatotoxicity effects of noise and toluene, 100 dB white noise and 1000 ppm toluene vapors were generated during two consecutive weeks in healthy male New Zealand White rabbits. Non-simultaneous exposure to noise and toluene increased liver enzymes and the serum levels of superoxide dismutase, malondialdehyde, and total antioxidant capacity, and also decreased serum level of glutathione peroxidase. Alanine transaminase, aspartate transaminase, gamma-glutamyl transferase, malondialdehyde, total antioxidant capacity, and superoxide dismutase levels increased by simultaneous exposure to noise and toluene. Furthermore, catalase and alkaline phosphatase level decreased by simultaneous exposure to noise and toluene. The hematoxylin and eosin stain (H&E) experiments indicated significant swelling, lipidosis, eosinophilic cytoplasm, pyknosis, karyorrhexis, and disruption of the cytoplasmic membrane in the liver tissue due to exposure to noise, toluene and simultaneous exposure to them.

An assessment of the cytotoxic effects of graphene nanoparticles on the epithelial cells of the human lung.

Nanomaterials are widely used nowadays in a range of technological and biomedical fields. Graphene as a nanomaterial used in the health-care sector and in workplaces has raised some concerns about its toxicity. This study aimed to evaluate the cytotoxicity of graphene nanoparticles (GNPs) on the A549 epithelial cells of the human lung. The GNPs were synthesized from graphite by the modified Hummer method. The physicochemical characteristics of GNPs were identified by the transmission electron microscope, the scanning electron microscope, and the Brunauer-Emmett-Teller method. The hydrodynamic size of GNPs in the dispersion media was examined using the dynamic light scattering technique. The GNPs were dispersed, after which the A549 cells were cultured. Finally, the cell viability was assayed by the MTT assay. The statistical analysis of variance was used to describe the relationship between the concentration/time variables and the GNP-induced cell deaths. The probit regression model was also used to achieve toxicological indicators. The results showed that the toxicological effects of GNPs on the A549 epithelial cells of the human lung are dose- and time-dependent. The GNPs were more cytotoxic after a 72-h exposure period compared to a 24-h and 48-h exposure period. The inhibitory concentration of 50% and "no observed adverse effect concentration" were estimated to be 40,653.1 and 0.059 µg/mL, respectively. The results of this study can be helpful in developing the occupational exposure limit for GNPs and in improving occupational health programs in workplaces. However, more investigation is needed to specify the toxicological mechanisms of GNPs.

Psychometric properties of the Persian version of the Fleishman Job Analysis Survey (FJAS).

BACKGROUND: Job analysis is one of the most important and widely used processes to determine job duties, identify and reduce potential risks, and specify the skills and facilities required for each job at the highest level of occupational safety and health. OBJECTIVE: This study aimed to perform psychometric analyses of the Persian version of the Fleishman Job Analysis Survey (FJAS). METHODS: A cross-sectional study was conducted among 31 drivers. Participants were selected by random sampling. Ten occupational health and ergonomics experts confirmed the validity of the survey. First, we calculated the survey's CVR and CVI. Then, we used ICC and Cronbach's alpha coefficients to evaluate the survey's reliability. Data analysis utilized SPSS 21. RESULTS: 78% of the participants were male and 22% were female. The mean age±SD of the participants was 39.1±11.82 years. The reliability and validity of the short version survey showed that the value of ICC and Cronbach's alpha coefficient was 0.96, and CVR was 0.75. Moreover, the values of CVI for simplicity, clarity, and relevance were 0.87, 1, and 0.73, respectively. The long version's ICC and CVR were 0.96 and 0.97, respectively. Simplicity, clarity, and relevance CVI scores were 0.9, 0.94, and 0.95. CONCLUSION: The results of this study showed that the Persian version of the Fleischman Job Analysis Survey has the necessary validity and reliability for job analysis, so it can be used for driving professional or research purposes. Moreover, this survey is an effective tool for obtaining accurate and complete knowledge of job tasks and requirements.

Occupational Exposure to Metal Fumes Among Iranian Welders: Systematic Review and Simulation-Based Health Risk Assessment.

