دو ماهنامه سلامت کار ایران
سال شانزدهم شماره 2 (خرداد و تیر 1398)

 Road traffic crashes and its deaths and injuries are one of the main public health problems in all over the world especially in Low and Middle Income Countries (LMICs). Road traffic crashes resulting in deaths, physical and psychological problems, and economic costs which have damages on families and communities. The number of road traffic deaths was exceeded from 1.3 million in 2016. Most of the road traffic injuries are belong to low and middle-income countries of the world. Road traffic injury is the eight leading causes of deaths for all ages, while it is largely neglected. 
There are several effective factors in road traffic crashes. The socio-economic status is known as important factors related to health status, although its influence is not fully understood on different aspects of health. People who live in low socioeconomic status suffer from the disease and injuries two times more than others. The results of the studies show that fatal and non-fatal injuries have an inverse relationship with socio-economic status. The socio-economic status is known as important factors related to health status. People who live in low socioeconomic status suffer from the disease and injuries two times more than others. The results of the studies show that fatal and non-fatal injuries have an inverse relationship with SES. However, there is a lack of enough information about the effects of socioeconomic status on road traffic crashes and its related outcomes. 
The incidence rate of road traffic injuries and its related deaths have a relationship with socio-economic status. In the international level, these incidences vary between the High-income countries and Low and Middle-income countries. Moreover, the incidences of road traffic injuries and deaths vary between the different socio-economic groups in each country.
The socio-economic status is known as the main predictor factor in different aspects of health. The importance of socio-economic status will increase in regarding this point which the outcomes of road traffic crashes are sometimes irreversible. However, the effect of socioeconomic status on the many aspects of health is not fully understood. Identifying the socio-economic status factors related to the outcomes of road traffic crashes can provide a good opportunity for policy makers and managers to use preventive interventions in high-risk groups.  This study used an analytical cross-sectional design. The studied sample was people who injured because of road traffic crashes and referred to Pour-Sina hospital in the city of Rasht. Rasht is the central city of Guilan province. Guilan province is located in the north of Iran and the rate of road traffic crashes is high in this province. The collection of data has been done by two researchers. The data collection questioner trained in order to meet the quality assurance and prevention the information bias. The using questionnaires consisted of two parts. The first part was a checklist to collecting the demographic information including the; age, gender, a marital status which obtained from hospital records. Moreover, collecting the crash information such as; the location of the injury, the type of injury, the severity of injury (based on Injury Severity Score), the clinical outcome of the patient which were extracted from hospital records. The second part of the instrument was related to socio-economic issues. For this purpose, the standardized questionnaire was used which the validity and reliability of that were confirmed in the previous study. In the cases that the injured people had died or were unable to interview due to the severity of the injuries, the interview was conducted with one of the close relatives (father, mother, brother or sister) and after obtaining informed consent.
In order to determine the socio-economic status factors (that are a combination of variables), the principal components analysis was used. Principal component analysis simplifies the data and reduces the number of variables. To extracted the factor/factors from the variables, the Varimax rotation method was used. The Varimax rotation is used if factors are assumed to be uncorrelated which is known as orthogonal rotation. In this study, the Eigenvalue greater than 1 was chosen. After determining the factor, the variables that were present in each factor were identified.
To obtain the main socio-economic status factors the method of principal component analysis was used. To assess the interest of the implementation of the principal component analysis on a data, Bartlett’s sphericity test and the KMO index were used. The main SES factors were determined and in order to assess the relationship between these factors and death and severity of injuries related to road traffic crashes, the logistic regression with the Backward-LR method was used. The analysis was adjusted on the variable of age and sex of patients. For the severity of the injury, the ISS scale was grouped (ISS> 15, ISS = <15) and it is considered as the dependent variable in the Logistic Regression model. The ISS scale above 15 is considered to be a severe injury All analyses were performed using the SPSS software version 20. The significance level of the tests in this study was considered 0.05.  In this study, 300 traumatic patients were recruited. From all, 234 patients (78%) were male. The mean age of injured patients was 34.25 years old (19.07). The ISS scale was grouped (ISS> 15, ISS = <15). the ISS scale above 15 is considered to be a severe injury. The severe injury (ISS > 15) was observed among 245 (81.7%) patients. 
Bartlett’s sphericity test and the KMO index showed that there is a good correlation between the studied variables and the using of principal component analysis is feasible. The p-value for the Bartlett test is significant and the KMO index is more than 0.5. Some socio-economic status factors had a relationship with the outcomes of death and the severity of the injury of patients. There were three factors which affect the outcome of road traffic crashes. The first factor includes the following variables; household cost, the education level of an injured person, and the education level of the mother. The second factor includes the variables of; job, owning the mobile and motorcyclist. The third factor includes the variables of; income and fathers job. The results of logistic regression analysis showed that factor 3 (family income and father's job) had a significant relationship with the outcome of traumatic death. For this factor, the odds ratios of 0.45 (CI 95%; 0.042- 0.83) for deaths and 0.65 (CI 95%; 0.45- 0.90) for the severity of injuries was obtained. The highest SES had the lowest deaths and injuries. 
There was a relationship between economic factors and the severity of the trauma, the economic-social third factor including variables; family income and father's occupation were identified as an effective factor in the severity of trauma. The odds ratio for the third factor (household income and father's occupation) was 0.68 (95% confidence interval: 0.452-0.908).  The results of this study showed that social economic factors affect both the deaths and the severity of injuries. The results of this study showed that the third factor (family income and father's job) had a significant relationship with traumatic death. In other words, the mortality rate of road traffic crashes is high among families with a low level of socio-economic status. Considering the high rates of deaths and severe injuries caused by traffic accidents in Iran compared to other countries, it is necessary economic and social factors will be considered as effective factors on deaths and injuries in road traffic policy-making and planning.

Air pollution reduction is important in health being of people and environment. Applying of an effective and efficient strategy is key consideration in facing with environmental challenges of management and control of air pollution. Recently, the main effort of environmental researchers is finding low cost and effective methods to control of environmental pollutants. Pollution prevention and control account as main techniques of pollution reduction. However, the prevention role is important than pollution control. Implementation of control practices and using of effective devices and technical equipments is necessary to achieve control strategy of pollution. One of the most important steps in air pollution control is selection the appropriate control equipment. Several factors included in selection of proper and technical equipments such as; cost, designing, efficiency, and etc. Choosing of proper control devices with lower emission rate of pollutants would result in lower destruction and environmental costs. Desired decision should be based on different criteria of socio-economic, and management. Choosing of appropriate control devices by consideration of various characteristics is complicated. Recently, one of the management challenges is selection of control devices based on the socio-economical, technical and environmental criteria. MADM models are one of the supportive decision systems applied for priority, and selection of best alternative. These methods seek for choosing the best and effective alternative by considering of multiple criteria. The aim of the present study is selection of air pollution control technologies with considering appropriate aspects of socio-economic and techno-practical criteria. Selection of suitable and effective control devices is key factor in prevention of losing human and financial capital. In this research, MADM technique based on fuzzy TOPSIS method has been used for appropriate selection of air pollution control equipment and pollution management. By literature review and cooperation of air pollution experts, common technologies in fields of air pollution included in petrochemical industries have been identified and keyed. Firstly, primarily questionnaire is prepared and then its reliability and validity were done using Lawshe's method. Five criteria including filtration efficiency, cost, maintainability, design ability and size for rating the control technologies related to air pollutants include of (NOX, SOX and CO) have been considered.  Criteria weighting has been done using Shannon entropy and Fuzzy TOPSIS technique has been applied for prioritize of indicators. Data bank of primarily questions including pollution control technologies about three categories of air pollutants (NOx, SOx, and CO) has been collected and organized to provide final questionnaire. Then, questionnaire has been distributed between expert panel with air pollution discipline to complete it. After that, the weight of study criteria (including; cost, treatment efficiency, size, maintenance, design and build up) is identified using Shannon entropy method. The answers of expert panel to questionnaire were verbal. So, there was a need to be converted as scales with analytical property. As, doing mathematical operations on descriptive qualitative variables were impossible. Therefore, descriptive variables have been converted to fuzzy scales. In this research, triangular fuzzy values have been used. Fuzzy TOPSIS technique has been applied for ranking of indicators. Accordingly, it is implemented during 7 steps including; choosing proper fuzzy scale of measurement, provide decision matrix (calculation of importance degree of each indicator for every criterion), weighting of decision matrix, normalize weighted decision matrix, determination of positive and negative fuzzy ideal responses, identify distance of each indicator, and determination of closeness coefficient of indicators to ranking indicators.   The results of study illustrate that final weighting of study's criteria based on expert panel opinions and using Shannon entropy technique is different for each pollutant (Table 1).
Table 1. Final weighting of study's criteria based on Shannon entropy technique in terms of each pollutant




