فهرست مطالب مهدی قاسم خانی

Safety signs are an important tool as converting information for recognizing the event, type, severity, and control of actual hazards in the environment.  The main importance of displaying safety signs is to prevent injury and aware people of the potential hazards in particular situations in different environments. The aim of this study was conducted to determine the level of perception of Tehran city train passengers about the existing safety and warning signs and to provide an appropriate solution to improve the perception level at the metro stations.

Because the lack of access to the standard questionnaire in the present research, a researcher-created questionnaire was used based on design and manufacturing criteria, test and installation methods accordance to ISO 9186 and ISO 3864 international standards. For this purpose, by forming an expert panel, the research questions were identified and evaluated in relation to the topic, the degree of clarity, and the ease of comprehension. Stratified random sampling was conducted against 390 persons. And the Chi-square tests for datum analysis were performed using SPSS software.

According to the results, the highest perceived symbols belong to smoking symbol with 98 percent and 97 percent perceive the symbol prohibited entry of domestic animals. Symbol “no entry” with 5 percent of Understanding with the lowest level was understandable. The analytical results of this study can be a direct impact on understanding due to education level (Pvalue <0.001) and negative impact on the understanding of symbols mentioned age and income (Pvalue <0.003).

Considering the increasing development of metro lines and the results of the different understanding of each symbol in order to remove or eliminate the hazards, further studies are a necessity. The use of training for ergonomic redesign symbols is undeniable, and decision makers need to devote appropriate resources to teaching symptoms. The visual components of the environment affect the clarity and readability of the symptoms. The shape and size of a sign and board, as well as the size of the letters and position, are effective in understanding. Therefore, in addition to designing based on the psychological and physiological principles, other important factors such as continuous adjustment of symbols distance and height are necessary. When designing text for signs and signs, the space of letters, the space between the lines, the position of symbols and decorative patterns, the margins and the use of upper or lower case letters (in Latin) are important.

Health hazards under heat stress conditions are well known and many industrial workers expose to heat stressful environments. Protection of the health of workers with suitable productivity is very important; the idea requires adoption of a heat stress index that is both reliable and easy to use. Recent studies have found that Thermal Work Limit (TWL) performs better than Wet Bulb Globe Temperature (WBGT) as a predictor of the impact of environmental heat stress. The aims of this study was to evaluate the heat stress level using TWL and WBGT in indoor and outdoor work environments، as well as to identify the correlation between the values of indices in order to determine the optimal index.

The study was undertaken in June 2014 on an onshore drilling rig workers (21 subjects) as indoor group and administrative personnel (31 subjects) as outdoor group of National Iranian Drilling Company (NIDC) located in Ahvaz. Both TWL and WBGT were used to assess the thermal stress at the beginning، middle and end of the shift over 3 consecutive days. All analyses were performed using SPSS version 18.

Based on TWL and WBGT values no significant thermal stress was identified in the indoor working group، but in the outdoor group، the TWL shown different evaluation compared to WBGT. There was significant correlation between the indices at all three shifts in both groups (p-value<0. 05).

WBGT values exceeded of TLV، whereas no case of heat illness was reported during 3 days of the study among the outdoor group. Therefore، the TWL has been shown to be more realistic index than WBGT which was found to be too conservative and inappropriate.

Cement dust is one of the workplace harmful chemicals. There is a disagreement about respiratory effects of cement. The main purpose of this study was to investigate the respiratory effects of exposure to cement dust.

The subjects consisted of 148 male workers (94 workers with current exposure to cement dust and 54 healthy unexposed employees as a referent group). Respiratory symptom questionnaires, as suggested by the American Thoracic Society, were administered to them. Determination of exposure was carried out by personal dust monitoring. Furthermore, the subjects underwent lung function tests by a spirometer. The data were analyzed applying t test and chi-square test.

The mean values of respirable and dust concentrations were estimated to be 7.70± 1.2 and 67.4± 5.4 mg/m3. Significant decrements in the parameters of pulmonary function were noted (p<0.05).

The findings of this study indicate that a strong association exists between exposure to cement dust and the prevalence of respiratory symptoms and functional impairments of the lungs.