There have been numerous reports of welder's worker exposure to metal fumes. Carcinogenic and non-carcinogenic (neurological, dermal, and etc.) effects are the adverse outcomes of exposure to welding fumes. In this review study, data were collected from previous studies conducted in Iran from 1900 to 2020. The risk of carcinogenicity and non-carcinogenicity due to exposure to welding metal fumes was assessed using the United States Environmental Protection Agency (USEPA) method based on the Monte Carlo simulation (MCS). Results showed mean of metal fume concentration in gas welding was in the range of 1.8248 to 1060.6 (µg/m3) and in arc welding was 54.935 to 4882.72 (µg/m3). The mean concentration of fumes in gas welding is below the recommended American Conference of Governmental Industrial Hygienists (ACGIH) standard exposure limit except for manganese, and in the arc welding, all metal fume concentrations are below the standard exposure limit except for manganese and aluminum. The results showed that the risk of carcinogenicity due to exposure to nickel, manganese in both gas and arc welding, and cadmium in gas welding was higher than standard level (hazard quotient (HQ) more than 1). Cancer risk due to exposure to nickel in both gas and arc welding was probable (1 × 10-6 < cancer risk (CR) < 1 × 10-4). Health risk assessment showed that welders are exposed to health risks. Preventive measures should be applied in welding workplaces to reduce the concentrations of metal fumes.

The impact of operational factors on degradation of formaldehyde as a human carcinogen using Ag3 PO4 /TiO2 photocatalyst.

Background: The International Agency for Research on Cancer (IARC) identified formaldehyde as a carcinogen in 2004, yet formaldehyde is widely used in health care settings and various industries. In recent years, photocatalytic oxidation has been developed as a potential technique for removing pollutants arising from organic chemical agents and consequently promoting the health indices. This study investigated the effect of operational factors in optimizing formaldehyde removal from the air using Ag3 PO4 /TiO2 photocatalyst. Methods: An experimental study was designed to investigate the effect of operational factors on the efficiency of formaldehyde degradation. The variables investigated in this study include pollutant retention time, initial pollutant concentration and relative humidity. Sol-gel method was used to synthesize the nano-composite photocatalyst. An ideal experimental design was carried out based on Box-Behnken design (BBD) with response surface methodology (RSM). The sample size in this study includes all the glasses coated with Ag3 PO4 /TiO2 photocatalyst. Results: The maximum formaldehyde degradation of 32% was obtained at the initial concentration of 2 ppm, 20% relative humidity, and 90 minutes of retention time. Based on the statistical results, the correlation coefficient of the present study for the impact of operational factors on formaldehyde degradation was 0.9635, which means that there is only 3.65% probability of error in the model. Conclusion: The operational factors examined in this study (retention time, relative humidity, and initial formaldehyde concentration) were significantly influential in the degradation efficiency of formaldehyde by the photocatalyst. Due to the high exposure of employees and clients of health and treatment centers to formaldehyde as a carcinogenic substance, the results of this study can be used in ventilation systems to remove environmental pollutants in health care centers and other occupational settings.

Barriers and Challenges to Human Factors/Ergonomics Knowledge Transfer to Small Business Enterprises in an Industrially Developing Country.

OCCUPATIONAL APPLICATIONWe found that small business enterprises (SBEs) face intra- and extra-organizational barriers in different dimensions related to their work system to practically implement human factors/ergonomics (HFE) knowledge transfer and to achieve its benefits in an industrially developing country. Utilizing a three-zone lens, we evaluated the feasibility of overcoming the barriers identified by stakeholders, especially ergonomists. To overcome the identified barriers in practice, three types of macroergonomics interventions (top-down, middle-out, and bottom-up) were distinguished through macroergonomics theory. The bottom-up approach of macroergonomics, as a participatory HFE intervention, was considered as the entry point to overcome the perceived barriers in the first zone of the lens, which included such themes as lack of competence, lack of involvement and interaction, and inefficient training and learning approaches. This approach focused on improving emotional literacy as a care zone among the small business enterprise personnel.