No.
Final weighting for each pollutant
Cost
Size
Maintenance
Efficiency
Designing


1
Wi ( NOX)
0.212
0.063
0.047
0.378
0.300


2
Wi( SOX)
0.278
0.165
0.059
0.390
0.107


3
Wi( CO)
0.111
0.154
0.042
0.651
0.042



Fuzziness decision matrix of control technologies for three types of pollutants is given in Table 2.
Table 2. Fuzziness decision matrix of control technologies



Pollutant
Control technology
Cost
Size
Maintenance
Efficiency
Designing


NOx
Selective catalytic reduction (SCR)
(1.13, 1.52, 2.26)
(0.61, 0.86, 1.06)
(0.45, 0.67, 0.89)
(0.68, 0.88, 0. 99)
(0.4, 0. 61, 0. 82)


Non Selective catalytic reduction (NSCR)
(1.14, 1.48, 2.18)
(0.51, 0.75, 0.97)
(0.46, 0.73, 0.96)
(0.54, 0.74, 0.88)
(0.6, 0.83, 1)


Non- thermal plasma
(1.26, 1.64, 2.35)
(0.56, 0.78, 0.97)
(0.5, 0.7, 0.9)
(0.69, 0.88, 1)
(0.53, 0.73, 0.9)


Plasma- catalytic hybrid process
(1.12, 1.5, 2.14)
(0.55, 0.79, 1)
(0.51, 0.76, 1)
(0.73, 0.91, 1)
(0.55, 0.78, 0.96)


Scrubber
(1, 1.25, 1.76)
(0.53, 0.76, 0.99)
(0.51, 0.76, 0.98)
(0.49, 0.69, 0.86)
(0.6, 0.82, 0.98)


SOX
Scrubber
(4.67, 6.53, 8.2)
(5, 6.93, 8.6)
(4.13, 5.93, 7.47)
(6.07, 7.8, 8.93)
(5.67, 7.4, 8.6)


Catalytic
(2.53, 4.13, 5.93)
(4.33, 6.13, 7.87)
(3.93, 5.73, 7.27)
(5.93, 7.67, 8.73)
(4.33, 6.13, 7.53)


Flare
(2.87, 4.4, 6.13)
(3.4, 5.2, 6.93)
(3.27, 4.93, 6.6)
(4.6, 6.47, 8)
(4.4, 6.27, 7.73)


High Stack
(3.8, 5.2, 6.53)
(3.27, 4.73, 6.27)
(4.2, 5.8, 7.13)
(3.07, 4.57, 6.14)
(4, 5.53, 6.87)


Active carbon
(2.6, 4.2, 6)
(4.13, 5.93, 7.6)
(3.27, 4/.93, 6.73)
(4.47, 6.07, 7.6)
(4.4, 6.13, 7.67)


CO
Non- thermal plasma
(2.73, 4.27, 5.93)
(3.87, 5.8, 7.53)
(4.27, 6, 7.67)
(7, 8.73, 9.73)
(4.87, 6.8, 8.4)


Plasma- catalytic hybrid process
(3.2, 4.87, 6.6)
(4.33, 6.33, 8.07)
(4.27, 6.13, 7.87)
(6.87, 8.53, 9.6)
(5.07, 6.8, 8.2)


Flare
(3.33, 4.87, 6.47)
(3.13, 4.87, 6.73)
(3.4, 5.07, 6.73)
(4.33, 6.07, 7.6)
(4.13, 5.73, 7.13)


High Stack
(3.07, 4.6, 6.2)
(2.93, 4.6, 6.47)
(4.2, 5.93, 7.53)
(2.93, 4.4, 6.07)
(4.4, 6, 7.4)


Scrubber
(4.07, 5.87, 7.47)
(4.4, 6.27, 7.8)
(3.8, 5.47, 7.07)
(5.53, 7.07, 8.13)
(5.07, 6.67, 8)


After weighting of decision matrix it has been normalized and then positive and negative fuzzy ideal answers are determined. Then, distance of each indicator has been identified and closeness coefficient of indicators is reported to ranking of control technologies based on pollutant type (Table 3).
Table 3. Priority of selected optimum technologies for air pollution treatment in present study 



Control technology of NOx
+D
-D
CCi
Rank
Control technology of SOx
+D
-D
CCi
Rank
Control technology of CO
+D
-D
CCi
Rank


Selective catalytic reduction (SCR)
0.104
0.143
0.5782
4
Scrubber
0.272
0.201
0.4254
4
Non- thermal plasma
0.011
0.313
0.9657
1


Non Selective catalytic reduction (NSCR)
0.102
0.142
0.5808
3
Catalytic
0.038
0.435
0.9194
1
Plasma- catalytic hybrid process
0.022
0.302
0.9316
2


Non- thermal plasma
0.046
0.199
0.8129
1
Flare
0.172
0.304
0.6384
3
Flare
0.217
0.108
0.3327
4


Plasma- catalytic hybrid process
0.054
0.189
0.7769
2
High Stack
0.382
0.098
0.2049
5
High Stack
0.313
0.011
0.0341
5


Scrubber
0.181
0.063
0.2584
5
Active carbon
0.123
0.351
0.7407
2
Scrubber
0.138
0.211
0.6049
3





