International Journal of Occupational Hygiene
Volume:1 Issue: 1, Jul 2009

An air filter is a significant element of any mechanical ventilation system. However, the importance and performance evaluation of air filters have not been well publicized and related scientific reports are scarce. In this study, a transportable, off-line, air filter-testing unit (the Unit) was designed and utilized to simulate the filter housing of a mechanical ventilation system. The Unit was designed, assembled, and operated in a laboratory. To demonstrate the applications of the Unit, a series of air filter handling and installation scenarios was performed to determine the characteristic curve and capture efficiencies of a selected set of HEPA filters. The research project produced a transportable, closed system air filter testing unit. The Unit incorporated a fan, a damper to adjust air flowrate, a filter-housing (consisting of a mixing chamber, a filter-frame, and a pressure-gauge), and ducting with ports to introduce challenge particles and monitor them after filtration. By using the Unit, the detrimental effects of damaged filter-media, damaged filter-gasket, and improper installation of air filters on their capture efficiencies were clearly demonstrated. An air filter testing unit, similar to the Unit presented here, can readily be designed, fabricated, and assembled to simulate the filter-housing of mechanical ventilation systems. The assembled unit can be used (1) to determine capture efficiency of air filters and their characteristic curve, (2) to demonstrate the negative effects of improper handling and installation of air filters, and (3) as an effective investigative and educational tool.

Exposure to cold work environment is an occupational health hazard and poses adverse effect on workers health, performance and productivity. This study was performed in a cold food-storage warehouse complex in Tehran-Iran in order to evaluate the workers'' exposure to cold stress. Twenty nine exposed workers and 33 non-exposed workers as control subject were included in this study. Climatic factors were measured based on ISO 7996 at the three levels of workers height. Physiological factors including skin temperature (ISO 9886), oral temperature (ISO 9886) blood pressure, pulse rate, workload (ISO 8996) were determined. Cloth insulation was estimated according to ISO 9920. The IREQ (IREQneut and IREQmin) were calculated following ISO/TR 11079 guidelines, and then, IREQ indices were compared with estimated cloth insulation through t-test. IREQmin in locations with above and below 0°C was 1.7 and 3.63 clo, respectively. Exposed and control subjects had similar blood chemistry and physiological factors. The skin temperature in the extremities was considerably lower in the exposed subjects. The rate of pain (mostly in the knees, musculoskeletal, and pleurodynia) and skin cooling were higher in the exposed subjects. Lower skin temperature in the extremities and pain in the knees, musculoskeletal, and pleurodynia were the major health issues in this cold food-storage facility.

The aim of the present study was to assess the industrial noise pollution and its effects on the blood pressure of workers during activities in textile factory in Ilam,which is situated in west of Iran. A cross-sectional study was performed on a group included 81 workers and 30 people as sample and control group, respectively. A questionnaire was filled out and then the other measurements including the total sound pressure level, weight, height, pulse, blood pressure and all the rest of medical examinations have been respectively done. The average sound pressure level measured for sample and control group was respectively (94.86 ±6.63) and (61.93 ± 4.56) dBA. The result also showed that by taking mean values for each quantitative variable, statistically only the age has significant difference between opposing groups. Sound frequency analysis in A and C networks over a frequency range between 125 to 16000 Hz revealed a significant differences in such away that sound pressure level for the sample group was higher than the limited threshold (85 dBA). Moreover, the results from the survey of the total sound pressure level in A –and C – weighted according to blood pressure status, BMI and age indicate a significant statistical correlation between the mentioned variables. A highly significant correlation was found by test between the level of sound pressure, blood pressure status, BMI and the age group in different octave band center frequencies. It is concluded that planning for working hours of workers to decrease the noise exposure and employment of young workers with appropriate BMI may reduce the adverse effects of noise.

Greater levels of complexity in tunnelling with Tunnel Boring Machine (TBM) allow higher chances of failures that may increase the potential hazardous risks. This paper presents the results of a study on TBM reliability using risk analysis. Machinery Failure Mode and Effect analysis was applied to analyze the risks of a TBM using QS9000 and SAE.J1739 recommendations. For this purpose, 48 failure modes were postulated for the TBM main systems and all subsystems. Afterwards, the effects of every failure were listed. Safeguards or controls that might prevent or mitigate the effects of each failure were also listed. In the final step, essential remedial actions to prevent or mitigate the failure were recommended. Risk Matrix was developed for each possible failure to be used for risk ranking. For this, the Risk Priority Number (RPN) was estimated for each failure mode for pro and post application of control measures to identify the most critical failures. The results revealed that 7 failure modes had risk priority numbers higher than 80 therefore, they were categorized unacceptable. Cutter head stop due to bad rock condition with RPN=240 was the significant critical failure. The results also showed that 3 failure modes in TBM required modification due to high Severity rate. The findings from this study were applied to a long tunnel under construction and significantly reduced the accidents during the next two years tunnelling period. It can be concluded that MFMEA is a superb tool for TBM reliability evaluation and promotion.

