مجله مهندسی بهداشت حرفه ای
سال یکم شماره 2 (تابستان 1393)

Many studies were conducted to determine the effects of heat stress on human performance. However, they could not reach a decisive conclusion, mainly due to a large variation in experimental conditions and tests. This study investigated cognitive performance of university students exposed to different levels of heat stress under laboratory condition. In this cross sectional study,33 students aged 23-35 years performed cognitive tests. Participants were exposed to four Wet Bulb Globe Temperature (WBGT) of 18, 22, 29 and 33 ºC under laboratory conditions while performing CPT tests to investigate attention and reaction time. The maximum percentage of continues attention (99.67%) belonged to WBGT of 22 º C, and at the upper and lower levels of exposure (WBGT of 18 and 33 º C) percentage of attention was reduced. Although the percentage of attention was changed in different levels of heat stress, statistical analysis did not show any significant differences in attention between levels of heat stress (Pvalue>0.05). In addition, increase in WBGT index from 22-33 º C increased the reaction time. At the WBGT of 33 º C, statistical analysis showed significant difference in reaction time compared to other heat stress levels(Pvalue<0.05). The results revealed that in the CPT test, exposure to heat stress at levels of occupational exposure limit,wouldimprove performances, but exposure to higher levels of heat stress woulddecrease it.

Cutting leads to production of different hazardous agents such as fumes, particles, gases and vapors. In various studies, the effects of fumes, gases, and vapors on workers and environment have been proved. Meanwhile, cutting alloying plates with plasma cutting machine due to containing various alloy materials produces a lot of air pollution. Therefore, using the ventilation system to remove the mentioned pollution has always been noteworthy. This study was performed on plasma cutting machine at Mobarakeh Steel Company. At first, according to ASTM the elements from alloy plates with optical emission spectrometry crm-35000-quantometery were detected, the air pollution from cutting the mentioned plates was sampled and measured using NIOSH 7300 method and according to the ACGIH:VS-72-20, VS-70-12, VS-70-11 VS-916 push-pull ventilation with bag filter collector was designed. Results of sampling from pollution of cutting the alloy material, concentration of iron, lead and cadmium fumes were more than the standard limits. After calculation for push system, air flow volume of 195.163 cfm, outgoing air velocity of 5937.4 fpm and for pull system air flow volume of 12498 cfm, minimum duct velocity of 3000 fpm and velocity pressure of duct of 0.717 inwg, for fan, total pressure of 6.301 inwg, static pressure of 0.587 inwg and power of 20.65 Bhp and for collector with pulse jet cleaning system air to cloth ratio of 7 and dimensions of 6.88ft × 6.56ft × 9.84ft were obtained. The result of study indicated that push pull ventilation compared to other ventilation system s for plasma cutting has more efficiency and makes suitable control for pollution.

Dermal exposure to chemical agents can result in a variety of occupational diseases and disorders, including occupational skin diseases and systemic toxicity. T he present paper focused on transport properties of nanocomposite based on carboxylated nitrile butadiene rubber (XNBR)-nanoclay. In this study, XNBR gloves nanocomposite were prepared at different amounts of nanoclay; i.e. 3, 6, 9 phr (parts per hundred of rubber). Swelling procedure was conducted for different nanocomposites using two neat organic solvents (i.e. Carbon tetrachloride (CCl4) and Ethyl acetate). Near Fickian diffusion was observed for XNBR based nanocomposites containing different amounts of nanoclay. The permeability coefficients were higher for ethyl acetate compared to CCl4 in all XNBR nanocomposites. In addition, a significant decrease was observed in the permeability coefficients of the selected solvent XNBR3. Analysis of transport properties of synthesized nanocomposites illustrated that application of these materials seems promising for manufacturing protective gloves.

High prevalence of musculoskeletal pain in dentistry represents the importance of investigation of working conditions in this profession to reduce musculoskeletal disorders.The purpose of this study was to determine the postural load on the upper limb postural using macro LUBA technique and the prevalence of musculoskeletal disorders.

This study was conducted on 30 post graduate dental students of Hamadan University of Medical Sciences. LUBA technique was used to evaluate the postural load. The Nordic questionnaire was used to assess the prevalence of musculoskeletal disorders. The results were analyzed using SPSS version 16.

The prevalence of musculoskeletal disorders was as follows; neck(63.3%), back (43.3%), back (30%), knee (20%), shoulder(13%), wrist (10%), legs (10 %), elbows(6.7%) and thigh(0%). The maximum postural load index was 23 for women and 21for men. In total, 50 % of dentists were in group 3, 33 % of dentists in group 4 and 16.7 % in group 2 of the corrective measures. There was no significant association b etween demographic variables and presence of musculoskeletal disorders. Besides, there was no significant association between the presence of pain in upper limbs and the postural load index (Pvalue > 0.05).