As we can see from Table 3, Cold plasma technology with closeness coefficient of 0.8129 was identified as the most appropriate filtration technology for treatment of NOX pollutant at the petrochemical industry. It has been choose as proper and selective option due to selective and effective treatment efficiency of this technology for NOx pollutant, very low energy consumption and safe performance of reactor because of very low amperage. Plasma- catalytic hybrid process has been selected as secondary priority because of costly selective catalyst and also generation of unwanted byproducts. Catalytic based methods with closeness coefficient of 0.9194 possess higher ranking for SOX control compared to other techniques and carbon active technology placed at the secondary rank. The main reasons in catalytic priority are high efficiency, availability of absorbent chemical materials, easy and low cost of designing and build up that technology. In priority of control technologies for CO removal, non- thermal plasma technology with closeness coefficient of 0.9679 has been identified as the best technology and plasma catalytic hybrid process placed at the next priority. It has been known that one dimensional attitude to proper decision-making process is inefficient. Also, comprehensive considerations in management methods to make appropriate decisions are undeniable. Fuzzy TOPSIS technique is a reliable method to achieve effective and efficient technology based on different and multiple criteria. Selection of appropriate control equipment using multi attribute decision making methods and consideration of multiple criteria using Fuzzy TOPSIS method are possible. In present study, selection of appropriate control technologies using Fuzzy TOPSIS technique is addressed for some pollutants including NOX, SOX and CO. Recognition, prioritize, and selection of proper technologies with low cost and effective performance in field of environmental pollution control according to effective criteria are undeniable requirements of optimum consumption of project's resources. Thus, new designs of control technologies with emphasize on effective efficiency should be identified. Multi attribute decision making method known as efficient tool in this subject. It is applied for prioritize treatment technologies with low uncertainty especially, in petrochemical industries with high level of some considerations including; socio-economic, techno-operational, and environmental.

Growth of labor productivity is one of the most important factors of development and competitiveness of the economy. In targeting economic growth, a significant contribution is being made to improve productivity. Labor productivity in a community has several socio-economic dimensions. Since labor productivity reflects the level of production and performance of people in the community, it is therefore very close to general well-being, because when a society produces its population, it has more prosperity and resources than a lower-productivity economy. The situation of labor productivity determines the success of an economy in competing with other economies, with lower finished product costs and lower prices that may not be feasible for a low productivity economy and exit from market competition. Worker productivity in a community is one of the key multivariate variables, which is always a matter for the attention of community planners and policymakers. The importance of this issue for developing economies, such as Iran, is twofold; in fact, one of the main priorities of the Iranian economy is to improve productivity, which is, of course, in large-scale programs of the community, such as development plans (in development programs, it is usually said that one-third of economic growth will be achieved through improved productivity) Or general policies such as resistance policies and policies to reduce dependence on oil and enhance the competitiveness of the Iranian economy. Although productivity improvements in the Iranian economy have always been seriously addressed, significant improvement in productivity, especially compared with other economies, has been a mystery of numerous theoretical and empirical studies. One of the reasons for failure to improve the productivity indicators in Iran is that less attention has been paid to the relationships and determinants of productivity. Hence, effective factors on improving the productivity, has been the focus of attention of researchers in different fields. One of the most important determinants of labor productivity is the improvement of health indicators in the society.The health status of people in the community is regarded as human capital, whose health costs and community health as a net investment and treatment costs reduce the effects of illness as an alternative investment. Through various channels, health can affect the level of production and productivity of a country. First, directly in most cases, healthy people work better than others and have a more creative and ready mind. Healthier workers are physically and mentally stronger, they are less likely to go to work and gain a living. Health also has indirect effects on production and productivity. For example, improving health in the workforce will have the incentive to continue to study and acquire better skills, because improving health will, on the one hand, increase the attractiveness of investment in education and educational opportunities. Also, increasing health and health indicators in the society will help people save more by reducing mortality and increasing their life expectancy. Physical capital has increased as a result of increased popularity in society, and it will also indirectly affect labor productivity. Applying people with higher education in an economy, due to more human capital, leads to increased labor productivity and economic growth. At the firm level, the general health of the workforce reduces job stress and thus improves their productivity. Therefore, safety in the work environment is directly related to the ability to perform work. Of course, the health of the workforce is not just about their physical condition, but their mental health and communication with affection and respect in the workplace will improve their performance.
Unfortunately, the impact of health expenditures on improving productivity has been underestimated in Iran. Therefore, the purpose of this study is to examine the effect of health expenditure on proving labor productivity in Iran. 

The present study has investigated the relationship between gross domestic product (GDP) and labor productivity using time series data related to the sharing of health expenditure during the period of 1351-1394. Due to the long-term nature of the effect of health expenditure on labor productivity, Johansson-Juselius co-integration has been used. One of the key concepts of econometric studies, especially in time series data, is the problem of the steady-state variables over time. If the time series variables used are not proportional to the model coefficients, while there may not be any relation or conception between the model variables, the coefficient of determination of its R2 can be very high and cause inaccurate inferences in this case. Of course, at macro level, we usually encounter non-invariant variables, and variables overlap from their previous path over time. Therefore, while it may be possible for two variables to diverge from their original paths and, in fact, to be non-negative, but they may move in one direction (They may be convergent). In econometrics, the concept of convergence is used to examine the long-run relationship between variables. The concept of convergence is that when two or more times series variables are linked to one another, based on theoretical foundations, to form a long-term equilibrium relationship, it may be that the series itself has a random process, but in the long run They follow each other well, so that the difference between them is stable (mana). Therefore, the concept of co-integration is a long-term equilibrium relationship that the economic system moves over time. The methodology is used to determine the number of convergent variables among the variables by first applying the maximum value of the special value and the effect test presented by Johansen and known as the likelihood ratio statistics. Then the Co-integration Equation and Vector Error Correction Model (VECM) are estimated. we also implicitly explained the impact of other variables such as education, per capita capital and urbanization on labor productivity.

The results indicate that per capita health expenditure has a positive and significant effect on labor productivity in long-term with a coefficient of 0.36. As the one percent increase in per capita expenditure of health improves the productivity of labor force in Iran by as much as 0.36 percent. Expenditures on education and physical per capita also have a positive and significant effect on labor productivity with coefficients of 0.41 and 0.09. But in terms of urbanization, urbanization is often associated with improved productivity, given that economic development theories have economic development with urbanization. What the current study suggests is that the rate of urbanization has not only been accompanied by improved labor productivity in Iran in the long run, but also urbanization has a negative and significant effect on the productivity of labor in Iran with a coefficient of 0.02. The short-term convergence rate (ECM coefficient) to long-term equilibrium value is -0.3 / 0, which indicates the high speed of the moderation, so that it takes less than three periods to adjust the short-term value to long-term equilibrium

The present study shows that for budgeting of health sector, the long-term goals of it, namely, the impact of it on productivity and consequently economic growth and development should be considered. The results indicate that long-term health expenditures have a positive and significant effect on improving labor productivity. A one-percent increase in health spending will improve the labor productivity index by 0.36. A one percent increase in higher education costs will also increase labor productivity by 0.4 percentage points. The health and education sector has long-term effects and should not expect short-term results to be spent on these sectors, and policy-makers in general should increase the share of health and education of national income over time. Labor productivity. Another result of the study is the positive and significant impact of the existence of physical capital on labor productivity. This result is also consistent with theoretical and empirical expectations. Having a work tool and improving its technology can enhance human performance. Basically, one of the limitations of developing countries is the lack of sufficient funds for labor force recruitment. By mobilizing domestic and foreign capital, policymakers will be able to utilize more labor force and increase labor productivity by providing technological and capitalist needs. The present study shows that in order to improve the productivity of labor force in Iran, special attention should be paid to health and education. Eventually, the growth of urbanization in Iran leads to a confounding phenomenon and reduces the labor efficiency. Although based on economic theory, urbanization has been accompanied by economic development for developed countries, the results of this study shows that this category has not been true for Iran. Urbanization in Iran is not the developmental one, but due to the lack of facilities in rural areas, the unequal distribution of facilities at the geographical level, local unemployment and the increase in land prices and housing in urban areas; therefore, it cannot be expected that in the Iranian economy, urbanization along with Improvement of development indicators, but on the contrary, because of its disproportionate growth with socioeconomic facilities, the consequences of environmental degradation, pollution, traffic, inequality, destruction of social indicators and, consequently, the health of people in these areas, and therefore have a negative impact on labor productivity Laid down. Therefore, it is suggested that community planners move towards decentralization policies and improve business conditions in rural areas.

