عنوان مقاله [English]
According to the studies conducted in this field exposure to dust particles can increase the heart disease and respiratory problems, particularly among vulnerable groups including children and the elderly. Being located in the dust belt of West Asian region, Khuzestan province in southwestern Iran has been facing severe dust problems since 2001. According to the necessity to further investigate the effects of this phenomenon, the present study was conducted to investigate the statistical relationship between the dust level and cardiopulmonary mortality in Khuzestan province during 2006-2016. The research results, conducted using Pearson Correlation test, one-way analysis of variance (ANOVA) and Variance-Based Structural Equations (PLS), showed that there is a positive and significant relationship between dust and cardiopulmonary mortality. Also, dust and cardiac mortality showed the highest correlation with eight months delay. According to the ANOVA test results, all significant at 0.01 level, under the same dusty conditions, there is a significant difference between cardiopulmonary mortality in age groups below 10 and over 65 years with other groups. According to the path coefficient values and t-statistic calculated by structural equation method, it can be found that men are more vulnerable to dust than women. It is predicted that a 1% increase in monthly dust can cause a 0.31% and 0.28% increase in cardiac mortality and also a 0.41% and 0.30% increase in respiratory mortality in vulnerable and less vulnerable groups, respectively. These findings indicate the need for urgent planning to address the dust problem, as well as training and culturalization in dealing with this dangerous phenomenon.
Dust phenomena, as one of the major environmental concerns caused by human interference and unreasonable use of natural resources, has been prevalent in recent years. Dust refers to a mass of sedimentary solid particles smaller than 50 microns in diameter that disperses into the atmosphere, resulting in a 1-2 km decrease in horizontal view. Dust storms are events which naturally occur in arid and semi-arid areas, especially in subtropical latitudes. One of the most known sources of dust is the west of Asia, including Arabian Peninsula, Syria, Iraq, and southwest of Iran. Studies suggests that different sectors different sectors, including agriculture, civil infrastructure, industry, economy, tourism, and healthcare can be affected by the dust phenomenon. According to new findings, dust particles are more dangerous to public health compared to what was previously thought. Infiltration of these particles into the airbags by breathing polluted air increases the likelihood of respiratory disorders, cardiovascular disorders, eye inflammation, skin rashes, meningococcal meningitis, hepatic and cerebral necrosis, and abortion. In Iran, 29 provinces have been affected by the dust phenomenon in recent years. Being located in the dust belt in the West Asian region, Khuzestan province in southwestern Iran has been facing severe dust problems since 2001. Also, a 2011 World Health Organization report identifies Ahwaz as the world's most polluted city in terms of particles with an annual average of 372 micrograms per cubic meter PM10. Hence, more attention needs to be paid by researchers to the effects of this phenomenon in the field of health. Accordingly, the present study was conducted to investigate the statistical relationship between the dust events and cardiopulmonary mortality by sex and in sensitive and non-sensitive age groups in Khuzestan province during 2006-2016.
Two categories of data were used for the purpose of this research:
A) Dust data: including monitoring and horizontal view codes in Khuzestan province for the period of 2004-2016 which were obtained hourly from the Meteorological Organization and filtered and separated based on eleven dust codes of World Meteorological Organization (including 06, 07, 08, 09, 30, 31, 32, 33, 34, 35, and 98). Then, the frequency of dust events was classified on a monthly scale based on the data available in three main groups including local dust, trans-local dust and dust storms.
B) Mortality data related to Khuzestan province during the period of 2004-2016, collected monthly from the National Organization for Civil Registration. The cardiac and respiratory mortality data were categorized into two groups of vulnerable (age group lower than 10 years and upper than 60 years old) and less vulnerable. Then, they were studied for each female and male groups, separately.
The Pearson Correlation test was used to reveal the relationship between monthly dust data and cardiopulmonary mortality. The One-Way Analysis of Variance (ANOVA) was used to compare the effect of dust between the two vulnerable and less vulnerable groups. Also according to the research structure, which is based on the formative model, the variance-based structural equation techniques(Partial Least Square), including indices unidimensionality, Structural Reliability, Convergent Validity, coefficient of determination R2, Cohen effect size (F2) and path coefficient were used.
Results and discussion:
According to the results of correlation test, dust and respiratory mortality have a strong (r = 0.698) and significant (at 99% confidence level) correlation. Respiratory mortality is higher in the first months after a dust storm, but its correlation gradually declines. The correlation between cardiac mortality in the early months after the dust event is weak, but has a strong and significant correlation after a delay of more than 6 months, with the highest correlation of r = .551 in 99% confidence level after an eight-month delay.
According to the results of one-way analysis of variance between vulnerable and less vulnerable groups, inter-group dispersion was higher than intra-group dispersion and as a result, there was a significant difference between vulnerable and less vulnerable groups when facing with dust. These results are significant at 99% confidence level.
According to the results of variance-based structural equations (PLS), all factor loadings are greater than 0.4 and, therefore, the indices unidimensionality is confirmed. Structural reliability and convergent validity coefficients for all variables are greater than 0.6 and 0.5, respectively, and as a result, the measurement pattern is confirmed. Based on the path coefficient values and t-statistic calculated in the model for the vulnerable groups, all path coefficients were positive and greater than 0.1 for all variables except for female cardiac mortality. Accordingly, all path coefficients, except for the dust path coefficient and female cardiac mortality, have a clear effect at the 5% significance level, and the sign of all path coefficients is positive with the values more than 0.1, except for dust and female cardiopulmonary mortality in the less vulnerable groups. Also, the t-statistic is greater than 1.96 for all variables except for female cardiopulmonary mortality.
According to the results, there is a positive and significant relationship between dust and cardiopulmonary mortality. Also, dust and cardiac mortality showed the highest correlation with eight months delay. The results also show that there is a significant difference between cardiopulmonary mortality in age groups below 10 and over 65 years with other groups in the same dusty conditions. Also, in similar situations, men are more vulnerable to dust than women, and it is predicted that a 1% increase in monthly dust can cause a 0.31% and 0.28% increase in cardiac mortality and also a 0.41% and 0.30% increase in respiratory mortality in vulnerable and less vulnerable groups, respectively in Khuzestan province. These findings indicate the need for urgent planning to address the dust problem, as well as training and culturalization in dealing with this dangerous phenomenon.