Background: The human factors/ergonomics (HFE) knowledge transfer process is one of the potential challenges for organizations in industrially developing countries (IDCs), especially in small business enterprises (SBEs).Purpose: We explored perceived barriers and challenges to the practical implementation of HFE knowledge transfer to SBEs in Iran, as an IDC, to improve their work systems.Methods: An exploratory qualitative study was conducted using a conventional content analysis. To identify perceived barriers, we conducted individual interviews (n = 38) and a focus-group discussion (n = 17) with the participation of the SBEs personnel and the officials of related organizations. Inductive content analysis was used for data analysis. We then categorized the identified perceived barriers (themes) to determine the feasibility of overcoming them.Results: Regarding perceived barriers, the following nine themes were extracted: lack of competence, resistance to change, technological infrastructure problems, lack of involvement and interaction, using an inappropriate mode of knowledge, lack of culture-building about HFE, inefficient training and learning approaches, lack of scientific management, and extra-organizational problems. Further, a three-zone lens was identified for the extracted themes to check the feasibility of overcoming them.Conclusions: We identified nine intra- and extra-organizational barriers in the HFE knowledge transfer process to SBEs. We further evaluated the ways of overcoming perceived barriers defined in the three-zone lens to adapt them for building creative workplace culture zones (care, creative, and improvement). We distinguished three types of macroergonomics interventions (top-down, middle-out, and bottom-up) and three supporting strategies, including, knowledge, management and employees, and participatory HFE.

DNA damage in foundry workers using non-invasive micronucleus cytome assay.

Workers in the foundry industry are exposed to hazardous chemical agents such as metal fumes, gases, vapor of molten metal, and respirable dust and hazardous physical agents such as heat, noise, and electromagnetic fields. Co-exposures to hazardous physical and chemical agents in foundry workplaces may cause DNA damage in workers. This study aimed to evaluate DNA damage in foundry workers. Thirty-three exposed foundry workers as a exposure groups and 33 non-exposed individuals as a control groups participated in this study. Buccal micronucleus cytome (BMCyt assay) assay was used to assess DNA damage. Results showed that foundry workers were under exposure to hazardous chemical and physical agents such as metal fumes and noise. The percentage of micronucleus (MN) cells in exposure group (0.59 ± 0.93 %) were statistically higher than control group (0.23 ± 0.23 %) (P < 0.05) %). Also, the percentage of nuclear bud cells and binucleated cells in exposure group were statistically higher than control group (P < 0.05). The percentage of differentiated normal cells were significantly higher in the control group compared to the exposed group (P < 0.05). Foundry workers are at risk of DNA damage; therefore, prevention measures need to be implemented to reduce exposure to air pollutants in foundry workplaces.

Cancer risk assessment of exposure to asbestos during old building demolition.

BACKGROUND: Years ago, the use of asbestos in construction materials was common. Although asbestos has been recently banned in many countries, exposure to asbestos during old building demolition is not unexpected. OBJECTIVE: The aim of this study is to assess the concentration of exposure to asbestos and estimate its cancer risk among old building demolition workers. METHODS: In this study, personal air samples were collected during building demolition. The number of asbestos fibers in collected samples were determined according to the NIOSH-7400 standard method. Chemical compositions of fibers were assessed using scanning electron microscopy (SEM). The carcinogenic risk of exposure to asbestos was determined based on the recommended United State Environmental Protection Agency (USEPA) method and Monte-Carlo simulation used to estimate the probability of cancer. RESULTS: Chemical analysis confirmed the presence of asbestos in collected air samples, and 67% of counted fibers were asbestos. In a number of buildings, workers had exposed to asbestos that was higher than occupational exposure limit (0.10 f/ml). Results of cancer risk estimation showed that cancer risk were considerable among workers. CONCLUSION: Implementation of asbestos risk management program such as separation of asbestos containing material, personal protective equipment's and use of wet method in demolition could minimize asbestos exposure during old building demolition.

Carcinogenic and non-carcinogenic risk of exposure to metal fume in different types of welding processes.