Nowadays, global warming and climate change have become one of the controversial topics that have an impact on the health of individuals and the threat to human life. In recent decades, particular attention has been paid to the issue of environmental change and its impact from different perspectives. Many studies have been conducted to study these effects (generally from a non-occupational perspective) around the world. But from a job standpoint, the probable effects of global warming on occupational health are under reached, although its trend is growing. Outdoor workers are one of the most vulnerable groups of people directly affected by global warming. Climate change and global warming can cause many health problems, one of the most important of which is the development of thermal stresses and related disorders in outdoor occupational exposures.  Iran is a large country with very wide climatic diversity, with 35. 5% of it in complete arid, 29.2% of the arid, 20.1% of the semi- arid, 5% of the Mediterranean and 10% of the Wet climates in the country. Thus, more than 82% of the territory of the country is located in the arid and semi-arid region of the world. The average rainfall is 250 mm, less than one third world-wide (860 mm), and its dispersion degree is very high in the country. Increasing the average temperature can lead to warmer days and longer and more frequent heat waves. This, in turn, can increase the risk of heat-related diseases such as heat stroke, heat cramp, heat exhaustion, etc., and even in advanced cases, causes death. These effects are likely to be different in different regions, based on the sensitivity of the community, the amount and duration of exposure, as well as the ability of individuals to adapt to temperature variations. So, the main objective of this study was to investigate temperature changes in different climates of Iran in the coming decades in order to obtain an adequate understanding of the heat stress state in outdoor environments.

The environmental parameters required in this study were air temperature (ta), wet temperature (tw) and relative humidity (RH) which are determined by calibrated devices. At the same time, the WBGT temperature index was also measured and recorded using the calibrated WBGT meter, Casella model. All measurements were carried out at three times throughout the day, including 9 am, 12 noon and 3 pm, indicating the initial, mid, and final hours of shift work in the studied environments in the country, respectively. In order to cover this study throughout the country, and taking into account all the existing climates in the country, with the exception of areas with cold- dry and cold- humid climates, which often include the western and northwest parts of the country, 9 climatic zones in each country were selected in that country. A total of 495 measurement series of environmental parameters were carried out in nine climates (55 measurements per each climate). All measurements were done in outdoor settings such as open pit mines, asphalt and road workers, farmers, cement factories and shipbuilding industries. The selection of industries and locations was also performed randomly. Selected sites in this study, each representing different climates in the country, included cities of Ahwaz, Bandar Abbas, Rasht, Gorgan, Kerman, Yazd, Sari, Qom and Mashhad.

The Arc / GIS 8.0 software was used to generalize the data from a meteorological station to other weather stations in a similar climatic zone, and the environmental parameter values ​​measured at each station were similar to the other meteorological stations in the same climate were linked. Thus, in the GIS information layers, different climate zones were determined using two parameters of air temperature and humidity. In this process, the gathered spot data was converted into regional data. In addition, the long-term data for each climate zone (between 1965 and 2010), including the minimum and maximum daily air temperature, rainfall and sunshine, were used to generalize the data to other similar climate zones. Finally, using the weather behavior of previous periods at the studied stations, the weather conditions between 2011 and 2100 using the LARS-WG model and a coupled atmosphere-ocean general circulation model (HadCM3) for each of the 9 weather stations, simulations were performed. Then, according to the goal of the study that emphasizes the stress on outdoor work space, this model evaluates climate change in different regions based on daily maximum and minimum temperatures up to 2100 at 25-year intervals.


Based on the results, a temperature increase with different intensities is expected in the next decade. In addition, the pattern of variations was almost the same for all stations studied. On the other hand, slight changes in the average daily minimum and maximum air temperature are observed until 2025. These changes were not very different in the spring and summer. After that, by 2075, the temperature increase is observed with a gentle slope, and thereafter, until 2100, no significant changes are observed for most of the stations. However, there is a significant increase in the average daily minimum and maximum temperatures in summer compared to spring. According to the results of the model, the highest temperature rise in 2075 is expected in most parts of the country. 

In general, the mean and standard deviation (M ± SD) of expected changes at minimum and maximum temperatures were 1.34 ± 1.41 °C and 1.29 ± 1.40 °C for spring and 2.38 ± 2.44 °C and 2.34± 2.48 °C for the summer, respectively. The respective values, regardless of the season (spring or summer) were1.86 ± 2.05 °C and 1.82 ± 2.07 °C for the minimum and maximum temperature changes, respectively. In general, it can be said that the average temperature of different climates of Iran will increase by about 2 °C until 2100. 

The results of the thermal stresses in the nine areas studied, which were simultaneously with other environmental parameters of the study, showed that in the spring, except for climatic zones 5 and 6, which are related to the cities of Yazd and Bandar Abbas, at least at 12 noon, no significant stress was observed in any of the affected areas. However, over time and approaching the afternoon (until around 3:00 pm), many other climatic zones, including sites 2, 7 and 8 (cities such as Ahvaz, Sari and Gorgan) , In addition to sites 5 and 6, will be in a stressed state even in the afternoon. 

In other words, in almost all parts of the country, especially in the middle and end of shift work, there is heat stress in the summer or even in many areas in the spring. The lowest WBGT index was 17.5 ± 0.99 °C for the early hours of the morning (in the spring and in the northern regions of the country) and the maximum is 35.10 ± 0.55 °C for noon and evening hours (in the summer and in the southern regions of the country). In general, the analysis of temperature differences and heat stress in different parts of the country also shows that parts of the country that have the greatest impact on climate change are the central and southern regions of the country. 

These findings clearly show that many workers, especially those working in outdoor environments, are currently in an environmentally unfavorable condition (regardless of any possible increase in temperature as a result of climate change) and they suffer from the dangers and complications of thermal stress.

Considering the objectives of the study as well as the obtaining results about climate change during the current century (about 2 °C), it can be expected that the trend of changes in thermal stress in the country will also change in most parts of the country similar to the trend of temperature changes in the country in the coming decades.

Climate change caused by global warming and, as a result, increased heat stress, especially for outdoor workers, is a very important issue that has relatively similar effects in different parts of the world. Based on the obtained results, an increase of about 2 degrees Celsius to the average temperature of the air, regardless of the changes in other parameters affecting heat stress such as relative humidity, air velocity and radiant temperature, can put several parts of the country under thermal stress conditions. In other words, the different areas and external environments that are currently in terms of acceptable thermal stress status will suffer from heat stress due to climate change and rising temperatures in the coming decades. For example, it is expected that the northwest, west, and northern and central parts of the country will be exposed to heat stress. 