This study showed high levels of p ostural load index and musculoskeletal disorders among dental students of Hamadan University of Medical Sciences. High levels of p ostural load index indicate a high level of risk, which requires immediate corrective action and intervention.

Efficient Illuminance, ColorTemperature (CT), Color Rendering Index (CRI) and luminance regulations are the necessary needs for designing workplaces. The aim of this study was to investigate optical components in commercial Compact Fluorescent Lamps (CFLs).

In this study, 48 coil compact fluorescent lamps available at Hamadan city market with some brands and cover (warm – cool) were selected. Illuminance of lamps was measured using lux meter model INS-DX-200 and luminance was measured usinG HAGNER-S2. Color chracteristics were measured using spectoradiometer model Light Spex-3 - Gretag Macbet h.

The mean CRI of studied CFLs was 83.67% ± 6.06 and CCT of them was 4212± 1668 °K. Statistical test of the balanced illuminance and luminance in studied lamps had not significant differences between warm light and cool light color lamps(Pvalue> 0.05).Besides,they had significant differences between balanced Illuminance based on domestic and foreign companies (Pvalue< 0.01).Comparing means showed that balanced illuminance of the domestic lamps was more than foreign products.

According to the study, due to variations in quantity and quality factors, consumers should pay attention to brands and valid quality certificate of CFLs. Since the mean illuminance of the lamps in one-meter distance was about 54 Lx/10W and in 2-meter distance was 22 Lx/10W, needed precautions should be madetouse CFLs in designing general and local electric lightings.

The aim of chemical risk assessment is to identify and evaluate risks originated from chemicals usages. This study aims to design a practical tool for facilitating chemical risk assessment. The proposed software was derived from chemical risk assessment method which was recommended by Ministry of Human Resources of Malaysia. All of the processes in question are designed in operating system software. Based on some revisions, this software was developed using Visual Basic (VB) titled as SQCRA. The developed software was used for chemical risk assessment in Narges Vegetale Oil Company in Shiraz (center of Iran). The output of software showed that the level of risk derived from sulfuric acid, phosphoric acid, aluminum sulphate, nickel catalyst, acetic acid used as a raw material were 2.4, 2.84, 2.3, 3.5 and 2.66, respectively. Moreover, risk rank and proposed control methods for each of these materials were determined. The developed software calculates the health risk level based on the degree of hazard and exposure in shorttime and without using risk matrix and chemical formula. After determining the risk rank, the software proposes the control procedures to reduce occupational exposure.

Idnetifying causes of occupational accidents is a key issue to prevent these accidents. The present study aimed to identify and analyze debilitating accidents in the construction industry during a two-year period (2010 - 2011 years). This was an analytical cross-sectional study. The study data included information about all debilitating accidents occurred within two years. Data collection was performed according to the accident report forms in construction sites. Data analysis was performed using SPSS software version 16. The level of significance was considered as P=0.05. The mean age and job experience of injured people were 27.95±6.95 and 2.34±2.00 years, respectively. Most injuries to people were reported in hand (35.4%), legs (28.3%) and back (20.4%). Most of accident types were respectively related to slipping and falling (26.1%), throwing objects (21.7%), falls (18.6%), abrasion (16.8%) and clash (16.4%). Moreover, the main causes of accidents were related to lack of housekeeping (97.3%), lack of proper training (85.8%), lack of PPE (73.0%), unsafe acts (63.3%), unsafe conditions (32.3%) and equipment (22.6%). Analyzing causes of disabling accidents in the construction industry showed that important factors in these accidents included lack of housekeeping, failure to provide proper training, lack of suitable PPE, unsafe acts, unsafe conditions and equipment for the construction jobs.

Assessment of physical risk factors related to musculoskeletal disorders is performed by different methods including observational methods. Validity of these methods are important in workplaces. The purpose of this study was to investigate the reliability of the Washington States ergonomics checklist as an observational method. This descriptive-analytical study was performed on 50 workers and three tasks in a mattress manufacturing industry. The checklist completed by first group (non-specialists) and second group (ergonomic specialists) in the selected tasks. After assessment, the coefficient of agreement between observers with kappa value was analyzed using SPSS (version 16) software. The first group of observers disagreed about the risk factors of hand force related to caution zone jobs checklist and awkward posture related to hazard zone jobs checklist and kappa value were 0.349, 0.360 and 0.847, respectively. In the second group of observers, kappa values were 0.847 and 0.719 respectively about awkward posture and hand force risk factors. Findings of this study showed that reliability of this method had been weak to good according to calculated kappa values between observers in the first group and good to excellent in the second group and there is possibility error in comparison between the two groups, which might be due to nonspecific nature of this tool and lack the necessary skills of the observers.