The international agency for cancer research (IARC) has classified welding fumes as definitive carcinogens. The aim of the present study was to assess health risk due to exposure to welding fumes in different welding types. In this study, exposure to fumes of iron (Fe), chromium (Cr), and nickel (Ni) in the breathing zone air of 31 welder engaged in arc, argon and CO2 welding was assessed. Carcinogenic and non-carcinogenic risk assessments due to exposure to fumes were performed using the method proposed by the Environmental Protection Agency (EPA) by Monte Carlo simulation. The results showed that in the CO2 welding, concentration of Ni, Cr, and Fe was lower than the 8-h Time-Weighted Average Threshold Limit Value (TWA-TLV), recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). In argon welding, Cr and Fe concentrations were higher than the TWA-TLV. In arc welding, concentrations of Ni and Fe were more than the TWA-TLV. In addition, the risk of non-carcinogenicity due to exposure to Ni and Fe in all three types of welding was more than standard level (HQ>1). The results indicated that the welders are at health risk due to exposure to metal fumes. Preventive exposure control measures such as local ventilation need to be implemented in welding workplaces.

Micronucleus assay of DNA damage among welders: Effects of welding processes.

Metal fumes, gases, noise, and radiation are hazardous occupational exposures that may be encountered by welders. We have evaluated DNA damage among welders; the buccal micronucleus cytome (BMCyt) assay was used. Thirty-four exposed welders (cases) and an equal number of non-welders (controls) participated in this study. Cell types including basal, early and late differentiated cells with micronucleus (MN), dense chromatin, karyorrhectic, pyknotic, karyolitic, and binucleated cells (NBUD) were measured. Damage levels among, arc, argon, and CO2 welders were statistically significantly higher, compared to the control group. Results showed that mean of MN and NBUDs as indicators of DNA damages among arc, argon and CO2 welding's were significantly higher compared to control group. Also, the mean of DNA damage levels were statistically higher among the arc welders than among the argon or CO2 welders; and levels were higher among the argon welders than the CO2 welders. Preventative measures need to be implemented to reduce exposure to harmful agents during welding.

Toxicity of Carbon-Based Nanomaterials in the Human Lung: A Comparative In-Vitro Study.

Background: Carbon-based nanomaterials (CBNs) are the key elements in nanotechnology. The main challenge presented by CBNs is their relationship with the toxicity exposed in the biological systems, because of the incomplete information on their toxicity. This study is aimed to compare the cytotoxicity of graphite nanoparticles (GRNPs), graphene nanoparticles (GNPs), and multi-walled carbon nanotubes (MWCNTs) in A549 cells. Materials and Methods: The physicochemical properties of nanomaterials were determined by instrumental techniques. CBNs were dispersed by the nongenotoxic standard procedure. After the cells were cultured, they were exposed to different concentrations of CBNs. Cellular viability was determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. Moreover, toxicological indicators were obtained using linear probit regression. Results: The degree of cytotoxicity of CBNs in A549 cells was related to the time and, particularly, dose. At the concentrations of lower than 300 µg/mL, GNPs had stronger toxicity than MWCNTs, but the cytotoxic effects were reversed with the increase of the concentrations. The no-observed-adverse-effect concentration (NOAEC) of GRNPs, GNPs, and MWCNTs was 1.76, 0.06, and 0.65 µg/mL, respectively. Conclusion: The results indicated that CBNs were toxic and GNPs had stronger toxicity than the others. The experimental results can be useful in increasing the knowledge about the toxicity and health risk management of CBNs.

Cognitive performance and electroencephalographic variations in air traffic controllers under various mental workload and time of day.

The aim of this study was to investigate the effects of mental workload (MWL) and time of day on cognitive performance and electroencephalographic (EEG) parameters of air traffic controllers. EEG signals recorded while 20 professional air traffic controllers performed cognitive tasks [A-X Continuous Performance Test (AX-CPT) and 3-back working memory task] after they were exposed to two levels of task difficulty (high and low MWL) in the morning and afternoon. Significant decreases in cognitive performance were found when the levels of task difficulty increased in both tasks. The results confirmed the sensitivity of the theta and beta activities to levels of task difficulty in the 3-back task, while they were not affected in the AX-CPT. Theta and beta activities were influenced by time of day in the AX-CPT. The findings provide guidance for application of changes in EEG parameters when MWL level is manipulated during the day that could be implemented in future for the development of real-time monitoring systems to improve aviation safety.