In addition, most of the southern and central parts of the country, which are currently in heat stress, will be in a worse situation. Therefore, preventive interventions such as open outdoor environments design, shading in industrial areas, designing cool rest areas to reduce exposure to heat, developing work and rest programs, attention to acclimatization to the environment and observing public health programs, can play an important role in reducing the adverse health effects of climate change and the increase in temperature on exposed outdoor workers.

Hazard identification is a critical factor to ensure safe design and operation of systems in the process industries. Process industries are one of the most complex systems, with a variety of equipment, control systems, and executive procedures. In these industries, the use of hazardous materials as raw materials or products is quite common. Interactions between technical components, human factors, and organizational and managerial issues can lead to defects and accidents. Therefore, ensuring safety in the process industries can be a very complicated task. The process industries had led to many accidents with very severe consequences. For example, the explosion and fire of the Piper Alpha oil platform with 167 people killed in 1988, the explosion and fire at Esso gas in Longford, with 2 deaths in Australia in 1988, the explosion of the BP refinery with the death of 15 people in Texas in the year 2005 and Deepwater Horizon in 2010 could be mentioned.
In order to prevent the occurrence of accidents or reduce the likelihood of occurrence and the severity of the consequences, various techniques have been developed to identify the hazards. However, due to the complexity of the unique conditions of process industries and resource constraints, always the most appropriate technique for identifying hazards should be used. Hazard identification and risk assessment are the implications of system safety since the mid-twentieth century, with the emergence of an action-oriented approach to safety. Since then, several methods have been developed to identify the hazard and evaluate risk in various manufacturing processes. Various generations of these techniques have been presented and each one is trying to provide the best formula or mental patterns to assessors to identify the hazards. Typically, the choice of hazard identification method is based on the frequency of application of that method in a particular industry and the degree of its acceptance among the experts in that industry. But sometimes the situation is not clear and the decision is somewhat difficult. In this situation, experts face a multi-criteria decision-making problem. Multi-criteria decision-making methods are used in situations where there are many alternatives and criteria. Selecting an inappropriate method to identify the hazards in the process industry could lead to a large number of hazards and waste of resources. Therefore, the aim of this study is to identify effective criteria in selecting the most appropriate method for identifying hazards in process industries and determining the most appropriate method in this industry.

In this study, to select the most appropriate methods for identifying hazards in process industries, Preliminary Hazard Analysis (PHA), Hazard and Operability Study (HAZOP), Subsystem Hazard Analysis (SSHA), System Hazard Analysis (SHA), Operability & Support Hazard Analysis (O&SHA), Fault Tree Analysis (FTA), Energy Trace and Barrier Analysis (ETBA), Software Hazard Analysis (SWHA), Failure Mode & Effects Analysis (FMEA), Management Oversights & Risk Tree (MORT), Chang Analysis (CA), and Job Safety Analysis (JSA) techniques were used. Also, in order to assess the hazard identification methods, ‘the cost of implementation of the technique, user-friendly features, flexibility, implementation time of the technique, the human resources required to perform safety analysis, the possibility of using the technique in the most phases of the system life cycle, history of using technique in similar industries, technique’s logic, experience of analysis team, reliability and depth of the analysis of the technique, dependence on information and data, and equipment needed to implement the technique’ criteria were used based on the opinions of the research team. In order to select important criteria from a set of criteria, a panel of experts with a work experience of at least 5 years comprised of 9 PhDs in occupational health, 3 PhDs in chemistry, 1 specialist in risk management, 6 MScs in HSE and 1 PhD in environment were used. Expert’s opinions about the importance of each of the criteria were gathered through a questionnaire composed of the five "Very good, good, moderate, weak and very weak" spectrum. Finally, using one sample t-test in SPSS 16 software was used to determine the important criteria according to the expert’s opinion.
In order to determine and select the most appropriate method for identifying hazards in the process industry, according to experts’ comments based on the existence of an internal relationship between the evaluation criteria of the methods, ANP technique was used. Initially, in order to obtain the weights of each criterion, internal relations and alternatives, a panel of experts with a work experience of at least 5 years, consisting of 5 PhDs in occupational health, 1 risk management specialist, 2 PhDs in chemistry and 2 MScs in HSE were selected. In the following, the number of paired comparisons in each questionnaire was calculated to determine the weight and importance of the factors. The way of completing the paired comparison questionnaire was to first explain to each of the experts the parameters of the questionnaire and how to complete the paired comparison using the 9-way suggested range by saaty. It should be noted that each of the experts completed the questionnaires alone. The weight vector of each of the criteria and alternatives was calculated by pair comparisons for each expert. Since a panel of experts has been used in this study for the sake of completeness, the geometric meaning was taken from all of the matrices drawn from the experts. Inconsistency ratio by 0.1 bases for pairwise comparison Matrices was calculated. Subsequently, the formation of the inverted supermatrix, the calculation of the superharmonic matrix and the calculation of the supermatrix Mandar distribution were performed. In this study, Super Decision software version 2.6.0 was used to determine the weight of criteria and alternatives by ANP method.

The statistical analysis of one sample T-test was based on the opinions of 20 experts in order to determine the important criteria for participating in the proposed ANP model structure at 95% confidence level, 6 of the 12 criteria were selected. These criteria were ‘experience of analysis team, reliability, and depth of the analysis of the technique, dependence on information and data, history of using the technique in similar industries, flexibility, and the possibility of using the technique in the most phases of the system life cycle’.
Criteria obtained from the last stage were pairwise comparison by the experts' opinions. The inconsistency ratio was 0.058. The results showed that the reliability and the depth of the analysis of the technique criterion with a normalized weight of 0.21 has the highest weight and is in the first priority. In the following, based on the obtained weights, ‘the possibility of using the technique in the most phases of the system life cycle (0.206), flexibility (0.201), dependence on information and data (0.106), experience of analysis team (0.189), and history of using technique in similar industries (0.088)’ criteria were prioritized, respectively. In this study, based on expert panel comments, there was an internal relationship between reliability and depth of the analysis of the technique, flexibility, and dependence on information and data criteria.
The supermatrix represents the relationships between the components of the network, through which the final weight of the alternatives can be achieved according to the importance of criteria and their internal relations. Accordingly, the normalized weight and the importance of the alternatives (hazard identification methods) were obtained. Based on the results, the HAZOP (0.1396), FMEA (0.1385), ETBA (0.1197), FTA (0.0984), PHA (0.0875), SHA (0.0806), CA (0.0769), O&SHA (0.0735), SWHA (0.0574), MORT (0.0495), SSHA (0.0395) and JSA (0.0389) were the most preferred techniques in order to identify hazards in process industries.