While the OECD test guidelines and mostly animal assays have been used to study the toxic effects of chemicals for many years, very little is known about the potential toxicity of vast majority of inhaled chemicals. Considering large number of chemicals and complex mixtures present in indoor and outdoor air, heavy reliance on animal test methods appear to be not adequate. Continuing scientific developments are needed to improve the process of safety evaluation for the vast number of chemicals and inhaled materials. The aim of this study was to optimise in vitro methods for toxicity testing of airborne contaminants. An integrated approach was designed in which appropriate exposure techniques were developed. A diversified range of in vitro assays using multiple human cell systems were implemented. Direct exposure of cells to airborne contaminants was developed by culturing cells on porous membranes in conjunction with a horizontal diffusion chamber system. Dose-response curves were generated allowing the measurement of toxicity endpoints. Toxicity ranking of test chemicals, based on obtained IC50 (50% inhibitory concentration) values, in different human cells and in vitro assays were determined. Airborne IC50 values were calculated for selected volatile organic compounds (xylene; 5350 ± 328 ppm > toluene; 10500 ± 527 ppm) and gaseous contaminants (NO2; 11 ± 3.54 ppm > SO2; 48 ± 2.83 ppm > and NH3; 199 ± 1.41 ppm). Results of this research indicate the significant potential of in vitro methods as an advanced technology for toxicity assessment of airborne contaminants.

T-shape profile barriers are one of the most successful barriers among many different profiles. It has been shown that using welled diffusers on the top of T-shaped barriers makes a reactive barrier that shows better performance than that of any other used profile barriers compared with their equivalent absorbent barrier. The contribution of the top surface of reactive T-profile barriers to their efficiency in the shadow zone is discussed in this paper. The new multiple impedance discontinuity (NMID) method was used on a few multi-welled surfaces and the application of the findings on the diffuser T-profile barrier along with a descriptive theory of the welled surface effect was presented. An acceptable agreement between the result of the NMID model and BEM method for a few welled surfaces were found. The area-averaged impedance model was also used in the NMID model and it was found that this model can be a good performance indicator for a multi-welled surface. In order to explain the contribution of the top surface of a T-profile barrier, it is adequate to use the NMID model on a mixed ground equivalent to the top surface of the barrier where the source and receiver are located at near the ground where the separation of source and receiver is identical with the overall span of the cap. The effect of average admittance of top surface is dominant and the effect of the impedance discontinuity is overshadowed by this effect.

Health care workers are among the groups with high frequently of exposure to workplace violence and the real dimensions of this problem have not yet been clearly defined. The aim of this study was to review the exposure of nurses to physical violence. In this cross sectional descriptive study, a total 450 nurses completed a standard questionnaire. The survey elicited demographic information and various aspect of personal experience of violence. Data collection lasted for about six months (September 2006 to March 2007) in three academic hospitals of Baqiyatallah University of Medical Science in Iran. Ninety six nurses (21.3%) reported at least one exposure to physical violence during one year ago. Exposure was more among nurses with more than 10 years of work experience. Most of the invasions were done by patients'' fellows. In internal wards violence exposure had been occurred more than other ones. Sections of employment and types of employment had statistical differences among exposure or non-exposure groups (P=0.03). Due to some doubt of nurses in expressing violence experiences and recalling bias, explanation of relative low prevalence of violence exposure should be done cautiously. It is necessary that some comprehensive and screening researches be implemented and preventive program as well as proper management plus reporting system be designed.

Research has shown that shift work, in particular night work, can have negative effects on the health, safety and well-being of workers. Our study assessed, in a hospital setting, the effects of bright light (BL) on general health and psychological problems during night shift work. In an experimental design, 15 female nurses at a general hospital that located in Tehran were exposed to moderate bright light (2000 lx) during night work. The evaluation of general health status, job stress, and burnout syndrome conditions was done as follows: The 28-item General Health Questionnaire (GHQ-28) was used as a screening tool for the detection of general health status; for assessing the level of stress, perception stress scale (PSS) was filled; and for burnout syndrome conditions, burnout self-report questionnaire (BSR) was completed. T-test and paired t-test analysis were used to assess the association between BL exposure for a total of 30 min during each night shift and changes in general health status, job stress and burnout syndrome. This study clearly shows that BL administration could not reduce anxiety symptoms, somatic symptoms, severe depression and improved social dysfunction significantly during night shift. However, BL exposure significantly decreased the perception stress (P=0.008) and burnout syndrome (P=0.06) during night permanent shift. These results suggest that BL might have provoked changes in perception stress and burnout syndrome of nurses working night permanent shift.