Toxicopathological changes induced by combined exposure to noise and toluene in New Zealand White rabbits.

Noise and toluene can have significant adverse effects on different systems in the human body, but little is known about their combination. The aim of this study was to see how their combined action reflects on serum levels of inflammatory cytokines tumour necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1ß), body weight, and pathological changes in the heart, lung, stomach, and spleen tissues. To do that we exposed New Zealand rabbits to 1000 mg/L toluene and 100 dB of white noise in a chamber specifically designed for the purpose over two consecutive weeks. Serum levels of TNF-α and IL-1ß were measured with the enzyme-linked immunosorbent assay (ELISA), whereas Bax and Bcl-2 expressions in tissues were determined with real-time polymerase chain reaction (PCR). Noise and toluene changed TNF-α and IL-1ß serum levels on different days following the end of exposure and significantly increased the Bax/Bcl-2 ratio in the lung and spleen. In addition, they induced different pathological changes in the heart, lung, spleen, and stomach tissues. This study has confirmed that exposure to noise and toluene can induce a range of toxicopathological changes, probably by inducing inflammatory pathways and apoptosis, but their combined effects look weaker than those of its components, although histopathological findings suggest the opposite.

Evaluating the airborne asbestos dispersion in enclosed parking lots in Iran.

Each time a car's brakes are used, asbestos is dispersed in the air. Breathing the air in enclosed parking lots can expose people working in these places to asbestos. This study aimed to evaluate the airborne asbestos dispersion in enclosed parking lots. In this study, 35 air samples were collected from six enclosed parking lots in Tabriz City. The samples were analyzed quantitatively by phase contrast microscopy (PCM) and qualitatively by a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray analyzer. The mean of fiber concentrations was found 0.155 ± 0.069 PCM f/cc. The SEM data demonstrated that the fibers consisted of synthetic fibers (69.57%) and asbestos (30.43%). Fiber concentrations in many enclosed parking lots in the city were higher than the threshold limit value-time weighted average of the American Conference of Governmental Industrial Hygienists and Occupational Exposure Limits of Iran. However, further investigations are needed to clarify asbestos exposure in such places.

Inflammatory and immunological changes caused by noise exposure: A systematic review.

Today, due to the growth of industries and spread of the use of various instruments and devices that produce high noise levels, it is necessary to pay more attention to the effects of exposure to noise on organs and tissues in the body. The importance of the immune system in fighting external and pathogenic factors has raised the need to consider external factors (such as harmful physical factors) and make efforts to avoid producing them. In this systematic review, 811 potentially relevant studies were found in Google Scholar, PubMed, and Web of Science databases, of which 32 different English-written articles were included in the study. The method of searching and systematically reviewing articles was based on the assessment tool of the multiple systematic reviews (AMSTAR) method. The results of this study suggested that noise could affect the function of the immune system and its components by affecting other systems and organs of the body, including the central nervous system, auditory system, circulatory system, and endocrine gland. Moreover, it can be hypothesized that noise affects immune system by producing the NADPH oxidase (Nox) and reactive oxygen species (ROS).

Nephrotoxic effects caused by co-exposure to noise and toluene in New Zealand white rabbits: A biochemical and histopathological study.

The biological and renal effects made by simultaneous and non-simultaneous exposure to toluene and noise were investigated. Twenty-four New Zealand white rabbits were exposed to 100 dB of white noise and 1000 ppm of toluene vapor for two weeks. The examined biochemical factors were urea, uric acid, creatinine, glucose, triglyceride, cholesterol, and albumin serum levels, measured on different days after the end of the exposure. Moreover, glutathione peroxidase activity (GPX), malondialdehyde dismutase activity (MDA), and superoxide dismutase (SOD) parameters were measured in the kidney tissue. The hematoxylin and eosin staining method was used for histopathological experiments. Overall, the noise increased albumin, uric acid, creatinine, and glucose levels, but it decreased urea, cholesterol, and triglyceride levels. Toluene decreased albumin, uric acid, and urea levels, while it increased creatinine, triglyceride, cholesterol, and glucose levels. Simultaneous exposure to noise and toluene decreased albumin, uric acid, cholesterol, and urea levels, whereas it increased creatinine, glucose, and triglyceride levels. GPX, MDA, and SOD levels increased by simultaneous and non-simultaneous exposure to noise and toluene. Furthermore, massive tubular degeneration, tubular cell vacuolization, glomerular disorganization, congestion, glomerular cell shrinkage, and unclear brush border were detected in the kidney tissue.