One of the biggest problems in the process industries is the selection of the most appropriate method for identifying hazards and risk scenarios, why so determining the correct control measures is conditional on complete identification of the risk scenarios. In general, the purpose of this study was to explain a structured method for selecting a risk identification method in the industry so that experts and analysts take into account the criteria affecting the application of a method and the degree of importance of each criterion in choosing the appropriate technique for their purpose. In this regard, the process industries have been selected as a high-risk industry, which has been significantly developed in Iran. In this industry, a specific method for identifying hazards called HAZOP has been presented, and the results of this study showed that this technique is at the top of possible choices. However, other techniques such as FMEA are also applicable to these industries. Accordingly, the HAZOP, FMEA, FTA, PHA, SHA, CA, O&SHA, SWHA, MORT, SSHA, and JSA methods were identified as the most preferred techniques for identifying hazards in the process industries by experts. Also, the implementation of this study showed that in other industries that have not been provided with a specific method, a systematic selection of hazard identification methods is possible.
The results of this study showed that, despite the various criteria for selecting a risk identification method, some of the criteria are more important and their significance and the internal relationship could be estimated using multi-criteria decision-making techniques such as ANP.
One of the limitations of this study is extracting hazard identification techniques and evaluation criteria from one source. Another limitation of this study is the use of exact numbers scale in the process of weighing the criteria and alternatives based on verbal expressions. Therefore, it is suggested that the proposed ANP model be solved under fuzzy conditions in future studies in order to eliminate the probabilistic ambiguity and possible uncertainty in verbal expressions.

One of the factors affecting the health of people in the community is the health status of food procurement distribution and supply. Overlooking and controlling of these centers is the responsibility of environmental health inspectors. Considering the importance of interaction between environmental health inspectors and providers of food supply, distribution and supply centers, and its impact on the implementation of health rules and regulations by the principal, the main objective of this study is to identify the factors affecting the interaction between environmental health inspectors and providers of procurement centers, Distributing and supplying food, as well as identifying the weaknesses and strengths of the system and the environmental health inspection method from the perspective of inspectors and operators. The health condition of supply centres, distribution and supply of food affects the health of the people of the society, which is why it is important to supervise the control of these centres in order to provide food security at a high degree. In Iran, monitoring centres, distribution and supply of food in order to protect the health of consumers from these centres will be directed at the Health Department of Medical Sciences of the Universities of Medical Sciencesacross the country. The proper monitoring and control of these centres has an effective and effective role in preventing and spreading epidemics and epidemics, causing public health and preventing waste of financial resources. In industrialized countries, about 30 % of people are suffering from water and food, while in third world countries, about 80 % of all diseases and 33 per cent of deaths are caused by water use and contaminated food. Therefore, experts and health experts have an important role in planning, implementation and management of health activities all over the local, national and global levels, as part of the advisory process in planning, implementation and management of health activities all over the local, national and global levels. control, distribution, and supply of food were always accompanied by many problems and defects, which in many cases caused the dissatisfaction of consumers. One of the most important of these problems is the failure of the operators to comply with the relevant health laws so that most of the time the enforcement of the regulations and health considerations have been accompanied by the resistance and refusal of the operators. For example, in 2016 alone 40 percent of the supply, distribution and supply of food in the country were in good health condition. there are few studies and researches on the issues of the work of health inspectors of the environment, which are not widely distributed to the long history and variety of work and function of the health inspectors of the environment and its importance. according to the importance of interaction between the health inspectors and the operators of supply centers, distribution and supply of food and its impact on the enforcement of laws and health orders from the incumbent, there has been no specific qualitative study in this regard. the main purpose of this study is to identify the factors affecting the interaction between the health inspectors of the environment and operators of supply centers, distribution and supply of food as well as identifying the strengths and weaknesses of the system and the environment of the environment from the viewpoint of inspectors and operators and became aware.                                                                                           

This study is an applied study, and qualitative analysis of quality content analysis has been done. Participants included eight environmental health experts and six providers of food procurement, distribution and supply centers, Sample selection criteria were sample-based samples that were selected based on objective sampling. The criterion for the determination of the number of samples in this research was theoretical saturation of the researcher. Data was collected using semi-structured individual interviews. Interviews were recorded and then rewritten and analyzed using Maxqda 10 software and codes, subclasses and classes were identified And then for each of the 24 subclasses, a separate interpretation was written. in order to identify the key concepts and concepts in the text, the text of the interviews was written in line and word to each sentence or the keyword, and the initial codes were identified. In the next step, the same initial codes are grouped into one sub - floor and then the main classes of combination of the following categoriesCommon concepts were formed. It has been tried to make the highest heterogeneity among the classes and the highest heterogeneity among the classes. Initially, the classes were named, but it did not have the name of abstraction. By performing a continuous comparison of the same classes, the same themes were merged and finally extracted from the main themes. Also, for assessing codes, subclasses and classes derived from Densin and Linak criteria, including credibility, transferability, trust, and verifiability were used. to determine the validity and validity of the data, the researcher has a long - term relationship with research sites that has helped attract the confidence of the participants and the correct understanding of the environment by the researcher, the maximum diversity in selecting the participants and the right strategy in selecting the sample is to reassure the participants about confidentiality of information and their freedom in the study including means of credit enhancement. To provide data confidence, after analyzing the text of interviews by the researcher, the text of some of the interviews was available to some expert colleagues in order to compare them with the coding of the data, the data can be provided. in fact, the similarity of the second - type code was provided by the researcher's coding so that in the context of one of the interviews, 85 % of the codes written by researcher and the latter were similar. It was, in fact, used the review method by colleagues in this way that the text was copied and coded and analyzed by the colleagues in order to obtain consensus agreements in order to provide the data transmission capability, interview questions, codes, categories and generally the findings of the study were related to other knowledgeable individuals and experts and their comments about the fit of the findings were examined. in order to verify the data and determine the authenticity of the codes from the interviews, the information was confirmed by the participants. So, after interviewing, data mining and coding, the research has again turned to individual participants in the study and examined their approval from the literature and thus evaluation of samples was done from the literature and thus agreement and approval of the participants were obtained.

participation in this research is the first group, experts and health inspectors of the environment with an average age of 41 (65)from both sexes (seven male and one female), with a bachelor's degree (six)and master " s (two), with an average of 75 / 17 (43), and in the second category, operators and operators Managers of the development, distribution and supply of food with an average age of 45 (65), all males, with certificate (one person)and diploma (four persons), with the average history record of 25 years (43 years). After analyzing the data in this study, 338 primary codes were extracted. After analyzing the extracted codes, the codes were classified in six main categories and 24 sub-classes. The main classes are the factors related to education, the focus of the monitoring system, legal measures, the inspection method, the acceptance of the rules by the curator, the attention of the inspector to the managerial and geographical conditions.

The opinions expressed in the interviews by the two groups of inspectors and attendants have many points of contact. This sharing of views between inspectors and attendants can provide the interaction fields between them as well. According to the expressed opinions, it is necessary to modify some methods and approaches in the health inspection of the food procurement, distribution and supply centers, Complete lack of focuson legal tools to change the behavior of operators and paying attention to the implementation of participatory training methods that have been less considered to date to increase the co-operation of service providers and agreed upon by both group of interviewees. Also, the entry of Self-reported health companies to the field of environmental health inspection and its consequence was one of the important issues that the inspectors and the operators looked at in this study with suspicion. Therefore, more attention should be paid to its implementation. The opinions of the interviewees (two groups of inspectors and operators)have a lot of sharing points about the various issues in health inspections. it is suggested that the opinions of operators as one of the stakeholders on the environment of the environment in decisions are investigated. The sharing of opinion between inspectors and operators can provide the fields of interaction between inspectors and operators. According to most participants, the necessity of reforming some methods and approaches is essential in health inspection of supply centres, distribution and supply of food. The focus and focus of the training and empowerment of investigators and the training of operators in modern ways and the lack of complete focus on legal instruments for the change of operators ' behaviour and attention to the implementation of corporate educational practices that have been less noticed today is necessary to enhance the cooperation of operators. It is also possible to consider some of the inspections as an advisory and training inspection at the curator " s workplace. according to the inspectors, under article 13 of the executive code of article 13 of the provisions of article 13 of the provisions of article 13 of the provisions of article 13 of the provision of edible, drinking, cosmetic and sanitary procedures and changing the procedures of legal action in the comprehensive audit system, the auditors are not yet familiar with the law and the executive procedure of recording checks and carrying out legal action has encountered some problems. On the other hand, the introduction of self - declaration to the area of health inspection and its outcome was an important issue in which the study was regarded by investigators and officials in doubt and doubt. Therefore, further consideration should be made about its implementation. finally, with regard to the extent of the activity of health inspectors from medical sciences at the university of medical sciences throughout the country as well as the small number of studies and researches related to various fields of auditors, inspectors are scientifically studied and analyzed and the effectiveness of activities such as inspection and sampling of food is analyzed as well as the effect of inspection from operators ' point of view. From the strengths of this study, it is possible to point out that for the first time with a qualitative study of defects and challenges and views of both groups of health inspectors of the environment and operators of supply centers, distribution and supply of food were examined and explored.