Apoptosis and DNA damage induced by silica nanoparticles and formaldehyde in human lung epithelial cells.

Human exposure to silica nanoparticles (SNPs) and formaldehyde (FA) is increasing and this has raised some concerns over their possible toxic effects on the exposed working populations. Notwithstanding several studies in this area, the combined toxicological effects of these contaminants have not been yet studied. Therefore, this in vitro study was designed to evaluate the SNPs and FA combined toxicity on human lung epithelial cells (A549 cells). The cells were exposed to SNPs and FA separately and in combined form and the single and combined toxicity of SNPs and FA were evaluated by focusing on cellular viability, DNA damage, and apoptosis via MTT, DAPI staining, DNA ladder, and Annexin V-FITC apoptosis assays. The results showed a significant increase in cytotoxicity, DNA damage, and chromatin fragmentation and late apoptotic\necrotic rates in combined treated cells compared with SNPs and FA-treated cells (P value < 0.05). Two-factorial analysis showed an additive toxic interaction between SNPs and FA. Eventually, this can be deduced that workers exposed simultaneously to SNPs and FA may be at high risk compared with exposure to each other.

Occupational fatigue and mental health complaints among 8-hour shift workers of petrochemical industries in Iran.

BACKGROUND: Shift working is unavoidable in many industries with continual material processing such as petrochemical plants. So, the adverse effects of shift working on workers should be seriously considered. OBJECTIVE: This cross-sectional study evaluated occupational fatigue and mental health complaints and their relationship in rotating 8-hour shift workers. METHOD: In this study, 287 shift workers participated. The Multidimensional Fatigue Inventory (MFI-20) and General Health Questionnaire (GHQ-28) were used to evaluate the level of fatigue and mental health, respectively. RESULT: A relatively high prevalence of mental health complaints (particularly social dysfunction) and fatigue (especially general fatigue) were found among the study population. In general, 43.4% of participants reported a mental health problem. A moderate correlation was found between fatigue and mental health (r = 0.58). The stepwise regression model revealed that fatigue was significantly related only to "anxiety and insomnia" and "severe depression". CONCLUSION: This study revealed that the 8 h shift workers in studied areas are exposed to a considerable risk of mental health and fatigue. So, improving the ergonomics and health aspects of the workplace is recommended to reduce related risk factors.

Fatigue and Psychological Distress: A Case Study Among Shift Workers of an Iranian Petrochemical Plant, During 2013, in Bushehr.

BACKGROUND: Shift work is a well-recognized occupational health hazard in both industrialized and industrially developing countries. Prolonged working time, day/night shift rotation, circadian rhythm and sleep disorders, family and social problems are the most important features of shift working, which have serious complications. OBJECTIVES: The present study evaluated the fatigue and psychological distress and their relationship among shift workers, in a petrochemical plant (Southern Pars gas field) in Southwest Iran. MATERIALS AND METHODS: In this cross-sectional field study, 400 shift workers from a plant were involved, with participation rate of 72.5% (290 persons). The multidimensional fatigue inventory (MFI-20) and general health questionnaire (GHQ-28) were used to evaluate the level of fatigue and psychological distress, respectively. RESULTS: The results showed that the fatigue and psychological distress (particularly social dysfunction, anxiety and insomnia) are frequent among 12-hour shift workers (the total MFI and total GHQ scores were 42.68 ± 17.88 and 34.66 ± 18.56). A relatively strong positive correlation was found between fatigue and psychological distress (r = 0.62). The results of the stepwise regression model indicated that the psychological distress was significantly related only to general fatigue, mental fatigue and reduced motivation, whereas it was not to the physical fatigue and reduced activity. CONCLUSIONS: The study findings highlight the importance of the mental aspect of fatigue in this working group. These results have possible implications for workers' health and well-being and for the design of shift work systems, for industrial workers.