All construction projects carry some levels of risk. The construction projects involve numerous uncertainties, multiple intricacies, varies techniques, and divergent environments. So that, workers in the construction industry are at greater risk because of the dynamic nature of the activities and momentous changes in working conditions in comparison with other industries. The construction projects involve many factors, interdependencies, and correlations, which makes determination of exact cause and effect very difficult. Therefore, these factors play a significant role in decision making and may affect performance of a project.
The construction process frequently requires workers to work at height. The risks associated with working at height are often increased by adding accessibility and mobility restrictions. Falling from height is one of the most important causes of workers' fatality in the construction industries and constitutes a paramount part of the safety plans in the construction projects. Identifying the effective factors and sub-factors in the occurrence of this accident will be helpful in setting priorities for preventing and providing solutions in reducing their severity. The purpose of this study was to investigate and identify the factors and sub-factors affecting falling from height accidents and to determine the cause and effect relationships among them in the construction projects, using the fuzzy-DEMATEL technique.

In order to carry out this descriptive-analytical study, information of the Occupational Health and Safety (OHS) department of five construction projects have been used. The statistical society of the present study was the workers of five construction projects of a gas refinery in the south of Iran, which 4000 people, on average, were involved in these projects from 2011 to 2015. After reviewing the scientific literature, project reports, and guidelines, factors and sub-factors affecting the occurrence of falling from height accidents in the construction projects were determined based on the experts opinions. Snowball method was used to identify experts and determine the statistical society. Fuzzy-DEMATEL technique, as one of the methods of decision making based on paired comparisons, was used to identify the cause and effect relationships among factors and sub-factors. Based on this technique, the pairwise comparison matrices of the factors and sub-factors were formed and sent to 10 health and safety experts. Next, the views of experts were aggregated via the mean fuzzy method, and then the cause and effect relationships were determined based on them. The step-by-step process of the research is as follows: 
Step 1: Identifying research factors and sub-factors
All of the reported events were investigated between 2011 and 2015 and 74 out of 377 occupational accidents were considered as falling from height accidents. Considering the information of OHS department and literature review of effective factors in the occurrence of construction accidents, 70 factors and sub-factors were identified as effective factors in falling from height accidents. According to the objectives of the study and status of the projects, the identified factors and sub-factors divided to 3 main factors (organizational, individual, and environmental factors) and 14 sub-factors (management commitment, safety culture, mutual understanding, supervision/inspection, and size organization/project as an organizational factors; education, training hours, personal protective equipment (PPE), age/experience, and psychological/occupational stresses as an individual factors; thermal stress, interference, level smoothness, work platform height as an environmental factors).
Step 2: Data analysis and use of DEMATEL technique
In this research, Fuzzy-DEMATEL technique was used to construct a sequence of extracted data. This technique is one of the decision making methods based on pair comparisons with the benefit of expert’s judgment. The concept of this approach is based on the assumption that a system consists of a set of criteria and the pairwise comparisons of relationships between these criteria can be modeled by mathematical equations. DEMATEL technique is an approach to identify the cause and effect relationships among multiple factors in order to properly understand the problem. In general, it is very difficult to determine the opinion of experts with precise numerical values, especially in terms of uncertainty since the results of the decision depend heavily on unclear and subjective arbitrary judgments. These uncertainty conditions have led to the introduction of a fuzzy logic in the metamaterial technique. Therefore, in the Fuzzy-DEMATEL technique, fuzzy language is used which facilitates decision making in uncertainty conditions [37]. All calculations were performed in Excel (version 2013). The steps to implement this technique have been presented step-by-step based on the study of Li et al.
I) Calculation the direct relation matrix:After gathering the experts' view, a fuzzy direct relationship matrix ( ) was formed and the fuzzy mean method was used to aggregate the views of experts. Assuming that n experts have expressed their idea about the relationship between the indices and each component of the fuzzy direct matrix is displayed by then by can be calculated from Eq. (1) as follows: 

II) Normalizing the direct relation matrix:To normalize the values of the direct contact matrix, of each row must be calculated. Then, the fuzzy normal matrix ( ) can be calculated from Eq. (2) by dividing each component of by the maximum attained :
III) Calculation of the total-relation matrix
To calculate the total-relation matrix, the fuzzy normalized matrix is divided to three definite matrices as follows:
Then, the identify matrix is formed and the following operations are performed:
Then, the fuzzy total-relation matrix is computed by using Eq. (4).

The results of this research showed that among the main factors, organizational and individual factors were known as causal factors, which indicates importance of these factors and their impact on other effective factors in falling from height accidents. On the other hand, among various sub-factors, the management commitment, safety culture, monitoring and inspection, organization/project size, education, and work platform height had the highest effects on the falling from height accidents and were considered as causal variables. In the present study, management commitment, as one of the organizational sub-factors, had the highest impact and was considered as a causal variable.
According to the findings of this study, it can be concluded that four organizational sub-factors of mutual understanding, management commitment, safety culture and organization/project size, one individual sub-factor of education, and work platform height as an environmental sub-factor had the significant impact and were among the causal variables, while the rest of sub-factors were the effect variables. Also, the monitoring/inspection sub-factor has the highest interaction with and impact on other sub-factors.

Falling from height is considered as one of the most important accidents, leading to death and physical injuries in construction projects. The findings of this study showed that a greater attention to organizational factors and their dimensions (as hidden and effective causes to prevent falling from height incidents) is necessary since an organization plays an important role in the design of work processes, design and implementation of safety management systems, commitment to safety and employee participation, and choosing the best people according to the requirements for the health and safety programs of the projects. The results of this study also showed that it is necessary to pay more attention to the management commitment and awareness of the workforce by training them in the construction projects. Hence, a greater attention to organizational factors and their sub-factors in the construction industry is essential for preventing falling from height incidents. Therefore, more attention to the organizational factor and its sub-factors in the construction industry is required to prevent falling from height accidents.
Keywords: Falling from height, Fuzzy-DEMATEL technique, Construction projects, Workers.

In recent years, in most countries of the world, the provision of a calming environment without disturbing noise has become a need, which has subsequently led to significant growth in noise control techniques. It is now well documented that prolonged over-exposure to the excessive levels of environmental noise not only induces disabling hearing impairment but also contributes to numerous adverse health effects such as stress, irritability, hypertension, cardiovascular diseases, annoyance, and sleep disturbance. Working in noisy environments has also been reported to be linked with increased workplace accidents, aggression and anti-social behaviours. Based on the World Health Organization (WHO), occupational noise accounts for 16% of the disabling hearing loss in adults (more than four million DALYs), with estimates of disease burden ranging from 7% in developed countries to 21% in underdeveloped and developing nations.
There are several methods to reduce the noise pollution and control the sound of the working environment; one of the methods of controlling sound propagation path is the use of insulation and sound absorption. Sound control improvements with using sound absorption materials have provided a suitable opportunity to study noise reduction and acoustic attenuation by using a variety of porous materials. Increasing concerns about the adverse effects of the use of synthetic sound absorbing materials on the health of individuals has provided a favorable ground for the development of research on the use of natural fibers as insulators and absorbents. During the last two decades, there has been considerable interest in the use of lignocellulosic fibres for various purposes such as sustainable acoustic absorbers.  Bio-based composites of acoustic absorbers are mainly biodegradable and non-toxic and have low weight, low density and low cost and can be used as alternatives to the absorbers made of synthetic fibres.
Every year, in Iran, significant amounts of agricultural waste containing lignocellulosic fibres are burnt or disposed of improperly due to the lack of a proper recycling system and reusing mechanisms. However, a large proportion of such waste can be used for various uses. Iran as the second largest producer of dates in the world, and having large date palm plantations, faces the scourge of harvesting and pruning palm trees each year, which are largely suitable for use.
Therefore, the purpose of the present study was to investigate the acoustic behaviour of composite samples made of date palm natural fibres by predicting their sound absorption coefficients with the related experimental models and comparing the results with the data obtained from the experimental tests.

In this study, the natural date palm waste fibers were procured from Tabas city in southern Khorasan province in Iran. Having transferred to the laboratory, the raw DPFs were rinsed with distilled water before being placed inside an oven at 70 °C for 24 hours to dry and get a fixed weight. The DPFs were then cut into smaller pieces by a pair of scissors and crushed and pressed through a 2 mm mesh sieve to make their size fairly homogenous. In order to bind the fibers together and form a composite, polyvinyl alcohol (Sigma-Aldrich) was utilized. PVA is a polymeric chemical binder with high solubility in water and is known to be a biodegradable material reportedly used as natural fiber binder in previous studies.
In order to prepare 5% PVA concentration, 5 g of the substance was first weighed by a scale and later dissolved in 100 ml of distilled water. The solution was then stirred with a magnet at 80 °C for 3 hours. Having prepared the solution, the fibers were soaked with it to bind. The fibers were then shaped by an aluminum mold (by compression molding) to be fitted inside the impedance tube (internal diameter of 100 mm) and form samples with thicknesses of 20, 30 and 40 mm with a constant density of 200 kg/ m3. After the molding process, the samples were left at room temperature for 12 hours to dry completely before being transferred to the laboratory for absorption coefficient measurement. SEM images showed that outer diameter of the DPFs ranged from 200 to 720 μm and the mean diameter, the density and porosity of them were 420 μm, 930 kg/m3 and >80% respectively. The measurement of normal incidence absorption coefficients of the samples with a constant density and three different thicknesses a different air gaps was performed by an impedance tube and based on ISO 10534-2. Afterwards, by creating the appropriate codes in MATLAB software, using the differential equation algorithm, the predicted sound absorption coefficients for the Delany-Bazley, Micky, and Johnson-Champoux-Allard models were calculated. In fact, such algorithm searches for the three parameters until the best fit (minimized difference) is observed between the experimental and theoretical absorption curves. Therefore, the experimental sound absorption curve for the samples of the corresponding date palm fibers was first determined by the impedance tube system. We followed the same method proposed by Atalla and Panneton.

The results from the laboratory data for the three thicknesses of 20, 30 and 40 mm of the sample absorbers of DPF and the impact of the air gaps on their sound absorption coefficients are presented. Using the mathematical model, the sound absorption coefficient in the frequency range of 125-6300 Hz was next coded by MATLAB software. As shown in this paper, the predicted values of the physical parameters of the DPF were measured using differential equation algorithm in the MATLAB software through the available laboratory data such as the thickness, density, airflow resistivity and absorption coefficient. Later, the prediction error rate determined by the JCA model - shown on the right axes is compared to the data obtained from the experiments. The results showed that the sound absorption coefficients of the samples fabricated from date palm fibres, significantly increased with increasing the frequency. Moreover, the increase in the thickness of the samples with a constant density has a major role in attenuating the sound waves, especially in lower frequencies (less than 1000 Hz). Comparison of experimental data and models output showed that by increasing the thickness, the predicted values for the acoustic absorption coefficient of the samples approach the values obtained from the experimental tests. As can be seen, the JCA model has a fair accuracy in predicting the absorption coefficient in different thicknesses compared to the Delany-Bazley and Micki models.
Thus, this model at 20, 30- and 40-mm thickness and lower frequency range (63-1600 Hz) showed different prediction accuracies of 23%, 6% and 11% respectively, while at higher frequency range (1600-6300 Hz) came up with 9%, 6% and 4% prediction accuracies. Thus, such agreement is considered as significant in the higher frequency range. These findings also indicate that the outputs of the JCA model, rather than two other models, are closer to the data obtained from the experimental tests for setting the sound absorption coefficients. It is therefore concluded that the JCA model (compared to the Delaney-Basile and Mickey models) has included more dominant parameters that might impact the physical properties of the samples such as thickness, mass density, sample resistance against airflow, tortuosity, viscous and thermal characteristic length. Introduction of air gap behind the DPF samples in the impedance tube transfers the maximum values of sound absorption coefficient from the upper to the lower frequency range. The results indicate that, as the sample distance from the rigid surface of the backing (up to 30 mm) increases, the sound absorption coefficient at frequencies lower than 1000 Hz will rise as well. As a result, used in this study absorbing materials with an air cavity behind them seems to play a significant role in lower production cost, and thinner layers of absorbing materials yield better absorption coefficients. The reason for this behavior is probably due to the increased impedance of absorbing material. In this case, the acoustic resonance transferred towards lower frequencies and thus improved the values of absorption performance in that range. As a result, it seems that the use of absorbing material, while having a layer of air behind them, can reduce the cost and material consumption. Thus, thinner samples made of coir fibers would provide superior values of sound absorption coefficients.

Date palm fibres have a great potential for attenuating the energy of sound waves. Elevated levels of sound absorption can be attributed to a longer dissipative process of viscous and thermal conduction between air and the absorber.  Therefore, increasing the thickness of the sample will contribute to higher amounts of sound absorption coefficient.
On the other hand, natural fibers are still not as popular as synthetic fibers due to the properties such as low adhesion, high fiber diameter, low resistance to moisture and vulnerability to fungi. Therefore, it is obvious that these factors can affect the absorption coefficient of sound and the quality and durability of acoustic panels made of such natural fibers. In order to eliminate these defects, nanotechnology can be employed to achieve superior properties and better conditions by utilizing the best of these natural materials. Evidently this is the issue that should be taken into account in developing sound absorbers which are originated from the natural fibers.